Battery-2010's blog

Protactinium,Uranium,Neptunium

Protactinium,Uranium,Neptunium

Protactinium is a chemical element with the symbol Pa and atomic number 91. It is a dense, silvery-gray metal which readily reacts with oxygen, water vapor and inorganic acids. It forms various chemical compounds where protactinium is usually present in the oxidation state +5, but can also assume +4 and even +2 or +3 states. The average concentrations of protactinium in the Earth's crust is typically on the order of a few parts per trillion, but may reach up to a few parts per million in some uraninite ore deposits.Sony A1258274A Battery

Because of the scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside of scientific research, and for this purpose, protactinium is mostly extracted from spent nuclear fuel.

Protactinium was first identified in 1913 by Kasimir Fajans and Oswald Helmuth Göhring and named brevium because of the shorthalf-life of the specific isotope studied, namely protactinium-234. Sony VGP-BPL10 Battery

A more stable isotope of protactinium was discovered in 1918, and therefore the name was changed to protoactinium and then to protactinium in 1949. The new name meant "parent ofactinium" and reflected the fact that actinium is a product of radioactive decay of protactinium. Sony VGP-BPS10 Battery

The longest-lived and most abundant (nearly 100%) naturally occurring isotope of protactinium, protactinium-231, has a half-life of 32,760 years and is a decay product of uranium-235. Much smaller trace amounts of the short-lived nuclear isomerprotactinium-234m occur in the decay chain of uranium-238. Protactinium-233 results from the decay of thorium-233 as part of the chain of events used to produce uranium-233 by neutron irradiation of thorium-232. Sony VGP-BPS10/S Battery

It is an undesired intermediate product in thorium-based nuclear reactors and is therefore removed from the active zone of the reactor during the breeding process. Analysis of the relative concentrations of various uranium, thorium and protactinium isotopes in water and minerals is used in radiometric datingof sediments which are up to 175,000 years old and in modeling of various geological processes. Sony VGP-BPS10A/B Battery

In 1871, Dmitri Mendeleev predicted the existence of an element between thorium and uranium.[3] The actinide element group was unknown at the time. Therefore, uranium was positioned below tungsten, and thorium below zirconium, leaving the space below tantalum empty, and until the 1950s periodic tables were published with this structure.[4] Sony VGP-BPS10B Battery

For a long time chemists searched for eka-tantalum as an element with similar chemical properties as tantalum, making a discovery of protactinium nearly impossible.

In 1900, William Crookes isolated protactinium as an intensely radioactive material from uranium; Sony VGP-BPS10A Battery

however, he could not characterize it as a new chemical element and thus named it uranium-X.[3][5] Crookes dissolved uranium nitrate in ether, the residual aqueous phase contains most of the 234
90Th and 234
91Pa. His method was still used in the 1950s to isolate 234
90Th and 234
91Pafrom uranium compounds.[6] Protactinium was first identified in 1913, when Kasimir Fajans and Oswald Helmuth Göhring encountered the isotope 234Pa during their studies of the decay chains of uranium-238: 238Sony VGP-BPS11 Battery
92U ? 234
90Th ? 234
91Pa ? 234
92U. They named the new element brevium (from the Latin word, brevis, meaning brief or short) because of its short half-life, 6.7 hours for 234
91Pa.[7][8][9][10] Sony VGP-BPL11 Battery

In 1918, two groups of scientists, led by Otto Hahn and Lise Meitner of Germany and Frederick Soddy and John Cranston of Great Britain, independently discovered another isotope of protactinium, 231Pa having much longer half-life of about 32,000 years. Thus the name brevium was changed to protoactinium as the new element was part of the decay chain of uranium-235 before the actinium (from Greek: ?????? = protos meaning first, before). Sony VGP-BPL12 Battery

For ease of pronunciation, the name was shortened to protactinium by the IUPAC in 1949.[11][12] The discovery of protactinium completed the last gap in the early versions of the periodic table, proposed by Mendeleev in 1869, and it brought to fame the involved scientists, particularly Meitner.[13] Sony VGP-BPS12 Battery

Aristid von Grosse produced 2 milligrams of Pa2O5 in 1927,[14] and in 1934 first isolated elemental protactinium from 0.1 milligrams of Pa2O5.[15] He used two different procedures: in the first one, protactinium oxide was irradiated by 35 keV electrons in vacuum. In another method, called the van Arkel–de Boer process, the oxide was chemically converted to a halide(chloride, bromide or iodide) and then reduced in a vacuum with an electrically heated metallic filament:[11][16] Sony VGP-BPL13 Battery

2 PaI5 ? 2 Pa + 5 I2

In 1961, the British Atomic Energy Authority (UKAEA) produced 125 grams of 99.9% pure protactinium by processing 60 tonnes of waste material in a 12-stage process, at a cost of about 500,000 USD.[11] For many years, this was the world's only significant supply of protactinium, which was provided to various laboratories for scientific studies.[3] Sony VGP-BPS13 Battery

Oak Ridge National Laboratory in the US is currently providing protactinium at a cost of about 280 USD/gram.[17]

Occurrence

Protactinium is one of the rarest and most expensive naturally occurring elements. It is found in the form of two isotopes –231Pa and 234Pa, with the isotope 234Pa occurring in two different energy states. Sony VGP-BPS13/B Battery

Nearly all natural protactinium is protactinium-231. It is an alpha emitter and is formed by the decay of uranium-235, whereas the beta radiating protactinium-234 is produced as a result of uranium-238 decay. Nearly all uranium-238 (99.8%) decays first to the 234mPa isomer.[18] Sony VGP-BPS13/S Battery

Sony VGP-BPS13/S Battery

Protactinium occurs in uraninite (pitchblende) at concentrations of about 0.3-3 parts 231Pa per million parts (ppm) of ore.[3]Whereas the usual content is closer to 0.3 ppm[19] (e.g. in Jáchymov, Czech Republic[20]), some ores from the Democratic Republic of the Congo have about 3 ppm.[11] Sony VGP-BPS13A/B Battery

Protactinium is homogeneously dispersed in most natural materials and in water, but at much lower concentrations on the order of one part per trillion, that corresponds to the radioactivity of 0.1 picocuries (pCi)/g. There is about 500 times more protactinium in sandy soil particles than in water, even the water present in the same sample of soil. Much higher ratios of 2,000 and above are measured in loam soils and clays, such asbentonite.[18][21] Sony VGP-BPS13A/S Battery

In nuclear reactors

Two major protactinium isotopes, 231Pa and 233Pa are produced from thorium in nuclear reactors; both are undesirable and are usually removed, thereby adding complexity to the reactor design and operation. In particular, 232Th via (n,2n) reactions produces 231Th which quickly (half-life 25.5 hours) decays to 231Pa. Sony VGP-BPS13AS Battery

The last isotope, while not a transuranic waste, has a long half-life of 32,760 years and is a major contributor to the long term radiotoxicity of spent nuclear fuel.[22]

Protactinium-233 is formed upon neutron capture by 232Th. It further either decays to uranium-233 or captures another neutron and converts into the non-fissile uranium-234.[23] 233Sony VGP-BPS13B/B Battery

Pa has a relatively long half-life of 27 days and high cross section for neutron capture (the so-called "neutron poison"). Thus instead of rapidly decaying to the useful 233U, a significant fraction of233Pa converts to non-fissile isotopes and consumes neutrons, degrading the reactor efficiency. To avoid this, 233Pa is extracted from the active zone of thorium molten salt reactors, during their operation, so that it only decays to 233U. Sony VGP-BPS13B/Q Battery

This is achieved using several meters tall columns of molten bismuth with lithium dissolved in it. In a simplified scenario, lithium selectively reduces protactinium salts to protactinium metal which is then extracted from the molten-salt cycle, and bismuth is merely a carrier. It is chosen because of its low melting point (271 °C), low vapor pressure, good solubility for lithium and actinides, and immiscibility with molten halides.[22] Sony VGP-BPS13B/S Battery

Preparation

Before the advent of nuclear reactors, protactinium was separated for scientific experiments from uranium ores. Nowadays, it is mostly produced as an intermediate product of nuclear fission in thorium high-temperature reactors: Sony VGP-BPS13Q Battery

Protactinium metal can be prepared by reduction of its fluoride with calcium fluoride,[24] lithium or barium at a temperature of 1300–1400 °C.[25][26]

Physical and chemical properties

Protactinium is an actinide which is positioned in the periodic table to the left of uranium and to the right of thorium, and many of its physical properties are intermediate between those two actinides. Sony VGP-BPS13S Battery

So, protactinium is more dense and rigid than thorium but is lighter than uranium, and its melting point is lower than that of thorium and higher than that of uranium. The thermal expansion, electrical and thermal conductivities of these three elements are comparable and are typical of "poor metals". The estimated shear modulus of protactinium is similar to that of titanium.[27] Sony VGP-BPL7 Battery

Protactinium is a metal with silvery-gray luster that is preserved for some time in air.[11][28] Protactinium easily reacts with oxygen, water vapor and acids, but not with alkali metals.[3]

At room temperature, protactinium crystallizes in body-centered tetragonal structure which can be regarded as distorted body-centered cubic lattice; Sony VGP-BPS7 Battery

this structure does not change upon compression up to 53 GPa. The structure changes to face-centered cubic (fcc) upon cooling from high temperature, at about 1200 °C.[24][29] The thermal expansion coefficient of the tetragonal phase between room temperature and 700 °C is 9.9×10?6/°C.[24] Sony VGP-BPL8 Battery

Protactinium is paramagnetic and no magnetic transitions are known for it at any temperature.[30] It becomes superconductive at temperatures below 1.4 K.[3][25]Protactinium tetrachloride is paramagnetic at room temperature but turns ferromagnetic upon cooling to 182 K.[31] Sony VGP-BPL8A Battery

Protactinium exists in two major oxidation states, +4 and +5, both in solids and solutions, and the +3 and +2 states were observed in some solid phases. As the electron configuration of the neutral atom is 7s26d15f2, the +5 oxidation state corresponds to the low-energy (and thus favored) 5f0 configuration. Sony VGP-BPL8B Battery

Both +4 and +5 states easily form hydroxides in water with the predominant ions being Pa(OH)3+, Pa(OH)22+, Pa(OH)3+ and Pa(OH)4, all colorless.[32] Other known protactinium ions include PaCl22+, PaSO42+, PaF3+, PaF22+, PaF6–, PaF72– and PaF83–.[33][34]

Chemical compounds

Here a, b and c are lattice constants in picometers, No is space group number and Z is the number of formula units per unit cell; Sony VGP-BPS8 Battery

fccstands for the face-centered cubic symmetry. Density was not measured directly but calculated from the lattice parameters.

Oxides and oxygen-containing salts

Protactinium oxides are known for the metal oxidation states +2, +4 and +5. Sony VGP-BPS8A Battery

The most stable is white pentoxide Pa2O5, which can be produced by igniting protactinium(V) hydroxide in air at a temperature of 500 °C.[42] Its crystal structure is cubic, and the chemical composition is often non-stoichiometric, described as PaO2.25. Another phase of this oxide with orthorhombic symmetry has also been reported.[26][43] Sony VGP-BPS8B Battery

The black dioxide PaO2 is obtained from the pentoxide by reducing it at 1550 °C with hydrogen. It is not readily soluble in either dilute or concentrated nitric, hydrochloric or sulfuric acids, but easily dissolves in hydrofluoric acid.[26] Sony VGP-BPL9 Battery

The dioxide can be converted back to pentoxide by heating in oxygen-containing atmosphere to 1100 °C.[43] The monoxide PaO has only been observed as a thin coating on protactinium metal, but not in an isolated bulk form.[26]

Protactinium forms mixed binary oxides with various metals. Sony VGP-BPS9 Battery

With alkali metals A, the crystals have a chemical formula APaO3and perovskite structure, or A3PaO4 and distorted rock-salt structure, or A7PaO6 where oxygen atoms for a hexagonal close-packed lattice. In all these materials, protactinium ions are octahedrally coordinated.[44][45] Sony VGP-BPS9/B Battery

The pentoxide Pa2O5 combines with rare-earth metal oxides R2O3 to form various nonstoichiometric mixed-oxides, also of perovskite structure.[46]

Protactinium oxides are basic; they easily convert to hydroxides and can form various salts, such as sulfates, phosphates, nitrates, etc. Sony VGP-BPS9/S Battery

The nitrate is usually white but can be brown due to radiolytic decomposition. Heating the nitrate in air at 400 °C converts it to the white protactinium pentoxide.[47] The polytrioxophosphate Pa(PO3)4 can be produced by reacting difluoride sulfate PaF2SO4with phosphoric acid (H3PO4) under inert gas atmosphere. Sony VGP-BPS9A Battery

Heating the product to about 900 °C eliminates the reaction by-products such as hydrofluoric acid, sulfur trioxide and phosphoric anhydride. Heating to higher temperatures in an inert atmosphere decomposes Pa(PO3)4 into the diphosphate PaP2O7, which is analogous to diphosphates of other actinides. Sony VGP-BPS9A/B Battery

In the diphosphate, the PO3 groups form pyramids of C2v symmetry. Heating PaP2O7 in air to 1400 °C decomposes it into the pentoxides of phosphorus and protactinium.[40]

Halides

Protactinium(V) fluoride forms white crystals where protactinium ions are arranged in pentagonal bipyramids and coordinated by 7 other ions. Sony VGP-BPS9A/S Battery

The coordination is the same in protactinium(V) chloride, but the color is yellow. The coordination changes to octahedral in the brown protactinium(V) bromide and is unknown for protactinium(V) iodide. The protactinium coordination in all its tetrahalides is 8, but the arrangement is square antiprismatic in protactinium(IV) fluoride and dodecahedral in the chloride and bromide. Sony VGP-BPS9B Battery

Sony VGP-BPX11 Battery

Brown-colored protactinium(III) iodide has been reported where protactinium ions are 8-coordinated in a bicapped trigonal prismatic arrangement.[48]

Protactinium(V) fluoride and protactinium(V) chloride have a polymeric structure of monoclinic symmetry. Sony VGP-BPL18 Battery

There, within one polymeric chain, all the halide atoms lie in one graphite-like plane and form planar pentagons around the protactinium ions. The coordination 7 of protactinium originates from the 5 halide atoms and two bonds to protactinium atoms belonging to the nearby chains. Sony VGP-BPS18 Battery

These compounds easily hydrolyze in water.[49] The pentachloride melts at 300 °C and sublimates at even lower temperatures.

Protactinium(V) fluoride can be prepared by reacting protactinium oxide with either bromine pentafluoride or bromine trifluoride at about 600 °C, and protactinium(IV) fluoride is obtained from the oxide and a mixture of hydrogen and hydrogen fluoride at 600 °C;Sony VGP-BPL20 Battery

a large excess of hydrogen is required to remove atmospheric oxygen leaks into the reaction.[26]

Protactinium(V) chloride is prepared by reacting protactinium oxide with carbon tetrachloride at temperature of 200–300 °C.[26]The by-products (such as PaOCl3) are removed by fractional sublimation.[38] Sony VGP-BPS20/B Battery

Reduction of protactinium(V) chloride with hydrogen at about 800 °C yields protactinium(IV) chloride – a yellow-green solid which sublimes in vacuum at 400 °C; it can also be obtained directly from protactinium dioxide by treating it with carbon tetrachloride at 400 °C.[26] Sony VGP-BPS20/S Battery

Protactinium bromides are produced by the action of aluminum bromide, hydrogen bromide, carbon tetrabromide or a mixture of hydrogen bromide and thionyl bromide on protactinium oxide. An alternative reaction is between protactinium pentachloride and hydrogen bromide or thionyl bromide.[26] Sony VGP-BPL21 Battery

Protactinium(V) bromide has two similar monoclinic forms, one is obtained by sublimation at 400–410 °C and another by sublimation at slightly lower temperature of 390–400 °C.[37][39]

Protactinium iodides result from the oxides and aluminum iodide or ammonium iodide heated to 600 °C.[26] Sony VGP-BPS21 Battery

Protactinium(III) iodide was obtained by heating protactinium(V) iodide in vacuum.[49] As with oxides, protactinium forms mixed halides with alkali metals. Among those, most remarkable is Na3PaF8 where protactinium ion is symmetrically surrounded by 8 F–ions which form a nearly perfect cube.[33] Sony VGP-BPS21/S Battery

More complex protactinium fluorides are also known such as Pa2F9[49] and ternary fluorides of the types MPaF6 (M = Li, Na, K, Rb, Cs or NH4), M2PaF7 (M = K, Rb, Cs or NH4) and M3PaF8 (M = Li, Na, Rb, Cs), all being white crystalline solids. The MPaF6 formula can be represented as a combination of MF and PaF5. Sony VGP-BPS21A Battery

These compounds can be obtained by evaporating a hydrofluoric acid solution containing these both complexes. For the small alkali cations like Na, the crystal structure is tetragonal, whereas it lowers to orthorphombic for larger cations K+, Rb+, Cs+ or NH4+. A similar variation was observed for the M2PaF7 fluorides, namely the crystal symmetry was dependent on the cation and differed for Cs2PaF7 and M2PaF7 (M = K, Rb or NH4).[34] Sony VGP-BPS21A/B Battery

Other inorganic compounds

Oxyhalides and oxysulfides of protactinium are known. PaOBr3 has a monoclinic structure composed of double-chain units where protactinium has coordination 7 and is arranged into pentagonal bipyramids. Sony VGP-BPS21B Battery

The chains are interconnected through oxygen and bromine atoms, and each oxygen atom is related to three Pa atoms.[37] PaOS is a light-yellow non-volatile solid with a cubic crystal lattice isostructural to that of other actinide oxysulfides. It is obtained by reacting protactinium(V) chloride with a mixture of hydrogen sulfide and carbon disulfide at 900 °C.[26] Sony VGP-BPL22 Battery

In hydrides and nitrides, protactinium has a low oxidation state of about +3. The hydride is obtained by direct action of hydrogen on the metal at 250 °C, and the nitride is a product of ammonia and protactinium tetrachloride or pentachloride. This bright yellow solid is stable to heating to 800 °C in vacuum. Sony VGP-BPS22 Battery

Protactinium carbide PaC is formed by reduction of protactinium tetrafluoride with barium in a carbon crucible at a temperature of about 1400 °C.[26] Protactinium forms borohydrides which include Pa(BH4)4. It has an unusual polymeric structure with helical chains where the protactinium atom has coordination number of 12 and is surrounded by six BH4– ions.[50] Sony VGP-BPS22/A Battery

Organometallic compounds

Protactinium(IV) forms a tetrahedral complex tetrakis(cyclopentadienyl)protactinium(IV) (or Pa(C5H5)4) with four cyclopentadienyl rings, which can be synthesized by reacting protactinium(IV) chloride with molten Be(C5H5)2. One ring can be substituted with a halide atom.[51] Sony VGP-BPS22A Battery

Another organometallic complex is golden-yellow bis(?-cyclooctatetraene) protactinium, Pa(C8H8)2, which is analogous in structure touranocene. There, the metal atom is sandwiched between two cyclooctatetraeneligands. Similar to uranocene, it can be prepared by reacting protactinium tetrachloride with dipotassium cyclooctatetraenide, K2C8H8, in tetrahydrofuran.[41] Sony VGP-BPL23 Battery

Twenty-nine radioisotopes of protactinium have been discovered, the most stable being 231Pa with a half-life of 32,760 years, 233Pa with a half-life of 27 days, and 230Pa with a half-life of 17.4 days. All of the remaining isotopes have half-lives shorter than 1.6 days, and the majority of these have half-lives less than 1.8 seconds. Sony VGP-BPS23 Battery

Protactinium also has two nuclear isomers, 217mPa (half-life 1.2 milliseconds) and 234mPa (half-life 1.17 minutes).[52]

The primary decay mode for isotopes of protactinium lighter than (and including) the most stable isotope 231Pa (i.e., 212Pa to 231Pa) is alpha decay and the primary mode for the heavier isotopes (i.e., 232Pa to 240Pa) is beta decay. Sony VGP-BPS23/B Battery

The primary decay products of isotopes of protactinium lighter than (and including) 231Pa areactinium isotopes and the primary decay products for the heavier isotopes of protactinium are uranium isotopes.[52]

Applications

Although protactinium is located in the periodic table between uranium and thorium, Sony VGP-BPS23/D Battery

which both have numerous applications, owing to its scarcity, high radioactivity and high toxicity, there are currently no uses for protactinium outside of scientific research.[18]

Protactinium-231 arises from the decay of uranium-235 formed in nuclear reactors, and by the reaction 232Th + n ? 231Th + 2n and subsequent beta decay. Sony VGP-BPS23/G Battery

It may support a nuclear chain reaction, which could in principle be used to build nuclear weapons. The physicist Walter Seifritz once estimated the associated critical mass as 750±180 kg,[53] but this possibility (of a chain reaction) has been ruled out by other nuclear physicists since then.[54] Sony VGP-BPS23/P Battery

Sony VGP-BPS23/W Battery

With the advent of highly sensitive mass spectrometers, an application of 231Pa as a tracer in geology and paleoceanography has become possible. So, the ratio of protactinium-231 to thorium-230 is used for radiometric dating of sediments which are up to 175,000 years old and in modeling of the formation of minerals.[19] Sony Limited Edition 007 Battery

In particular, its evaluation in oceanic sediments allowed to reconstruct the movements of North Atlantic water bodies during the last melting of Ice Age glaciers.[55]Some of the protactinium-related dating variations rely on the analysis of the relative concentrations for several long-living members of the uranium decay chain – uranium, thorium and protactinium, for example. Sony VAIO VGC-LB15 Battery

These elements have 6, 5 and 4 f-electrons in the outer shell and thus favor +6, +5 and +4 oxidation states, respectively, and show different physical and chemical properties. So, thorium and protactinium, but not uranium compounds are poorly soluble in aqueous solutions, and precipitate into sediments; the precipitation rate is faster for thorium than for protactinium. Sony VGN-AR Series Battery

Besides, the concentration analysis for both protactinium-231 (half-life 32,750 years) and thorium-230 (half-life 75,380 years) allows to improve the accuracy compared to when only one isotope is measured; this double-isotope method is also weakly sensitive to inhomogeneities in the spatial distribution of the isotopes and to variations in their precipitation rate.[19][56] Sony VGN-CR Series Battery

Precautions

Protactinium is both toxic and highly radioactive and thus all manipulations with it are performed in a sealed glove box. Its major isotope 231Pa has a specific activity of 0.048 Ci/gram and primarily emits alpha-particles of the energy 5 MeV, which can be stopped by a thin layer of any material. Sony VIAO VGN-G Series Battery

However, it slowly decays, with the half-life of 32,760 years, into 227Ac, which has a specific activity of 74 Ci/gram, emits both alpha and beta radiation, and has a much shorter half-life of 22 years. 227Ac, in turn, decays into lighter isotopes with even shorter half-lives and much greater specific activities (SA), as summarized in the table below.[18] Sony VIAO VGN-G118 Battery

As protactinium is present in small amounts in most natural products and materials, it is ingested with food or water and inhaled with air. Only about 0.05% of ingested protactinium is absorbed into the blood and the remainder is excreted. From the blood, about 40% of the protactinium deposits in the bones, about 15% goes to the liver, 2% to the kidneys, and the rest leaves the body. Sony VIAO VGN-G118CN/B Battery

The biological half-life of protactinium is about 50 years in the bones, whereas in other organs the kinetics has a fast and slow component. So in the liver 70% of protactinium have a half-life of 10 days and 30% remain for 60 days. The corresponding values for kidneys are 20% (10 days) and 80% (60 days). Sony VIAO VGN-G118CN/T Battery

In all these organs, protactinium promotes cancer via its radioactivity.[18][47] The maximum safe dose of Pa in the human body is 0.03 µCi that corresponds to 0.5 micrograms of 231Pa. This isotope is 2.5×108 times more toxic than hydrocyanic acid.[57] The maximum allowed concentrations of 231Pa in the air is 3×10?4 Bq/m3. Sony VIAO VGN-G218 Battery

Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. The uranium nucleus binds between 141 and 146 neutrons, establishing six isotopes (U-233 through U-238), Sony VGN-TZ121 Battery

the most common of which are uranium-238 (146 neutrons) and uranium-235 (143 neutrons). All isotopes are unstable and uranium is weakly radioactive. Uranium has the second highest atomic weight of the naturally occurring elements, lighter only than plutonium-244.[3] Sony VGN-TZ13 Battery

Its density is about 70% higher than that of lead, but not as dense as goldor tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite. Sony VGN-TZ131 Battery

Sony VGN-TZ132N Battery

In nature, uranium is found as uranium-238 (99.2742%), uranium-235 (0.7204%), and a very small amount of uranium-234(0.0054%). Uranium decays slowly by emitting an alpha particle. The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years,[4] making them useful in dating the age of the Earth. Sony VGN-TZ132/N Battery

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 has the distinction of being the only naturally occurring fissile isotope. Uranium-238 is fissionable by fast neutrons, and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Sony VGN-TZ17N Battery

Another fissile isotope, uranium-233, can be produced from natural thorium and is also important in nuclear technology. While uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons, uranium-235 and to a lesser degree uranium-233 have a much higher fission cross-section for slow neutrons. Sony VGN-TZ16N Battery

In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors, and produces the fissile material for nuclear weapons.Depleted uranium (238U) is used in kinetic energy penetrators and armor plating.[5]

Uranium is used as a colorant in uranium glass, producing orange-red to lemon yellow hues. Sony VGN-TZ18N Battery

It was also used for tinting and shading in early photography. The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal and its radioactive properties were discovered in 1896 by Antoine Becquerel. Sony VAIO VGN-AR47G/E1 Battery

Research by Enrico Fermi and others starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold Warbetween the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239. Sony VAIO VGN-AR520E Battery

The security of those weapons and their fissile material following the breakup of the Soviet Union in 1991 is an ongoing concern for public health and safety.[6]See Nuclear proliferation.

Characteristics

When refined, uranium is a silvery white, weakly radioactive metal, which is harder than most elements. Sony VAIO VGN-AR53DB Battery

It is malleable, ductile, slightly paramagnetic, strongly electropositive and is a poorelectrical conductor.[7][8] Uranium metal has very high density, being approximately 70% denser than lead, but slightly less dense than gold.

Uranium metal reacts with almost all nonmetallic elements and their compounds, with reactivity increasing with temperature.[9]Sony VAIO VGN-AR54DB Battery

Hydrochloric and nitric acids dissolve uranium, but nonoxidizing acids attack the element very slowly.[7] When finely divided, it can react with cold water; in air, uranium metal becomes coated with a dark layer of uranium oxide.[8] Uranium in ores is extracted chemically and converted into uranium dioxide or other chemical forms usable in industry. Sony VAIO VGN-AR550E Battery

Uranium-235 was the first isotope that was found to be fissile. Other naturally occurring isotopes are fissionable, but not fissile. Upon bombardment with slow neutrons, its uranium-235isotope will most of the time divide into two smaller nuclei, releasing nuclear binding energyand more neutrons. Sony VAIO VGN-AR55DB Battery

If too many of these neutrons are absorbed by other uranium-235 nuclei, anuclear chain reaction occurs that results in a burst of heat or (in special circumstances) an explosion. In a nuclear reactor, such a chain reaction is slowed and controlled by a neutron poison, absorbing some of the free neutrons. Sony VAIO VGN-AR630E Battery

Such neutron absorbent materials are often part of reactor control rods (seenuclear reactor physics for a description of this process of reactor control).

As little as 15 lb (7 kg) of uranium-235 can be used to make an atomic bomb.[10] The first nuclear bomb used in war, Little Boy, Sony VAIO VGN-AR64DB Battery

relied on uranium fission, while the very first nuclear explosive (The gadget) and the bomb that destroyed Nagasaki (Fat Man) were plutonium bombs.

Uranium metal has three allotropic forms:[11]

• ? (orthorhombic) stable up to 660 °C
• ? (tetragonal) stable from 660 °C to 760 °C

? (body-centered cubic) from 760 °C to melting point—this is the most malleable and ductile state. Sony VAIO VGN-AR65DB Battery

Military

The major application of uranium in the military sector is in high-density penetrators. This ammunition consists of depleted uranium(DU) alloyed with 1–2% other elements. At high impact speed, the density, hardness, and pyrophoricity of the projectile enable destruction of heavily armored targets. Sony VAIO VGN-AR660U Battery

Tank armor and other removable vehicle armorare also hardened with depleted uranium plates. The use of DU became politically and environmentally contentious after the use of DU munitions by the US, UK and other countries during wars in the Persian Gulf and the Balkans raised questions of uranium compounds left in the soil (see Gulf War Syndrome).[10] Sony VAIO VGN-AR690U Battery

Depleted uranium is also used as a shielding material in some containers used to store and transport radioactive materials. While the metal itself is radioactive, its high density makes it more effective than lead in halting radiation from strong sources such as radium.[7] Other uses of DU include counterweights for aircraft control surfaces, as ballast for missile re-entry vehicles and as a shielding material.[8] Sony VAIO VGN-AR71ZU Battery

Due to its high density, this material is found in inertial guidance systems and in gyroscopic compasses.[8] DU is preferred over similarly dense metals due to its ability to be easily machined and cast as well as its relatively low cost.[12] Counter to popular belief, the main risk of exposure to DU is chemical poisoning by uranium oxide rather than radioactivity (uranium being only a weak alpha emitter). Sony VAIO VGN-AR730E/B Battery

During the later stages of World War II, the entire Cold War, and to a lesser extent afterwards, uranium-235 has been used as the fissile explosive material to produce nuclear weapons. Initially, two major types of fission bombs were built: Sony VAIO VGN-AR73DB Battery

a relatively simple device that uses uranium-235 and a more complicated mechanism that uses plutonium-239 derived from uranium-238. Later, a much more complicated and far more powerful type of fission/fusion bomb (thermonuclear weapon) was built, that uses a plutonium-based device to cause a mixture of tritium and deuterium to undergo nuclear fusion. Sony VAIO VGN-AR74DB Battery

Such bombs are jacketed in a non-fissile (unenriched) uranium case, and they derive more than half their power from the fission of this material by fast neutrons from the nuclear fusion process.[13]

Civilian

The most visible civilian use of uranium is as the thermal power source used in nuclear power plants. Sony VAIO VGN-AR75UDB Battery

The main use of uranium in the civilian sector is to fuel nuclear power plants. One kilogram of uranium-235 can theoretically produce about 80 terajoules of energy (8×1013 joules), assuming complete fission; as much energy as 3000 tonnes of coal.[5]

Commercial nuclear power plants use fuel that is typically enriched to around 3% uranium-235.[5] Sony VAIO VGN-AR790U/B Battery

The CANDU and Magnox designs are the only commercial reactors capable of using unenriched uranium fuel. Fuel used for United States Navy reactors is typically highly enriched in uranium-235 (the exact values are classified). In a breeder reactor, uranium-238 can also be converted intoplutonium through the following reaction:[8] 238U (n, gamma) ? 239U -(beta) ? 239Np -(beta) ? 239Pu.Sony VAIO VGN-AR820E Battery

Before the discovery of radioactivity, uranium was primarily used in small amounts for yellow glass and pottery glazes, such as uranium glass and in Fiestaware.

The discovery and isolation of radium in uranium ore (pitchblende) by Marie Curie sparked the development of uranium mining to extract the radium, which was used to make glow-in-the-dark paints for clock and aircraft dials.[14] Sony VAIO VGN-AR830E Battery

This left a prodigious quantity of uranium as a waste product, since it takes three metric tons of uranium to extract one gram of radium. This waste product was diverted to the glazing industry, making uranium glazes very inexpensive and abundant. Besides the pottery glazes, uranium tileglazes accounted for the bulk of the use, including common bathroom and kitchen tiles which can be produced in green, yellow, mauve, black, blue, red and other colors. Sony VAIO VGN-AR83S Battery

Uranium was also used in photographic chemicals (especially uranium nitrate as a toner),[8] in lamp filaments, to improve the appearance of dentures, and in the leather and wood industries for stains and dyes. Uranium salts are mordants of silk or wool. Uranyl acetate and uranyl formate are used as electron-dense "stains" in transmission electron microscopy, Sony VAIO VGN-AR83US Battery

to increase the contrast of biological specimens in ultrathin sections and in negative staining of viruses, isolated cell organelles and macromolecules.

The discovery of the radioactivity of uranium ushered in additional scientific and practical uses of the element. Sony VAIO VGN-AR84S Battery

The long half-life of the isotope uranium-238 (4.51×109 years) makes it well-suited for use in estimating the age of the earliest igneous rocks and for other types of radiometric dating, including uranium-thorium dating and uranium-lead dating. Uranium metal is used for X-raytargets in the making of high-energy X-rays.[8] Sony VAIO VGN-AR84US Battery

Prehistoric naturally occurring fission

In 1972 French physicist Francis Perrin discovered fifteen ancient and no longer active natural nuclear fission reactors in three separate ore deposits at the Oklomine in Gabon, West Africa, collectively known as the Oklo Fossil Reactors. Sony VAIO VGN-AR85S Battery

The ore deposit is 1.7 billion years old; then, uranium-235 constituted about three percent of the total uranium on Earth.[15] This is high enough to permit a sustained nuclear fission chain reaction to occur, provided other supporting conditions exist. Sony VAIO VGN-AR85US Battery

The capacity of the surrounding sediment to contain the nuclear waste products has been cited by the U.S. federal government as supporting evidence for the feasibility to store spent nuclear fuel at the Yucca Mountain nuclear waste repository.[15]

Pre-discovery use

The use of uranium in its natural oxide form dates back to at least the year 79 CE, when it was used to add a yellow color to ceramicglazes.[8] Sony VAIO VGN-AR870EA Battery

Yellow glass with 1% uranium oxide was found in a Roman villa on Cape Posillipo in the Bay of Naples, Italy by R. T. Gunther of the University of Oxford in 1912.[16] Starting in the lateMiddle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic) and was used as a coloring agent in the local glassmakingindustry.[17] Sony VAIO VGN-AR890U Battery

In the early 19th century, the world's only known sources of uranium ore were these mines.

Discovery

The discovery of the element is credited to the German chemist Martin Heinrich Klaproth. While he was working in his experimental laboratory in Berlin in 1789, Klaproth was able to precipitate a yellow compound (likely sodium diuranate) by dissolvingpitchblendein nitric acid and neutralizing the solution with sodium hydroxide.[17] Sony VAIO VGN-AR93S Battery

Klaproth assumed the yellow substance was the oxide of a yet-undiscovered element and heated it with charcoal to obtain a black powder, which he thought was the newly discovered metal itself (in fact, that powder was an oxide of uranium).[17][18] He named the newly discovered element after the planet Uranus, Sony VAIO VGN-AR93US Battery

which had been discovered eight years earlier by William Herschel (who had named the planet after the primordialGreek god of the sky).[19]

In 1841, Eugène-Melchior Péligot, Professor of Analytical Chemistry at the Conservatoire National des Arts et Métiers (Central School of Arts and Manufactures) in Paris, isolated the first sample of uranium metal by heating uranium tetrachloridewithpotassium.[17][20] Sony VAIO VGN-AR94S Battery

Uranium was not seen as being particularly dangerous during much of the 19th century, leading to the development of various uses for the element. One such use for the oxide was the aforementioned but no longer secret coloring of pottery and glass.

Antoine Henri Becquerel discovered radioactivity by using uranium in 1896.[9] Sony VAIO VGN-AR94US Battery

Becquerel made the discovery in Paris by leaving a sample of a uranium salt, K2UO2(SO4)2 (potassium uranyl sulfate), on top of an unexposed photographic plate in a drawer and noting that the plate had become 'fogged'.[21] He determined that a form of invisible light or rays emitted by uranium had exposed the plate. Sony VAIO VGN-AR95S Battery

Fission research

A team led by Enrico Fermi in 1934 observed that bombarding uranium with neutrons produces the emission of beta rays (electronsorpositrons from the elements produced; see beta particle).[22] Sony VAIO VGN-AR95US Battery

 

The fission products were at first mistaken for new elements of atomic numbers 93 and 94, which the Dean of the Faculty of Rome, Orso Mario Corbino, christened ausonium and hesperium, respectively.[23][24][25][26] The experiments leading to the discovery of uranium's ability to fission (break apart) into lighter elements and release binding energy were conducted by Otto Hahn and Fritz Strassmann[22] in Hahn's laboratory in Berlin. Sony VAIO VGN-AW110J/H Battery

Lise Meitner and her nephew, physicist Otto Robert Frisch, published the physical explanation in February 1939 and named the process 'nuclear fission'.[27] Soon after, Fermi hypothesized that the fission of uranium might release enough neutrons to sustain a fission reaction. Sony VAIO VGN-AW11M/H Battery

Confirmation of this hypothesis came in 1939, and later work found that on average about 2.5 neutrons are released by each fission of the rare uranium isotope uranium-235.[22] Further work found that the far more common uranium-238 isotope can be transmuted into plutonium, which, like uranium-235, is also fissionable by thermal neutrons. Sony VAIO VGN-AW11S/B Battery

These discoveries led numerous countries to begin working on the development of nuclear weapons and nuclear power.

On 2 December 1942, as part of the Manhattan Project, another team led by Enrico Fermi was able to initiate the first artificial self-sustained nuclear chain reaction, Chicago Pile-1. Sony VAIO VGN-AW11XU/Q Battery

Working in a lab below the stands of Stagg Field at the University of Chicago, the team created the conditions needed for such a reaction by piling together 400 tons (360 tonnes) of graphite, 58 tons (53 tonnes) of uranium oxide, and six tons (five and a half tonnes) of uranium metal.[22] Sony VAIO VGN-AW11Z/B Battery

Bombs

Two major types of atomic bombs were developed by the United States during World War II: a uranium-based device (codenamed "Little Boy") whose fissile material was highly enriched uranium, and a plutonium-based device (see Trinity test and "Fat Man") whose plutonium was derived from uranium-238. Sony VAIO VGN-AW120J/H Battery

The uranium-based Little Boy device became the first nuclear weapon used in war when it was detonated over the Japanese city of Hiroshima on 6 August 1945. Exploding with a yield equivalent to 12,500 tonnes of TNT, the blast and thermal wave of the bomb destroyed nearly 50,000 buildings and killed approximately 75,000 people (see Atomic bombings of Hiroshima and Nagasaki).[21Sony VAIO VGN-AW150Y/H Battery

] Initially it was believed that uranium was relatively rare, and that nuclear proliferationcould be avoided by simply buying up all known uranium stocks, but within a decade large deposits of it were discovered in many places around the world.[28]

Reactors

The X-10 Graphite Reactor at Oak Ridge National Laboratory (ORNL) in Oak Ridge, Sony VAIO VGN-AW160J/Q Battery

Tennessee, formerly known as the Clinton Pile and X-10 Pile, was the world's second artificial nuclear reactor (after Enrico Fermi's Chicago Pile) and was the first reactor designed and built for continuous operation. The Experimental Breeder Reactor I at the Idaho National Laboratory (INL) near Arco, Idahobecame the first nuclear reactor to create electricity on 20 December 1951. Sony VAIO VGN-AW170Y/Q Battery

Sony VAIO VGN-AW180Y/Q Battery

Initially, four 150-watt light bulbs were lit by the reactor, but improvements eventually enabled it to power the whole facility (later, the town of Arco became the first in the world to have all its electricity come from nuclear power).[29] The world's first commercial scale nuclear power station, Obninsk in the Soviet Union, began generation with its reactor AM-1 on 27 June 1954. Sony VAIO VGN-AW190JAH Battery

Other early nuclear power plants were Calder Hall in England which began generation on 17 October 1956[30]and the Shippingport Atomic Power Station in Pennsylvania which began on 26 May 1958. Nuclear power was used for the first time for propulsion by a submarine, the USS Nautilus, in 1954.[22] Sony VAIO VGN-AW190NAB Battery

Contamination and the Cold War legacy

Above-ground nuclear tests by the Soviet Union and the United States in the 1950s and early 1960s and by France into the 1970s and 1980s[12] spread a significant amount of fallout from uranium daughter isotopes around the world.[31] Additional fallout and pollution occurred from several nuclear accidents.[32][33] Sony VAIO VGN-AW190NBB Battery

Uranium miners have a higher incidence of cancer. An excess risk of lung cancer among Navajo uranium miners, for example, has been documented and linked to their occupation.[34] The Radiation Exposure Compensation Act, a 1990 law, required $100,000 in "compassion payments" to uranium miners diagnosed with cancer or other respiratory ailments.[35] Sony VAIO VGN-AW190NCB Battery

During the Cold War between the Soviet Union and the United States, huge stockpiles of uranium were amassed and tens of thousands of nuclear weapons were created using enriched uranium and plutonium made from uranium. Since the break-up of the Soviet Unionin 1991, Sony VAIO VGN-AW190YAB Battery

an estimated 600 tons (540 tonnes) of highly enriched weapons grade uranium (enough to make 40,000 nuclear warheads) have been stored in often inadequately guarded facilities in the Russian Federation and several other former Soviet states.[10] Police in Asia, Europe, and South America on at least 16 occasions from 1993 to 2005 have intercepted shipments of smuggled bomb-grade uranium or plutonium, Sony VAIO VGN-AW190YBB Battery

most of which was from ex-Soviet sources.[10] From 1993 to 2005 the Material Protection, Control, and Accounting Program, operated by the federal government of the United States, spent approximately US $550 million to help safeguard uranium and plutonium stockpiles in Russia.[10] Sony VAIO VGN-AW190YCB Battery

This money was used for improvements and security enhancements at research and storage facilities. Scientific American reported in February 2006 that some of the facilities security consisted of chain link fences which were in severe states of disrepair. According to an interview from the article, one facility had been storing samples of enriched (weapons grade) uranium in a broom closet before the improvement project; Sony VAIO VGN-AW190YDB Battery

another had been keeping track of its stock of nuclear warheads using index cards kept in a shoe box.[36]

Biotic and abiotic

Uranium is a naturally occurring element that can be found in low levels within all rock, soil, and water. Uranium is also the highest-numbered element to be found naturally in significant quantities on earth and is always found combined with other elements.[8]Sony VAIO VGN-AW220J/B Battery

Along with all elements having atomic weights higher than that of iron, it is only naturally formed in supernovae.[37]The decay of uranium, thorium, and potassium-40 in the Earth's mantle is thought to be the main source of heat[38][39] that keeps the outer coreliquid and drives mantle convection, which in turn drives plate tectonics. Sony VAIO VGN-AW230J/H Battery

Uranium's average concentration in the Earth's crust is (depending on the reference) 2 to 4 parts per million,[7][12] or about 40 times as abundant as silver.[9] The Earth's crust from the surface to 25 km (15 mi) down is calculated to contain 1017 kg (2×1017 lb) of uranium while the oceans may contain 1013 kg (2×1013 lb).[7] Sony VAIO VGN-AW235J/B Battery

The concentration of uranium in soil ranges from 0.7 to 11 parts per million (up to 15 parts per million in farmland soil due to use of phosphate fertilizers), and its concentration in sea water is 3 parts per billion.[12]

Uranium is more plentiful than antimony, tin, cadmium, mercury, or silver, and it is about as abundant as arsenicormolybdenum.[8][12] Sony VAIO VGN-AW290JFQ Battery

Uranium is found in hundreds of minerals including uraninite (the most common uranium ore), carnotite, autunite,uranophane, torbernite, and coffinite.[8] Significant concentrations of uranium occur in some substances such as phosphate rock deposits, and minerals such as lignite, and monazite sands in uranium-rich ores[8] (it is recovered commercially from sources with as little as 0.1% uranium[9]). Sony VAIO VGN-AW41JF Battery

Some bacteria such as S. putrefaciens and G. metallireducens have been shown to reduce U(VI) to U(IV).[40]

Some organisms, such as the lichen Trapelia involuta or microorganisms such as the bacterium Citrobacter, can absorb concentrations of uranium that are up to 300 times higher than in their environment.[41] Sony VAIO VGN-AW41JF/H Battery

Citrobacter species absorb uranyl ions when given glycerol phosphate (or other similar organic phosphates). After one day, one gram of bacteria can encrust themselves with nine grams of uranyl phosphate crystals; this creates the possibility that these organisms could be used in bioremediationtodecontaminate uranium-polluted water.[17][42] Sony VAIO VGN-AW41MF Battery

In nature, uranium(VI) forms highly soluble carbonate complexes at alkaline pH. This leads to an increase in mobility and availability of uranium to groundwater and soil from nuclear wastes which leads to health hazards. However, it is difficult to precipitate uranium as phosphate in the presence of excess carbonate at alkaline pH. Sony VAIO VGN-AW41MF/H Battery

A Sphingomonas sp. strain BSAR-1 has been found to express a high activity alkaline phosphatase (PhoK) that has been applied for bioprecipitation of uranium as uranyl phosphate species from alkaline solutions. The precipitation ability was enhanced by overexpressing PhoK protein in E. coli.[43] Sony VAIO VGN-AW41XH Battery

Plants absorb some uranium from soil. Dry weight concentrations of uranium in plants range from 5 to 60 parts per billion, and ash from burnt wood can have concentrations up to 4 parts per million.[17] Dry weight concentrations of uranium in food plants are typically lower with one to two micrograms per day ingested through the food people eat.[17] Sony VAIO VGN-AW41XH/Q Battery

Production and mining

The worldwide production of uranium in 2009 amounted to 50,572 tonnes, of which 27.3% was mined in Kazakhstan. Other important uranium mining countries are Canada (20.1%), Australia (15.7%), Namibia (9.1%), Russia (7.0%), and Niger (6.4%).[44]Sony VAIO VGN-AW41ZF Battery

Uranium ore is mined in several ways: by open pit, underground, in-situ leaching, and borehole mining (see uranium mining).[5]Low-grade uranium ore mined typically contains 0.01 to 0.25% uranium oxides. Extensive measures must be employed to extract the metal from its ore.[45] Sony VAIO VGN-AW41ZF/B Battery

High-grade ores found in Athabasca Basin deposits in Saskatchewan, Canada can contain up to 23% uranium oxides on average.[46]Uranium ore is crushed and rendered into a fine powder and then leached with either an acid or alkali. Theleachate is subjected to one of several sequences of precipitation, solvent extraction, and ion exchange. Sony VAIO VGN-AW50DB/H Battery

The resulting mixture, called yellowcake, contains at least 75% uranium oxides. Yellowcake is then calcined to remove impurities from the milling process before refining and conversion.[47]

Commercial-grade uranium can be produced through the reduction of uranium halides with alkali or alkaline earth metals.[8Sony VAIO VGN-AW51JGB Battery

]Uranium metal can also be prepared through electrolysis of KU5 or UF4, dissolved in molten calcium chloride (CaCl2) and sodium chloride(NaCl) solution.[8] Very pure uranium is produced through the thermal decomposition of uranium halides on a hot filament.[8] Sony VAIO VGN-AW52JGB Battery

Resources and reserves

It is estimated that 5.5 million tonnes of uranium ore reserves are economically viable at US$59/lb,[48] while 35 million tonnes are classed as mineral resources (reasonable prospects for eventual economic extraction).[49] Sony VAIO VGN-AW53FB Battery

An additional 4.6 billion tonnes of uranium are estimated to be in sea water (Japanese scientists in the 1980s showed that extraction of uranium from sea water usingion exchangers was technically feasible).[50][51] There have been experiments to extract uranium from sea water,[52] but the yield has been low due to the carbonate present in the water. Sony VAIO VGN-AW70B/Q Battery

Exploration for uranium is increasing with US$200 million being spent world wide in 2005, a 54% increase on the previous year,[49]thanks to growing prices on uranium market. This trend continued through 2006, when expenditure on exploration rocketed to over $774 million, an increase of over 250% compared to 2004. Sony VAIO VGN-AW71JB Battery

The OECD Nuclear Energy Agency said exploration figures for 2007 would likely match those for 2006.[48]

Australia has 31% of the world's uranium ore reserves[53] and the world's largest single uranium deposit, located at the Olympic DamMine in South Australia.[54] Sony VAIO VGN-AW72JB Battery

Some nuclear fuel comes from nuclear weapons being dismantled,[55] such as from the Megatons to Megawatts Program.

Supply

In 2005, seventeen countries produced concentrated uranium oxides, with Canada (27.9% of world production) and Australia(22.8%) being the largest producers and Kazakhstan (10.5%),Sony VAIO VGN-AW73FB Battery

Russia (8.0%), Namibia (7.5%), Niger (7.4%), Uzbekistan (5.5%), the United States (2.5%), Argentina (2.1%), Ukraine (1.9%) and China (1.7%) also producing significant amounts.[57] Kazakhstan continues to increase production and may have become the world's largest producer of uranium by 2009 with an expected production of 12,826 tonnes, Sony VAIO VGN-AW80NS Battery

compared to Canada with 11,100 tonnes and Australia with 9,430 tonnes.[58][59] The ultimate available uranium is believed to be sufficient for at least the next 85 years[49] although some studies indicate underinvestment in the late twentieth century may produce supply problems in the 21st century.[60] Sony VAIO VGN-AW80S Battery

Kenneth S. Deffeyes and Ian D. MacGregor point out that uranium deposits seem to be log-normal distributed. There is a 300-fold increase in the amount of uranium recoverable for each tenfold decrease in ore grade."[61] In other words, there is little high grade ore and proportionately much more low grade ore available. Sony VAIO VGN-AW80US Battery

Oxidation states and oxides

Calcined uranium yellowcake as produced in many large mills contains a distribution of uranium oxidation species in various forms ranging from most oxidized to least oxidized. Particles with short residence times in a calciner will generally be less oxidized than those with long retention times or particles recovered in the stack scrubber. Sony VAIO VGN-AW81DS Battery

Uranium content is usually referenced to U3O8, which dates to the days of the Manhattan project when U3O8 was used as an analytical chemistry reporting standard.

Phase relationships in the uranium-oxygen system are complex. The most important oxidation states of uranium are uranium(IV) and uranium(VI), and their two corresponding oxides are, respectively, uranium dioxide (UO2) and uranium trioxide (UO3).[62]Sony VAIO VGN-AW81JS Battery

Otheruranium oxides such as uranium monoxide (UO), diuranium pentoxide (U2O5), and uranium peroxide (UO4·2H2O) also exist.

The most common forms of uranium oxide are triuranium octaoxide (U3O8) and UO2.[63] Both oxide forms are solids that have low solubility in water and are relatively stable over a wide range of environmental conditions. Sony VAIO VGN-AW81YS Battery

Triuranium octaoxide is (depending on conditions) the most stable compound of uranium and is the form most commonly found in nature. Uranium dioxide is the form in which uranium is most commonly used as a nuclear reactor fuel.[63] At ambient temperatures, UO2 will gradually convert to U3O8. Sony VAIO VGN-AW82DS Battery

Because of their stability, uranium oxides are generally considered the preferred chemical form for storage or disposal.[63]

Aqueous chemistry

Salts of all four oxidation states of uranium are water-soluble and may be studied in aqueous solutions. Sony VAIO VGN-AW82JS Battery

The oxidation states are U3+(brown-red), U4+ (green), UO2+ (unstable), and UO22+ (yellow).[64] A few solid and semi-metallic compounds such as UO and US exist for the formal oxidation state uranium(II), but no simple ions are known to exist in solution for that state. Sony VAIO VGN-AW82YS Battery

Ions of U3+liberate hydrogen fromwater and are therefore considered to be highly unstable. The UO22+ ion represents the uranium(VI) state and is known to form compounds such as uranyl carbonate, uranyl chloride and uranyl sulfate. UO22+ also forms complexes with various organic chelating agents, the most commonly encountered of which is uranyl acetate.[64] Sony VAIO VGN-AW83FS Battery

Carbonates

The interactions of carbonate anions with uranium(VI) cause the Pourbaix diagram to change greatly when the medium is changed from water to a carbonate containing solution. While the vast majority of carbonates are insoluble in water (students are often taught that all carbonates other than those of alkali metals are insoluble in water), Sony VAIO VGN-AW83GS Battery

uranium carbonates are often soluble in water. This is because a U(VI) cation is able to bind two terminal oxides and three or more carbonates to form anionic complexes.

Effects of pH

The uranium fraction diagrams in the presence of carbonate illustrate this further: Sony VAIO VGN-AW83HS Battery

when the pH of a uranium(VI) solution increases, the uranium is converted to a hydrated uranium oxide hydroxide and at high pHs it becomes an anionic hydroxide complex.

When carbonate is added, uranium is converted to a series of carbonate complexes if the pH is increased. Sony VAIO VGN-AW90NS Battery

One effect of these reactions is increased solubility of uranium in the pH range 6 to 8, a fact which has a direct bearing on the long term stability of spent uranium dioxide nuclear fuels.

Hydrides, carbides and nitrides

Uranium metal heated to 250 to 300 °C (482 to 572 °F) reacts with hydrogen to form uranium hydride. Even higher temperatures will reversibly remove the hydrogen. Sony VAIO VGN-AW90S Battery

This property makes uranium hydrides convenient starting materials to create reactive uranium powder along with various uranium carbide, nitride, and halidecompounds.[66] Two crystal modifications of uranium hydride exist: an ? form that is obtained at low temperatures and a ? form that is created when the formation temperature is above 250 °C.[66] Sony VAIO VGN-AW90US Battery

Uranium carbides and uranium nitrides are both relatively inert semimetallic compounds that are minimally soluble in acids, react with water, and can ignite in airto form U3O8.[66] Carbides of uranium include uranium monocarbide (UC), uranium dicarbide (UC2), and diuranium tricarbide (U2C3). Sony VAIO VGN-AW91CDS Battery

Both UC and UC2 are formed by adding carbon to molten uranium or by exposing the metal to carbon monoxide at high temperatures. Stable below 1800 °C, U2C3 is prepared by subjecting a heated mixture of UC and UC2 to mechanical stress.[67]Uranium nitrides obtained by direct exposure of the metal to nitrogen include uranium mononitride (UN), uranium dinitride (UN2), and diuranium trinitride (U2N3).[67] Sony VAIO VGN-AW91CJS Battery

All uranium fluorides are created using uranium tetrafluoride (UF4); UF4 itself is prepared by hydrofluorination of uranium dioxide.[66] Reduction of UF4 with hydrogen at 1000 °C produces uranium trifluoride (UF3). Under the right conditions of temperature and pressure, the reaction of solid UF4 with gaseous uranium hexafluoride (UF6) can form the intermediate fluorides ofU2F9, U4F17, and UF5.[66] Sony VAIO VGN-AW91CYS Battery

At room temperatures, UF6 has a high vapor pressure, making it useful in the gaseous diffusion process to separate uranium-235 from the common uranium-238 isotope. This compound can be prepared from uranium dioxide and uranium hydride by the following process:[66] Sony VAIO VGN-AW91DS Battery

UO2 + 4 HF ? UF4 + 2 H2O (500 °C, endothermic)

UF4 + F2 ? UF6 (350 °C, endothermic)

The resulting UF6, a white solid, is highly reactive (by fluorination), easily sublimes (emitting a nearly perfect gas vapor), and is the most volatile compound of uranium known to exist.[66] Sony VAIO VGN-AW91JS Battery

One method of preparing uranium tetrachloride (UCl4) is to directly combine chlorine with either uranium metal or uranium hydride. The reduction of UCl4 by hydrogen produces uranium trichloride (UCl3) while the higher chlorides of uranium are prepared by reaction with additional chlorine.[66] All uranium chlorides react with water and air. Sony VAIO VGN-AW91YS Battery

Bromides and iodides of uranium are formed by direct reaction of, respectively, bromine and iodine with uranium or by adding UH3to those element's acids.[66] Known examples include: UBr3, UBr4, UI3, and UI4. Uranium oxyhalides are water-soluble and include UO2F2, UOCl2, UO2Cl2, and UO2Br2. Stability of the oxyhalides decrease as the atomic weight of the component halide increases.[66] Sony VAIO VGN-AW92CDS Battery

Natural concentrations

Natural uranium consists of three major isotopes: uranium-238 (99.28% natural abundance), uranium-235 (0.71%), and uranium-234 (0.0054%). All three are radioactive, emitting alpha particles, with the exception that all three of these isotopes have small probabilities of undergoing spontaneous fission, rather than alpha emission. Sony VAIO VGN-AW92CJS Battery

Uranium-238 is the most stable isotope of uranium, with a half-life of about 4.468×109 years, roughly the age of the Earth. Uranium-235 has a half-life of about 7.13×108 years, and uranium-234 has a half-life of about 2.48×105 years.[68] For natural uranium, about 49% of its alpha rays are emitted by each of 238U atom, and also 49% by 234U Sony VAIO VGN-AW92CYS Battery

(since the latter is formed from the former) and about 2.0% of them by the 235U. When the Earth was young, probably about one-fifth of its uranium was uranium-235, but the percentage of 234U was probably much lower than this. Sony VAIO VGN-AW92DS Battery

Uranium-238 is usually an ? emitter – unless it undergoes spontaneous fission – decaying through the "Uranium Series" of nuclear decay, which has 18 members, all of which eventually decay into lead-206, by a variety of different decay paths.[9] Sony VAIO VGN-AW92JS Battery

The decay series of 235U, which is called the "Actinium Series" has 15 members, all of which eventually decay into lead-207.[9] The constant rates of decay in these decay series makes the comparison of the ratios of parent to daughter elements useful in radiometric dating.

Uranium-234 is a member of the "Uranium Series", and it decays to lead-206 through a series of relatively short-lived isotopes. Sony VAIO VGN-AW92YS Battery

Uranium-233 is made from thorium-232 by neutron bombardment, usually in a nuclear reactor, and 233U is also fissile.[8] Its decay series ends with thallium-205.

Uranium-235 is important for both nuclear reactors and nuclear weapons, because it is the only uranium isotope existing in nature on Earth in any significant amount that is fissile. Sony VAIO VGN-AW93FS Battery

This means it can be split into two or three fragments (fission products) by thermal neutrons.[9]

Uranium-238 is not fissile, but is a fertile isotope, because after neutron activation it can produce plutonium-239, another fissile isotope. Sony VAIO VGN-AW93GS Battery

Indeed, the 238U nucleus can absorb one neutron to produce the radioactive isotope uranium-239. 239U decays by beta emission to neptunium-239, also a beta-emitter, that decays in its turn, within a few days into plutonium-239. 239Pu was used as fissile material in the first atomic bomb detonated in the "Trinity test" on 15 July 1945 in New Mexico.[22] Sony VAIO VGN-AW93HS Battery

Enrichment

In nature, uranium is found as uranium-238 (99.2742%) and uranium-235 (0.7204%). Isotope separation concentrates (enriches) the fissionable uranium-235 for nuclear weapons and most nuclear power plants, except for gas cooled reactors and pressurised heavy water reactors. Sony VAIO VGN-AW93ZFS Battery

Most neutrons released by a fissioning atom of uranium-235 must impact other uranium-235 atoms to sustain thenuclear chain reaction. The concentration and amount of uranium-235 needed to achieve this is called a 'critical mass'.

To be considered 'enriched', the uranium-235 fraction should be between 3% and 5%.[69] Sony VAIO VGN-AW93ZGS Battery

This process produces huge quantities of uranium that is depleted of uranium-235 and with a correspondingly increased fraction of uranium-238, called depleted uranium or 'DU'. To be considered 'depleted', the uranium-235 isotope concentration should be no more than 0.3%.[70] Sony VAIO VGN-AW93ZHS Battery

 

The price of uranium has risen since 2001, so enrichment tailings containing more than 0.35% uranium-235 are being considered for re-enrichment, driving the price of depleted uranium hexafluoride above $130 per kilogram in July, 2007 from $5 in 2001.[70]

The gas centrifuge process, where gaseous uranium hexafluoride (UF6) is separated by the difference in molecular weight between235UF6 and 238UF6 using high-speed centrifuges, Sony VAIO VGN-BZ11EN Battery

is the cheapest and leading enrichment process.[21] The gaseous diffusionprocess had been the leading method for enrichment and was used in the Manhattan Project. In this process, uranium hexafluoride is repeatedly diffused through a silver-zinc membrane, and the different isotopes of uranium are separated by diffusion rate (since uranium 238 is heavier it diffuses slightly slower than uranium-235).[21] Sony VAIO VGN-BZ11MN Battery

The molecular laser isotope separation method employs alaser beam of precise energy to sever the bond between uranium-235 and fluorine. This leaves uranium-238 bonded to fluorine and allows uranium-235 metal to precipitate from the solution.[5] An alternative laser method of enrichment is known as atomic vapor laser isotope separation (AVLIS) and employs visible tunable lasers such as dye lasers.[71] Sony VAIO VGN-BZ11XN Battery

Another method used is liquid thermal diffusion.[7]

Human exposure

A person can be exposed to uranium (or its radioactive daughters such as radon) by inhaling dust in air or by ingesting contaminated water and food. The amount of uranium in air is usually very small; Sony VAIO VGN-BZ12VN Battery

however, people who work in factories that process phosphatefertilizers, live near government facilities that made or tested nuclear weapons, live or work near a modern battlefield where depleted uranium weapons have been used, or live or work near a coal-fired power plant, facilities that mine or process uranium ore, or enrich uranium for reactor fuel, may have increased exposure to uranium.[72][73] Sony VAIO VGN-BZ12XN Battery

Houses or structures that are over uranium deposits (either natural or man-made slag deposits) may have an increased incidence of exposure to radon gas.

Most ingested uranium is excreted during digestion. Only 0.5% is absorbed when insoluble forms of uranium, such as its oxide, are ingested, whereas absorption of the more soluble uranyl ion can be up to 5%.[17] Sony VAIO VGN-BZ31VT Battery

However, soluble uranium compounds tend to quickly pass through the body whereas insoluble uranium compounds, especially when inhaled by way of dust into the lungs, pose a more serious exposure hazard. After entering the bloodstream, the absorbed uranium tends to bioaccumulate and stay for many years in bone tissue because of uranium's affinity for phosphates.[17] Sony VAIO VGN-BZ31XT Battery

Uranium is not absorbed through the skin, and alpha particlesreleased by uranium cannot penetrate the skin.

Incorporated uranium becomes uranyl ions, which accumulate in bone, liver, kidney, and reproductive tissues. Uranium can be decontaminated from steel surfaces[74]and aquifers.[75] Sony VAIO VGN-BZ560 Battery

Effects and precautions

Normal functioning of the kidney, brain, liver, heart, and other systems can be affected by uranium exposure, because, besides being weakly radioactive, uranium is atoxic metal.[17][76][77] Uranium is also a reproductive toxicant.[78][79] Sony VAIO VGN-BZ560N24 Battery

Radiological effects are generally local because alpha radiation, the primary form of 238U decay, has a very short range, and will not penetrate skin. Uranyl(UO2+
) ions, such as from uranium trioxide or uranyl nitrate and other hexavalent uranium compounds, have been shown to cause birth defects and immune system damage in laboratory animals.[80] Sony VAIO VGN-BZ560N30 Battery

While the CDC has published one study that no human cancer has been seen as a result of exposure to natural or depleted uranium,[81] exposure to uranium and its decay products, especially radon, are widely known and significant health threats.[12]Exposure to strontium-90, iodine-131, and other fission products is unrelated to uranium exposure, Sony VAIO VGN-BZ560P Battery

but may result from medical procedures or exposure to spent reactor fuel or fallout from nuclear weapons.[82]Although accidental inhalation exposure to a high concentration of uranium hexafluoride has resulted in human fatalities, those deaths were associated with generation of highly toxic hydrofluoric acid and uranyl fluoride rather than with uranium itself.[83] Sony VAIO VGN-BZ560P20 Battery

Sony VAIO VGN-BZ560P22 Battery

Finely divided uranium metal presents a fire hazard because uranium is pyrophoric; small grains will ignite spontaneously in air at room temperature.[8]

Uranium metal is commonly handled with gloves as a sufficient precaution.[84] Uranium concentrate is handled and contained so as to ensure that people do not inhale or ingest it. Sony VAIO VGN-BZ560P28 Battery

Neptunium is a chemical element with the symbol Np and atomic number 93. A radioactivemetal, neptunium is the first transuranic element and belongs to the actinide series. Its most stable isotope, 237Np, is a by-product of nuclear reactorsand plutonium production and it can be used as a component in neutron detection equipment. Sony VAIO VGN-BZ560P30 Battery

Neptunium is also found in trace amounts in uranium ores due to transmutation reactions.[3]

The periodic table of Dmitri Mendeleev published in the 1870s showed a " — " in place after uranium similar to several other places for at that point undiscovered elements. Also a publication of the known radioactive isotopes by Kasimir Fajans shows the empty place after uranium.[4] Sony VAIO VGN-BZ560P34 Battery

At least three times, discoveries of the element 93 were falsely reported, as bohemium and ausonium in 1934 and thensequanium in 1939. The name neptunium has previously been considered for other elements. Sony VAIO VGN-BZ561 Battery

The search for element 93 in minerals was encumbered by the fact that the predictions on the chemical properties of element 93 were based on a periodic table which lacked the actinides series and therefore placed thorium below hafnium, protactinium below tantalum and uranium below tungsten. Sony VAIO VGN-BZ561N20 Battery

This periodic table suggested that element 93, at that point often named eka-rhenium, should be similar to manganese or rhenium. With this misconception it was impossible to isolate element 93 from minerals although later neptunium was found in uranium ore in 1952.[5]

Enrico Fermi believed that bombarding uranium with neutrons and subsequent beta decay would lead to the formation of element 93. Sony VAIO VGN-BZ561P20 Battery

Chemical separation of the new formed elements from the uranium yielded material with low half-life and therefore Fermi announced the discovery of a new element in 1934,[6] though this was soon found to be mistaken. Soon it was speculated[7] and later proven[8]that most of the material is created by nuclear fission of uranium by neutrons. Sony VAIO VGN-BZ562P Battery

Small quantities of neptunium had to be produced in Otto Hahn's experiments in late 1930s as a result of decay of 239U. Hahn and his colleagues experimentally confirmed production and chemical properties of 239U, but were unsuccessful at isolating and detecting neptunium.[9Sony VAIO VGN-BZ563P Battery

Neptunium (named for the planet Neptune, the next planet out from Uranus, after which uranium was named) was discoveredbyEdwin McMillan and Philip H. Abelson in 1940 at the Berkeley Radiation Laboratory of the University of California, Berkeley. The team produced the neptunium isotope 239Np (2.4 day half-life) by bombarding uranium with slow moving neutrons.Sony VAIO VGN-BZAAFS Battery

It was the first transuranium element produced synthetically and the first actinide series transuranium element discovered.[10]

Occurrence

Trace amounts of neptunium are found naturally as decay products from transmutation reactions in uranium ores.[3]Artificial237Np is produced through the reduction of 237NpF3 with barium or lithium vapor at around 1200 °C and is most often extracted from spent nuclear fuel rods as a by-product in plutonium production. Sony VAIO VGN-BZAAHS Battery

2 NpF3 + 3 Ba ? 2 Np + 3 BaF2

By weight, neptunium-237 discharges are about 5% as great as plutonium discharges and about 0.05% of spent nuclear fueldischarges.[11]

Characteristics

Silvery in appearance, neptunium metal is fairly chemically reactive and is found in at least three allotropes:[3] Sony VAIO VGN-BZAANS Battery

• ?-neptunium, orthorhombic, density 20.45 g/cm3[12]
• ?-neptunium (above 280 °C), tetragonal, density (313 °C) 19.36 g/cm3[12]
• ?-neptunium (above 577 °C), cubic, density (600 °C) 18 g/cm3[12]

Neptunium has the largest liquid range of any element, 3363 K, between the melting point and boiling point. It is the densest element of all actinoids. Sony VAIO VGN-BZAAPS Battery

19 neptunium radioisotopes have been characterized, with the most stable being 237Np with a half-life of 2.14 million years,236Np with a half-life of 154,000 years, and 235Np with a half-life of 396.1 days. All of the remaining radioactive isotopes have half-lives that are less than 4.5 days, and the majority of these have half-lives that are less than 50 minutes. Sony VAIO VGN-CR11H/B Battery

This element also has 4 meta states, with the most stable being 236mNp (t½ 22.5 hours).

The isotopes of neptunium range in atomic weight from 225.0339 u (225Np) to 244.068 u (244Np). The primary decay mode before the most stable isotope, 237Np, is electron capture (with a good deal of alpha emission), and the primary mode after is beta emission.Sony VAIO VGN-CR11S/L Battery

The primary decay products before 237Np are element 92 (uranium) isotopes (alpha emission produces element 91,protactinium, however) and the primary products after are element 94 (plutonium) isotopes.

237Np is fissionable.[13] 237Np eventually decays to form bismuth-209, unlike most other common heavy nuclei which decay to make isotopes of lead. This decay chain is known as the neptunium series. Sony VAIO VGN-CR11S/P Battery

Synthesis

Chemically, neptunium is prepared by the reduction of NpF3 with barium or lithium vapor at about 1200 °C.[3] Most Np is produced in nuclear reactions:

When an 235U atom captures a neutron, it is converted to an excited state of 236U. Sony VAIO VGN-CR11S/W Battery

About 81% of the excited 236U nuclei undergo fission, but the remainder decay to the ground state of 236U by emitting gamma radiation. Further neutron capturecreates 237U which has a half-life of 7 days and thus quickly decays to 237Np through beta decay. During beta decay, the excited 237U emits an electron, while the atomic weak interaction converts a neutron to a proton, thus creating 237Np. Sony VAIO VGN-CR11Z/R Battery

• 237U is also produced via an (n,2n) reaction with 238U. This only happens with very energetic neutrons.
• 237Np is the product of alpha decay of 241Am.

Heavier isotopes of neptunium decay quickly, and lighter isotopes of neptunium cannot be produced by neutron capture, so chemical separation of neptunium from cooledspent nuclear fuel gives nearly pure 237Np. Sony VAIO VGN-CR120E/L Battery

Chemistry

This element has four ionic oxidation states while in solution:

• Np3+ (pale purple), analogous to the rare earth ion Pm3+
• Np4+ (yellow green)
• NpO2+ (green blue)
• NpO22+ (pale pink)

Neptunium(III) hydroxide is not soluble in water and does not dissolve in excess alkali. Neptunium(III) is susceptible to oxidation in contact to air forming neptunium(IV).[14][15] Sony VAIO VGN-CR120E/P Battery

Neptunium forms tri- and tetrahalides such as NpF3, NpF4, NpCl4, NpBr3, NpI3, and oxides of the various compositions such as are found in the uranium-oxygen system, including Np3O8 and NpO2.

Neptunium(VI) fluoride, NpF6, is volatile like uranium hexafluoride. Sony VAIO VGN-CR120E/R Battery

Neptunium, like protactinium, uranium, plutonium, and americium readily forms a linear dioxo neptunyl core (NpO2n+), in its 5+ and 6+ oxidation states, which readily complexes with hard O-donor ligands such as OH–, NO2–, NO3–, and SO42– to form soluble anionic complexes which tend to be readily mobile with low affinities to soil. Sony VAIO VGN-CR120E/W Battery

Precursor in plutonium-238 production

237Np is irradiated with neutrons to create 238Pu, an alpha emitter for radioisotope thermal generators for spacecraft and military applications. 237Np will capture a neutron to form 238Np and beta decay with a half-life of two days to 238Pu.[16] Sony VAIO VGN-CR125E/B Battery

238Pu also exists in sizable quantities in spent nuclear fuel but would have to be separated from other isotopes of plutonium.

Weapons applications

Neptunium is fissionable, and could theoretically be used as fuel in a fast neutron reactor or a nuclear weapon. Sony VAIO VGN-CR13/B Battery

In 1992, the U.S. Department of Energy declassified the statement that neptunium-237 "can be used for a nuclear explosive device".[17] It is not believed that an actual weapon has ever been constructed using neptunium. As of 2009, the world production of neptunium-237 by commercial power reactors was over 1000 critical masses a year, but to extract the isotope from irradiated fuel elements would be a major industrial undertaking. Sony VAIO VGN-CR13/L Battery

In September 2002, researchers at the University of California's Los Alamos National Laboratory briefly created the first known nuclear critical mass using neptunium in combination with shells of enriched uranium (U-235), discovering that the critical mass of a bare sphere of neptunium-237 "ranges from kilogram weights in the high fifties to low sixties,"[1] showing that it "is about as good a bomb material as U-235."[13] Sony VAIO VGN-CR13/P Battery

The United States Federal government made plans in March 2004 to move America's supply of separated neptunium to a nuclear-waste disposal site in Nevada.

Physics applications

237Np is used in devices for detecting high-energy (MeV) neutrons.[18] Sony VAIO VGN-CR13/R Battery

Role in nuclear waste

Neptunium-237 is the most mobile actinide in the deep geological repository environment.[19] This makes it and its predecessors such as americium-241 candidates of interest for destruction by nuclear transmutation.[20] Sony VAIO VGN-CR13/W Battery

Neptunium accumulates in commercial household ionization-chamber smoke detectors from decay of the (typically) 0.2 microgram of americium-241 initially present as a source of ionizing radiation. With a half-life of 432 years, the americium-241 in a smoke detector includes about 3% neptunium after 20 years, and about 15% after 100 years. Sony VAIO VGN-CR131E/L Battery

Sony VAIO VGN-CR13G Battery

Due to its long half-life neptunium becomes the major contributor of the total radiation in 10,000 years. As it is unclear what happens to the containment in that long time span, an extraction of the neptunium would minimize the contamination of the environment if the nuclear waste could be mobilized after several thousand years. Sony VAIO VGN-CR13G/B Battery,Sony VAIO VGN-CR13G/L Battery,Sony VAIO VGN-CR13G/P Battery,Sony VAIO VGN-CR13G/R Battery,Sony VAIO VGN-CR13G/W Battery,Sony VAIO VGN-CR13T/L Battery,Sony VAIO VGN-CR13T/P Battery,Sony VAIO VGN-CR13T/R Battery,Sony VAIO VGN-CR13T/W Battery,Sony VAIO VGN-CR15/B Battery,Sony VAIO VGN-CR150E/B Battery

 

Harold Macmillan

Harold Macmillan

Maurice Harold Macmillan, 1st Earl of Stockton, OM, PC (10 February 1894 – 29 December 1986) was Conservative Prime Minister of the United Kingdom from 10 January 1957 to 18 October 1963. HP Pavilion DV4 Battery

Nicknamed 'Supermac' and known for his pragmatism, wit and unflappability, Macmillan achieved notoriety before the Second World War as a Tory radical and critic of appeasement. Rising to high office as a protégé of wartime Prime Minister Winston Churchill, HP Pavilion DV4-1000 Battery

he believed in the post-war settlement and the necessity of a mixed economy, and in his premiership pursuedcorporatist policies to develop the domestic market as the engine of growth.[2] As a One Nation Tory of the Disraeliantradition, haunted by memories of the Great Depression, he championed a Keynesian strategy of public investment to maintain demand, HP Pavilion DV4-1000EA Battery

winning a second term in 1959 on an electioneering budget. Benefiting from favourable international conditions,[3] he presided over an age of affluence, marked by low unemployment and high if uneven growth. In his Bedford speech of July 1957 he told the nation they had 'never had it so good',[4] but warned of the dangers of inflation, summing up the fragile prosperity of the 1950s.[5] HP Pavilion DV4-1001 Battery

In international affairs, Macmillan rebuilt the special relationship with the United States from the wreckage of the Suez Crisis (of which he had been one of the architects), and redrew the world map by decolonising sub-Saharan Africa. Reconfiguring the nation's defences to meet the realities of the nuclear age, he ended National Service, strengthened the nuclear deterrentby acquiring Polaris, and pioneered the Nuclear Test Ban with the United States and the Soviet Union. HP Pavilion DV4-1001AX Battery

Belatedly recognising the dangers of strategic dependence, he sought a new role for Britain in Europe, but his unwillingness to disclose United States nuclear secrets to France contributed to a French veto of the United Kingdom's entry into the European Economic Community.[6] HP Pavilion DV4-1001TU Battery

Macmillan's government in its final year was rocked by the Vassall and Profumo scandals, which seemed to symbolise for therebellious youth of the 1960s the moral decay of the British establishment.[7] Resigning prematurely after a medical misdiagnosis, Macmillan lived out a long retirement as an elder statesman of global stature. He was as trenchant a critic of his successors in his old age as he had been of his predecessors in his youth. When asked what represented the greatest challenge for a statesman, Macmillan replied: 'Events, my dear boy, events'. HP Pavilion DV4-1001TX Battery

Family

Harold Macmillan was born at 52 Cadogan Place in Chelsea, London, to Maurice Crawford Macmillan (1853–1936), publisher, and Helen (Nellie) Artie Tarleton Belles (1856–1937), artist and socialite, from Spencer, Indiana in the United States.[9] He had two brothers, Daniel, eight years his senior, and Arthur, four years his senior.[10] His paternal grandfather, Daniel MacMillan(1813–1857), was the son of a Scottish crofter who founded Macmillan Publishers. HP Pavilion DV4-1002 Battery

Education

Macmillan's early education was intense and closely guided by his American mother. He was taught French at home every morning by a succession of nursery maids, and exercised daily at Mr Macpherson's Gymnasium and Dancing Academy, around the corner from the family home in Cadogan Place.[11] From the age of six or seven he received introductory lessons in classical Latin and Greek at Mr Gladstone's day school, close by in Sloane Square.[12] HP Pavilion DV4-1002AX Battery

Macmillan then attended Summer Fields School, Oxford (1903–6), but his time at Eton College (1906–10) was blighted by recurrent illness, starting with a near-fatal attack of pneumonia in his first half; he missed his final year after being invalided out,[13][14] and had to be taught at home by private tutors (1910–11), notably Ronald Knox, who did much to instil his High Church Anglicanism.[15] He went up to Balliol College, Oxford (1912–14), where he obtained a First in Mods (Latin and Greek, the first half of the four-year Oxford Greats course), and became an officer of the Oxford Union Society, before the outbreak of the First World War in August 1914.[citation needed] HP Pavilion DV4-1002TU Battery

War service

Macmillan served with distinction as a captain in the Grenadier Guards during the First World War, and was wounded on three occasions. During the Battle of the Somme, he spent an entire day wounded and lying in a slit trench with a bullet in his pelvis, reading the classical Greek playwright Aeschylus in the original language.[16] HP Pavilion DV4-1002TX Battery

Macmillan spent the final two years of the war in hospital undergoing a long series of operations, and saw no further active service.[17] His hip wound took four years to heal completely, and he was left with a slight shuffle to his walk and a limp grip in his right hand from a separate wound. As was common for contemporary former officers, he continued to be known as 'Captain Macmillan' until the early 1930s. HP Pavilion DV4-1003AX Battery

Canadian aide-de-campship

Of the 28 freshmen who started at Balliol with Macmillan, only he and one other survived.[18] As a result, he refused to return to Oxford, saying the university would never be the same.[19] He served instead in Ottawa, Canada, in 1919 as ADC to Victor Cavendish, 9th Duke of Devonshire, then Governor General of Canada, and his future father-in-law.[20] HP Pavilion DV4-1003TU Battery

Publishing

On his return to London in 1920 he joined the family firm Macmillan Publishers as a junior partner, remaining with the company until his appointment to ministerial office in 1940.

Personal lifeHP Pavilion DV4-1003TX Battery

Marriage

Macmillan married Lady Dorothy Cavendish, the daughter of the 9th Duke of Devonshire, on 21 April 1920. Her great-uncle was Spencer Cavendish, 8th Duke of Devonshire, who was leader of the Liberal Party in the 1870s, and a close colleague of William Ewart Gladstone, Joseph Chamberlain and Lord Salisbury. HP Pavilion DV4-1004AX Battery

Lady Dorothy was also descended from William Cavendish, 4th Duke of Devonshire, who served as Prime Minister from 1756–1757 in communion with Newcastle and Pitt the Elder. Her nephew William Cavendish, Marquess of Hartington married Kathleen, a sister of John F. Kennedy. In 1929 Lady Dorothy began a life-long affair with the Conservative politician Robert Boothby, an arrangement which scandalised high society but remained unknown to the general public.[21HP Pavilion DV4-1004TU Battery

The stress caused by this may have contributed to Macmillan's nervous breakdown in 1931.[22]

Macmillan was in close friendship in old age with Ava Anderson, Viscountess Waverley, née Bodley (1896–1973), the widow of John Anderson, 1st Viscount Waverley.[24]Eileen O'Casey, née Reynolds (1900–1995), the actress wife of Irish dramatist Seán O'Casey, was another female friend of Macmillan, who published her husband's plays. HP Pavilion DV4-1004TX Battery

Although she is said to have replaced Lady Dorothy in Macmillan's affections, there is disagreement over how intimate they became after the death of their respective spouses, and whether he proposed.[25][26][27][28] HP Pavilion DV4-1005TX Battery

Political career

Private Member (1924–1929, 1931–1940)

Elected to the House of Commons in 1924 for the depressed northern industrial constituency of Stockton-on-Tees, Macmillan lost his seat in 1929 in the face of high regional unemployment, but returned in 1931. He spent the 1930s on the backbenches, with his championing of economic planning, HP Pavilion DV4-1006TX Battery

anti-appeasement ideals and sharp criticism of Stanley Baldwin and Neville Chamberlain serving to isolate him from the party leadership. During this time (1938) he published the first edition of his book The Middle Way, which advocated a broadly centrist political philosophy both domestically and internationally. HP Pavilion DV4-1007TX Battery

Supply Parliamentary Secretary (1940–1942)

In the Second World War Macmillan at last attained office, serving in the wartime coalition government as the Parliamentary Secretary to the Ministry of Supply from 1940 to 1942. The task of the department was to provide armaments and other equipment to the British Army and Royal Air Force. Macmillan travelled up and down the country to co-ordinate production, working with some success under Lord Beaverbrook to increase the supply and quality of armoured vehicles.[29] HP Pavilion DV4-1008TX Battery

Colonial Under-Secretary (1942)

Macmillan was appointed as Under-Secretary of State for the Colonies in 1942, in his own words, 'leaving a madhouse in order to enter a mausoleum'.[30] Though a junior minister he was sworn of the Privy Council and spoke in the House of Commons for successive Colonial Secretaries Lord Moyne and Lord Cranborne. Macmillan was given responsibility for increasing colonial production and trade, and signalled the future direction of British policy when in June 1942 he declared: HP Pavilion DV4-1009TX Battery

The governing principle of the Colonial Empire should be the principle of partnership between the various elements composing it. Out of partnership comes understanding and friendship. Within the fabric of the Commonwealth lies the future of the Colonial territories.[31] HP Pavilion DV4-1010TX Battery

Macmillan attained real power and Cabinet rank upon being sent to North Africa in 1942 as British government representative to the Allies in the Mediterranean, reporting directly to Prime Minister Winston Churchill over the head of the Foreign Secretary, Anthony Eden. During this assignment Macmillan served as liaison and mediator between Churchill and US General Dwight D. Eisenhower in North Africa, building a rapport with the latter that would prove helpful in his later career.[32] HP Pavilion DV4-1011TX Battery

As minister resident with a roving commission, Macmillan also the minister advising General Keightley of V Corps, the senior Allied commander in Austria responsible for Operation Keelhaul, which included the forced repatriation of up to 70,000 prisoners of war to the Soviet Union and Josip Broz Tito's Yugoslavia in 1945. HP Pavilion DV4-1012TX Battery

The deportations and Macmillan's involvement later became a source of controversy because of the harsh treatment meted out to Nazi collaborators and anti-partisans by the receiving countries, and because in the confusion V Corps went beyond the terms agreed at Yaltaand Allied Forces Headquarters directives by repatriating 4000 White Russian troops and 11,000 civilian family members who could not properly be regarded as Soviet citizens.[33][34][35] HP Pavilion DV4-1013TX Battery

Air Secretary (1945)

Macmillan returned to England after the European war and was Secretary of State for Air for two months in Churchill's caretaker government, 'much of which was taken up in electioneering', there being 'nothing much to be done in the way of forward planning'.[36] He felt himself 'almost a stranger at home',[37] and lost his seat in the landslide Labour victory of 1945, but soon returned to Parliament in a November 1945 by-election in Bromley. HP Pavilion DV4-1014NR Battery

Housing Minister (1951–1954)

With the Conservative victory in 1951 Macmillan became Minister of Housing under Churchill, who entrusted Macmillan with fulfilling the latter's conference promise to build 300,000 houses per year. 'It is a gamble—it will make or mar your political career,' Churchill said, 'but every humble home will bless your name if you succeed.'[38] Macmillan achieved the target a year ahead of schedule.[39] HP Pavilion DV4-1014TX Battery

Defence Minister (1954–1955)

Macmillan served as Minister of Defence from October 1954, but found his authority restricted by Churchill's personal involvement.[40] In the opinion of The Economist: 'He gave the impression that his own undoubted capacity for imaginative running of his own show melted way when an august superior was breathing down his neck.'[41] HP Pavilion DV4-1015TX Battery

A major theme of Macmillan's tenure at Defence was the ministry's growing reliance on the nuclear deterrent, in the view of some critics, to the detriment of conventional forces.[42] The Defence White Paper of February 1955, announcing the decision to produce the hydrogen bomb, received bipartisan support.[43] HP Pavilion DV4-1015TX Battery

By this time Macmillan had lost the wire-rimmed glasses, toothy grin and brylcreemed hair of wartime photographs, and instead grew his hair thick and glossy, had his teeth capped and walked with the ramrod bearing of a former Guards officer—acquiring the distinguished appearance of his later career. HP Pavilion DV4-1016TX Battery

Foreign Secretary (1955)

Macmillan served as Foreign Secretary in April–December 1955 in the government of Anthony Eden. Returning from the Geneva Summit of that year he made headlines by declaring: 'There ain’t gonna be no war.'[44] Of the role of Foreign Secretary Macmillan famously observed:

Nothing he can say can do very much good and almost anything he may say may do a great deal of harm. Anything he says that is not obvious is dangerous; whatever is not trite is risky. He is forever poised between the cliché and the indiscretion.[45] HP Pavilion DV4-1017TX Battery

Chancellor of the Exchequer (1955–1957)

Macmillan served as Chancellor of the Exchequer 1955–1957. In this office he insisted that Eden's de facto deputy Rab Butler not be treated as senior to him, and threatened resignation until he was allowed to cut bread and milk subsidies. One of Macmillan's innovations at the Treasury was the introduction of premium bonds,[46] announced in his budget of 17 April 1956.[47] Although the Labour Opposition initially decried the sale as a 'squalid raffle', it proved an immediate hit with the public. HP Pavilion DV4-1018TX Battery

During the Suez Crisis, when Britain invaded Egypt in collusion with France, and Israel, according to Labour leader Harold Wilson, Macmillan was 'first in, first out': first very supportive of the invasion, then a prime mover in Britain's humiliating withdrawal in the wake of the financial crisis caused by pressure from the U.S. government.[48] HP Pavilion DV4-1019TX Battery

Since the Egyptian Revolution of 1952, relations between Britain and Egypt deteriorated. The Egyptian government, which came to be dominated byGamal Abdel Nasser, was opposed to the British imperial presence in the Arab World. The Egyptian nationialisation of the Suez Canal by President Nasser on 26 July 1956 prompted the British government of Anthony Eden to commence plans for invading Egypt, regaining the Canal, and toppling Nasser. Macmillan wrote in his diary: HP Pavilion DV4-1020TX Battery

"If Nasser 'gets away with it', we are done for. The whole Arab world will despise us ... Nuri [es-Said, British-backed prime minister of Iraq] and our friends will fall. It may well be the end of British influence and strength forever. So, in the last resort, we must use force and defy opinion, here and overseas".[49] HP Pavilion DV4-1020US Battery

Macmillan was heavily involved in the secret planning of the invasion with France, and Israel. It was he who first suggested collusion with Israel.[50] Macmillan knew President Eisenhower well, but misjudged his strong opposition to a military solution to the issue. Macmillan met privately with Eisenhower on 25 September 1956 and convinced himself that the US would not oppose the Anglo-French-Israeli invasion.[51] HP Pavilion DV4-1021TX Battery

The treasury was his portfolio, but he did not recognize the financial disaster that could result from U.S. government actions. Sterling was draining out of the Bank of England at an alarming rate, and it was getting worse. The Canal was blocked by the Egyptians, and most oil shipments were delayed as tankers had to go all the way around Africa. HP Pavilion DV4-1024TX Battery

The U.S. government refused any financial help until Britain withdrew its forces from Egypt. When he did realise it, he reversed himself and called for withdrawal on the U.S. terms, while exaggerating the financial crisis. Faced with Macmillan's prediction of doom, the cabinet had no choice but to accept the American terms and withdraw. HP Pavilion DV4-1025TX Battery

Ultimately, the Suez Canal remained in Egyptian hands, and Nasser's government continued its support of Arab and African national resistance movements opposed to the British Empire in the region, and the continent.[52] The debacle destroyed Prime Minister Eden's political standing and his physical health; he had to resign, leaving the door to 10 Downing Street open for his deputy Rab Butler or Macmillan.[53] HP Pavilion DV4-1026TX Battery

In later life Macmillan was open about his failure to read Eisenhower's thoughts correctly and much regretted the damage done to Anglo-American relations. However he always maintained that the Anglo-French military response to the nationalisation of the Canal had been for the best.[54] HP Pavilion DV4-1027TX Battery

Prime Minister (1957–1963)

First government (1957–1959)

Anthony Eden resigned in January 1957. At that time the Conservative Party had no formal mechanism for selecting a new leader, effectively leaving the choice of the new leader, and Prime Minister, in the hands of the Sovereign, Queen Elizabeth II. The Queen appointed Macmillan Prime Minister after taking advice from Winston Churchill and Robert Gascoyne-Cecil, 5th Marquess of Salisbury, surprising some observers who expected that Rab Butler would be chosen. HP Pavilion DV4-1028TX Battery

The political situation after Suez was so desperate that on taking office on 10 January he told the Queen he could not guarantee his government would last "six weeks" - though ultimately he would be in charge of the government for more than six years.[55] HP Pavilion DV4-1028US Battery

Macmillan populated his government with many who had studied at the same school as he: he filled government posts with 35 former Etonians, 7 of whom sat in Cabinet.[56] He was also devoted to family members: when Andrew Cavendish, 11th Duke of Devonshire was later appointed (Minister for Colonial Affairs from 1963 to 1964 amongst other positions) he described his uncle's behaviour as "the greatest act of nepotism ever".[57] HP Pavilion DV4-1029TX Battery

He was nicknamed Supermac in 1958 by cartoonist Victor 'Vicky' Weisz. It was intended as mockery, but backfired, coming to be used in a neutral or friendly fashion. Weisz tried to label him with other names, including "Mac the Knife" at the time of widespread cabinet changes in 1962, but none of these caught on.[58] HP Pavilion DV4-1030EE Battery

Economy

Macmillan brought the monetary concerns of the Exchequer into office; the economy was his prime concern. His One Nation approach to the economy was to seek high or full employment. This contrasted with his mainly monetarist Treasury ministers who argued that any support of sterling required strict controls on money and hence an unavoidable rise in unemployment. HP Pavilion DV4-1030EI Battery

Their advice was rejected and in January 1958 the three Treasury ministers Peter Thorneycroft, the Chancellor of the Exchequer,Nigel Birch, Economic Secretary to the Treasury, and Enoch Powell, the Financial Secretary to the Treasury, resigned. Macmillan, away on a tour of the Commonwealth, brushed aside this incident as 'a little local difficulty'. HP Pavilion DV4-1030EJ Battery

Foreign policy

Macmillan took close control of foreign policy. He worked to narrow the post-Suez Crisis rift with the United States, where his wartime friendship with Dwight D. Eisenhower was key; the two had a productive conference in Bermuda as early as March 1957. HP Pavilion DV4-1030EN Battery

In February 1959 Macmillan became the first Western leader to visit the Soviet Union since the Second World War.[59] Talks with Nikita Khrushchev eased tensions in East-West relations over West Berlin and led to an agreement in principle to stop nuclear tests and to hold a further summit meeting of Allied and Soviet heads of government.[60] HP Pavilion DV4-1030TX Battery

In the Middle East, faced by the 1958 collapse of the Baghdad Pact and the spread of Soviet influence, Macmillan acted decisively to restore the confidence ofPersian Gulf allies, using the Royal Air Force and special forces to defeat a revolt backed by Saudi Arabia and Egypt against the Sultan of Oman in July 1957,[61]deploying airborne battalions to defend Jordan against Syrian subversion in July 1958,[62] and deterring a threatened Iraqi invasion of Kuwait by landing a brigade group in July 1960.[63] HP Pavilion DV4-1031TX Battery

Macmillan was also a major proponent and architect of decolonisation. The Gold Coast was granted independence as Ghana, and the Federation of Malaya achieved independence within the Commonwealth of Nations in 1957. HP Pavilion DV4-1032TX Battery

In April 1957 Macmillan reaffirmed his strong support for the British nuclear deterrent. A succession of prime ministers since the Second World War had been determined to persuade the United States to revive wartime co-operation in the area of nuclear weapons research. Macmillan believed that one way to encourage such co-operation would be for the United Kingdom to speed up the development of its ownhydrogen bomb, which was successfully tested on 8 November 1957. HP Pavilion DV4-1033TX Battery

acmillan's decision led to increased demands on the Windscale and (subsequently) Calder Hall nuclear plants to produce plutonium for military purposes.[64] As a result the safety margins of the radioactive materials inside the Windscale reactor were eroded. This contributed to the Windscale accident on the night of 10 October 1957, in which a fire broke out in the plutonium plant of Pile No. 1,HP Pavilion DV4-1034TX Battery

and nuclear contaminants travelled up a chimney where the filters blocked some but not all of the contaminated material. The radioactive cloud spread to south-east England and fallout reached mainland Europe. Although scientists had warned of the dangers of such an accident for some time, the government blamed the workers who had put out the fire for 'an error of judgement', rather than the political pressure for fast-tracking the megaton bomb.[65][66] HP Pavilion DV4-1035LA Battery

Macmillan, concerned that public confidence in the nuclear programme might be shaken and that technical information might be misused by opponents of defence co-operation in the US Congress, withheld all but the summary of a report into the Windscale fire prepared for theAtomic Energy Authority by Sir William Penney, director of the Atomic Weapons Research Establishment.[67] HP Pavilion DV4-1035TX Battery

While subsequently released files show that 'Macmillan's cuts were few and covered up few technical details',[68] and that even the full report at the time found no danger to public health, later official estimates acknowledged the release of polonium-210 may have led directly to 25 to 50 deaths, and anti-nuclear groups linked it to 1,000 fatal cancers.[69][70] HP Pavilion DV4-1036TX Battery

On 25 March 1957 Macmillan also acceded to Eisenhower's request to base 60 Thor IRBMs in England under joint control, to replace the nuclear bombers of the Strategic Air Command, which had been stationed under joint control in the country since 1948, and were approaching obsolescence. HP Pavilion DV4-1037TX Battery

Partly as a consequence of this favour, in late October 1957, the US McMahon Act was eased to facilitate nuclear co-operation between the two governments, initially with a view to producing cleaner weapons and reducing the need for duplicate testing.[71] The Mutual Defence Agreement followed on 3 July 1958, speeding up British ballistic missile development,[72]notwithstanding unease expressed at the time about the impetus co-operation might give to atomic proliferation by arousing the jealousy of France and other allies.[73] HP Pavilion DV4-1038TX Battery

Election campaign (1959)

Macmillan led the Conservatives to victory in the October 1959 general election, increasing his party's majority from 67 to 107 seats. The successful campaign was based on the economic improvements achieved; the slogan "Life's Better Under the Conservatives" was matched by Macmillan's own remark, '"indeed let us be frank about it — most of our people have never had it so good,"[74] usually paraphrased as "You've never had it so good." Such rhetoric reflected a new reality of working-class affluence; it has been argued: "The key factor in the Conservative victory was that average real pay for industrial workers had risen since Churchill’s 1951 victory by over 20 per cent".[75] HP Pavilion DV4-1039TX Battery

The Daily Mirror newspaper, despite being staunch supporters of the Labour Party, wished Macmillan "good luck" on their front page after his election win.[76]

Second government (1959–1963) HP Pavilion DV4-1040EE Battery

Economy

Britain's balance of payments problems led to the imposition of a wage freeze in 1961 and, amongst other factors, this caused the government to lose popularity and a series of by-elections in March 1962.

Fearing for his own position, Macmillan organised a major Cabinet change in July 1962—also named 'the night of long knives' as a symbol of his alleged betrayal of the Conservative party. Eight junior Ministers were sacked at the same time. HP Pavilion DV4-1040EI Battery

The Cabinet changes were widely seen as a sign of panic, and the young Liberal MP Jeremy Thorpe said of Macmillan's dismissal of so many of his colleagues, 'greater love hath no man than this, than to lay down his friends for his life'.

Macmillan supported the creation of the National Incomes Commission as a means to institute controls on income as part of his growth-without-inflation policy. A further series of subtle indicators and controls were also introduced during his premiership. HP Pavilion DV4-1040TX Battery

Foreign policy

The special relationship with the United States continued after the election of President John F. Kennedy, whosesister had married a nephew of Macmillan's wife. The Prime Minister was supportive throughout the Cuban missile crisisof 1962 and Kennedy consulted him by telephone every day. HP Pavilion DV4-1041TX Battery

The British Ambassador David Ormsby-Gore was a close family friend of the President and actively involved in White House discussions on how to resolve the crisis.

Macmillan's first government had seen the first phase of the sub-Saharan African independence movement, which accelerated under his second government. His celebrated 'wind of change' speech in Cape Town on his African tour in February 1960 is considered a landmark in the process of decolonisation. HP Pavilion DV4-1042TX Battery

Nigeria, the Southern Cameroons and British Somaliland were granted independence in 1960, Sierra Leone and Tanganyikain 1961, Uganda in 1962, and Kenya in 1963. Zanzibar merged with Tanganyika to form Tanzania in 1963. All remained within the Commonwealth but British Somaliland, which merged with Italian Somaliland to form Somalia. HP Pavilion DV4-1043TX Battery

Macmillan's policy overrode the hostility of white minorities and the Conservative Monday Club. South Africa left the multiracial Commonwealth in 1961 and Macmillan acquiesced to the dissolution of the Central African Federation by the end of 1963.

In Southeast Asia, Malaya and the then-crown colonies of Sabah (British North Borneo), Sarawak and Singapore became independent as Malaysia in 1963. HP Pavilion DV4-1044TX Battery

The speedy transfer of power maintained the goodwill of the new nations but critics contended it was premature. In justification Macmillan quoted Lord Macaulay in 1851:

Many politicians of our time are in the habit of laying it down as a self-evident proposition that no people ought to be free until they are fit to use their freedom. The maxim is worthy of the fool in the old story, who resolved not to go into the water till he had learnt to swim. If men are to wait for liberty till they become wise and good in slavery, they may indeed wait for ever.[77]

Skybolt crisisHP Pavilion DV4-1045TX Battery

Macmillan cancelled the Blue Streak ballistic missile system in April 1960 over concerns about its vulnerability to a pre-emptive attack, but continued with the development of the air launched Blue Steel stand-off bomb, which was about to enter trials. As the eventual replacement for Blue Steel, he opted for Britain to join the American Skybolt missile development project. HP Pavilion DV4-1046TX Battery

From the same year Macmillan also permitted the U.S. Navy to station Polaris submarines at Holy Loch, Scotland, as a replacement for Thor. When Skybolt was in turn unilaterally cancelled by U.S. Secretary of Defense Robert McNamara, Macmillan negotiated with President John F. Kennedy the purchase of Polaris missiles from the United States under the Nassau agreement in December 1962.HP Pavilion DV4-1047TX Battery

Partial Test Ban Treaty (1963)

Macmillan was also a force in the successful negotiations leading to the signing of the 1963 Partial Test Ban Treaty by the United Kingdom, the United States and the Soviet Union. His previous attempt to create an agreement at the May 1960 summit in Paris had collapsed due to the U-2 Crisis of 1960. HP Pavilion DV4-1048TX Battery

Europe

Macmillan worked with states outside the European Economic Community (EEC) to form the European Free Trade Association (EFTA), which from 3 May 1960 established a free-trade area between the member countries. Macmillan also saw the value of rapprochement with the EEC, to which his government sought belated entry. HP Pavilion DV4-1049TX Battery

In the event, Britain's application to join was vetoed by French president Charles de Gaulle on 29 January 1963, in part due to de Gaulle's fear that 'the end would be a colossal Atlantic Community dependent on America', and in part in anger at the Anglo-American nuclear deal, from which France, technologically lagging far behind, had been excluded.[78] HP Pavilion DV4-1050 Battery

Profumo affair

The Profumo affair of 1963 permanently damaged the credibility of Macmillan's government. He survived a Parliamentary vote with a majority of 69, one fewer than had been thought necessary for his survival, and was afterwards joined in the smoking-room only by his son and son-in-law, not by any Cabinet minister. Nonetheless, Butler and Maudling (who was very popular with backbench MPs at that time) declined to push for his resignation, especially after a tide of support from Conservative activists around the country. HP Pavilion DV4-1050EE Battery

Retirement (1963–1986)

Resignation

The Profumo affair may have exacerbated Macmillan's ill-health. He was taken ill on the eve of the Conservative Party conference, diagnosed incorrectly with inoperable prostate cancer. Consequently, he resigned on 18 October 1963. He felt privately that he was being hounded from office by a backbench minority: HP Pavilion DV4-1050EL Battery

Some few will be content with the success they have had in the assassination of their leader and will not care very much who the successor is.... They are a band that in the end does not amount to more than 15 or 20 at the most.[79] HP Pavilion DV4-1050EP Battery

Succession

Macmillan was succeeded as Prime Minister by the Foreign Secretary Alec Douglas-Home in a controversial move; it was alleged that Macmillan had pulled strings and utilised the party's grandees, nicknamed 'The Magic Circle', to ensure that Butler was not chosen as his successor.

Macmillan initially refused a peerage and retired from politics in September 1964, a month before the 1964 which the Conservatives narrowly lost to Labour, now led by Harold Wilson.[80]

Oxford Chancellor (1960–1986) HP Pavilion DV4-1050ER Battery

Macmillan had been elected Chancellor of the University of Oxford in 1960, in a campaign masterminded by Hugh Trevor-Roper, and continued in this distinguished office for life, frequently presiding over college events, making speeches and tirelessly raising funds. According to Sir Patrick Neill QC, the vice-chancellor, Macmillan 'would talk late into the night with eager groups of students who were often startled by the radical views he put forward, well into his last decade.'HP Pavilion DV4-1050TX Battery

Political interventions

Macmillan made occasional political interventions in retirement. Responding to a remark made by Labour Prime Minister Harold Wilson about not having boots in which to go to school, Macmillan retorted: 'If Mr Wilson did not have boots to go to school that is because he was too big for them.'[82] HP Pavilion DV4-1051 Battery

Macmillan accepted the distinction of the Order of Merit from the Queen in 1976. In October of that year he called for 'a Government of National Unity', including all parties, that could command the public support to resolve the economic crisis. Asked who could lead such a coalition, he replied: "Mr Gladstone formed his last Government when he was eighty-three. I'm only eighty-two. You mustn't put temptation in my way."[83] His plea was interpreted by party leaders as a bid for power and rejected. HP Pavilion DV4-1051TX Battery

Macmillan still travelled widely, visiting China in October 1979, where he held talks with its leader, senior Vice-Premier Deng Xiaoping.[84]

Relations with Margaret Thatcher

Macmillan found himself drawn more actively into politics after Margaret Thatcher became Conservative leader in February 1975,[85] and Prime Minister in May 1979 when the Tories ended Labour's five-year rule with an election win,[86] and the record of his own premiership came under attack from the monetarists in the party, whose theories she supported. In a celebrated speech he wondered aloud where such theories had come from: HP Pavilion DV4-1052 Battery

Was it America? Or was it Tibet? It is quite true, many of Your Lordships will remember it operating in the nursery. How do you treat a cold? One nannysaid, 'Feed a cold'; she was a neo-Keynesian. The other said, 'Starve a cold'; she was a monetarist.[87]

HP Pavilion DV4-1052TX Battery

On Macmillan's advice in April 1982 Thatcher excluded the Treasury from her Falklands War Cabinet. She later said: 'I never regretted following Harold Macmillan's advice. We were never tempted to compromise the security of our forces for financial reasons. Everything we did was governed by military necessity.'[88] HP Pavilion DV4-1053 Battery

Macmillan finally accepted a peerage on 10 February 1984[89] and was created Earl of Stockton and Viscount Macmillan of Ovenden. He took the title from his former parliamentary seat on the border of the Durham coalfields, and in his maiden speech in the House of Lords he criticised Thatcher's handling of the coal miners' strike and her characterisation of striking miners as 'the enemy within'.[90] He received an unprecedented standing ovation for his oration which included the words: HP Pavilion DV4-1053TX Battery

It breaks my heart to see—and I cannot interfere—what is happening in our country today. This terrible strike, by the best men in the world, who beat the Kaiser's and Hitler's armies and never gave in. It is pointless and we cannot afford that kind of thing. Then there is the growing division of Conservative prosperity in the south and the ailing north and Midlands. We used to have battles and rows but they were quarrels. Now there is a new kind of wicked hatred that has been brought in by different types of people.[87] HP Pavilion DV4-1054TX Battery

As Chancellor of Oxford Lord Stockton condemned the university's refusal in February 1985 to award Thatcher an honorary degree. He noted that the decision represented a break with tradition, and predicted that the snub would rebound on the university.[91]

HP Pavilion DV4-1055TX Battery

Stockton is widely supposed to have likened Margaret Thatcher's policy of privatisation to 'selling the family silver'. His precise quote, at a dinner of the Tory Reform Group at the Royal Overseas League on 8 November 1985, was on the subject of the sale of assets commonplace among individuals or states when they encountered financial difficulties: 'First of all the Georgian silver goes. And then all that nice furniture that used to be in the salon. Then the Canalettos go.' Profitable parts of the steel industry and the railways had been privatised, along with British Telecom: 'They were like two Rembrandts still left.'[92] HP Pavilion DV4-1070 Battery

Stockton's speech was much commented on and a few days later he made a speech in the House of Lords, referring to it:

When I ventured the other day to criticise the system I was, I am afraid, misunderstood. As a Conservative, I am naturally in favour of returning into private ownership and private management all those means of production and distribution which are now controlled by state capitalism. I am sure they will be more efficient. What I ventured to question was the using of these huge sums as if they were income.[93] HP Pavilion DV4-1070EE Battery

In the last month of his life, he mournfully observed:

Sixty-three years ago... the unemployment figure (in Stockton-on-Tees) was then 29%. Last November... the unemployment (there) is 28%. A rather sad end to one's life.

Harold Macmillan, 1st Earl of Stockton, died on 29 December 1986, at Birch Grove, the Macmillan family mansion on the edge ofAshdown Forest near Chelwood Gate in East Sussex. HP Pavilion DV4-1070EF Battery

He was aged 92 years and 322 days—the greatest age attained by a British Prime Minister until surpassed by James Callaghan on 14 February 2005. His grandson and heir Alexander, Viscount Macmillan of Ovenden, said: 'In the last 48 hours he was very weak but entirely reasonable and intelligent. His last words were, "I think I will go to sleep now".'[94][95] HP Pavilion DV4-1070ER Battery

Margaret Thatcher, on receiving the news, hailed him as 'a very remarkable man and a very great patriot', and said that his dislike of 'selling the family silver' had never come between them. He was 'unique in the affection of the British people'.[96] HP Pavilion DV4-1070ES Battery

Tributes came from around the world. US President Ronald Reagan said: 'The American people share in the loss of a voice of wisdom and humanity who, with eloquence and gentle wit, brought to the problems of today the experience of a long life of public service.'[81] Outlawed African National Congress president Oliver Tambo sent his condolences: HP Pavilion DV4-1080EI Battery

'As South Africans we shall always remember him for his efforts to encourage the apartheid regime to bow to the winds of change that continue to blow in South Africa.'[81] Commonwealth Secretary-General Sir Shridath Ramphal affirmed: 'His own leadership in providing from Britain a worthy response to African national consciousness shaped the post-war era and made the modern Commonwealth possible.'[81] HP Pavilion DV4-1080EO Battery

A private funeral was held on 5 January 1987 at St Giles Church, Horsted Keynes, West Sussex, where Lord Stockton had regularly worshipped and read the lesson.[97] Two hundred mourners attended,[95] including 64 members of the Macmillan family, Thatcher and former premiers Lord Home of the Hirsel and Edward Heath, Lord Hailsham of St Marylebone,[94] and 'scores of country neighbours'.[97] The Prince of Wales sent a wreath 'in admiring memory'.[94]Stockton was buried beside his wife, Lady Dorothy, and next to the graves of his parents and of his son, Maurice Macmillan.[97] HP Pavilion DV4-1080ES Battery

The House of Commons paid its tribute on 12 January 1987, with much reference made to the dead statesman's book, The Middle Way.[98] Thatcher said: 'In his retirement Harold Macmillan occupied a unique place in the nation's affections', while Labour leader Neil Kinnock struck a more critical note: HP Pavilion DV4-1090EO Battery

A public memorial service, attended by the Queen and thousands of mourners, was held on 10 February 1987 in Westminster Abbey.[99]

Stockton's son Maurice had become heir to the earldom, but predeceased him suddenly a month after his father's elevation. The 1st Earl was succeeded instead by his grandson, Maurice's son, Alexander, Lord Macmillan, who become the 2nd Earl of Stockton. HP Pavilion DV4-1090ES Battery

Winston Churchill

Sir Winston Leonard Spencer-Churchill, KG, OM, CH, TD, PC, DL, FRS, Hon. RA (30 November 1874 – 24 January 1965) was a BritishConservative politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice (1940–45 and 1951–55).HP Pavilion DV4-1100 Battery

A noted statesman and orator, Churchill was also an officer in the British Army, a historian, a writer, and an artist. He is the only British prime minister to have received the Nobel Prize in Literature, and was the first person to be made an Honorary Citizen of the United States.

Churchill was born into the aristocratic family of the Dukes of Marlborough. HP Pavilion DV4-1100EA Battery

His father, Lord Randolph Churchill, was a charismatic politician who served as Chancellor of the Exchequer; his mother, Jenny Jerome, an American socialite. As a young army officer, he saw action in British India, the Sudan and the Second Boer War. He gained fame as a war correspondent and through books he wrote about his campaigns. HP Pavilion DV4-1101 Battery

At the forefront of politics for fifty years, he held many political and cabinet positions. Before the First World War, he served as President of the Board of Trade, Home Secretary and First Lord of the Admiralty as part of the Asquith Liberal government. HP Pavilion DV4-1101TU Battery

During the war, he continued as First Lord of the Admiralty until the disastrous Gallipoli Campaign, which he had sponsored, caused his departure from government. He then served briefly on the Western Front, commanding the 6th Battalion of the Royal Scots Fusiliers. He returned to government as Minister of Munitions, Secretary of State for War, HP Pavilion DV4-1101TX Battery

and Secretary of State for Air. After the War, Churchill served as Chancellor of the Exchequer in the Conservative (Baldwin) government of 1924–29, controversially returning the pound sterling in 1925 to the gold standard at its pre-War parity, a move widely seen as creating deflationary pressure on the UK economy. Also controversial were Churchill's opposition to increased home rule for India, and his resistance to the 1936 abdication of Edward VIII. HP Pavilion DV4-1102 Battery

Out of office and politically "in the wilderness" during the 1930s, Churchill took the lead in warning about the danger from Hitler and in campaigning for rearmament. On the outbreak of the Second World War, he was again appointed First Lord of the Admiralty. Following the resignation of Neville Chamberlain on 10 May 1940, Churchill became Prime Minister. HP Pavilion DV4-1102TU Battery

His steadfast refusal to consider defeat, surrender or a compromise peace helped inspire British resistance, especially during the difficult early days of the War when Britain stood alone in its active opposition to Hitler. Churchill was particularly noted for his speeches and radio broadcasts, which helped inspire the British people. He led Britain as Prime Minister until victory had been secured over Nazi Germany. HP Pavilion DV4-1102TX Battery

After the Conservative Party lost the 1945 election, he became Leader of the Opposition. In 1951, he again became Prime Minister, before retiring in 1955. Upon his death, Elizabeth II granted him the honour of a state funeral, which saw one of the largest assemblies of world statesmen ever.[1] Named the Greatest Briton of all-time in a 2002 poll, Churchill is widely regarded as being among the most influential persons in British history. HP Pavilion DV4-1103TU Battery

Born into the aristocratic family of the Dukes of Marlborough, a branch of the noble Spencer family,[2] Winston Leonard Spencer-Churchill, like his father, used the surname Churchill in public life.[3] His ancestor George Spencer had changed his surname to Spencer-Churchill in 1817 when he became Duke of Marlborough, to highlight his descent from John Churchill, 1st Duke of Marlborough. HP Pavilion DV4-1103TX Battery

Winston's father, Lord Randolph Churchill, the third son of John Spencer-Churchill, 7th Duke of Marlborough, was a politician; and his mother, Lady Randolph Churchill (née Jennie Jerome) was the daughter of American millionaire Leonard Jerome. Winston was born on 30 November 1874, two months prematurely, in a bedroom in Blenheim Palace, Woodstock, Oxfordshire,[4] HP Pavilion DV4-1104TU Battery

From age two to six, he lived in Dublin where his Grandfather had been appointed Viceroy and employed Churchill's father as his private secretary. Churchill's brother, John Strange Spencer-Churchill, was born during this time in Ireland. It has been claimed that the young Winston first developed his fascination with military matters from watching the many parades pass by the Vice Regal Lodge (now Áras an Uachtaráin, the official residence of the President of Ireland).[5][6] HP Pavilion DV4-1104TX Battery

Winston's earliest exposure to education occurred in Dublin, where a governess tried teaching him reading, writing and arithmetic (his first reading book was called 'Reading Without Tears'). With limited contact with his parents, Churchill became very close to his nanny, 'Mrs' Elizabeth Anne Everest, whom he used to call "Old Woom" and who served as his confidante, nurse and mother substitute.[7] The two spent many happy hours playing in Phoenix Park.[8] HP Pavilion DV4-1105EF Battery

Independent and rebellious by nature, Churchill generally did poorly in school, for which he was punished. He was educated at three independent schools: St. George's School, Ascot, Berkshire, followed by Brunswick School in Hove, near Brighton (the school has since been renamed Stoke Brunswick School and relocated to Ashurst Wood in West Sussex) and then atHarrow School from 17 April 1888. HP Pavilion DV4-1105EM Battery

Within weeks of his arrival at Harrow, Churchill had joined the Harrow Rifle Corps.[9] He earned high marks in English and History and was the school's fencing champion.

He was rarely visited by his mother and he wrote letters begging her either to come to the school or to allow him to come home. HP Pavilion DV4-1105TU Battery

His relationship with his father was a distant one; he once remarked that they barely spoke to one another.[10] His father died on 24 January 1895, aged 45, leaving Churchill with the conviction that he too would die young and so should be quick about making his mark on the world.[11] HP Pavilion DV4-1105TX Battery

Speech impediment

Many authors writing in the 1920s and 1930s, before sound recording became common, mentioned Churchill's stutter in terms such as 'severe' or 'agonizing' and Churchill described himself as having a "speech impediment" which he worked to overcome. His dentures were specially designed to aid his speech (Demosthenes' pebbles).[12] HP Pavilion DV4-1106EE Battery

After many years of public speeches carefully prepared to not only inspire, but also to avoid hesitations, he could finally state, "My impediment is no hindrance".[13]

The Churchill Centre, however, flatly denies the claim that Churchill stuttered, while confirming that he did have difficulty pronouncing the letter S and spoke with a lisp[14] as did his father.[15]

Marriage and childrenHP Pavilion DV4-1106EM Battery

Churchill met his future wife, Clementine Hozier, in 1904 at a ball in Crewe House, home of theEarl of Crewe and Crewe's wife Margaret Primrose (daughter of Archibald Primrose, 5th Earl of Rosebery and Hannah Rothschild).[16] In 1908, they met again at a dinner party hosted by Lady St Helier. Churchill found himself seated beside Clementine, and they soon began a lifelong romance.[17] He proposed to Clementine during a house party at Blenheim Palace on 10 August 1908, in a small Temple of Diana.[18] HP Pavilion DV4-1106TX Battery

On 12 September 1908, they were married in St. Margaret's, Westminster. The church was packed; theBishop of St Asaph conducted the service.[19] The couple spent their honeymoon at Highgrove Housein Eastcote.[20] In March 1909, the couple moved to a house at 33 Eccleston Square. HP Pavilion DV4-1107TX Battery

Their first child, Diana, was born in London on 11 July 1909. After the pregnancy, Clementine moved to Sussex to recover, while Diana stayed in London with her nanny.[21] On 28 May 1911, their second child, Randolph, was born at 33 Eccleston Square.[22] HP Pavilion DV4-1108TX Battery

Their third child, Sarah, was born on 7 October 1914 at Admiralty House. The birth was marked with anxiety for Clementine, as Winston had been sent to Antwerp by the Cabinet to "stiffen the resistance of the beleaguered city" after news that the Belgians intended to surrender the town.[23] HP Pavilion DV4-1109TX Battery

Clementine gave birth to her fourth child, Marigold Frances Churchill, on 15 November 1918, four days after the official end of the First World War.[24] In the early days of August 1921, the Churchills' children were entrusted to a French nursery governess in Kent named Mlle Rose. Clementine, meanwhile, travelled to Eaton Hall to play tennis with Hugh Grosvenor, 2nd Duke of Westminster and his family. HP Pavilion DV4-1110EO Battery

While still under the care of Mlle Rose, Marigold had a cold, but was reported to have recovered from the illness. As the illness progressed with hardly any notice, it turned into septicaemia. Following advice from a landlady, Rose sent for Clementine. However the illness turned fatal on 23 August 1921, and Marigold was buried in the Kensal Green Cemetery three days later.[25]

On 15 September 1922, the Churchills' last child was born, Mary. Later that month, the Churchills bought Chartwell, which would be Winston's home until his death in 1965.[26][27] HP Pavilion DV4-1110TX Battery

Military service

After Churchill left Harrow in 1893, he applied to attend the Royal Military College, Sandhurst. It took three attempts before he passed the entrance exam; he applied for cavalry rather than infantry because the grade requirement was lower and did not require him to learn mathematics, HP Pavilion DV4-1111TX Battery

which he disliked. He graduated eighth out of a class of 150 in December 1894,[28] and although he could now have transferred to an infantry regiment as his father had wished, chose to remain with the cavalry and was commissioned as a Cornet(Second Lieutenant) in the 4th Queen's Own Hussars on 20 February 1895.[9] In 1941, he received the honour of being appointed Colonel of the Hussars.HP Pavilion DV4-1112TX Battery

Churchill's pay as a second lieutenant in the 4th Hussars was £300. However, he believed that he needed at least a further £500 (equivalent to £25,000 in 2001 terms) to support a style of life equal to other officers of the regiment. His mother provided an allowance of £400 per year, but this was repeatedly overspent. According to biographer Roy Jenkins, this is one reason he took an interest in war correspondence.[29] HP Pavilion DV4-1113TX Battery

He did not intend to follow a conventional career of promotion through army ranks, but to seek out all possible chances of military action and used his mother's and family influence in high society to arrange postings to active campaigns. His writings both brought him to the attention of the public, and earned him significant additional income. He acted as a war correspondent for several London newspapers[30] and wrote his own books about the campaigns. HP Pavilion DV4-1114NR Battery

Cuba

In 1895, Churchill travelled to Cuba to observe the Spanish fight the Cuban guerrillas; he had obtained a commission to write about the conflict from the Daily Graphic. To his delight, he came under fire for the first time on his twenty-first birthday.[9] He had fond memories of Cuba as a "...large, rich, beautiful island..."[31] HP Pavilion DV4-1114TX Battery

While there, he soon acquired a taste for Havana cigars, which he would smoke for the rest of his life. While in New York, he stayed at the home ofBourke Cockran, an admirer of his mother. Bourke was an established American politician, and a member of the House of Representatives. He greatly influenced Churchill, both in his approach to oratory and politics, and encouraging a love of America.[32] HP Pavilion DV4-1115EF Battery

He soon received word that his nanny, Mrs Everest, was dying; he then returned to England and stayed with her for a week until she died. He wrote in his journal "She was my favourite friend." In My Early Life he wrote: "She had been my dearest and most intimate friend during the whole of the twenty years I had lived."[33] HP Pavilion DV4-1115TX Battery

India

In early October 1896, he was transferred to Bombay, British India. He was considered one of the best polo players in his regiment and led his team to many prestigious tournament victories.[34]

In 1897, Churchill attempted to travel to both report and, if necessary, fight in the Greco-Turkish War, but this conflict effectively ended before he could arrive. Later, while preparing for a leave in England, he heard that three brigades of theBritish Army were going to fight against a Pashtun tribe in the North West Frontier of India and he asked his superior officer if he could join the fight.[35] HP Pavilion DV4-1116TX Battery

He fought under the command of General Jeffery, who was the commander of the second brigade operating in Malakand, in the Frontier region of British India. Jeffery sent him with fifteen scouts to explore the Mamund Valley; while on reconnaissance, they encountered an enemy tribe, dismounted from their horses and opened fire. HP Pavilion DV4-1117CA Battery

After an hour of shooting, their reinforcements, the 35th Sikhs arrived, and the fire gradually ceased and the brigade and the Sikhs marched on. Hundreds of tribesmen then ambushed them and opened fire, forcing them to retreat. HP Pavilion DV4-1117TX Battery

As they were retreating four men were carrying an injured officer but the fierceness of the fight forced them to leave him behind. The man who was left behind was slashed to death before Churchill's eyes; afterwards he wrote of the killer, "I forgot everything else at this moment except a desire to kill this man."[36] However the Sikhs' numbers were being depleted so the next commanding officer told Churchill to get the rest of the men and boys to safety. HP Pavilion DV4-1118CA Battery

Before he left he asked for a note so he would not be charged with desertion.[37] He received the note, quickly signed, and headed up the hill and alerted the other brigade, whereupon they then engaged the army. The fighting in the region dragged on for another two weeks before the dead could be recovered. He wrote in his journal: "Whether it was worth it I cannot tell."[36][38] HP Pavilion DV4-1118TX Battery

An account of the Siege of Malakand was published in December 1900 as The Story of the Malakand Field Force. He received £600 for his account. During the campaign, he also wrote articles for the newspapers The Pioneer and The Daily Telegraph.[39] His account of the battle was one of his first published stories, for which he received £5 per column from The Daily Telegraph.[40] HP Pavilion DV4-1119TX Battery

Sudan and Oldham

under the command of General Herbert Kitchener. During this time he encountered two military officers with whom he would work during the First World War: Douglas Haig, then a captain and David Beatty, then a gunboat lieutenant.[41] While in the Sudan, he participated in what has been described as the last meaningful British cavalry charge, at the Battle of Omdurman in September 1898.[42] HP Pavilion DV4-1120BR Battery

He also worked as a war correspondent for the Morning Post. By October 1898, he had returned to Britain and begun his two-volume work; The River War, an account of the reconquest of the Sudan which was published the following year. Churchill resigned from the British Army effective from 5 May 1899. HP Pavilion DV4-1120TX Battery

Main article: Oldham by-election, 1899

He soon had his first opportunity to begin a Parliamentary career, when he was invited by Robert Ascroft to be the secondConservative Party candidate in Ascroft's Oldham constituency. Ascroft's sudden death caused a double by-election and Churchill was one of the candidates. In the midst of a national trend against the Conservatives, both seats were lost; however Churchill impressed by his vigorous campaigning. HP Pavilion DV4-1120US Battery

South Africa

Having failed at Oldham, Churchill looked about for some other opportunity to advance his career. On 12 October 1899, the Second Boer War between Britain and the Boer Republics broke out and he obtained a commission to act as war correspondent for the Morning Post with a salary of £250 per month. He rushed to sail on the same ship as the newly appointed British commander, Sir Redvers Buller. HP Pavilion DV4-1121BR Battery

After some weeks in exposed areas he accompanied a scouting expedition in an armoured train, leading to his capture and imprisonment in a POW camp in Pretoria (converted school building for Pretoria High School for Girls). His actions during the ambush of the train led to speculation that he would be awarded the Victoria Cross, Britain's highest award for gallantry in the face of the enemy, but this did not occur.[9] HP Pavilion DV4-1121CA Battery

He escaped from the prison camp and travelled almost 300 miles (480 km) to Portuguese Lourenço Marques in Delagoa Bay, with the assistance of an English mine manager.[43] His escape made him a minor national hero for a time in Britain, though instead of returning home, he rejoined General Buller's army on its march to relieve the British at the Siege of Ladysmith and take Pretoria.[44] This time, although continuing as a war correspondent, he gained a commission in the South African Light Horse. HP Pavilion DV4-1121TX Battery

He was among the first British troops into Ladysmith and Pretoria. He and his cousin, the Duke of Marlborough, were able to get ahead of the rest of the troops in Pretoria, where they demanded and received the surrender of 52 Boer prison camp guards.[45] HP Pavilion DV4-1122TX Battery

In 1900, Churchill returned to England on the RMS Dunottar Castle, the same ship on which he set sail for South Africa eight months earlier.[47] He there published London to Ladysmith and a second volume of Boer war experiences, Ian Hamilton's March. Churchill stood again for parliament in Oldham in the general election of 1900 and won (his Conservative colleague, Crisp, was defeated) in the contest for two seats.[48][49] After the 1900 general election he embarked on a speaking tour of Britain, followed by tours of the United States and Canada, earning in excess of £5,000.[50] HP Pavilion DV4-1123LA Battery

Territorial service

In 1900, he retired from the regular army and in 1902 joined the Imperial Yeomanry where he was commissioned as a Captain in the Queen's Own Oxfordshire Hussars on 4 January 1902.[51] In April 1905, he was promoted to Major and appointed to command of the Henley Squadron of the Queen's Own Oxfordshire Hussars.[52] In September 1916, he transferred to the territorial reserves of officers where he remained till retiring in 1924, at the age of fifty.[52] HP Pavilion DV4-1123TX Battery

Western front

Churchill was First Lord of the Admiralty at the start of the First World War, but was obliged to leave the war cabinet after the disastrous Battle of Gallipoli. He attempted to obtain an appointment as a brigade commander, but settled for command of a battalion. After spending some time as a Major with the 2nd Battalion, Grenadier Guards, he was appointed Lieutenant-Colonel, HP Pavilion DV4-1123US Battery

commanding the 6th Battalion, Royal Scots Fusiliers (part of the9th (Scottish) Division), on 1 January 1916. Correspondence with his wife shows that his intent in taking up active service was to rehabilitate his reputation, but this was balanced by the serious risk of being killed. As a commander he continued to exhibit the reckless daring which had been a hallmark of all his military actions, although he disapproved strongly of the mass slaughter involved in many western front actions.[53] HP Pavilion DV4-1124LA Battery

Lord Deedes opined to a gathering of the Royal Historical Society in 2001 why Churchill went to the front line: "He was with Grenadier Guards, who were dry at battalion headquarters. They very much liked tea and condensed milk, which had no great appeal to Winston, but alcohol was permitted in the front line, in the trenches. So he suggested to the colonel that he really ought to see more of the war and get into the front line. This was highly commended by the colonel, who thought it was a very good thing to do."[54] HP Pavilion DV4-1124NR Battery

Political career to the Second World War

Early years in Parliament

Churchill stood again for the seat of Oldham at the 1900 general election. After winning the seat, he went on a speaking tour throughout Britain and the United States, raising £10,000 for himself (about £800,000 today[55]). In Parliament, he became associated with a faction of the Conservative Party led by Lord Hugh Cecil; the Hughligans. During his first parliamentary session, he opposed the government's military expenditure[56] and Joseph Chamberlain's proposal of extensive tariffs, which were intended to protect Britain's economic dominance. HP Pavilion DV4-1124TX Battery

His own constituency effectively deselected him, although he continued to sit for Oldham until the next general election. After the Whitsun recess in 1904 he crossed the floor to sit as a member of theLiberal Party. As a Liberal, he continued to campaign for free trade. When the Liberals took office with Henry Campbell-Bannermanas prime minister, in December 1905, Churchill became Under-Secretary of State for the Colonies dealing mainly with South Africa after the Boer War. From 1903 until 1905, Churchill was also engaged in writing Lord Randolph Churchill, a two-volume biography of his father which was published in 1906 and received much critical acclaim.[57] HP Pavilion DV4-1125BR Battery

llowing his deselection in the seat of Oldham, Churchill was invited to stand for Manchester North West. He won the seat at the1906 general election with a majority of 1,214 and represented the seat for two years, until 1908.[58] When Campbell-Bannerman was succeeded by Herbert Henry Asquith in 1908, Churchill was promoted to the Cabinet as President of the Board of Trade.[49] Under the law at the time, a newly appointed Cabinet Minister was obliged to seek re-election at a by-election; Churchill lost his seat but was soon back as a member for Dundee constituency. HP Pavilion DV4-1125LA Battery

As President of the Board of Trade he joined newly appointed ChancellorLloyd George in opposing First Lord of the Admiralty, Reginald McKenna's proposed huge expenditure for the construction of Navydreadnought warships, and in supporting the Liberal reforms.[59] In 1908, he introduced the Trade Boards Bill setting up the first minimum wages in Britain,[60] In 1909, he set up Labour Exchanges to help unemployed people find work.[61] HP Pavilion DV4-1125NR Battery

He helped draft the first unemployment pension legislation, the National Insurance Act of 1911.[62] As a supporter of eugenics, he participated in the drafting of the Mental Deficiency Act 1913, although the Act eventually passed rejected his preferred method of sterilisation of the feeble-minded in favour of their confinement in institutions.[63] HP Pavilion DV4-1125TX Battery

Churchill also assisted in passing the People's Budget[64] becoming President of the Budget League, an organisation set up in response to the opposition's "Budget Protest League".[65] The budget included the introduction of new taxes on the wealthy to allow for the creation of new social welfare programmes. After the budget bill was sent to the Commons in 1909 and passed, it went to the House of Lords, where it was vetoed. HP Pavilion DV4-1126LA Battery

The Liberals then fought and won two general elections in January and December 1910 to gain a mandate for their reforms. The budget was then passed following the Parliament Act 1911 for which he also campaigned. In 1910, he was promoted to Home Secretary. His term was controversial, after his responses to the Siege of Sidney Street and thedispute at the Cambrian Colliery and the suffragettes. HP Pavilion DV4-1126TX Battery

In 1910, a number of coal miners in the Rhondda Valley began what has come to be known as the Tonypandy Riot.[59] The Chief Constable of Glamorgan requested troops be sent in to help police quell the rioting. Churchill, learning that the troops were already travelling, allowed them to go as far as Swindon and Cardiff but blocked their deployment. On 9 November, The Timescriticised this decision. In spite of this, the rumour persists that Churchill had ordered troops to attack, and his reputation in Wales and in Labour circles never recovered.[66] HP Pavilion DV4-1127LA Battery

In early January 1911, Churchill made a controversial visit to the Siege of Sidney Street in London. There is some uncertainty as to whether he attempted to give operational commands, and his presence attracted much criticism. After an inquest, Arthur Balfour remarked, "he [Churchill] and a photographer were both risking valuable lives. I understand what the photographer was doing, but what was the right honourable gentleman doing?"[67] HP Pavilion DV4-1127TX Battery

A biographer,Roy Jenkins, suggests that he went simply because "he could not resist going to see the fun himself" and that he did not issue commands.[68] Another account said the police had the miscreants – Latvian anarchists wanted for murder – surrounded in a house but Churchill, called in the Scots Guards from the Tower of London and, dressed in top hat and astrakhan collar greatcoat, directed operations. HP Pavilion DV4-1128TX Battery

The house caught fire and Churchill prevented the fire brigade from dousing the flames so the men inside were burned to death. "I thought it better to let the house burn down rather than spend good British lives in rescuing those ferocious rascals."[69]

Churchill's proposed solution to the suffragette issue was a referendum on the issue, but this found no favour with Herbert Henry Asquith and women's suffrage remained unresolved until after the First World War.[70] HP Pavilion DV4-1129LA Battery

In 1911, Churchill was transferred to the office of the First Lord of the Admiralty, a post he held into the First World War. He gave impetus to several reform efforts, including development of naval aviation (he undertook flying lessons himself),[71] the construction of new and larger warships, the development of tanks, and the switch from coal to oil in the Royal Navy.[72]

First World War and the Post War CoalitionHP Pavilion DV4-1129TX Battery

On 5 October 1914, Churchill went to Antwerp, which the Belgian government proposed to evacuate. The Royal Marine Brigade was there and at Churchill's urgings the 1st and 2nd Naval Brigades were also committed. Antwerp fell on 10 October with the loss of 2500 men. At the time he was attacked for squandering resources.[73] It is more likely that his actions prolonged the resistance by a week (Belgium had proposed surrendering Antwerp on 3 October) and that this time saved Calais and Dunkirk.[74] HP Pavilion DV4-1130BR Battery

Churchill was involved with the development of the tank, which was financed from naval research funds.[75] He then headed the Landships Committee which was responsible for creating the first tank corps and, although a decade later development of the battle tank would be seen as a tactical victory, at the time it was seen as misappropriation of funds.[75] In 1915, he was one of the political and military engineers of the disastrous Gallipoli landings on the Dardanelles during the First World War.[76] He took much of the blame for the fiasco, and when Prime Minister Asquith formed an all-party coalition government, the Conservatives demanded his demotion as the price for entry.[77] HP Pavilion DV4-1130TX Battery

For several months Churchill served in the sinecure of Chancellor of the Duchy of Lancaster. However on 15 November 1915 he resigned from the government, feeling his energies were not being used[78] and, though remaining an MP, served for several months on theWestern Front commanding the 6th Battalion of the Royal Scots Fusiliers, with the rank of lieutenant colonel.[79][80] While in command he personally made 36 forays into no man's land, and his section of the front at Ploegsteert became one of the most active.[80] In March 1916, Churchill returned to England after he had become restless in France and wished to speak again in the House of Commons.[81] HP Pavilion DV4-1131BR Battery

Future prime minister David Lloyd George acidly commented: "You will one day discover that the state of mind revealed in (your) letter is the reason why you do not win trust even where you command admiration. In every line of it, national interests are completely overshadowed by your personal concern."[82] HP Pavilion DV4-1131TX Battery

In July 1917, Churchill was appointed Minister of Munitions, and in January 1919, Secretary of State for War and Secretary of State for Air. He was the main architect of the Ten Year Rule, a principle that allowed the Treasury to dominate and control strategic, foreign and financial policies under the assumption that "there would be no great European war for the next five or ten years".[83] HP Pavilion DV4-1132TX Battery

A major preoccupation of his tenure in the War Office was the Allied intervention in the Russian Civil War. Churchill was a staunch advocate of foreign intervention, declaring that Bolshevism must be "strangled in its cradle".[84] He secured, from a divided and loosely organised Cabinet, intensification and prolongation of the British involvement beyond the wishes of any major group in Parliament or the nation—and in the face of the bitter hostility of Labour. HP Pavilion DV4-1133TX Battery

In 1920, after the last British forces had been withdrawn, Churchill was instrumental in having arms sent to the Poles when they invaded Ukraine.He was also instrumental in having para-military forces (Black and Tans & Auxiliaries) intervene in the Anglo-Irish War.[85] He became Secretary of State for the Colonies in 1921 and was a signatory of the Anglo-Irish Treaty of 1921, which established the Irish Free State. HP Pavilion DV4-1134TX Battery

Churchill was involved in the lengthy negotiations of the treaty and to protect British maritime interests, he engineered part of the Irish Free State agreement to include three Treaty Ports—Queenstown (Cobh),Berehaven and Lough Swilly—which could be used as Atlantic bases by the Royal Navy.[86] In 1938, however, under the terms of the Chamberlain-De Valera Anglo-Irish Trade Agreement the bases were returned to the Irish Free State. HP Pavilion DV4-1135BR Battery

Churchill advocated the use of tear gas on Kurdish tribesmen in Iraq,[87] Though the British did consider the use of poison gas in putting down Kurdish rebellions, it was not used, as conventional bombing was considered effective.[88]

In 1923, he acted as a paid consultant for Burmah Oil (now BP plc) to lobby the British government to allow Burmah to have exclusive rights to Persian (Iraqi) oil resources, which were successfully granted.[89] HP Pavilion DV4-1135EE Battery

Rejoining the Conservative Party—Chancellor of the Exchequer

In September, the Conservative Party withdrew from the Coalition government following a meeting of backbenchers dissatisfied with the handling of the Chanak Crisis, a move that precipitated the looming October 1922 General Election. Churchill fell ill during the campaign, and had to have an appendicectomy. This made it difficult for him to campaign, and a further setback was the internal division that continued to beset the Liberal Party. HP Pavilion DV4-1135EI Battery

He came only fourth in the poll for Dundee, losing to the prohibitionist Edwin Scrymgeour. Churchill later quipped that he left Dundee "without an office, without a seat, without a party and without an appendix".[58] He stood for the Liberals again in the 1923 general election, losing in Leicester, and then as an independent, first without success in a by-election in the Westminster Abbey constituency, and then successfully in the general election of 1924 for Epping. The following year, he formally rejoined the Conservative Party, commenting wryly that "anyone can rat, but it takes a certain ingenuity to re-rat."[58][90] HP Pavilion DV4-1135TX Battery

Churchill was appointed Chancellor of the Exchequer in 1924 under Stanley Baldwin and oversaw Britain's disastrous return to the Gold Standard, which resulted in deflation, unemployment, and the miners' strike that led to the General Strike of 1926.[91] His decision, announced in the 1924 Budget, came after long consultation with various economists including John Maynard Keynes, the Permanent Secretary to the Treasury, Sir Otto Niemeyer and the board of the Bank of EnglandHP Pavilion DV4-1136BR Battery

. This decision prompted Keynes to write The Economic Consequences of Mr. Churchill, arguing that the return to the gold standard at the pre-war parity in 1925 (£1=$4.86) would lead to a world depression. However, the decision was generally popular and seen as 'sound economics' although it was opposed by Lord Beaverbrook and the Federation of British Industries.[92]

Churchill later regarded this as the greatest mistake of his life. HP Pavilion DV4-1136TX Battery

However in discussions at the time with former Chancellor McKenna, Churchill acknowledged that the return to the gold standard and the resulting 'dear money' policy was economically bad. In those discussions he maintained the policy as fundamentally political—a return to the pre-war conditions in which he believed.[93] In his speech on the Bill he said "I will tell you what it [the return to the Gold Standard] will shackle us to. It will shackle us to reality."[94] HP Pavilion DV4-1137TX Battery

The return to the pre-war exchange rate and to the Gold Standard depressed industries. The most affected was the coal industry. Already suffering from declining output as shipping switched to oil, as basic British industries like cotton came under more competition in export markets, the return to the pre-war exchange was estimated to add up to 10% in costs to the industry. In July 1925, a Commission of Inquiry reported generally favouring the miners, rather than the mine owners' position.[95] Baldwin, with Churchill's support proposed a subsidy to the industry while a Royal Commission prepared a further report. HP Pavilion DV4-1138TX Battery

That Commission solved nothing and the miners' dispute led to the General Strike of 1926, Churchill was reported to have suggested that machine guns be used on the striking miners. Churchill edited the Government's newspaper, the British Gazette, and, during the dispute, he argued that "either the country will break the General Strike, HP Pavilion DV4-1139TX Battery

or the General Strike will break the country" and claimed that the fascism of Benito Mussolini had "rendered a service to the whole world," showing, as it had, "a way to combat subversive forces"—that is, he considered the regime to be a bulwark against the perceived threat of Communist revolution. At one point, Churchill went as far as to call Mussolini the "Roman genius... the greatest lawgiver among men."[96] HP Pavilion DV4-1140EK Battery

Later economists, as well as people at the time, also criticised Churchill's budget measures. These were seen as assisting the generally prosperous rentier banking and salaried classes (to which Churchill and his associates generally belonged) at the expense of manufacturers and exporters which were known then to be suffering from imports and from competition in traditional export markets,[97] and as paring the Armed Forces too heavily.[98] HP Pavilion DV4-1140GO Battery

Political isolation

The Conservative government was defeated in the 1929 General Election. Churchill did not seek election to the Conservative Business Committee, the official leadership of the Conservative MPs. Over the next two years, Churchill became estranged from the Conservative leadership over the issues of protective tariffs and Indian Home Rule and by his political views and by his friendships with press barons, financiers and people whose characters were seen as dubious. HP Pavilion DV4-1140TX Battery

When Ramsay MacDonald formed theNational Government in 1931, Churchill was not invited to join the Cabinet. He was at the low point in his career, in a period known as "the wilderness years".[99]

He spent much of the next few years concentrating on his writing, including Marlborough: His Life and Times—a biography of his ancestor John Churchill, 1st Duke of Marlborough—and A History of the English Speaking Peoples (though the latter was not published until well after the Second World War),[99] Great Contemporaries and many newspaper articles and collections of speeches. HP Pavilion DV4-1141TX Battery

He was one of the best paid writers of his time.[99] His political views, set forth in his 1930 Romanes Election and published as Parliamentary Government and the Economic Problem (republished in 1932 in his collection of essays "Thoughts and Adventures") involved abandoning universal suffrage, a return to a property franchise, proportional representation for the major cities and an economic 'sub parliament'.[100]

Indian independence HP Pavilion DV4-1142TX Battery

See also: Simon Commission and Government of India Act 1935

Churchill opposed Mohandas Gandhi's peaceful disobedience revolt and the Indian Independence movement in the 1930s, arguing that the Round Table Conference "was a frightful prospect".[101] Later reports indicate that Churchill favoured letting Gandhi die if he went on a hunger strike.[102]During the first half of the 1930s, Churchill was outspoken in his opposition to granting Dominion status to India. He was a founder of the India Defence League, a group dedicated to the preservation of British power in India. HP Pavilion DV4-1143GO Battery

Churchill brooked no moderation. "The truth is," he declared in 1930, "that Gandhi-ism and everything it stands for will have to be grappled with and crushed."[103] In speeches and press articles in this period he forecast widespread unemployment in Britain and civil strife in India should independence be granted.[104] The Viceroy Lord Irwin, who had been appointed by the prior Conservative Government, eHP Pavilion DV4-1143TX Battery

ed in the Round Table Conference in early 1931 and then announced the Government's policy that India should be granted Dominion Status. In this the Government was supported by the Liberal Party and, officially at least, by the Conservative Party. Churchill denounced the Round Table Conference.

At a meeting of the West Essex Conservativ HP Pavilion DV4-1144TX Battery

e Association specially convened so Churchill could explain his position he said, "It is alarming and also nauseating to see Mr Gandhi, a seditious Middle Temple lawyer, now posing as a fakir of a type well-known in the East, striding half-naked up the steps of the Vice-regal palace... to parley on equal terms with the representative of the King-Emperor."[105] He called the Indian National Congress leaders "Brahmins who mouth and patter principles of Western Liberalism".[106] HP Pavilion DV4-1144US Battery

Two incidents damaged Churchill's reputation greatly within the Conservative Party in this period. Both were taken as attacks on the Conservative front bench. The first was his speech on the eve of the St George by-election in April 1931. In a secure Conservative seat, the official Conservative candidate Duff Cooper was opposed by an independent Conservative. The independent was supported by Lord Rothermere, Lord Beaverbrook and their respective newspapers. Although arranged before the by-election was set,[107]HP Pavilion DV4-1145BR Battery

Churchill's speech was seen as supporting the independent candidate and as a part of the press baron's campaign against Baldwin. Baldwin's position was strengthened when Duff Cooper won, and when the civil disobedience campaign in India ceased with the Gandhi-Irwin Pact. The second issue was a claim by Churchill that Sir Samuel Hoare and Lord Derby had pressured the Manchester Chamber of Commerce to change evidence it had given to the Joint Select Committee considering the Government of India Bill, and in doing so had breached Parliamentary privilege. HP Pavilion DV4-1145GO Battery

He had the matter referred to the House of CommonsPrivilege Committee which after investigations, in which Churchill gave evidence, reported to the House that there had been no breach.[108] The report was debated on 13 June. Churchill was unable to find a single supporter in the House and the debate ended without a division.

Churchill permanently broke with Stanley Baldwin over Indian independence and never again held any office while Baldwin was prime minister. Some historians see his basic attitude to India as being set out in his book My Early Life (1930).[109] HP Pavilion DV4-1145TX Battery

Another source of controversy about Churchill's attitude towards Indian affairs arises over what some historians term the Indian 'nationalist approach' to the Bengal famine of 1943, which has sought to place significant blame on Churchill's wartime government for the excessive mortality of up to three million people.[110][111][112] While some commentators point to the disruption of the traditional marketing system and maladministration at the provincial level,[113] HP Pavilion DV4-1146TX Battery

Arthur Herman, author of Churchill and Gandhi, contends, 'The real cause was the fall of Burma to the Japanese, which cut off India's main supply of rice imports when domestic sources fell short...[though] it is true that Churchill opposed diverting food supplies and transports from other theatres to India to cover the shortfall: this was wartime.'[114] HP Pavilion DV4-1147CL Battery

In response to an urgent request by the Secretary of State for India, Leo Amery, and Viceroy of India, Wavell, to release food stocks for India, Churchill responded with a telegram to Wavell asking, if food was so scarce, "why Gandhihadn't died yet."[115] In July 1940, newly in office, he welcomed reports of the emerging conflict between the Muslim League and the Indian Congress, hoping "it would be bitter and bloody".[103]

German rearmament and conflicts in Europe and AsiaHP Pavilion DV4-1147TX Battery

Beginning in 1932, when he opposed those who advocated giving Germany the right to military parity with France, Churchill spoke often of the dangers of Germany's rearmament.[116] He later, particularly in The Gathering Storm, portrayed himself as being for a time, a lone voice calling on Britain to strengthen itself to counter the belligerence of Germany.[117] However Lord Lloyd was the first to so agitate.[118] HP Pavilion DV4-1148TX Battery

Churchill's attitude toward the fascist dictators was ambiguous. In 1931, he warned against the League of Nations opposing the Japanese in Manchuria "I hope we shall try in England to understand the position of Japan, an ancient state.... On the one side they have the dark menace of Soviet Russia. On the other the chaos of China, four or five provinces of which are being tortured under Communist rule".[119] In contemporary newspaper articles he referred to the Spanish Republican government as a Communist front, and Franco's army as the "Anti-red movement".[120] He supported the Hoare-Laval Pact and continued up until 1937 to praise Benito Mussolini.[121] HP Pavilion DV4-1149TX Battery

Speaking in the House of Commons in 1937, Churchill said "I will not pretend that, if I had to choose between communism and Nazism, I would choose communism".[122] In a 1935 essay titled "Hitler and his Choice", which was republished in his 1937 book Great Contemporaries, Churchill expressed a hope that Hitler, if he so chose, and despite his rise to power through dictatorial action, hatred and cruelty, might yet "go down in history as the man who restored honour and peace of mind to the great Germanic nation and brought it back serene, helpful and strong to the forefront of the European family circle."[123] HP Pavilion DV4-1150BR Battery

Churchill's first major speech on defence on 7 February 1934 stressed the need to rebuild the Royal Air Force and to create a Ministry of Defence; his second, on 13 July urged a renewed role for the League of Nations. These three topics remained his themes until early 1936. In 1935, he was one of the founding members of The Focus, which brought together people of differing political backgrounds and occupations who were united in seeking "the defence of freedom and peace".[124] The Focus led to the formation of the much wider Arms and the Covenant Movement in 1936. HP Pavilion DV4-1150EO Battery

Churchill was holidaying in Spain when the Germans reoccupied the Rhineland in February 1936, and returned to a divided Britain. The Labour opposition was adamant in opposing sanctions and the National Government was divided between advocates of economic sanctions and those who said that even these would lead to a humiliating backdown by Britain as France would not support any intervention.[125] Churchill's speech on 9 March was measured, and praised by Neville Chamberlain as constructive. HP Pavilion DV4-1150EP Battery

But within weeks Churchill was passed over for the post of Minister for Co-ordination of Defence in favour of the Attorney General Sir Thomas Inskip.[126] Alan Taylorcalled this "an appointment rightly described as the most extraordinary since Caligula made his horse a consul".[127] In June 1936, Churchill organised a deputation of senior Conservatives who shared his concern to see Baldwin, Chamberlain and Halifax. HP Pavilion DV4-1150ER Battery

He had tried to have delegates from the other two parties and later wrote, "If the leaders of the Labour and Liberal oppositions had come with us there might have been a political situation so intense as to enforce remedial action".[128] As it was the meeting achieved little, Baldwin arguing that the Government was doing all it could, given the anti-war feeling of the electorate.[citation needed] HP Pavilion DV4-1150ES Battery

On 12 November Churchill returned to the topic. Speaking in the Address in Reply debate, after giving some specific instances of Germany's war preparedness, he said "The Government simply cannot make up their mind or they cannot get the prime minister to make up his mind. So they go on in strange paradox, decided only to be undecided, resolved to be irresolute, adamant for drift, solid for fluidity, all powerful for impotency. HP Pavilion DV4-1150TX Battery

And so we go on preparing more months more years precious perhaps vital for the greatness of Britain for the locusts to eat."[citation needed]

R. R. James called this one of Churchill's most brilliant speeches in this period, Baldwin's reply sounding weak and disturbing the House. The exchange gave new encouragement to the Arms and the Covenant Movement.[129] HP Pavilion DV4-1151TX Battery

Abdication crisis

Main article: Edward VIII abdication crisis

In June 1936, Walter Monckton told Churchill that the rumours that King Edward VIII intended to marry Mrs Wallis Simpson were true. Churchill then advised against the marriage and said he regarded Mrs Simpson's existing marriage as a 'safeguard'.[130] In November, he declined Lord Salisbury's invitation to be part of a delegation of senior Conservative backbenchers who met with Baldwin to discuss the matter. HP Pavilion DV4-1152TX Battery

On 25 November he, Attlee and Liberal leader Archibald Sinclair met with Baldwin, were told officially of the King's intention, and asked whether they would form an administration if Baldwin and the National Government resigned should the King not take the Ministry's advice. Both Attlee and Sinclair said they would not take office if invited to do so. Churchill's reply was that his attitude was a little different but he would support the government.[131] HP Pavilion DV4-1153TX Battery

The Abdication crisis became public, coming to a head in the first fortnight of December 1936. At this time Churchill publicly gave his support to the King. The first public meeting of the Arms and the Covenant Movement was on 3 December. Churchill was a major speaker and later wrote that in replying to the Vote of Thanks he made a declaration 'on the spur of the moment' asking for delay before any decision was made by either the King or his Cabinet.[132] Later that night Churchill saw the draft of the King's proposed wireless broadcast and spoke with Beaverbrook and the King's solicitor about it. HP Pavilion DV4-1154TX Battery

On 4 December, he met with the King and again urged delay in any decision about abdication. On 5 December, he issued a lengthy statement implying that the Ministry was applying unconstitutional pressure on the King to force him to make a hasty decision.[133] On 7 December he tried to address the Commons to plead for delay. He was shouted down. Seemingly staggered by the unanimous hostility of all Members he left.[134] HP Pavilion DV4-1155SE Battery

Churchill's reputation in Parliament and England as a whole was badly damaged. Some such as Alistair Cooke saw him as trying to build a King's Party.[135] Others likeHarold Macmillan were dismayed by the damage Churchill's support for the King had done to the Arms and the Covenant Movement.[136] Churchill himself later wrote "I was myself smitten in public opinion that it was the almost universal view that my political life was ended."[137] HP Pavilion DV4-1155TX Battery

Historians are divided about Churchill's motives in his support for Edward VIII. Some such as A J P Taylor see it as being an attempt to 'overthrow the government of feeble men'.[138] Others such as Rhode James see Churchill's motives as entirely honourable and disinterested, that he felt deeply for the King.[139] HP Pavilion DV4-1156TX Battery

Return from exile

Churchill later sought to portray himself as (to some extent) an isolated voice warning of the need to rearm against Germany. While it is true that he had a small following in the House of Commons during much of the 1930s he was given privileged information by some elements within the Government, particularly by disaffected civil servants in the War Ministry. The "Churchill group" in the later half of the decade consisted only of himself, Duncan Sandys and Brendan Bracken. HP Pavilion DV4-1157TX Battery

It was isolated from the other main factions within the Conservative Party pressing for faster rearmament and a stronger foreign policy.[140] Churchill continued to be consulted on many matters by the Government or seen as an alternative leader.[141]

Even during the time Churchill was campaigning against Indian independence, he received official and otherwise secret information.HP Pavilion DV4-1158TX Battery

From 1932, Churchill's neighbour, Major Desmond Morton with Ramsay MacDonald's approval, gave Churchill information on German air power.[142] From 1930 onwards Morton headed a department of the Committee of Imperial Defence charged with researching the defence preparedness of other nations. Lord Swinton as Secretary of State for Air, and with Baldwin's approval, in 1934 gave Churchill access to official and otherwise secret information. HP Pavilion DV4-1159TX Battery

Swinton did so, knowing Churchill would remain a critic of the government, but believing that an informed critic was better than one relying on rumour and hearsay.[143] Churchill was a fierce critic of Neville Chamberlain's appeasement of Adolf Hitler[144] and in a speech to the House of Commons, he bluntly and prophetically stated, "You were given the choice between war and dishonour. You chose dishonour, and you will have war."[145] HP Pavilion DV4-1160ES Battery

First term as prime minister

After the outbreak of the Second World War on 3 September 1939, the day Britain declared war on Germany, Churchill was appointed First Lord of the Admiralty and a member of the War Cabinet, as he had been during the first part of the First World War. When they were informed, the Board of the Admiralty sent a signal to the Fleet: "Winston is back".[146][147] In this job, he proved to be one of the highest-profile ministers during the so-called "Phoney War",HP Pavilion DV4-1160TX Battery

when the only noticeable action was at sea. Churchill advocated the pre-emptive occupation of the neutral Norwegian iron-ore port of Narvik and the iron mines in Kiruna, Sweden, early in the war. However, Chamberlain and the rest of the War Cabinet disagreed, and the operation was delayed until the successful German invasion of Norway. HP Pavilion DV4-1161TX Battery

Bitter beginnings of the war

On 10 May 1940, hours before the German invasion of France by a lightning advance through the Low Countries, it became clear that, following failure in Norway, the country had no confidence in Chamberlain's prosecution of the war and so Chamberlain resigned. The commonly accepted version of events states that Lord Halifax turned down the post of prime minister because he believed he could not govern effectively as a member of the House of Lords instead of the House of Commons. HP Pavilion DV4-1162TX Battery

Although the prime minister does not traditionally advise the King on the former's successor, Chamberlain wanted someone who would command the support of all three major parties in the House of Commons. A meeting between Chamberlain, Halifax, Churchill and David Margesson, the government Chief Whip, led to the recommendation of Churchill, and, as a constitutional monarch, George VI asked Churchill to be prime minister. Churchill's first act was to write to Chamberlain to thank him for his support.[148] HP Pavilion DV4-1163TX Battery

Churchill had been among the first to recognise the growing threat of Hitler long before the outset of the Second World War, and his warnings had gone largely unheeded. Although there was an element of British public and political sentiment favouring negotiated peace with a clearly ascendant Germany, among them the Foreign Secretary Lord Halifax, Churchill nonetheless refused to consider an armistice with Hitler's Germany.[149] His use of rhetoric hardened public opinion against a peaceful resolution and prepared the British for a long war.[150] HP Pavilion DV4-1164TX Battery

Coining the general term for the upcoming battle, Churchill stated in his "finest hour" speech to the House of Commons on 18 June 1940, "I expect that the Battle of Britain is about to begin."[151] By refusing an armistice with Germany, Churchill kept resistance alive in the British Empire and created the basis for the later Allied counter-attacks of 1942–45, with Britain serving as a platform for the supply of Soviet Union and the liberation of Western Europe. HP Pavilion DV4-1165TX Battery

In response to previous criticisms that there had been no clear single minister in charge of the prosecution of the war, Churchill created and took the additional position of Minister of Defence. He immediately put his friend and confidant, the industrialist and newspaper baron Lord Beaverbrook, in charge of aircraft production. It was Beaverbrook's business acumen that allowed Britain to quickly gear up aircraft production and engineering that eventually made the difference in the warHP Pavilion DV4-1166CA Battery

Churchill's speeches were a great inspiration to the embattled British. His first speech as prime minister was the famous "I have nothing to offer but blood, toil, tears, and sweat". He followed that closely with two other equally famous ones, given just before the Battle of Britain. One included the words:

we shall fight in France, we shall fight on the seas and oceans, we shall fight with growing confidence and growing strength in the air, we shall defend our island, whatever the cost may be, we shall fight on the beaches, we shall fight on the landing grounds, we shall fight in the fields and in the streets, we shall fight in the hills; we shall never surrender.[153] HP Pavilion DV4-1166TX Battery

The other:

Let us therefore brace ourselves to our duties, and so bear ourselves, that if the British Empire and its Commonwealth last for a thousand years, men will still say, 'This was their finest hour'.[154]

At the height of the Battle of Britain, his bracing survey of the situation included the memorable line "Never in the field of human conflict was so much owed by so many to so few", which engendered the enduring nickname The Few for the RAF fighter pilots who won it.[155] HP Pavilion DV4-1167TX Battery

He first spoke these famous words upon his exit from No. 11 Group's underground bunker at RAF Uxbridge, now known as the Battle of Britain Bunker on 16 August 1940. One of his most memorable war speeches came on 10 November 1942 at the Lord Mayor's Luncheon at Mansion House in London, in response to the Allied victory at the Second Battle of El Alamein. Churchill stated: HP Pavilion DV4-1168TX Battery

This is not the end. It is not even the beginning of the end. But it is, perhaps, the end of the beginning.[156]

Without having much in the way of sustenance or good news to offer the British people, he took a risk in deliberately choosing to emphasise the dangers instead.

"Rhetorical power", wrote Churchill, "is neither wholly bestowed, nor wholly acquired, but cultivated." Not all were impressed by his oratory. HP Pavilion DV4-1169TX Battery

Robert Menzies, prime minister of Australia and himself a gifted phrase-maker, said of Churchill during the Second World War: "His real tyrant is the glittering phrase so attractive to his mind that awkward facts have to give way."[157] Another associate wrote: "He is... the slave of the words which his mind forms about ideas.... And he can convince himself of almost every truth if it is once allowed thus to start on its wild career through his rhetorical machinery."[158] HP Pavilion DV4-1180BR Battery

Relations with the United States

Churchill's good relationship with Franklin D. Roosevelt secured vital food, oil and munitions via the North Atlantic shipping routes.[159] It was for this reason that Churchill was relieved when Roosevelt was re-elected in 1940. Upon re-election, Roosevelt immediately set about implementing a new method of providing military hardware and shipping to Britain without the need for monetary payment. HP Pavilion DV4-1190BR Battery

Put simply, Roosevelt persuaded Congress that repayment for this immensely costly service would take the form of defending the US; and so Lend-lease was born. Churchill had 12 strategic conferences with Roosevelt which covered the Atlantic Charter, Europe first strategy, the Declaration by the United Nations and other war policies. After Pearl Harbor was attacked, Churchill's first thought in anticipation of US help was, "We have won the war!"[160] On 26 December 1941, Churchill addressed a joint meeting of the US Congress, asking of Germany and Japan, "What kind of people do they think we are?"[161] HP Pavilion DV4-1190EA Battery

Churchill initiated theSpecial Operations Executive (SOE) under Hugh Dalton's Ministry of Economic Warfare, which established, conducted and fostered covert, subversive and partisan operations in occupied territories with notable success; and also the Commandos which established the pattern for most of the world's current Special Forces. The Russians referred to him as the "British Bulldog".HP Pavilion DV4-1190EJ Battery

Churchill's health was fragile, as shown by a mild heart attack he suffered in December 1941 at the White House and also in December 1943 when he contracted pneumonia. Despite this, he travelled over 100,000 miles (160,000 km) throughout the war to meet other national leaders. For security, he usually travelled using the alias Colonel Warden.[162] HP Pavilion DV4-1190EL Battery

Churchill was party to treaties that would redraw post-Second World War European and Asian boundaries. These were discussed as early as 1943. At the Second Quebec Conference in 1944 he drafted and, together with US President Franklin D. Roosevelt, signed a toned-down version of the original Morgenthau Plan, in which they pledged to convert Germany after its unconditional surrender "into a country primarily agricultural and pastoral in its character."[163] HP Pavilion DV4-1198ER Battery

Proposals for European boundaries and settlements were officially agreed to by Harry S. Truman, Churchill, and Joseph Stalin at Potsdam. Churchill's strong relationship with Harry Truman was also of great significance to both countries. While he clearly regretted the loss of his close friend and counterpart Roosevelt, Churchill was enormously supportive of Truman in his first days in office, calling him, "the type of leader the world needs when it needs him most."[164] HP Pavilion DV4-1199EA Battery

Relations with the Soviet Union

When Hitler invaded the Soviet Union, Winston Churchill, a vehement anti-Communist, famously stated "If Hitler invaded Hell, I would at least make a favourable reference to the Devil in the House of Commons," regarding his policy toward Stalin.[165] Soon, British supplies and tanks were flowing to help the Soviet Union.[166] HP Pavilion DV4-1199EE Battery

The Casablanca Declaration

A meeting of Allied powers held in Casablanca, Morocco, January 14–23, 1943, produced what was to be known as the “Casablanca Declaration.” In attendance were Churchill, Franklin Roosevelt and Charles de Gaulle. Joseph Stalin had bowed out, citing the need for his presence in the Soviet Union to attend to the Stalingrad crisis. It was in Casablanca that it was announced that the Allies would accept nothing less than “unconditional surrender” from the Axis powers. HP Pavilion DV4-1199EF Battery

“Unconditional surrender” has withstood the test of historical time to become a catch phrase epitomizing the implacable will and moral supremacy manifested by the Allied powers to countenance nothing less than the total annihilation of Nazism in Germany. That fascism in Germany, under certain conditions, could be a system of government tolerated by and integrated into the global community was likely a negotiable consideration for the Allies. In truth, Churchill was not committed to seeing the war through to Germany’s complete capitulation. HP Pavilion DV4-1199EO Battery

Both the United States and England hoped to come to some accommodation with Germany, which would allow the German army to help fight off the Soviet takeover of Eastern Europe. It was perceived that Communist domination was an inevitable strategy of Soviet Russia. To Churchill and the other Allied leaders, the real obstacle to preventing a mutual accommodation with Germany was Adolf Hitler. HP Pavilion DV4-1199EP Battery

Allen Dulles, the chief of OSS intelligence in Bern, Switzerland, maintained that the “Casablanca Declaration” was “merely a piece of paper to be scrapped without further ado if Germany would sue for peace. Hitler had to go.”[167]

The settlement concerning the borders of Poland, that is, the boundary between Poland and the Soviet Union and between Germany and Poland, was viewed as a betrayal in Poland during the post-war years, as it was established against the views of the Polish government in exile. HP Pavilion DV4-1199ER Battery

It was Winston Churchill, who tried to motivateMiko?ajczyk, who was prime minister of the Polish government in exile, to accept Stalin's wishes, but Miko?ajczyk refused. Churchill was convinced that the only way to alleviate tensions between the two populations was the transfer of people, to match the national borders.

As he expounded in the House of Commons on 15 December 1944, "Expulsion is the method which, insofar as we have been able to see, will be the most satisfactory and lasting. There will be no mixture of populations to cause endless trouble... A clean sweep will be made. HP Pavilion DV4-1199ES Battery

I am not alarmed by these transferences, which are more possible in modern conditions."[168][169] However the resulting expulsions of Germans were carried out in a way which resulted in much hardship and, according to a 1966 report by the West German Ministry of Refugees and Displaced Persons, the death of over 2.1 million. Churchill opposed the effective annexation of Poland by the Soviet Union and wrote bitterly about it in his books, but he was unable to prevent it at the conferences.[170] HP Pavilion DV4-1199ET Battery

Durg October 1944, he and Eden were in Moscow to meet with the Russian leadership. At this point, Russian forces were beginning to advance into various eastern European countries. Churchill held the view that until everything was formally and properly worked out at the Yalta conference, there had to be a temporary, war-time, working agreement with regard to who would run what.[171] The most significant of these meetings were held on 9 October 1944 in the Kremlin between Churchill and Stalin. HP Pavilion DV4-1200 CTO Battery

During the meeting, Poland and the Balkan problems were discussed.[172] Churchill recounted his speech to Stalin on the day:

Let us settle about our affairs in the Balkans. Your armies are in Rumania and Bulgaria. We have interests, missions, and agents there. Don't let us get at cross-purposes in small ways. So far as Britain and Russia are concerned, how would it do for you to have ninety per cent predominance in Rumania, for us to have ninety per cent of the say in Greece, and go fifty-fifty about Yugoslavia?[171] HP Pavilion DV4-1200 Battery

Stalin agreed to this Percentages Agreement, ticking a piece of paper as he heard the translation. In 1958, five years after the account of this meeting was published (in The Second World War), authorities of the Soviet Union denied that Stalin accepted the "imperialist proposal".[172]

One of the conclusions of the Yalta Conference was that the Allies would return all Soviet citizens that found themselves in the Allied zone to the Soviet Union. This immediately affected the Soviet prisoners of war liberated by the Allies, but was also extended to all Eastern Europeanrefugees.[173] Aleksandr Solzhenitsyn called the Operation Keelhaul "the last secret of World War II."[174] The operation decided the fate of up to two million post-war refugees fleeing eastern Europe.[175] HP Pavilion DV4-1201AU Battery

Dresden bombings controversy

Between 13–15 February 1945, British and US bombers attacked the German city of Dresden, which was crowded with German wounded and refugees.[176] Because of the cultural importance of the city, and of the number of civilian casualties close to the end of the war, this remains one of the most controversial Western Allied actions of the war. Following the bombing Churchill stated in a top secret telegram: HP Pavilion DV4-1201TU Battery

It seems to me that the moment has come when the question of bombing of German cities simply for the sake of increasing the terror, though under other pretexts, should be reviewed... I feel the need for more precise concentration upon military objectives such as oil and communications behind the immediate battle-zone, rather than on mere acts of terror and wanton destruction, however impressive.[177] HP Pavilion DV4-1201TX Battery

On reflection, under pressure from the Chiefs of Staff and in response to the views expressed by Sir Charles Portal (Chief of the Air Staff) and Sir Arthur Harris (AOC-in-C of RAF Bomber Command), among others, Churchill withdrew his memo and issued a new one.[178][179] This final version of the memo completed on 1 April 1945, stated: HP Pavilion DV4-1202AU Battery

It seems to me that the moment has come when the question of the so called 'area-bombing' of German cities should be reviewed from the point of view of our own interests. If we come into control of an entirely ruined land, there will be a great shortage of accommodation for ourselves and our allies... We must see to it that our attacks do no more harm to ourselves in the long run than they do to the enemy's war effort.[178][179] HP Pavilion DV4-1202TU Battery

Ultimately, responsibility for the British part of the attack lay with Churchill, which is why he has been criticised for allowing the bombings to occur. The German historian Jörg Friedrich claims that "Winston Churchill's decision to [area] bomb a shattered Germany between January and May 1945 was a war crime",[180] and writing in 2006 the philosopher A. C. Grayling questioned the whole strategic bombing campaign by the RAF, presenting the argument that although it was not a war crime it was a moral crime that undermines the Allies' contention that they fought a just war.[181] On the other hand, HP Pavilion DV4-1202TX Battery

it has also been asserted that Churchill's involvement in the bombing of Dresden was based on the strategic and tactical aspects of winning the war. The destruction of Dresden, while immense, was designed to expedite the defeat of Germany. As the historian and journalist Max Hastings said in an article subtitled "the Allied Bombing of Dresden": "I believe it is wrong to describe strategic bombing as a war crime, for this might be held to suggest some moral equivalence with the deeds of the Nazis. HP Pavilion DV4-1203AU Battery

Bombing represented a sincere, albeit mistaken, attempt to bring about Germany's military defeat." British historian Frederick Taylor asserts that "All sides bombed each other's cities during the war. Half a million Soviet citizens, for example, died from German bombing during the invasion and occupation of Russia. That's roughly equivalent to the number of German citizens who died from Allied raids. But the Allied bombing campaign was attached to military operations and ceased as soon as military operations ceased."[182] HP Pavilion DV4-1203TU Battery

The Second World War ends

In June 1944, the Allied Forces invaded Normandy and pushed the Nazi forces back into Germany on a broad front over the coming year. After being attacked on three fronts by the Allies, and in spite of Allied failures, such as Operation Market Garden, and German counter-attacks, including the Battle of the Bulge, Germany was eventually defeated. On 7 May 1945 at the SHAEFheadquarters in Rheims the Allies accepted Germany's surrender. On the same day in a BBC news flash John Snagge announced that 8 May would be Victory in Europe Day.[183] HP Pavilion DV4-1203TX Battery

On Victory in Europe Day, Churchill broadcast to the nation that Germany had surrendered and that a final cease fire on all fronts in Europe would come into effect at one minute past midnight that night.[184][185]Afterwards, Churchill told a huge crowd in Whitehall: "This is your victory." The people shouted: "No, it is yours", and Churchill then conducted them in the singing of Land of Hope and Glory. In the evening he made another broadcast to the nation asserting the defeat of Japan in the coming months.[49] The Japanese later surrendered on 15 August 1945. HP Pavilion DV4-1204AU Battery

As Europe celebrated peace at the end of six years of war, Churchill was concerned with the possibility that the celebrations would soon be brutally interrupted.[186] He concluded that the UK and the US must anticipate the Red Army ignoring previously agreed frontiers and agreements in Europe, and prepare to "impose upon Russia the will of the United States and the British Empire."[187]HP Pavilion DV4-1204TU Battery

According to the Operation Unthinkable plan ordered by Churchill and developed by the British Armed Forces, the Third World War could have started on 1 July 1945 with a sudden attack against the allied Soviet troops. The plan was rejected by the British Chiefs of Staff Committee as militarily unfeasible. HP Pavilion DV4-1204TX Battery

Leader of the opposition

Although Churchill's role in the Second World War had generated much support for him amongst the British population, he was defeated in the 1945 election.[188] Many reasons for this have been given, key among them being that a desire for post-war reform was widespread amongst the population and that the man who had led Britain in war was not seen as the man to lead the nation in peace.[189] HP Pavilion DV4-1205AU Battery

It was anticipated that Churchill would step down and hand over the leadership to Anthony Eden, who became his deputy after the election defeat, but Churchill (despite now being in his seventies) was determined to fight on as leader and Eden was too loyal to challenge his leadership. It would be another decade before Churchill finally did hand over the reins to Eden.

For six years he was to serve as the Leader of the Opposition. During these years Churchill continued to have an impact on world affairs. HP Pavilion DV4-1205TU Battery

During his March 1946 trip to the United States, Churchill famously lost a lot of money in a poker game with Harry Truman and his advisors.[191](He also liked to play Bezique, which he learned while serving in the Boer War.)

During this trip he gave his Iron Curtain speech about the USSR and the creation of the Eastern Bloc. Speaking on 5 March 1946 atWestminster College in Fulton, Missouri, he declared: HP Pavilion DV4-1205TX Battery

From Stettin in the Baltic to Trieste in the Adriatic, an Iron Curtain has descended across the continent. Behind that line lie all the capitals of the ancient states of Central and Eastern Europe. Warsaw, Berlin, Prague, Vienna, Budapest, Belgrade, Bucharest and Sofia, all these famous cities and the populations around them lie in what I must call the Soviet sphere.[192] HP Pavilion DV4-1206TU Battery

Churchill also argued strongly for British independence from the European Coal and Steel Community, which he saw as a Franco-German project. He saw Britain's place as separate from the continent, much more in-line with the countries of the Commonwealth and the Empire, and with the United States, the so-called Anglosphere.[193][194]

Churchill held the office of Deputy Lieutenant (DL) of Kent in 1949.[195]

Second term as prime ministerHP Pavilion DV4-1206TX Battery

Return to government and the decline of the British Empire

After the General Election of 1951, Churchill again held the office of Minister of Defence between October 1951 and January 1952. He also became prime minister in October 1951, and his third government—after the wartime national government and the brief caretaker government of 1945—lasted until his resignation in April 1955. HP Pavilion DV4-1207TU Battery

His domestic priorities in his last government were overshadowed by a series of foreign policy crises, which were partly the result of the continued decline of British military and imperial prestige and power. Being a strong proponent of Britain as an international power, Churchill would often meet such moments with direct action. One example was his dispatch of British troops to Kenya to deal with the Mau Mau rebellion.[196] Trying to retain what he could of the Empire, he once stated that, "I will not preside over a dismemberment."[196]

War in Malaya

fThis was followed by events which became known as the Malayan Emergency. In Malaya, a rebellion against British rule had been in progress since 1948.[197] HP Pavilion DV4-1207TX Battery

Once again, Churchill's government inherited a crisis, and Churchill chose to use direct military action against those in rebellion while attempting to build an alliance with those who were not.[49][198] While the rebellion was slowly being defeated, it was equally clear that colonial rule from Britain was no longer sustainable.[197][199]

Relations with the United States HP Pavilion DV4-1208TU Battery

Churchill also devoted much of his time in office to Anglo-American relations and, although Churchill did not always agree with President Dwight D. Eisenhower,[200]Churchill attempted to maintain the Special Relationship with the United States. He made four official transatlantic visits to America during his second term as prime minister.[201] HP Pavilion DV4-1208TX Battery

The series of strokes

Churchill had suffered a mild stroke while on holiday in the south of France in the summer of 1949. In June 1953, when he was 78, Churchill suffered a more severe stroke at 10 Downing Street. News of this was kept from the public and from Parliament, who were told that Churchill was suffering from exhaustion. HP Pavilion DV4-1209TX Battery

He went to his country home, Chartwell, to recuperate from the effects of the stroke which had affected his speech and ability to walk.[49] He returned to public life in October to make a speech at a Conservative Party conference at Margate.[49][202] However, aware that he was slowing down both physically and mentally, Churchill retired as prime minister in 1955 and was succeeded by Anthony Eden. He suffered another mild stroke in December 1956. HP Pavilion DV4-1210EA Battery

Retirement and death

Elizabeth II offered to create Churchill Duke of London, but this was declined due to the objections of his son Randolph, who would have inherited the title on his father's death.[203] After leaving the premiership, Churchill spent less time in parliament until he stood down at the 1964 General Election. As a mere "back-bencher," Churchill spent most of his retirement at Chartwell and at his home in Hyde Park Gate, in London.[49] HP Pavilion DV4-1210EF Battery

In e 1959 General Election Churchill's majority fell by more than a thousand, since many young voters in his constituency did not support an 85-year-old who could only enter the House of Commons in a wheelchair. As his mental and physical faculties decayed, he began to lose the battle he had fought for so long against the "black dog" of depression.[49] HP Pavilion DV4-1210EO Battery

There was speculation that Churchill may have had Alzheimer's disease in his last years, although others maintain that his reduced mental capacity was merely the result of a series of strokes. In 1963, US President John F. Kennedy, acting under authorisation granted by an Act of Congress, proclaimed him an Honorary Citizen of the United States,[204] but he was unable to attend the White House ceremony.[205]

Despite poor health, Churchill still tried to remain active in public life, and on St George's Day 1964, sent a message of congratulations to the surviving veterans of the 1918 Zeebrugge Raid who were attending a service of commemoration in Deal, Kent, where two casualties of the raid were buried in the Hamilton Road Cemetery. HP Pavilion DV4-1210ER Battery

On 15 January 1965, Churchill suffered a severe stroke that left him gravely ill. He died at his London home nine days later, at age 90, on the morning of Sunday 24 January 1965, 70 years to the day after his father's death.[205]

Funeral

By decree of the Queen, his body lay in state for three days and a state funeral service was held at St Paul's Cathedral on 30 January 1965.[206] Unusually, the Queen attended the funeral.[207] As his lead-lined coffin passed up the River Thames fromTower Pier to Festival Pier on the MV Havengore, dockers lowered their crane jibs in a salute.[208] HP Pavilion DV4-1210TU Battery

The Royal Artillery fired the 19-gun salute due a head of government, and the RAF staged a fly-by of sixteen English Electric Lightning fighters. The coffin was then taken the short distance to Waterloo station where it was loaded onto a specially prepared and painted carriage as part of the funeral train for its rail journey to Handborough,[209] seven miles north-west ofOxford. The funeral also saw one of the largest assemblages of statesmen in the world.[1] HP Pavilion DV4-1210TX Battery

The funeral train of Pullman coaches carrying his family mourners was hauled by Battle of Britain class steam locomotive No. 34051 Winston Churchill. In the fields along the route, and at the stations through which the train passed, thousands stood in silence to pay their last respects. At Churchill's request, he was buried in the family plot at St Martin's Church, Bladon, near Woodstock, not far from his birthplace at Blenheim Palace. HP Pavilion DV4-1211EA Battery

Churchill's funeral van—Southern Railway van S2464S—is now part of a preservation project with the Swanage Railway, having been repatriated to the UK in 2007 from the US, to where it had been exported in 1965.[210]

Later in 1965 a memorial to Churchill, cut by the engraver Reynolds Stone, was placed in Westminster Abbey. HP Pavilion DV4-1211TU Battery

Churchill as artist, historian, and writer

Winston Churchill was an accomplished artist and took great pleasure in painting, especially after his resignation as First Lord of the Admiralty in 1915.[211] He found a haven in art to overcome the spells of depression, or as he termed it, the "Black Dog", which he suffered throughout his life. As William Rees-Mogg has stated, "In his own life, he had to suffer the 'black dog' of depression. In his landscapes and still lives there is no sign of depression."[212] Churchill was persuaded and taught to paint by his artist friend, Paul Maze, whom he met during the First World War. HP Pavilion DV4-1211TX Battery

Maze was a great influence on Churchill's painting and became a lifelong painting companion.[213] He is best known for his impressionist scenes of landscape, many of which were painted while on holiday in the South of France, Egypt or Morocco.[212] He continued his hobby throughout his life and painted hundreds of paintings, many of which are on show in the studio at Chartwell as well as private collections.[214] Some of his paintings can today be seen in the Wendy and Emery Reves Collection at the Dallas Museum of Art. HP Pavilion DV4-1212LA Battery

Emery Reves and Winston Churchill indeed were close friends[215] and Churchill would often visit Emery and his wife in their villa in the South of France (villa La Pausa, originally built in 1927 for Gabrielle "Coco" Chanel). The villa was rebuilt within the museum in 1985 with a gallery of paintings and memorabilia from Sir Winston Churchill.[216][217] Most of his paintings are oil-based and feature landscapes, but he also did a number of interior scenes and portraits. HP Pavilion DV4-1212TU Battery

Due to obvious time constraints, Churchill attempted only one painting during the Second World War. He completed the painting from the tower of the Villa Taylor in Marrakesh.[218]

Despite his lifelong fame and upper-class origins, Churchill always struggled to keep his income at a level that would fund his extravagant lifestyle. MPs before 1946 received only a nominal salary (and in fact did not receive anything at all until theParliament Act 1911) so many had secondary professions from which to earn a living.[219] HP Pavilion DV4-1212TX Battery

From his first book in 1898 until his second stint as Prime Minister, Churchill's income was almost entirely made from writing books and opinion pieces for newspapers and magazines. The most famous of his newspaper articles are those that appeared in the Evening Standard from 1936 warning of the rise of Hitler and the danger of the policy of appeasement. HP Pavilion DV4-1213LA Battery

Churchill was also a prolific writer of books, writing a novel, two biographies, three volumes of memoirs, and several histories in addition to his many newspaper articles. He was awarded the Nobel Prize in Literature in 1953 "for his mastery of historical and biographical description as well as for brilliant oratory in defending exalted human values".[220] Two of his most famous works, published after his first premiership brought his international fame to new heights, were his six-volume memoir The Second World War and A History of the English-Speaking Peoples; a four-volume history covering the period from Caesar's invasions of Britain (55 BC) to the beginning of the First World War (1914).[221] HP Pavilion DV4-1213TU Battery

He was also an amateur bricklayer, building garden walls and even a cottage at Chartwell. As part of this hobby he joined the Amalgamated Union of Building Trade Workers.[222]

Honours

In addition to the honour of a state funeral, Churchill received a wide range of awards and other honours. For example, he was the first person to become an Honorary Citizen of the United States.[223] HP Pavilion DV4-1213TX Battery

In 1945, while Churchill was mentioned by Halvdan Koht as one of seven appropriate candidates for the Nobel Prize in Peace, the nomination went to Cordell Hull.[224]

Churchill received the Nobel Prize in Literature in 1953 for his numerous published works, especially his six-volume set The Second World War. In a 2002 BBC poll of the "100 Greatest Britons", he was proclaimed "The Greatest of Them All" based on approximately a million votes from BBC viewers.[225] Churchill was also rated as one of the most influential leaders in history byTIME.[226] Churchill College, Cambridge was founded in 1958 to memorialise him. HP Pavilion DV4-1214LA Battery

 

Polonium,Astatine,Radon

Polonium is a chemical element with the symbol Po and atomic number 84, discovered in 1898 byMarie Sk?odowska-Curieand Pierre Curie. A rare and highly radioactive element, polonium is chemically similar to bismuth[1]and tellurium, and it occurs in uranium ores. Polonium has been studied for possible use in heating spacecraft. Sony VAIO VPCEB1LFX Battery

As it is unstable, all isotopes of polonium are radioactive. There is disagreement as to whether polonium is a post-transition metalor metalloid.[2][3]

Characteristics

Polonium has 33 known isotopes, all of which are radioactive. They have atomic masses that range from 188 to 220 u. 210Po (half-life 138.4 days) is the most widely available. Sony VAIO VPCEB1LFX/BI Battery

209Po (half-life 103 years) and 208Po (half-life 2.9 years) can be made through the alpha, proton, or deuteron bombardment of lead or bismuth in a cyclotron.

210Po is an alpha emitter that has a half-life of 138.4 days; it decays directly to its stable daughter isotope, 206Pb. A milligram of 210Po emits about as many alpha particles per second as 4.5 grams of 226Ra. Sony VAIO VPCEB1LFX/WI Battery

A few curies (1 curie equals 37gigabecquerels, 1 Ci = 37 GBq) of 210Po emit a blue glow which is caused by excitation of surrounding air. A single gram of210Po generates 140 watts of power.[4] Because it emits many alpha particles, which are stopped within a very short distance in dense media and release their energy, 210Po has been used as a lightweight heat source to power thermoelectric cells inartificial satellites; Sony VAIO VPCEB1MFX Battery

for instance, 210Po heat source was also used in each of the Lunokhod rovers deployed on the surface of the Moon, to keep their internal components warm during the lunar nights.[5] Some anti-static brushes contain up to 500 microcuries (20 MBq) of 210Po as a source of charged particles for neutralizing static electricity in materials like photographic film.[6] Sony VAIO VPCEB1MFX/BI Battery

About one in 100,000 alpha emissions causes an excitation in the nucleus which then results in the emission of a gamma ray.[7]Because of its relatively high rate of alpha emissions, only about 1 in 100,000 result in releasing a gamma ray. But it is the alpha particles, not the side effect of an occasional gamma ray, that results in 210Po decay. Sony VAIO VPCEB1NFX Battery

Low gamma output renders gamma detection nearly impossible, with any emitted gamma nearly indistinguishable from background radiation. At 4.001 u, the alpha particle is too massive to penetrate most barriers, including intact human epidermis. If the skin is broken however, or the alpha emitter is ingested or inhaled, the high charge on the alpha particle will result in severe cellular damage. Sony VAIO VPCEB1NFX/B Battery

The high alpha decay of polonium renders alpha detection as the preferred method of quantifying this isotope in the laboratory.

Solid state form

Polonium is a radioactive element that exists in two metallic allotropes. The alpha form is the only known example of a simple cubiccrystal structure in a single atom basis, with an edge length of 335.2 picometres; the beta form is rhombohedral.[8][9] Sony VAIO VPCEB1NFX/L Battery

The structure of polonium has been characterized by X-ray diffraction [10][11] and electron diffraction.[12]

210Po (in common with 238Pu) has the ability to become airborne with ease: if a sample is heated in air to 55 °C (131 °F), 50% of it is vaporized in 45 hours, even though the melting point of polonium is 254 °C (489 °F) and its boiling point is 962 °C (1763 °F).[13][14]Sony VAIO VPCEB1NFX/P Battery

More than one hypothesis exists for how polonium does this; one suggestion is that small clusters of polonium atoms are spalled offby the alpha decay.

Chemistry

The chemistry of polonium is similar to that of tellurium and bismuth. Polonium dissolves readily in dilute acids, but is only slightly soluble in alkalis. Sony VAIO VPCEB1NFX/W Battery

The hydrogen compound PoH2 is liquid at room temperature (melting point ?36.1°C, boiling point35.3°C). Halides of the structure PoX2, PoX4 and PoX6 are known. The two oxides PoO2and PoO3 are the products of oxidation of polonium.[15]

It has been reported that some microbes can methylate polonium by the action of methylcobalamin.[16][17] Sony VAIO VPCEB1PFX Battery

This is similar to the way in which mercury, selenium and tellurium are methylated in living things to create organometallic compounds. As a result when considering the biochemistry of polonium one should consider the possibility that the polonium will follow the same biochemical pathways as selenium and tellurium. Sony VAIO VPCEB1PFX/B Battery

Also tentatively called "Radium F", polonium was discovered by Marie Sk?odowska-Curie and her husband Pierre Curie in 1898[18]and was named after Marie Curie's native land of Poland (Latin: Polonia)[19][20] Poland at the time was under Russian, Prussian, and Austrian partition, and did not exist as an independent country. Sony VAIO VPCEB1QGX Battery

It was Curie's hope that naming the element after her native land would publicize its lack of independence. Polonium may be the first element named to highlight a political controversy.[21]

This element was the first one discovered by the Curies while they were investigating the cause of pitchblende radioactivity. Sony VAIO VPCEB1QGX/BI Battery

The pitchblende, after removal of the radioactive elements uranium and thorium, was more radioactive than both the uranium and thorium put together. This spurred the Curies on to find additional radioactive elements. The Curies first separated out polonium from the pitchblende, and then within a few years, also isolated radium. Sony VAIO VPCEB1RGX Battery

Because of the small quantities present in nature, isolation of polonium from natural sources is complicated. The largest ever isolated batch from 37 tonnes of residues from radium production yielded only 40 Ci of polonium-210.[22] Sony VAIO VPCEB1RGX/BI Battery

Gamma counting

By means of radiometric methods such as gamma spectroscopy (or a method using a chemical separation followed by an activitymeasurement with a non-energy-dispersive counter), it is possible to measure the concentrations of radioisotopes and to distinguish one from another. Sony VAIO VPCEB20 Battery

In practice, background noise would be present and depending on the detector, the line width would be larger which would make it harder to identify and measure the isotope. In biological/medical work it is common to use the natural 40K present in all tissues/body fluids as a check of the equipment and as an internal standard. Sony VAIO VPCEC20 Battery

Alpha counting

The best way to test for (and measure) many alpha emitters is to use alpha-particle spectroscopy as it is common to place a drop of the test solution on a metal disk which is then dried out to give a uniform coating on the disk. This is then used as the test sample.Sony VAIO VPCEE20 Battery

If the thickness of the layer formed on the disk is too thick then the lines of the spectrum are broadened, this is because some of the energy of the alpha particlesis lost during their movement through the layer of active material. An alternative method is to use internal liquid scintillation where the sample is mixed with a scintillation cocktail. Sony VAIO VPCEF20 Battery

When the light emitted is then counted, some machines will record the amount of light energy per radioactive decay event. Due to the imperfections of the liquid scintillation method (such as a failure for all the photons to be detected, cloudy or coloured samples can be difficult to count) and the fact that random quenching can reduce the number of photons generated per radioactive decay it is possible to get a broadening of the alpha spectra obtained through liquid scintillation. Sony VAIO VPCF112FX/B Battery

It is likely that these liquid scintillation spectra will be subject to a Gaussian broadeningrather than the distortion exhibited when the layer of active material on a disk is too thick.

A third energy dispersive method for counting alpha particles is to use a semiconductor detector. Sony VAIO VPCF115FG/B Battery

From left to right the peaks are due to 209Po, 210Po, 239Pu and 241Am. The fact that isotopes such as 239Pu and 241Am have more than one alpha line indicates that the nucleus has the ability to be in different discrete energy levels (like a molecule can).

Occurrence and production

Polonium is a very rare element in nature because of the short half-life of all its isotopes. Sony VAIO VPCF116FGBI Battery

It is found in uranium ores at about 100 micrograms per metric ton (1 part in 1010), which is approximately 0.2% of the abundance of radium. The amounts in the Earth's crust are not harmful. Polonium has been found in tobacco smoke from tobacco leaves grown with phosphatefertilizers.[23][24][25] Sony VAIO VPCF117FJ/W Battery

Synthesis by (n,?) reaction

In 1934 an experiment showed that when natural 209Bi is bombarded with neutrons, 210Bi is created, which then decays to 210Po via ? decay. The final purification is done pyrochemically followed by liquid-liquid extraction techniques.[26] Sony VAIO VPCF117HG/BI Battery

Polonium may now be made in milligram amounts in this procedure which uses high neutron fluxes found in nuclear reactors. Only about 100 grams are produced each year, practically all of it in Russia, making polonium exceedingly rare.[27][28] Sony VAIO VPCF118FJ/W Battery

Synthesis by (p,n) and (p,2n) reactions

It has been found that the longer-lived isotopes of polonium can be formed by proton bombardment of bismuth using a cyclotron. Other more neutron rich isotopes can be formed by the irradiation of platinum with carbon nuclei.[29] Sony VAIO VPCF119FC Battery

Applications

When it is mixed or alloyed with beryllium, polonium can be a neutron source: beryllium releases a neutron upon absorption of an alpha particle that is supplied by210Po. It has been used in this capacity as a neutron trigger or initiator for nuclear weapons.[30]Other uses include the following. Sony VAIO VPCF119FC/BI Battery

Devices that eliminate static charges in textile mills and other places.[31] However, beta particle sources are more commonly used and are less dangerous. A non-radioactive alternative is to use a high-voltage DC power supply to ionise air positively or negatively as required.[32] Sony VAIO VPCF119FJ/BI Battery

• 210Po can be used as an atomic heat source to power radioisotope thermoelectric generators via thermoelectricmaterials.[33]
• Because of its very high toxicity, polonium can be used as a poison (see, for example, Alexander Litvinenko poisoning).

Polonium-containing anti-static brushes are used to remove dust on photographic film.[34] Sony VAIO VPCF11AFJ Battery

Overview

By mass, polonium-210 is around 250,000 times more toxic than hydrogen cyanide (the actual LD50 for 210Po is less than 1 microgram for an average adult (see below) compared with about 250 milligrams for hydrogen cyanide[35]). The main hazard is its intense radioactivity (as an alpha emitter), which makes it very difficult to handle safely: Sony VAIO VPCF11AGJ Battery

one gram of Po will self-heat to a temperature of around 500 °C (932 °F).[4] Even in microgram amounts, handling 210Po is extremely dangerous, requiring specialized equipment (a.o., alpha glove box under depression and equipped with high performance filters), adequate monitoring, and strict handling procedures to avoid any contamination. Sony VAIO VPCF11AHJ Battery

Alpha particles emitted by polonium will damage organic tissue easily if polonium is ingested, inhaled, or absorbed, although they do not penetrate the epidermis and hence are not hazardous as long as the alpha particles remain outside of the body. Meanwhile, bearing chemically resistant and "intact" gloves is a mandatory precautions to avoid transcutaneous diffusion of polonium directly through the skin. Sony VAIO VPCF11JFX/B Battery

Polonium delivered in concentrated nitric acid can easily diffuse through inadequate gloves (e.g., latex gloves) or the acid may damage the gloves.

Acute effects

The median lethal dose (LD50) for acute radiation exposure is generally about 4.5 Sv.[36] The committed effective dose equivalent210Po is 0.51 µSv/Bq if ingested, and 2.5 µSv/Bq if inhaled.[37] Sony VAIO VPCF11M1E Battery

Since 210Po has an activity of 166 TBq per gram (4,500 Ci/g)[37](1 gram produces 166×1012 decays per second), a fatal 4.5 Sv (J/kg) dose can be caused by ingesting 8.8 MBq (238 microcuries, µCi), about 50 nanograms (ng), or inhaling 1.8 MBq (48 µCi), about 10 ng. One gram of 210Po could thus in theory poison 20 million people of whom 10 million would die. Sony VAIO VPCF11M1E/H Battery

The actual toxicity of 210Po is lower than these estimates, because radiation exposure that is spread out over several weeks (the biological half-life of polonium in humans is 30 to 50 days[38]) is somewhat less damaging than an instantaneous dose. It has been estimated that a median lethal dose of 210Po is 0.015 GBq (0.4 mCi), or 0.089 micrograms, still an extremely small amount.[39][40] Sony VAIO VPCF11MFX/B Battery

Long term (chronic) effects

In addition to the acute effects, radiation exposure (both internal and external) carries a long-term risk of death from cancer of 5–10% per Sv.[36] The general population is exposed to small amounts of polonium as a radon daughter in indoor air; Sony VAIO VPCF11S1E Battery

the isotopes 214Po and 218Po are thought to cause the majority[41] of the estimated 15,000-22,000 lung cancer deaths in the US every year that have been attributed to indoor radon.[42] Tobacco smoking causes additional exposure to polonium.[43]

Regulatory exposure limits

The maximum allowable body burden for ingested 210Po is only 1.1 kBq (30 nCi), which is equivalent to a particle massing only 6.8 picograms. Sony VAIO VPCF11S1E/B Battery

The maximum permissible workplace concentration of airborne 210Po is about 10 Bq/m3 (3 × 10?10 µCi/cm3).[44] The target organs for polonium in humans are the spleen and liver.[45] As the spleen (150 g) and the liver (1.3 to 3 kg) are much smaller than the rest of the body, if the polonium is concentrated in these vital organs, it is a greater threat to life than the dose which would be suffered (on average) by the whole body if it were spread evenly throughout the body, in the same way as caesium or tritium (as T2O). Sony VAIO VPCF11Z1E Battery

210Po is widely used in industry, and readily available with little regulation or restriction. In the US, a tracking system run by the Nuclear Regulatory Commission will be implemented in 2007 to register purchases of more than 16 curies (590 GBq) of polonium 210 (enough to make up 5,000 lethal doses). Sony VAIO VPCF11Z1E/BI Battery

The IAEA "is said to be considering tighter regulations... There is talk that it might tighten the polonium reporting requirement by a factor of 10, to 1.6 curies (59 GBq)."[46]

Famous poisoning cases

Notably, the murder of Alexander Litvinenko, a Russian dissident, in 2006 was announced as due to 210Po poisoning[47][48](see Alexander Litvinenko poisoning). Sony VAIO VPCF11ZHJ Battery

According to Prof. Nick Priest of Middlesex University, an environmental toxicologist and radiation expert, speaking on Sky News on December 2, Litvinenko was probably the first person ever to die of the acute ?-radiation effects of 210Po.[49]

It has also been suggested that Irène Joliot-Curie was the first person ever to die from the radiation effects of polonium (due to a single intake) in 1956.[50] Sony VAIO VPCF127HGBI Battery

She was accidentally exposed to polonium in 1946 when a sealed capsule of the element exploded on her laboratory bench. A decade later, on 17 March 1956, she died in Paris from leukemia which may have been caused by that exposure.

According to the book The Bomb in the Basement, several death cases in Israel during 1957-1969 were caused by 210Po.[51] Sony VAIO VPCF137HG/BI Battery

A leak was discovered at a Weizmann Institutelaboratory in 1957. Traces of 210Po were found on the hands of professor Dror Sadeh, a physicist who researched radioactive materials. Medical tests indicated no harm, but the tests did not include bone marrow. Sadeh died from cancer. Sony VAIO VPC-P111KX/B Battery

One of his students died of leukemia, and two colleagues died after a few years, both from cancer. The issue was investigated secretly, and there was never any formal admission that a connection between the leak and the deaths had existed.[52]

Treatment

It has been suggested that chelation agents such as British Anti-Lewisite (dimercaprol) can be used to decontaminate humans.[53]Sony VAIO VPC-P111KX/D Battery

In one experiment, rats were given a fatal dose of 1.45 MBq/kg (8.7 ng/kg) of 210Po; all untreated rats were dead after 44 days, but 90% of the rats treated with the chelation agent HOEtTTC remained alive after 5 months.[54] Sony VAIO VPC-P111KX/G Battery

Commercial products containing polonium

Potentially lethal amounts of polonium are present in anti-static brushes sold to photographers.[55] In USA, the devices with no more than 500 µCi of (sealed) 210Po per unit can be bought in any amount under a "general license",[56] which means that a buyer need not be registered by any authorities. Sony VAIO VPC-P111KX/P Battery

Tiny amounts of such radioisotopes are sometimes used in the laboratory and for teaching purposes—typically of the order of 4–40 kBq (0.1–1.0 µCi), in the form of sealed sources, with the polonium deposited on a substrate or in a resin or polymer matrix—are often exempt from licensing by the NRC and similar authorities as they are not considered hazardous. Sony VAIO VPC-P111KX/W Battery

Small amounts of 210Po are manufactured for sale to the public in the United States as 'needle sources' for laboratory experimentation, and are retailed by scientific supply companies. The actual polonium is a layer of plating which in turn is plated with a material such as gold. Sony VAIO VPC-P112KX/B Battery

This allows the alpha radiation (used in experiments such as cloud chambers) while preventing the polonium from being released and presenting a toxic hazard. According to United Nuclear, they typically sell between four and eight sources per year.[57][58]

Occurrence in humans and the biosphere

The natural occurrence of polonium-210 is widespread in the biosphere, including in human tissues. Sony VAIO VPC-P112KX/D Battery

This is a consequence of a mechanistic chain involving naturalradioactive fallout. Radium-226 in the Earth's crust decays with the production of radon-220, some of which, during its 3.6-day half-life, diffuses into the atmosphere. Here it decays with the production of polonium-210, much of which, during its 138-day half-life, is washed back down to the Earth's surface, thus entering the biosphere.[59][60][61] Sony VAIO VPC-P112KX/G Battery

As early as the 1920s Lacassagne, using polonium provided by his colleague Marie Curie, showed that the element has a very specific pattern of uptake in rabbit tissues, with high concentrations particularly in liver, kidney and testes.[62] More recent evidence suggests that this behaviour results from polonium substituting for sulphur in S-containing amino-acids or related molecules[63][64] Sony VAIO VPC-P112KX/P Battery

and that similar patterns of distribution occur in human tissues.[65] Polonium is indeed an element naturally present in all humans, contributing appreciably to natural background dose, with wide geographical and cultural variations, and particularly high levels in arctic residents, for example.[66] Sony VAIO VPC-P112KX/W Battery

Tobacco

The presence of polonium in tobacco smoke has been known since the early 1960s.[67][68] Some of the world's biggest tobacco firms researched ways to remove the substance—to no avail—over a 40-year period but never published the results.[25] Sony VAIO VPCP113KX/B Battery

Radioactive polonium-210 contained in phosphate fertilizers is absorbed by the roots of plants (such as tobacco) and stored in its tissues.[69][70][71] Tobacco plants fertilized by rock phosphates contain polonium-210, which emits alpha radiation estimated to cause about 11,700 lung cancer deaths annually worldwide. Sony VAIO VPC-P113KX/B Battery

Astatine is a radioactive chemical element with the symbol At and atomic number 85. It occurs on the Earth only as the result of decay of heavier elements, and decays away rapidly, so much less is known about this element than its upper neighbors in the periodic table. Sony VAIO VPCP113KX/D Battery

However, research has shown this element follows periodic trends, being the heaviest known halogen, with melting and boiling points being higher than those of lighter halogens.

Astatine was first produced by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè in the University of California, Berkeley in 1940. Sony VAIO VPC-P113KX/D Battery

Three years later, it was found in nature; however, with an estimated amount of less than 28 grams (1 oz) at given time, astatine is the least abundant element in Earth's crust among non-transuranium elements. Among astatine isotopes, six (with mass numbers 214 to 219) are present in nature, but the most stable astatine-210 is not. Sony VAIO VPCP113KX/G Battery

The second longest-living astatine-211 is the only one to find a commercial use, being useful as an alpha emitter in medicine; however, only extremely small quantities are used, and in larger ones it is very hazardous, as it is intensely radioactive.

Until recently most of the chemical characteristics of astatine were inferred from comparison with other elements; however, important studies have already been done. Sony VAIO VPC-P113KX/G Battery

The main difference between astatine and iodine is that the HAt molecule is chemically a hydride rather than a halide; however, in a fashion similar to the lighter halogens, it is known to form ionic astatides with metals. Bonds to nonmetals result in positive oxidation states, with +1 best portrayed by monohalides and their derivatives, while the higher are characterized by bond to oxygen and carbon. Sony VAIO VPCP113KX/P Battery

Attempts to synthesize astatine fluoride have been met with failure.

General characteristics

Astatine is a highly radioactive element: its isotopes have their half-lives under half a day, decaying into those ofbismuth, polonium, radon, or other astatine isotopes. Among the first 103 elements, only francium and nobelium, the latter of which does not occur in nature, are less stable than astatine.[1] Sony VAIO VPC-P113KX/P Battery

Astatine is a halogen,[2] though it is more metallic than iodine. Research into astatine is limited by the very small quantities available, which is a consequence of its extremely short half-life;[3] however, it has been shown that astatine suits most periodic trends very well. Like other halogens, it is composed of diatomic At2 molecules on standard conditions.[4] Sony VAIO VPCP113KX/W Battery

Its melting and boiling point are estimated about 300 °C (575 °F) and 370 °C (700 °F), respectively. This allows astatine to fit well the trend in increase in melting and boiling points with the atomic number among halogens.[3]

The element is often cited to have the electronegativity of 2.2 (Pauling scale), as this is stated in Pauling's work,[5] Sony VAIO VPC-P113KX/W Battery

lower than that of iodine (2.5 in the original work and 2.66 now[6]) and same as hydrogen; the experiments have shown that the actual astatine electronegativity is slightly below that of hydrogen[7] (see below). It sublimes more readily than iodine, with lower vapor pressure; it also dissolves in water.[3] Sony VAIO VPC-P114KX/B Battery

There are 32 known isotopes of astatine, with atomic masses of of 191 and 193–223.[1] No stable or at least long-lived astatine isotope is known, and no such an isotope is expected to exist.[8]

Alpha decay energy follows the same trend as other heavy elements.[8] Lighter astatine isotopes have quite high energies of alpha decay, which get lower as the nuclei get heavier. Sony VAIO VPC-P114KX/D Battery

But astatine-211, the nucleus with 126 neutrons (126 is a magic number and corresponds to a filled neutron shell) has a significantly higher energy than the previous one. Despite having a similar half-life time with the previous isotope (8.1 hours for 210At and 7.2 hours for 211At), the alpha decay probability is way higher for the latter: 41.81% against only 0.18%.[1][note 2] Sony VAIO VPC-P114KX/G Battery

The two following isotopes release even more energy, with astatine-213 releasing the highest amount of energy of all astatine isotopes. For this reason, it is the shortest-lived astatine isotope.[8] Even though heavier astatine isotopes release less energy, no long-lived astatine isotope exists; this happens due to increasing role of beta decay.[8] Sony VAIO VPC-P114KX/P Battery

This decay mode is especially important for astatine: as early as 1950, it has been postulated that the element has no beta-stable isotopes (i.e. those that do not beta decay at all).[9] The mode has already been found for all astatine isotopes, except for 213At, 214At, 215At, 216mAt, and 217At.[1] Sony VAIO VPC-P114KX/W Battery

The most stable of them is astatine-210, which (as it has been mentioned) has a half-life of 8.1 hours. This isotope's primary decay mode is beta decay to a relatively long-lived (compared to astatine isotopes) alpha emitter, polonium-210. In total, only five isotopes have half-lives exceeding one hour, namely those with mass numbers between 207 and 211. Sony VAIO VPCP115JC Battery

The least stable ground state isotope is astatine-213, with a half-life of 125 ns. It alpha decays to the extremely long-lived (in practice, stable) bismuth-209.[1]

In nature, six astatine isotopes are present: astatine-214 to -219; they decay rapidly by primarily alpha decay, but are rapidly recreated by the decay of heavier elements as well. Sony VAIO VPCP115JC/B Battery

Astatine-215, -217, -218, and -219 are present in the major decay chains,[10]while astatine-214 and -216 (as well as astatine-215) occur as result of decay of natural protactinium.[8]

Astatine has 23 nuclear isomers (nuclei with of one or more nucleons (protons or neutrons) excited. Sony VAIO VPCP115JC/D Battery

A nuclear isomer may also be called a "meta state," which means the system has more internal energy than the "ground state" (the state with the lowest possible internal energy), making the former likely to decay into it, not always one isomer for one isotope. The most stable of them is astatine-202m1, which has a half-life of about 3 minutes; Sony VAIO VPCP115JC/G Battery

this is longer than those of all ground states, except for isotopes with mass numbers 203–211 and 220. The least stable one is astatine-214m1; its half-life of 265 ns is shorter than those of all ground states, except for astatine-213.[1]

In 1869, Dmitri Mendeleev published his periodic table. The space under iodine was empty; Sony VAIO VPCP115JC/P Battery

after Niels Bohr established the physical basis of the classification of chemical elements, it was suggested that there could be the fifth halogen. Before officially recognized discovery, it was called "eka-iodine," from Sanskrit eka, "one," to imply it was one space under iodine (in the same manner as eka-silicon, eka-boron, and others).[11] Scientists tried to find it in nature, which led to erroneous discoveries.[12] Sony VAIO VPCP115JC/W Battery

The first claimed discovery of eka-iodine was made by Fred Allison and associates at the Alabama Polytechnic Institute (now Auburn University) in 1931; the discoverers named element 85 "alabamine" and assigned it the symbol Ab, which were used for a few years.[13][14][15] Sony VAIO VPCP115KG Battery

In 1934, however, H. G. MacPherson of University of California, Berkeleydisproved the effectiveness of Allison's device and the validity of this discovery.[16] This erroneous discovery was followed by another claim in 1937, by the chemist Rajendralal De. Working in Dhaka, British India (now Bangladesh), he chose the name "dakin" for element 85, which he claimed to have isolated as the thorium series equivalent of Radium F (polonium-210) in the radium series. Sony VAIO VPCP116KG Battery

The properties he reported for dakin do not correspond to those of astatine, and its identity is not known.[17]

In 1940, the Swiss chemist Walter Minder announced the discovery of element 85 as the product of the beta decay of Radium A (polonium-218), choosing the name "helvetium" (from Helvetia, "Switzerland").Sony VAIO VPC-P116KX/B Battery

However, Berta Karlik and Traude Bernert were unsuccessful in reproducing his experiments, attributing the results to contamination of his radon stream.[18] (Radon-222 is the parent isotope of polonium-218.) In 1942, Minder, in collaboration with the English scientist Alice Leigh-Smith, announced the discovery of another isotope of element 85, presumed to be the product of Thorium A (polonium-216) beta decay. Sony VAIO VPC-P116KX/D Battery

They named this substance "anglo-helvetium,"[19] but Karlik and Bernert were again unable to reproduce these results.[20]

In 1940, Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè finally isolated the element at the University of California, Berkeley. Sony VAIO VPC-P116KX/G Battery

Instead of searching for the element in nature, the scientists actually created it by bombarding bismuth with alpha particles.[21] The name "astatine" comes from the Greek word ??????? astatos, meaning "unstable," due to the created isotope's propensity for radioactive decay (later, all isotopes of the element were shown to be unstable),[21] and the ending "-ine," found in the names of the four previously discovered halogens. Sony VAIO VPC-P116KX/P Battery

Three years later, astatine was found as a product of natural decay chains by Karlik and Bernert.[22][23] Since then, astatine has been found in three out of the four natural decay chains.[24]

Natural occurrence

Astatine is the rarest naturally occurring element among those that do not belong to the transuranium elements series, with the total amount in Earth's crust estimated to be less than 28 grams (1 oz) at given time.[25] Sony VAIO VPC-P116KX/W Battery

Astatine present at the formation of the Earth has long since decayed; natural astatine at present has formed through the decay of heavier elements. Previously thought to be the rarest element occurring on the Earth, astatine has lost this status to berkelium, atoms of which can be produced by neutron capture reactions and beta decay in very highly concentrated uranium-bearing deposits.[26] Sony VAIO VPCP118JC Battery

Six astatine isotopes occur naturally: these are astatine-214 to -219.[27] Because of their short half-lives, they are found only in traceamounts.[10] Although astatine is found on the Earth, there is no data of astatine occurrence in stars.[28]

Neptunium series, showing the decay products, including astatine-217, formed from neptunium-237. Sony VAIO VPCP118JC/B Battery

Four out of these isotopes (215At, 217At, 218At, and 219At) are found there due to their production in major natural decay chains. The father isotope of astatine-219, francium-223, alpha decays with a probability of only 0.006%, making this astatine isotope extremely rare even compared to other astatine isotopes, although its half-life is the longest of the natural astatine isotopes at 56 seconds.[1] Sony VAIO VPCP118JC/P Battery

This rare isotope decays to polonium-215, which itself beta decays to astatine-215 with an even smaller probability of 0.00023%; for this reason, the Americas to a depth of sixteen kilometers (10 mi) contains only a trillion astatine-215 atoms at given time.[29]Astatine-218 is found in nature as result of polonium-218 beta decay; Sony VAIO VPCP118JC/W Battery

like francium-223 and polonium-215, decay to an astatine isotope is not the primary decay mode.[10] Therefore, most Earth's astatine is astatine-217, whose father (francium-221) decays exclusively to this nuclide; its fathers, grandfathers, so on, decay to exclusively to one exact nuclide, to make only one possible way for the starting nuclide in the neptunium series, neptunium-237, to decay to astatine-217.[10] Sony VAIO VPC-P118KX/B Battery

The other remaining isotopes (214At and 216At, as well as 215At) are found as the result of triple alpha decay of the naturally present protactinium isotopes: 226Pa, 227Pa, and 228Pa.[27] These, however, are extremely rare, so they are often even not cited as natural astatine isotopes.[3][30]

Chemical reactivity and compounds

Astatine is the least reactive of the halogens, being less reactive than iodine;[31] Sony VAIO VPC-P118KX/D Battery

however, multiple compounds of astatine have been synthesized in microscopic amounts and studied as intensively as possible before their inevitable radioactive disintegration. The reactions are normally tested with dilute solutions of astatine mixed with larger amounts of iodine. The iodine acts as a carrier, ensuring that there is sufficient material for laboratory techniques such as filtration and precipitation to work.[20][32] Sony VAIO VPC-P118KX/G Battery

The most common compound of the element is hydrogen astatide.[3] The hydrogen astatide molecule has been calculated to have a dipole moment of 0.06 debyes, with hydrogen carrying the partial negative charge. Because astatine has a lower electronegativity when compared to hydrogen (unlike the other halogens), the molecule should more properly be called astatine monohydride;[7]Sony VAIO VPC-P118KX/P Battery

this reversal of polarity partially explains its lower stability compared to the other hydrogen halides. As it is easily oxidized, it is precipitated in aqueous nitric acid/silver(I) solution, forming silver(I) astatide, AgAt.[3]

Astatine is known to react with its lighter homologues iodine, bromine, and chlorine in the vapor state; Sony VAIO VPC-P118KX/W Battery

this reaction produces diatomic interhalogen compounds, with formulas AtI, AtBr, and AtCl.[2] The first two compounds may also be produced in water: astatine reacts with iodine/iodide solution to form AtI, whereas AtBr requires, aside from astatine, a iodine/iodine monobromide/bromide solution. Sony VAIO VPCP119JC Battery

The excess of iodides or bromides may lead to AtBr?
2 and AtI?
2 ions;[2] in a chloride solution, they may turn to species like AtCl?
2 or AtBrCl? via equilibrium.[33] No report of gas phase AtCl preparation has been shown, but oxidation of the element with dichromate (in nitric acid solution) showed that adding chloride turned the astatine into a molecule, either AtCl or AtOCl; Sony VAIO VPCP119JC/BI Battery

similarly, AtOCl?
2 or AtCl?
2 may be produced.[2] In a plasma ion source mass spectrometer, similar ions [AtI]+, [AtBr]+, and [AtCl]+ have been formed by introducing vapors of the lighter halogens to the helium-filled camera where astatine is situated, supporting the existence of stable neutral molecules in the plasma ion state.[2] Sony VAIO VPCP11S1E/B Battery

No astatine fluoride has not been discovered yet, and although its synthesis is thought to be possible, it may require a liquid halogen fluoride solvent; this has already been used for characterization of radon fluorides.[2]

The lower oxidation states are the starting point for astatine–oxygen bonds:[note 3] Sony VAIO VPC-P11S1E/B Battery

treating them with an oxygen-containing oxidizer leads to the formation of astatate ions, AtO?
3.[35] Further oxidation, e.g., by hypochlorite or electrochemical oxidation, was originally thought to form unstable astatine(VII), either as perastatic acid H5AtO6 (analogous to periodic acid) or perastatate AtO?
4;[3] however, this has never been confirmed.[36] Sony VAIO VPCP11S1E/D Battery

The intermediate states coprecipitate with several silver(I), thallium(I) or caesium oxysalts to form cationic astatine.[35] Astatine may also replace a hydrogen atom in benzene to form C6H5At, which may be oxidized to C6H5AtCl2 by chlorine; by treating this compound in an alkaline solution of hypochlorite, C6H5AtO2 may be produced.[35] Sony VAIO VPC-P11S1E/D Battery

Astatine may form bonds to the other chalcogens, such as S7At+ and At(CSN)?
2 with sulfur, a coordination selenocarbamide compound with selenium, and astatine–tellurium colloid with tellurium.[37]Additionally, astatine is known to bind to nitrogen,[38] lead,[39] and boron.[40] Sony VAIO VPCP11S1E/G Battery

Production

Astatine was first produced by bombarding bismuth with energetic alpha particles; this is still the major route used to create the relatively long-lived isotopes astatine-209 through -211. Astatine is only produced in microscopic quantities, with modern techniques allowing production runs of 2 terabecquerel (about 25 ?g).[42] Sony VAIO VPC-P11S1E/G Battery

The most important isotope is now astatine-211, being the only one to find a commercial use.[43] To produce the bismuth target, the metal is sputtered on a gold, copper, or aluminum surface, to form a 50–100 milligrams per centimeter squared bismuth layer (or, alternatively, bismuth oxide is pressed into a copper plate).[44] Sony VAIO VPCP11S1E/P Battery

The target is kept under a chemically neutral nitrogenatmosphere[45] and is cooled with water to prevent the premature astatine vaporization.[44] In a particle accelerator,[46] such as a cyclotron, alpha particles are collided with bismuth. Even though bismuth is composed of only one isotope, bismuth-209, the reaction may occur in three possible ways, producing astatine-209, -210, and -211. Sony VAIO VPCP11S1E/W Battery

In order to eliminate the undesired nuclides, the maximum energy of the reaction is set to 28 MeV. The produced astatine is then easily separated, as astatine sets itself free and a stream of the element is collected as a deposit on a glass cold finger.[45]

Separation

The freshly formed astatine is separated either chemically or via distillation.[47] Sony VAIO VPC-P11S1E/W Battery

Astatine is very volatile, even though less than iodine (in acidic solutions).[note 4] Out of such solutions, the iron(II) sulfate/sulfuric acid solution seems the most promising: it may provide the distillation of 90% of the element (85% of the solution distilled).[49]

If dry distillation is used, the element (after its formation) must be separated from the target and the traces of other radioisotopes.Sony VAIO VPCP11Z9E/B Battery

The target is heated to 300–600 °C (575–1100 °F). The freshly vaporized astatine (in form of a stream) is collected as a deposit on a glass cold finger.[49] To eliminate the polonium content in astatine, it is re-distilled.

However, astatine is thought to react with bismuth to form non-volatile compounds. Sony VAIO VPCS111FM/S Battery

This is likely to cause the low astatine outcome (up to 15%).[49]. If the temperature is raised to 700–800 °C (1275–1450 °F), 80% of astatine may be distilled, which may be explained by suggesting that the non-volatile astatine compounds decompose; however, bismuth begins to vaporize as well. Mixing the methods, up to 30% of astatine may result.[49] Sony VAIO VPCS115EC Battery

Chemical routes

Astatine may be extracted from acidic aqueous solutions using organic solvents. The distribution factor varies on the solvent: the highest one is 200, found in 0.01 M nitric acid/benzene system (the second highest is 91, in 0.01 M nitric acid/tetrachloromethane system).[50] Sony VAIO VPCS115FG Battery

In general, it is similar to iodine in that it dissolves in benzene, carbon disulfide, and tetrachloromethane (therefore, they have high distribution factors in systems with water), but, unlike iodine, it cannot be extracted from alkaline solutions of organic solvents, as it reacts with bases and disproportionates.[3] Sony VAIO VPCS117GG Battery

Diatomic interhalogen molecules (with iodine and bromine) have smaller distribution factors than dihalogens (where both atoms are the same), as the former are dipoles.[50] Separation from other elements is done via extraction from hydrochloric acid/isopropyl ether solutions. Iron(III) hydroxide may be used to remove the further traces. Using 8 M HCl solutions, outcome may be as high as 90%.[50] Sony VAIO VPCS117GGB Battery

When astatine is introduced into negatively charged chloro complexes and dissolved in chloride or hydrogen chloride (at best at 5–8 M, because the complex decomposes on a lower chloride concentration), such a complex can be sorbed on a cation resin; the same is true for the astatine cation.[51] Sony VAIO VPCS118EC Battery

Such astatine is originally inserted into tellurium, which is (together with polonium impurity) later washer away with hydrochloric acid/chlorine solution. Astatine is later desorbed via chloric water. The cation resin is processed with nitric acid solution (with a small dichromate content), and the solution is introduced to it, and later to nitric acid solution (to remove the chloride ions). Thereafter, astatine is desorbed with nitric acid/dichromate solution.[52] Sony VAIO VPCS119FJ/B Battery

Astatine partially coprecipitates from weakly acidic solutions with several hydroxides, silver(I) and thallium(I) iodides, several sulfides of heavy metals, silver metal, and tellurium. This is likely to be caused by adsorbation on the surface of the precipitate.[53] The adsorbation is suppressed by increasing the acidity of the solution, washing off the precipitate with acetone, or adding iodine; the latter proves the adsorbation character of the astatine coprecipitation.[53] Sony VAIO VPCS119GC Battery

The most important such a reaction is the one with tellurium, which is catalyzed by reducers like tin dichloride; however, the reaction does not occur in alkaline solutions. The amount of astatine precipitated does not rely on tellurium amount, reaching 90% in concentrated HCl (this reaction also eliminates different impurities).[53]Astatide and astatate have been shown to coprecipitate with iodide and iodate; Sony VAIO VPCS11AFJ Battery

they, however, cannot be washed off with acetone.[54] These methods are used most typically only when astatine is the result of a different, way rarer reaction of bismuth, lead, or thorium with high-energy protons.[54] Since such reactions produces hundreds less times astatine than the one involving bismuth and alpha particles. Therefore, the method used of separation should be effective; this one has proved to be so.[54] Sony VAIO VPCS11AGJ Battery

Uses and precautions

The newly formed astatine-211 is important in prostate cancer treatment. Once produced, astatine should be used quickly, as astatine-211 decays with a half-life of 7.2 hours; this, however, is long enough to permit multi-step labeling strategies. Sony VAIO VPCS11AHJ Battery

Astatine-211 can be used for targeted alpha particle radiotherapy, since it decays either via alpha decay to bismuth-207, or via electronic capture to an extremely short-lived nuclide of polonium-211, which itself alpha decays.[55] A selection of astatine-containing organic compounds and their medical applications can be seen in the table below: Sony VAIO VPCS11AVJ Battery

Similarly to iodine, astatine is collected by the thyroid gland, even though to a lesser extent; however, it concentrates in the liver if released to the body if the form of a radiocolloid.[44] The principled behavior difference between astatine-211 and iodine-131 (a radioactive iodine isotope, also used in medicine) is that astatine does not destroy the neighboring parathyroid gland, as it does not emit beta particles: Sony VAIO VPCS11J7E/B Battery

an average alpha particle released by astatine-211 runs about 70 µm, while a beta particle emitted by iodine-131 runs about 2 mm.[44] Thanks to its short half-life and small particle run, it is preferable to be used in diagnosis of diseases (compared to iodine-131).[44] However, it attacks the thyroid gland much stronger, and the repetative injection of the nuclide caused tissue destruction in the gland, followed by dysplasia in rats and monkeys. Sony VAIO VPCS11M1E/W Battery

When lethal quantities are added, morphological changes in other tissues are not found, with the possible exception of the breasts.

Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas, occurring naturally as the decay product of uranium or thorium. Sony VAIO VPCS11V9E Battery

Its most stable isotope, 222Rn, has a half-life of 3.8 days. Radon is one of the densest substances that remains a gas under normal conditions and is considered a health hazard due to its radioactivity. Intense radioactivity also hindered chemical studies of radon and only a few compounds are known. Sony VAIO VPCS11V9E/B Battery

Sony VAIO VPCS11X9E/B Battery

Radon is formed as part of the normal radioactive decay chain of uranium and thorium. Uranium and thorium have been around since the earth was formed and their most common isotope has a very long half-life (4.5 billion years). Uranium and thorium,radium, and thus radon, will continue to occur for millions of years at about the same concentrations as they do now.[1] Sony VAIO VPCS123FGB Battery

As the radioactive gas of radon decays, it produces new radioactive elements called radon daughters or decay products. Radon daughters are solids and stick to surfaces such as dust particles in the air. If contaminated dust is inhaled, these particles can stick to the airways of the lung and increase the risk of developing lung cancer.[2] Sony VAIO VPCS125EC Battery

Radon is responsible for the majority of the public exposure to ionizing radiation. It is often the single largest contributor to an individual's background radiation dose, and is the most variable from location to location. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as attics and basements. It can also be found in some spring waters and hot springs.[3] Sony VAIO VPCS128EC Battery

Epidemiological studies have shown a clear link between breathing high concentrations of radon and incidence of lung cancer. Thus, radon is considered a significant contaminant that affects indoor air quality worldwide. According to the United States Environmental Protection Agency, radon is the second most frequent cause of lung cancer, after cigarette smoking, causing 21,000 lung cancer deaths per year in the United States. Sony VAIO VPCS129GC Battery

About 2,900 of these deaths occur among people who have never smoked. While radon is the second most frequent cause of lung cancer, it is the number one cause among non-smokers, according to EPA estimates. [4]

Physical properties

Radon is a colorless and odorless gas, and therefore not detectable by human senses alone. Sony VAIO VPCS12C7E/B Battery

At standard temperature and pressure, radon forms a monatomic gas with a density of 9.73 kg/m3,[5] about 8 times the density of the Earth's atmosphere at sea level, 1.217 kg/m3.[6] Radon is one of the heaviest gases at room temperature and is the heaviest of the noble gases. Although colorless at standard temperature and pressure, when cooled below its freezing point of 202 K (?71 °C; ?96 °F), Sony VAIO VPCS12L9E/B Battery

radon has a brilliant phosphorescence which turns from yellow to orange-red as the temperature is lowered.[7] Uponcondensation, radon glows because of the intense radiation it produces.[8]

Chemical properties

Being a noble gas, radon is chemically not very reactive. However, the 3.8 day half-life of radon-222 makes it useful in physical sciences as a natural tracer. Sony VAIO VPCS12V9E/B Battery

Radon is a member of the zero-valence elements that are called noble gases. It is inert to most common chemical reactions, such as combustion, because the outer valence shellcontains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound.[9] 1037 kJ/mol is required to extract one electron from its shells (also known as the first ionization energy).[10] Sony VAIO VPCW111XX/P Battery

However, in accordance with periodic trends, radon has a lower electronegativity than the element one period before it, xenon, and is therefore more reactive. Radon is sparingly soluble in water, but more soluble than lighter noble gases. Radon is appreciably more soluble in organic liquids than in water. Sony VAIO VPCW111XX/PC Battery

Early studies concluded that the stability of radon hydrateshould be of the same order as that of the hydrates of chlorine (Cl2) or sulfur dioxide (SO2), and significantly higher than the stability of the hydrate of hydrogen sulfide (H2S).[11]

Because of its cost and radioactivity, experimental chemical research is seldom performed with radon, and as a result there are very few reported compounds of radon, Sony VAIO VPCW111XX/T Battery

all eitherfluorides or oxides. Radon can be oxidized by a few powerful oxidizing agents such asfluorine, thus forming radon fluoride.[12][13] It decomposes back to elements at a temperature of above 250 °C. It has a low volatility and was thought to be RnF2. But because of the short half-life of radon and the radioactivity of its compounds, it has not been possible to study the compound in any detail. Sony VAIO VPCW111XX/W Battery

Theoretical studies on this molecule predict that it should have a Rn-Fbond distance of 2.08 ?, and that the compound is thermodynamically more stable and less volatile than its lighter counterpart XeF2.[14]The octahedral molecule RnF6 was predicted to have an even lower enthalpy of formation than the difluoride.[15] The [RnF]+ ion is believed to form by the reaction:[16] Sony VAIO VPCW111XXP Battery

Rn (g) + 2 [O2]+[SbF6]? (s) ? [RnF]+[Sb2F11]? (s) + 2 O2 (g)

Radon oxides are among the few other reported compounds of radon.[17] Radon carbonyl RnCO has been predicted to be stable and to have a linear molecular geometry.[18] The molecules Rn2 and RnXe were found to be significantly stabilized by spin-orbit coupling.[19] Radon caged inside a fullerene has been proposed as a drug for tumors.[20] Sony VAIO VPCW111XXT Battery

Radon has no stable isotopes. However, 36 radioactive isotopes have been characterized, with their atomic masses ranging from 193 to 228.[21] The most stable isotope is 222Rn, which is a decay product of 226Ra, a decay product of 238U.[22] Among the daughters of 222Rn is also the highly unstable isotope 218Rn. Sony VAIO VPCW111XXW Battery

There are three other radon isotopes that have a half-life of over an hour: 211Rn, 210Rn and 224Rn. The 220Rn isotope is a natural decay product of the most stable thorium isotope (232Th), and is commonly referred to as thoron. It has a half-life of 55.6 seconds and also emits alpha radiation. Sony VAIO VPCW115XG Battery

Similarly, 219Rn is derived from the most stable isotope of actinium (227Ac)—named "actinon"—and is an alpha emitter with a half-life of 3.96 seconds.[21] No radon isotopes significantly occur in the neptunium(237Np) decay series. Sony VAIO VPCW115XGP Battery

Progenies

222Rn belongs to the radium and uranium-238 decay chain, and has a half-life of 3.8235 days. Its four first products (excluding marginal decay schemes) are very short-lived, meaning that the corresponding disintegrations are indicative of the initial radon distribution. Its decay goes through the following sequence:[21] Sony VAIO VPCW115XW/P Battery

• 222Rn, 3.8 days, alpha decaying to...
• 218Po, 3.10 minutes, alpha decaying to...
• 214Pb, 26.8 minutes, beta decaying to...
• 214Bi, 19.9 minutes, beta decaying to...
• 214Po, 0.1643 ms, alpha decaying to...

At the next step, 214Po decays to 210Pb, which has a much longer half-life of 22.3 years. Its progenies are: Sony VAIO VPCW115XW/T Battery

• 210Bi, 5.013 days, beta decaying to...
• 210Po, 138.376 days, alpha decaying to...
• 206Pb, stable.

The radon equilibrium factor[23] is the ratio between the activity of all short-period radon progenies (which are responsible for most of radon's biological effects), and the activity that would be at equilibrium with the radon parent. Sony VAIO VPCW115XW/W Battery

If a closed volume is constantly supplied with radon, the concentration of short-lived isotopes will increase until an equilibrium is reached where the rate of decay of each decay product will equal that of the radon itself. The equilibrium factor is 1 when both activities are equal, meaning that the decay products have stayed close to the radon parent long enough for the equilibrium to be reached, within a couple of hours. Sony VAIO VPCW117XC/P Battery

Under these conditions each additional pCi/L of radon will increase exposure, by 0.01 WL (see explanation of WL below). These conditions are not always met: in many homes, the equilibrium fraction is typically 40%; that is, there will be 0.004 WL of progeny for each pCi/L of radon in air.[24] 210Pb takes much longer (decades) to come in equilibrium with radon, but, if the environment permits accumulation of dust over extended periods of time, 210lead and its decay products may contribute to overall radiation levels as well. Sony VAIO VPCW117XC/T Battery

Because of their electrostatic charge, radon progenies adhere to surfaces or dust particles, whereas gaseous radon does not. Attachment removes them from the air, usually causing the equilibrium factor in the atmosphere to be less than one. The equilibrium factor is also lowered by air circulation or air filtration devices, and is increased by airborne dust particles, including cigarette smoke. Sony VAIO VPCW117XC/W Battery

In high concentrations, airborne radon isotopes contribute significantly to human health risk. The equilibrium factor found in epidemiological studies is 0.4.[25]

History and etymology

Radon was the fifth radioactive element to be discovered, in 1900 by Friedrich Ernst Dorn, after uranium, thorium, radium and polonium.[26][27][28] Sony VAIO VPCW119XJ Battery

In 1900 Dorn reported some experiments in which he noticed that radium compounds emanate a radioactive gas which he named Radium Emanation (Ra Em).[29] Before that, in 1899, Pierre and Marie Curie observed that the "gas" emitted by radium remained radioactive for a month.[30] Later that year, Robert B. Owens and Ernest Rutherford, Sony VAIO VPCW119XJ/P Battery

at McGill Universityin Montreal, noticed variations when trying to measure radiation from thorium oxide.[31] Rutherford noticed that the compounds of thorium continuously emit a radioactive gas which retain the radioactive powers for several minutes and called this gas "emanation" (from Latin "emanare"—to elapse and "emanatio"—expiration),[32] and later Thorium Emanation (Th Em).Sony VAIO VPCW119XJ/W Battery

In 1901, he demonstrated that the emanations are radioactive, but credited the Curies for the discovery of the element.[33] In 1903, similar emanations were observed from actinium by André-Louis Debierne[34][35] and were called Actinium Emanation (Ac Em).

Several names were suggested for these three gases: exradio, exthorio, and exactinio in 1904;[36] radon, thoron, and akton in 1918;[Sony VAIO VPCW11AXJ Battery

37]radeon, thoreon, and actineon in 1919,[38] and eventually radon, thoron, and actinon in 1920.[39] The likeness of the spectra of these three gases with those of argon, krypton, and xenon, and their observed chemical inertia led Sir William Ramsay to suggest in 1904 that the "emanations" might contain a new element of the noble gas family.[36] Sony VAIO VPCW11S1E/P Battery

In 1910, Sir William Ramsay and Robert Whytlaw-Gray isolated radon, determined its density, and determined that it was the heaviest known gas.[40] They wrote that "L'expression de l'émanation du radium est fort incommode," (the expression of radium emanation is very awkward) and suggested the new name niton (Nt) Sony VAIO VPCW11S1E/T Battery

(from the Latin "nitens" meaning "shining") in order to emphasize the property of gases that cause the phosphorescence of some substances,[40] and in 1912 it was accepted by the International Commission for Atomic Weights. In 1923, the International Committee for Chemical Elements and International Union of Pure and Applied Chemistry (IUPAC) chose among the names radon (Rn), thoron (Tn), and actinon (An). Sony VAIO VPCW11S1E/W Battery

Later, when isotopes were numbered instead of named, the element took the name of the most stable isotope, radon, while Tn was renamed 220Rn and An was renamed 219Rn. As late as the 1960s, the element was also referred to simply as emanation.[41] The first synthesized compound of radon, radon fluoride, was obtained in 1962.[42] Sony VAIO VPCW121AX Battery

The danger of high exposure to radon in mines, where exposures reaching 1,000,000 Bq/m3 can be found, has long been known. In 1530,Paracelsus described a wasting disease of miners, the mala metallorum, and Georg Agricola recommended ventilation in mines to avoid this mountain sickness (Bergsucht).[43][44] In 1879, this condition was identified as lung cancer by Herting and Hesse in their investigation of miners from Schneeberg, Germany. Sony VAIO VPCW126AG Battery

The first major studies with radon and health occurred in the context of uranium mining in theJoachimsthal region of Bohemia.[45]In the US, studies and mitigation only followed decades of health effects on uranium miners of theSouthwestern United States employed during the early Cold War; standards were not implemented until 1971.[46] Sony VAIO VPCW127JC/P Battery

The presence of radon in indoor air was documented as early as 1950. Beginning in the 1970’s research was initiated to address sources of indoor radon, determinants of concentration, health effects, and approaches to mitigation. In the United States, the problem of indoor radon received widespread publicity and intensified investigation after a widely publicized incident in 1984. Sony VAIO VPCW127JC/T Battery

During routine monitoring at a Pennsylvania nuclear power plant, a worker was found to be contaminated with radioactivity. A high contamination of radon in his home was subsequently identified as responsible for the contamination.[47]

Concentration units

All discussions of radon concentrations in the environment refer to 222Rn. Sony VAIO VPCW127JC/W Battery

While the average rate of production of220Rn (from the thorium decay series) is about the same as 222Rn, the amount of 220Rn in the environment is much less than that of 222Rn because of the short half-life of 220Rn (1 minute versus 4 days).[1]

Radon concentration is usually measured in the atmosphere, in becquerel per cubic meter (Bq/m3), the SI derived unit. Sony VAIO VPCW127JC/WZ Battery

Typical domestic exposures are about 100 Bq/m3 indoors, and 10–20 Bq/m3 outdoors.[citation needed]

It is often measured in picocuries per liter (pCi/L) in the USA, with 1 pCi/L=37 Bq/m3.[24]

In the mining industry, the exposition is traditionally measured in working level (WL), and the cumulative exposition in working level month (WLM): Sony VAIO VPCW12AAJ Battery

1 WL equals any combination of short-lived 222Rn progeny (218Po, 214Pb, 214Bi, and 214Po) in 1 liter of air that releases 1.3 × 105MeV of potential alpha energy;[24] one WL is equivalent to 2.08 × 10?5joules per cubic meter of air (J/m3).[1] The SI unit of cumulative exposure is expressed in joule-hours per cubic meter (J·h/m3). One WLM is equivalent to 3.6 × 10?3 J·h/m3. Sony VAIO VPCW12AKJ Battery

An exposure to 1 WL for 1 working month (170 hours) equals 1 WLM cumulative exposure.[citation needed]

A cumulative exposition of 1 WLM is roughly equivalent to living one year in an atmosphere with a radon concentration of 230 Bq/m3.[49]

Radon (222Rn), when released into the air, decays to 210Pb and other radioisotopes, the levels of 210Pb can be measured. The rate of deposition of this radioisotope is weather dependent. Sony VAIO VPCW12AVJ Battery

Radon concentrations found in natural environments are much too low to be detected by chemical means. A 1000 Bq/m3 (relatively high) concentration corresponds to 0.17 picogram per cubic meter. The average concentration of radon in the atmosphere is about 6×10?20 atoms of radon for each molecule in the air, or about 150 atoms in each ml of air.[50] Sony VAIO VPCW12S1E/P Battery

The radon activity of the Earth atmosphere originates from some tens of grams of radon, consistently replaced by decay of larger amounts of radium and uranium.[51]

Natural

Radon is produced by the radioactive decay of radium-226, which is found in uranium ores; phosphate rock; shales; metamorphic minerals such as granite, gneiss, and schist; Sony VAIO VPCW12S1E/T Battery

and, to a lesser degree, in common minerals such as limestone.[52] Every square mile of surface soil, to a depth of 6 inches (2.6 km2to a depth of 15 cm), contains approximately 1 gram of radium, which releases radon in small amounts to the atmosphere[1] On a global scale, it is estimated that 2,400 million curies (90 TBq) of radon are released from soil annually.[53] Sony VAIO VPCW12S1E/W Battery

Radon concentration varies widely from place to place. In the open air, it ranges from 1 to 100 Bq/m3, even less (0.1 Bq/m3) above the ocean. In caves or aerated mines, or ill-aerated houses, its concentration climbs to 20–2,000 Bq/m3.[54] Radon concentration can be much higher in mining contexts. Ventilation regulations instruct to maintain radon concentration in uranium mines under the "working level", Sony VAIO VPCW213AG/L Battery

with 95th percentile levels ranging up to nearly 3 WL (546 pCi 222Rn per liter of air; 20.2 kBq/m3, measured from 1976 to 1985).[1]The concentration in the air at the (unventilated) Gastein Healing Gallery averages 43 kBq/m3 (1.2 nCi/L) with maximal value of 160 kBq/m3 (4.3 nCi/L).[55] Sony VAIO VPCW213AG/P Battery

Radon mostly appears with the decay chain of the radium and uranium series (222Rn), and marginally with the thorium series (220Rn). The element emanates naturally from the ground, and some building materials, all over the world, wherever traces of uranium orthorium can be found, and particularly in regions with soils containing granite or shale, which have a higher concentration of uranium. Sony VAIO VPCW213AG/T Battery

However, not all granitic regions are prone to high emissions of radon. Being a rare gas, it usually migrates freely through faults and fragmented soils, and may accumulate in caves or water. Owing to its very short half-life (four days for 222Rn), radon concentration decreases very quickly when the distance from the production area increases. Radon concentration varies greatly with season and atmospheric conditions. Sony VAIO VPCW213AG/W Battery

For instance, it has been shown to accumulate in the air if there is a meteorological inversion and little wind.[56]

High concentrations of radon can be found in some spring waters and hot springs.[57] The towns of Boulder, Montana; Misasa; Bad Kreuznach, Germany; and the country of Japan have radium-rich springs which emit radon. Sony VAIO VPCW215AG/L Battery

To be classified as a radon mineral water, radon concentration must be above a minimum of 2 nCi/L (74 kBq/m3).[58] The activity of radon mineral water reaches 2,000 kBq/m3 in Merano and 4,000 kBq/m3 in Lurisia (Italy).[55]

Natural radon concentrations in Earth's atmosphere are so low that radon-rich water in contact with the atmosphere will continually lose radon by volatilization. Sony VAIO VPCW217JC Battery

Hence, ground water has a higher concentration of 222Rn than surface water, because radon is continuously produced by radioactive decay of 226Ra present in rocks. Likewise, the saturated zone of a soil frequently has a higher radon content than the unsaturated zone because of diffusional losses to the atmosphere.[59][60] Sony VAIO VPCW217JC/L Battery

In 1971, Apollo 15 passed 110 km (68 mi) above the Aristarchus plateau on the Moon, and detected a significant rise in alpha particles thought to be caused by the decay of 222Rn. The presence of 222Rn has been inferred later from data obtained from the Lunar Prospector alpha particle spectrometer.[61] Sony VAIO VPCW217JC/P Battery

Radon is found in some petroleum. Because radon has a similar pressure and temperature curve to propane, and oil refineriesseparate petrochemicals based on their boiling points, the piping carrying freshly separated propane in oil refineries can become radioactive because of decaying radon and its products.[62] Sony VAIO VPCW217JC/T Battery

Residues from the petroleum and natural gas industry often contain radium and its daughters. The sulfate scale from an oil well can be radium rich, while the water, oil, and gas from a well often contains radon. Radon decays to form solid radioisotopes which form coatings on the inside of pipework. [62] Sony VAIO VPCW217JC/W Battery

Accumulation in houses

The phenomenon of heightened radon contamination in homes was discovered by chance in 1985 after the stringent radiation testing conducted at a nuclear power plant entrance revealed that Stanley Watras, an engineer entering the plant, was contaminated by radioactive substances.[63] Sony VAIO VPCW218JC Battery

Typical domestic exposures are of approximately 100 Bq/m3indoors. Depending on how houses are built and ventilated, radon may accumulate in basements and dwellings. Radon can also seep into an indoor environment through cracks in solid floors, construction joints, cracks in walls, gaps in suspended floors, gaps around service pipes, cavities inside walls, and the water supply.[64] Sony VAIO VPCW218JC/L Battery

Radon concentrations in the same location may differ by a factor of two over a period of 1 hour. Also, the concentration in one room of a building may be significantly different than the concentration in an adjoining room.[1]

The distribution of radon concentrations tends to be asymmetrical around the average, the larger concentrations have a disproportionately greater weight. Sony VAIO VPCW218JC/P Battery

Indoor radon concentration is usually assumed to follow a lognormal distribution on a given territory.[65] Thus, the geometric mean is generally used for estimating the "average" radon concentration in an area.[66] The mean concentration ranges from less than 10 Bq/m3 to over 100 Bq/m3 in some European countries.[67] Sony VAIO VPCW218JC/T Battery

Typical geometric standard deviations found in studies range between 2 and 3, meaning (given the 68-95-99.7 rule) that the radon concentration is expected to be more than a hundred times the mean concentration for 2 to 3% of the cases.

The highest average radon concentrations in the United States are found in Iowa and in the Appalachian Mountain areas in southeastern Pennsylvania.[68] Sony VAIO VPCW218JC/W Battery

Some of the highest readings ever have been recorded in the Irish town of Mallow, County Cork, prompting local fears regarding lung cancer. Iowa has the highest average radon concentrations in the United States due to significant glaciation that ground the granitic rocks from the Canadian Shield and deposited it as soils making up the rich Iowa farmland.[69] Sony VAIO VPCW219AJ/L Battery

Many cities within the state, such as Iowa City, have passed requirements for radon-resistant construction in new homes. In a few locations,uranium tailings have been used for landfills and were subsequently built on, resulting in possible increased exposure to radon.[1]

Industrial production

Radon is obtained as a by-product of uraniferous ores processing after transferring into 1% solutions of hydrochloricor hydrobromic acids. Sony VAIO VPCW219AJ/P Battery

The gas mixture extracted from the solutions contains H2, O2, He, Rn, CO2, H2O and hydrocarbons. The mixture is purified by passing it over copper at 720 °C to remove the H2 and the O2, and then KOH and P2O5 are used to remove the acids and moisture by sorption. Radon is condensed by liquid nitrogen and purified from residue gases by sublimation.[70] Sony VAIO VPCW219AJ/W Battery

Radon commercialization is regulated, but it is available in small quantities for the calibration of 222Rn measurement systems, at a price of almost $6,000 per milliliter of radium solution (which only contains about 15 picograms of actual radon at a given moment).[71] Radon is produced by a solution of radium-226 (half-life of 1600 years). Sony VAIO VPCW21AAJ Battery

Radium-226 decays by alpha-particle emission, producing radon which collects over samples of radium-226 at a rate of about 1 mm3/day per gram of radium; equilibrium is quickly achieved and radon is produced in a steady flow, with an activity equal to that of the radium (50 Bq). Gaseous 222Rn (half-life of about four days) escapes from the capsule through diffusion.[72] Sony VAIO VPCW21AKJ Battery

An early-20th-century form of quackery was the treatment of maladies in a radiotorium.[73] It was a small, sealed room for patients to be exposed to radon for its "medicinal effects". The carcinogenic nature of radon due to its ionizing radiation became apparent later on. Radon's molecule-damaging radioactivity has been used to kill cancerous cells.[74] Sony VAIO VPCW21AVJ Battery

It does not, however, increase the health of healthy cells. In fact, the ionizing radiation causes the formation of free radicals, which results in genetic and other cell damage, resulting in increased rates of illness, including cancer.

Exposure to radon, a process known as radiation hormesis, has been suggested to mitigate auto-immune diseases such asarthritis.[75][76] Sony VAIO VPCY115FGS Battery

As a result, in the late 20th century and early 21st century, some "health mines" were established in Basin, Montana which attracted people seeking relief from health problems such as arthritis through limited exposure to radioactive mine water and radon. However, the practice is discouraged because of the well-documented ill effects of high-doses of radiation on the body.[77] Sony VAIO VPCY115FX/BI Battery

Radioactive water baths have been applied since 1906 in Jáchymov, Czech Republic, but even before radon discovery they were used in Bad Gastein, Austria. Radium-rich springs are also used in traditional Japanese onsen in Misasa, Tottori Prefecture. Drinking therapy is applied in Bad Brambach, Germany. Inhalation therapy is carried out in Gasteiner-Heilstollen, Sony VAIO VPCY115FXBI Battery

Austria, in ?wieradów-Zdrój, Czerniawa-Zdrój, Kowary, L?dek Zdrój, Poland, in Harghita B?i, Romania, and in Boulder, United States. In the United States and Europe there are several "radon spas," where people sit for minutes or hours in a high-radon atmosphere in the belief that low doses of radiation will invigorate or energize them.[76][78] Sony VAIO VPCY118EC Battery

Radon has been produced commercially for use in radiation therapy, but for the most part has been replaced by radionuclides made in accelerators and nuclear reactors. Radon has been used in implantable seeds, made of gold or glass, primarily used to treat cancers. The gold seeds were produced by filling a long tube with radon pumped from a radium source, the tube being then divided into short sections by crimping and cutting. Sony VAIO VPCY118GX/BI Battery

The gold layer keeps the radon within, and filters out the alpha and beta radiations, while allowing the gamma rays to escape (which kill the diseased tissue). The activities might range from 0.05 to 5 millicuries per seed (2 to 200 MBq).[74] The gamma rays are produced by radon and the first short-lived elements of its decay chain (218Po, 214Pb, 214Bi, 214Po). Sony VAIO VPCY119FJ/S Battery

Radon and its first decay products being very short-lived, the seed is left in place. After 12 half-lives (43 days), radon radioactivity is at 1/2000 of its original level. At this stage, the predominant residual activity originates from the radon decay product 210Pb, whose half-life (22.3 years) is 2000 times that or radon (and whose activity is thus 1/2000 of radon's), and its descendants 210Bi and 210Po, totalizing 0.03% of the initial seed activity. Sony VAIO VPCY11AFJ Battery

In the early part of the 20th century in the USA, gold which was contaminated with 210Pb entered the jewelry industry. This was from gold seeds which had held 222Rn that had been melted down after the radon had decayed.[79][80] Wearing a contaminated ring could lead to a skin exposition of 10 to 100 rad/day (0.4 to 4 mSv/h)[81] Sony VAIO VPCY11AGJ Battery

Scientific

Radon emanation from the soil varies with soil type and with surface uranium content, so outdoor radon concentrations can be used to track air masses to a limited degree. This fact has been put to use by some atmospheric scientists. Sony VAIO VPCY11AHJ Battery

Because of radon's rapid loss to air and comparatively rapid decay, radon is used in hydrologic research that studies the interaction between ground water and streams. Any significant concentration of radon in a stream is a good indicator that there are local inputs of ground water. Radon is also used in the dating of oil-containing soils because radon has a high affinity for oil-like substances. Sony VAIO VPCY11AVJ Battery

Radon soil-concentration has been used in an experimental way to map buried close-subsurface geological faults because concentrations are generally higher over the faults.[82] Similarly, it has found some limited use in prospecting for geothermal gradients.

Some researchers have investigated changes in groundwater radon concentrations for earthquake prediction. Sony VAIO VPCY11M1E/S Battery

Radon has a half-life of approximately 3.8 days, which means that it can be found only shortly after it has been produced in the radioactive decay chain. For this reason, it has been hypothesized that increases in radon concentration is due to the generation of new cracks underground, which would allow increased ground water circulation, flushing out radon. Sony VAIO VPCY11S1E Battery

The generation of new cracks might not unreasonably be assumed to precede major earthquakes. In the 1970s and 1980s, scientific measurements of radon emissions near faults found that earthquakes often occurred with no radon signal, and radon was often detected with no earthquake to follow. It was then dismissed by many as an unreliable indicator.[86] Sony VAIO VPCY11V9E/S Battery

However, as of 2009, it is under investigation as a possible precursor by NASA.[87]

Radon is a known pollutant emitted from geothermal power stations, though it disperses rapidly, and no radiological hazard has been demonstrated in various investigations. The trend in geothermal plants is to reinject all emissions by pumping deep underground, and this seems likely to ultimately decrease such radon hazards further. Sony VAIO VPCY218EC/BI Battery

In the 1950s, radon has been used in industrial radiography.[88]

Relative risk of lung cancer mortality by cumulative exposure to radon decay products (in WLM) from the combined data from 11 cohorts of underground hard rock miners. Though high exposures (>50 WLM) cause statistically significant excess cancers, the case of small exposures (10 WLM) is inconclusive and appears slightly beneficial in this study. Sony VAIO VPCY218EC/G Battery

Radon-222 has been classified by International Agency for Research on Cancer as being carcinogenic to humans,[89] and as a gas that can be inhaled, lung cancer is a particular concern for people exposed to high levels of radon for sustained periods of time. During the 1940s and 50s, when safety standards requiring expensive ventilation in mines were not widely implemented,[90] Sony VAIO VPCY218EC/L Battery

radon exposure was linked to lung cancer among non-smoking miners of uranium and other hard rock materials in what is now theCzech Republic, and later among miners from the Southwestern United States.[91][92][93]

Since that time, ventilation and other measures have been used to reduce radon levels in most affected mines that continue to operate. Sony VAIO VPCY218EC/P Battery

In recent years, the average annual exposure of uranium miners has fallen to levels similar to the concentrations inhaled in some homes. This has reduced the risk of occupationally induced cancer from radon, although health issues may persist for those who are currently employed in affected mines and for those who have been employed in them in the past.[94] As the relative risk for miners has decreased, so has the ability to detect excess risks among that population.[95] Sony VAIO VPCY21S1E/L Battery

Radon exposure (actually radon progeny) has been linked to lung cancer in numerous case-control studies performed in the United States, Europe and China. There are approximately 21,000 deaths per year in the USA due to radon-induced lung cancers.[96]

One of the most comprehensive radon studies performed in the United States by Dr. R. Sony VAIO VPCY21S1E/P Battery

William Field and colleagues found a 50% increased lung cancer risk even at the protracted exposures at the EPA's action level of 4 pCi/L. North American and European Pooled analyses further support these findings.[97] Many researchers have highlighted a theoretical possible increased risk ofleukemia of radon, but empirical support for this has not emerged.[98][99] Sony VAIO VPCY21S1E/SI Battery

The effects of radon if ingested are similarly unknown, although studies have found that its biological half-life ranges from 30–70 minutes, with 90 percent removal at 100 minutes. In 1999 National Research Council investigated the issue of radon in drinking water. The risks associated with ingestion was considered almost negligible.[100] Sony VAIO VPCZ110 Battery

As well as being ingested through drinking water, radon is also released from water when temperature is increased, pressure is decreased and when water is aerated. Optimum conditions for radon release and exposure occur during showering. Water with a radon concentration of 10 4 pCi/L can increase the indoor airborne radon concentration by 1 pCi/L under normal conditions of water use.[101] Sony VAIO VPCZ110GB/BI Battery

Domestic-level exposure

A controversial epidemiological study showing decreased cancer risk vs. radon domestic exposure (5 pCi/L ? 200 Bq/m3).[102]This study lacks individual level controls for smoking and radon exposure, and therefore lacks statistical power to draw conclusions on what would beradiation hormesis. Sony VAIO VPCZ112GD/S Battery

Because of this the error bars (which simply reflect the raw data variability) are probably too small.[103]

Most models of residential radon exposure are based on studies of miners, and direct estimates of the risks posed to homeowners would be more desirable.[94] Nonetheless, because of the difficulties of measuring the risk of radon relative to other contributors—namely smoking—models of their effect have often made use of them. Sony VAIO VPCZ112GX/S Battery

Radon has been considered the second leading cause of lung cancer and leading environmental cause of cancer mortality by theUnited States Environmental Protection Agency.[104] Others have reached similar conclusions for the United Kingdom [94] and France.[105] Radon exposure in homes and offices may arise from certain subsurface rock formations and also from certain building materials (e.g. some granites); Sony VAIO VPCZ114GX/S Battery

greatest risk of radon exposure arises from buildings which are tight, insufficiently ventilated and have leaks that let in soil air from the ground into basements and dwelling rooms.

The actionable concentration of radon in a home varies depending on the organization doing the recommendation, for example,Sony VAIO VPCZ115 Battery

the United States Environmental Protection Agency encourages that action be taken at concentrations as low as 74 Bq/m3(2 pCi/L),[106]and the European Union recommends action be taken when concentrations reach 400 Bq/m3 (11 pCi/L) for old houses and 200 Bq/m3(5 pCi/L) for new ones.[citation needed]

On 8 July 2010 the UK's Health Protection Agency issued new advice setting a "Target Level" of 100 Bq/m3 whilst retaining an "Action Level" of 200 Bq/m3.[107] Sony VAIO VPCZ115FC/B Battery

Radon and smoking

Results from epidemiological studies indicate that the risk of lung cancer increases with exposure to residential radon. However, there are always major uncertainties in these studies. A classical and well-known example of source of error is smoking. Sony VAIO VPCZ115FC/S Battery

In addition, smoking is the most important risk factor for lung cancer. In the West, tobacco smoke is estimated to cause about 90% of all lung cancers. There is a tendency for other hypothetical lung cancer risks to drown in the risk of smoking. Results from epidemiological studies must always be interpreted with caution. Sony VAIO VPCZ116 Battery

According to the EPA, the risk of lung cancer for smokers is significant due to synergistic effects of radon and smoking. For this population about 62 people in a total of 1,000 will die of lung cancer compared to 7 people in a total of 1,000 for people who have never smoked.[96]

Radon, like other known or suspected external risk factors for lung cancer, is a threat for smokers and former smokers. Sony VAIO VPCZ116GX/S Battery

This was clearly demonstrated by the European pooling study.[108] A commentary[109] to the pooling study stated: "it is not appropriate to talk simply of a risk from radon in homes. The risk is from smoking, compounded by a synergistic effect of radon for smokers. Without smoking, the effect seems to be so small as to be insignificant." Sony VAIO VPCZ117 Battery

A study[110] of radiation from postmastectomy radiotherapy shows that the simple models previously used to assess the combined and separate risks from radiation and smoking need to be developed. This is also supported by new discussion about the calculation method, LNT, which routinely has been used.[111] Sony VAIO VPCZ117FC/B Battery

Radon and passive smoking

An important question is if also passive smoking can cause a similar synergy effect with residential radon. This has been insufficiently studied. The basic data for the European pooling study makes it impossible to exclude that such synergy effect is an explanation for the (very limited) increase in the risk from radon that was stated for non-smokers. Sony VAIO VPCZ118 Battery

A study[112] from 2001 which included 436 cases (never smokers who had lung cancer), and a control group (1649 never smokers) showed that exposure to radon increased the risk of lung cancer in never smokers. But the group that had been exposed to passive smoking at home appeared to bear the entire risk increase, while those who were not exposed to passive smoking did not show any increased risk with increasing radon level. Sony VAIO VPCZ118GC/B Battery

This result needs confirmation by additional studies. Despite the startling results from 2001, new studies seem not to have been implemented.

Testing and mitigation

There are relatively simple tests for radon gas, but these tests are not commonly done, even in areas of known systematic hazards. Radon test kits are commercially available. Sony VAIO VPCZ118GX/S Battery

The short-term radon test kits used for screening purposes are inexpensive, in many cases free. The kit includes a collector that the user hangs in the lowest livable floor of the house for 2 to 7 days. The user then sends the collector to a laboratory for analysis. Long term kits, taking collections for up to one year, are also available. An open-land test kit can test radon emissions from the land before construction begins.[4] Sony VAIO VPCZ119 Battery

Radon levels fluctuate naturally, due to factors like transient weather conditions, so an initial test might not be an accurate assessment of a home's average radon level. Radon levels are at a maximum during the coolest part of the day when pressure differentials are greatest.[113] Therefore, a high result (over 4 pCi/L) justifies repeating the test before undertaking more expensive abatement projects. Sony VAIO VPCZ119FJ/S Battery

Measurements between 4 and 10 pCi/L warrant a long term radon test. Measurements over 10 pCi/L warrant only another short term test so that abatement measures are not unduly delayed. Purchasers of real estate are advised to delay or decline a purchase if the seller has not successfully abated radon to 4 pCi/L or less.[4] Sony VAIO VPCZ119GC/X Battery

Because the half-life of radon is only 3.8 days, removing or isolating the source will greatly reduce the hazard within a few weeks. Another method of reducing radon levels is to modify the building's ventilation. Generally, the indoor radon concentrations increase as ventilation rates decrease.[1] In a well ventilated place, the radon concentration tends to align with outdoor values (typically 10 Bq/m3, ranging from 1 to 100 Bq/m3).[4] Sony VAIO VPCZ119L Battery

Radon levels in indoor air can be lowered in a number of ways, from sub-slab depressurization to increasing the ventilation rate of the building. The four principal ways of reducing the amount of radon accumulating in a house are:[4][114]

Sub-slab depressurization (soil suction) by increasing under-floor ventilation; Sony VAIO VPCZ119R/B Battery

• Improving the ventilation of the house and avoiding the transport of radon from the basement into living rooms;
• Installing a radon sump system in the basement;

Installing a positive pressurization or positive supply ventilation system. Sony VAIO VPCZ119R/S Battery

According to the EPA's "A Citizen's Guide to Radon",[115] the method to reduce radon "primarily used is a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside", which is also called sub-slab depressurization, active soil depressurization, or soil suction. Sony VAIO VPCZ11AFJ Battery

Generally indoor radon can be mitigated by sub-slab depressurization and exhausting such radon-laden air to the outdoors, away from windows and other building openings. "EPA generally recommends methods which prevent the entry of radon. Soil suction, for example, prevents radon from entering your home by drawing the radon from below the home and venting it through a pipe, or pipes, Sony VAIO VPCZ11AGJ Battery

to the air above the home where it is quickly diluted" and "EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently" according to the EPA's "Consumer's Guide to Radon Reduction: How to fix your home".[116] Sony VAIO VPCZ11AVJ Battery

Positive-pressure ventilation systems can be combined with a heat exchanger to recover energy in the process of exchanging air with the outside, and simply exhausting basement air to the outside is not necessarily a viable solution as this can actually draw radon gas into a dwelling. Sony VAIO VPCZ11CGX/X Battery

Homes built on a crawl space may benefit from a radon collector installed under a "radon barrier" (a sheet of plastic that covers the crawl space).[4][117] For crawlspaces, the EPA states "An effective method to reduce radon levels in crawlspace homes involves covering the earth floor with a high-density plastic sheet. Sony VAIO VPCZ11DGX/SJ Battery

A vent pipe and fan are used to draw the radon from under the sheet and vent it to the outdoors. This form of soil suction is called submembrane suction, and when properly applied is the most effective way to reduce radon levels in crawlspace homes." Sony VAIO VPCZ11FHX/XQ Battery,Sony VAIO VPCZ11V9R/B Battery,Sony VAIO VPCZ11X9E/B Battery,Sony VAIO VPCZ11Z9E/B Battery,Sony VAIO VPCZ125GX/S Battery

 

Gold,Mercury

Gold is a chemical element with the symbol Au (from Latin: aurum "gold") and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Sony VAIO VGN-G21XP/B Battery

Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive solid chemical elements. The metal therefore occurs often in free elemental (native) form, as nuggets or grains in rocks, in veins and in alluvial deposits. Less commonly, it occurs in minerals as gold compounds, usually with tellurium. Sony VAIO VGN-G2AANS Battery

Gold resists attacks by individual acids, but it can be dissolved by the aqua regia (nitro-hydrochloric acid), so named because it dissolves gold. Gold also dissolves in alkaline solutions of cyanide, which have been used in mining. Gold dissolves in mercury, forming amalgam alloys. Sony VAIO VGN-G2AAPS Battery

Gold is insoluble in nitric acid, which dissolves silver and base metals, a property that has long been used to confirm the presence of gold in items, giving rise to the term the acid test.

Gold has been a valuable and highly sought-after precious metal for coinage, jewelry, and other arts since long before the beginning of recorded history. Sony VAIO VGN-G2AAPSA Battery

Gold standards have been the most common basis for monetary policies throughout human history, being widely supplanted by fiat currency only in the late 20th century. Gold has also been frequently linked to a wide variety of symbolisms and ideologies. A total of 165,000 tonnes of gold have been mined in human history, as of 2009. Sony VAIO VGN-G2AAPSB Battery

This is roughly equivalent to 5.3 billion troy ounces or, in terms of volume, about 8500 m3, or a cube 20.4 m on a side. The world consumption of new gold produced is about 50% in jewelry, 40% in investments, and 10% in industry.[3] Sony VAIO VGN-G2AAPSC Battery

Besides its widespread monetary and symbolic functions, gold has many practical uses in dentistry, electronics, and other fields. Its high malleability, ductility, resistance to corrosion and most other chemical reactions, and conductivity of electricity led to many uses of gold, including electric wiring, colored-glass production and even gold leaf eating. Sony VAIO VGN-G2KAN Battery

Characteristics

Gold is the most malleable and ductile of all metals; a single gram can be beaten into a sheet of 1 square meter, or an ounceinto 300 square feet. Gold leaf can be beaten thin enough to become translucent. Sony VAIO VGN-G2KANA Battery

The transmitted light appears greenish blue, because gold strongly reflects yellow and red.[4] Such semi-transparent sheets also strongly reflect infrared light, making them useful as infrared (radiant heat) shields in visors of heat-resistant suits, and in sun-visors for spacesuits.[5] Sony VAIO VGN-G2KBNA Battery

Gold readily creates alloys with many other metals. These alloys can be produced to modify the hardness and other metallurgical properties, to control melting point or to create exotic colors (see below).[6] Gold is a good conductor of heatand electricity and reflects infrared radiation strongly. Sony VAIO VGN-NR160E/S Battery

Chemically, it is unaffected by air, moisture and most corrosivereagents, and is therefore well suited for use in coins and jewelry and as a protective coating on other, more reactive, metals. However, it is not chemically inert.

Common oxidation states of gold include +1 (gold(I) or aurous compounds) and +3 (gold(III) or auric compounds). Sony VAIO VGN-NR160E/T Battery

Gold ions in solution are readily reduced and precipitated out as gold metal by adding any other metal as the reducing agent. The added metal is oxidized and dissolves allowing the gold to be displaced from solution and be recovered as a solid precipitate.

High quality pure metallic gold is tasteless and scentless, in keeping with its resistance to corrosion (it is metal ions which confer taste to metals).[7] Sony VAIO VGN-NR160E/W Battery

In addition, gold is very dense, a cubic meter weighing 19,300 kg. By comparison, the density of lead is 11,340 kg/m3, and that of the densest element, osmium, is 22,610 kg/m3.

Color

Whereas most other pure metals are gray or silvery white, gold is yellow. Sony VAIO VGN-NR180E/S Battery

This color is determined by the density of loosely bound (valence) electrons; those electrons oscillate as a collective "plasma" medium described in terms of a quasiparticle called plasmon. The frequency of these oscillations lies in the ultraviolet range for most metals, but it falls into the visible range for gold due to subtle relativistic effects that affect theorbitals around gold atoms.[8][9] Sony VAIO VGN-NR180E/T Battery

Similar effects impart a golden hue to metallic caesium(see relativistic quantum chemistry).

Common colored gold alloys such as rose gold can be created by the addition of various amounts of copper and silver, as indicated in the triangular diagram to the left. Alloys containing palladium or nickel are also important in commercial jewelry as these produce white gold alloys. Sony VAIO VGN-NR290E/S Battery

Less commonly, addition of manganese, aluminium, iron, indium and other elements can produce more unusual colors of gold for various applications.[6]

Isotopes

Gold has only one stable isotope, 197Au, which is also its only naturally occurring isotope. Thirty-six radioisotopes have been synthesized ranging in atomic mass from 169 to 205. Sony VAIO VGN-NR290E/T Battery

The most stable of these is 195Au with a half-life of 186.1 days. The least stable is 171Au, which decays by proton emission with a half-life of 30 µs. Most of gold's radioisotopes with atomic masses below 197 decay by some combination of proton emission, ? decay, and ?+ decay. The exceptions are 195Au, which decays by electron capture, and 196Au, which decays most often by electron capture (93%) with a minor ?- decay path (7%).[10] Sony VAIO VGN-NR298E/S Battery

All of gold's radioisotopes with atomic masses above 197 decay by ?- decay.[11]

At least 32 nuclear isomers have also been characterized, ranging in atomic mass from 170 to 200. Within that range, only178Au, 180Au, 181Au, 182Au, and 188Au do not have isomers. Gold's most stable isomer is 198m2Au with a half-life of 2.27 days. Sony VAIO VGN-NR460E/L Battery

Gold's least stable isomer is 177 m2Au with a half-life of only 7 ns. 184 m1Au has three decay paths: ?+ decay, isomeric transition, and alpha decay. No other isomer or isotope of gold has three decay paths.[11]

Monetary exchange

Gold has been widely used throughout the world as a vehicle for monetary exchange, Sony VAIO VGN-NR460E/P Battery

either by issuance and recognition of gold coins or other bare metal quantities, or through gold-convertible paper instruments by establishing gold standards in which the total value of issued money is represented in a store of gold reserves.

However, production has not grown in relation to the world's economies. Sony VAIO VGN-NR498E/L Battery

Today, gold mining output is declining.[12] With the sharp growth of economies in the 20th century, and increasing foreign exchange, the world's gold reserves and their trading market have become a small fraction of all markets and fixed exchange rates of currencies to gold were no longer sustained. Sony VAIO VGN-NR498E/S Battery

At the beginning of World War I the warring nations moved to a fractional gold standard, inflating their currencies to finance the war effort. After World War IIgold was replaced by a system of convertible currency following the Bretton Woods system. Sony VAIO VGN-NR498E/T Battery

Gold standards and the direct convertibility of currencies to gold have been abandoned by world governments, being replaced by fiat currency in their stead. Switzerland was the last country to tie its currency to gold; it backed 40% of its value until the Swiss joined the International Monetary Fund in 1999.[13] Sony VAIO VGN-NR498E/W Battery

Pure gold is too soft for day-to-day monetary use and is typically hardened by alloying with copper, silver or other base metals. The gold content of alloys is measured in carats (k). Pure gold is designated as 24k. English gold coins intended for circulation from 1526 into the 1930s were typically a standard 22k alloy called crown gold, Sony VAIO VGN-NR50 Battery

for hardness (American gold coins for circulation after 1837 contained the slightly lower amount of 0.900 fine gold, or 21.6 kt).

Investment

Many holders of gold store it in form of bullion coins or bars as a hedge against inflation or other economic disruptions. However, some economists do not believe gold serves as a hedge against inflation or currency depreciation.[14] Sony VAIO VGN-NR50B Battery

The ISO 4217 currency code of gold is XAU.

Modern bullion coins for investment or collector purposes do not require good mechanical wear properties; they are typically fine gold at 24k, although the American Gold Eagle, the British gold sovereign, and the South African Krugerrand continue to be minted in 22k metal in historical tradition. Sony VAIO VGN-NR51 Battery

The special issue Canadian Gold Maple Leaf coin contains the highest purity gold of any bullion coin, at 99.999% or 0.99999, while the popular issue Canadian Gold Maple Leaf coin has a purity of 99.99%.

Several other 99.99% pure gold coins are available. Sony VAIO VGN-NR51B Battery

In 2006, the United States Mint began production of the American Buffalo gold bullion coin with a purity of 99.99%. The Australian Gold Kangaroos were first coined in 1986 as the Australian Gold Nugget but changed the reverse design in 1989. Other popular modern coins include the Austrian Vienna Philharmonic bullion coin and the Chinese Gold Panda. Sony VAIO VGN-NR52 Battery

Jewelry

Because of the softness of pure (24k) gold, it is usually alloyed with base metals for use in jewelry, altering its hardness and ductility, melting point, color and other properties. Alloys with lower caratage, typically 22k, 18k, 14k or 10k, contain higher percentages of copper, or other base metals or silver or palladium in the alloy. Sony VAIO VGN-NR52B Battery

Copper is the most commonly used base metal, yielding a redder color.[15]

Eighteen-carat gold containing 25% copper is found in antique and Russian jewelry and has a distinct, though not dominant, copper cast, creating rose gold. Fourteen-carat gold-copper alloy is nearly identical in color to certain bronze alloys, and both may be used to produce police and other badges. Sony VAIO VGN-NR71B Battery

Blue gold can be made by alloying with iron and purple gold can be made by alloying withaluminium, although rarely done except in specialized jewelry. Blue gold is more brittle and therefore more difficult to work with when making jewelry.[15]

Fourteen and eighteen carat gold alloys with silver alone appear greenish-yellow and are referred to as green gold. Sony VAIO VGN-NR71B2 Battery

White gold alloys can be made with palladium or nickel. White 18-carat gold containing 17.3% nickel, 5.5% zinc and 2.2% copper is silvery in appearance. Nickel is toxic, however, and its release from nickel white gold is controlled by legislation in Europe.[15]

Alternative white gold alloys are available based on palladium, silver and other white metals,[15] but the palladium alloys are more expensive than those using nickel. Sony VAIO VGN-NR72B Battery

High-carat white gold alloys are far more resistant to corrosion than are either pure silver or sterling silver. The Japanese craft of Mokume-gane exploits the color contrasts between laminated colored gold alloys to produce decorative wood-grain effects. Sony VAIO VGN-NS10E/S Battery

Medicine

In medieval times, gold was often seen as beneficial for the health, in the belief that something so rare and beautiful could not be anything but healthy. Even some modern esotericists and forms of alternative medicine assign metallic gold a healing power.[16]Sony VAIO VGN-NS10J/S Battery

Some gold salts do have anti-inflammatory properties and are used as pharmaceuticals in the treatment of arthritis and other similar conditions.[17] However, only salts and radioisotopes of gold are of pharmacological value, as elemental (metallic) gold is inert to all chemicals it encounters inside the body. Sony VAIO VGN-NS10L/S Battery

In modern times, injectable gold has been proven to help to reduce the pain and swelling of rheumatoid arthritis and tuberculosis.[17][18]

Gold alloys are used in restorative dentistry, especially in tooth restorations, such as crowns and permanent bridges. Sony VAIO VGN-NS110E/L Battery

The gold alloys' slight malleability facilitates the creation of a superior molar mating surface with other teeth and produces results that are generally more satisfactory than those produced by the creation of porcelain crowns. The use of gold crowns in more prominent teeth such as incisors is favored in some cultures and discouraged in others. Sony VAIO VGN-NS110E/S Battery

Colloidal gold preparations (suspensions of gold nanoparticles) in water are intensely red-colored, and can be made with tightly controlled particle sizes up to a few tens of nanometers across by reduction of gold chloride with citrate or ascorbate ions. Colloidal gold is used in research applications in medicine, biology andmaterials science. Sony VAIO VGN-NS110E/W Battery

The technique of immunogold labeling exploits the ability of the gold particles to adsorb protein molecules onto their surfaces. Colloidal gold particles coated with specific antibodies can be used as probes for the presence and position of antigens on the surfaces of cells.[19] Sony VAIO VGN-NS115N/S Battery

In ultrathin sections of tissues viewed by electron microscopy, the immunogold labels appear as extremely dense round spots at the position of the antigen.[20] Colloidal gold is also the form of gold used as gold paint on ceramics prior to firing. Sony VAIO VGN-NS11ER/S Battery

Gold, or alloys of gold and palladium, are applied as conductive coating to biological specimens and other non-conducting materials such as plastics and glass to be viewed in a scanning electron microscope. The coating, which is usually applied by sputtering with an argon plasma, has a triple role in this application. Sony VAIO VGN-NS11E/S Battery

Gold's very high electrical conductivity drains electrical charge to earth, and its very high density provides stopping power for electrons in the electron beam, helping to limit the depth to which the electron beam penetrates the specimen. This improves definition of the position and topography of the specimen surface and increases thespatial resolution of the image. Sony VAIO VGN-NS11J/S Battery

Gold also produces a high output of secondary electrons when irradiated by an electron beam, and these low-energy electrons are the most commonly used signal source used in the scanning electron microscope.[21]

The isotope gold-198, (half-life 2.7 days) is used in some cancer treatments and for treating other diseases.[22] Sony VAIO VGN-NS11L/S Battery

Food and drink

• Gold can be used in food and has the E number 175.[23]

Gold leaf, flake or dust is used on and in some gourmet foods, notably sweets and drinks as decorative ingredient.[24] Sony VAIO VGN-NS11MR/S Battery

Gold flake was used by the nobility inMedieval Europe as a decoration in food and drinks, in the form of leaf, flakes or dust, either to demonstrate the host's wealth or in the belief that something that valuable and rare must be beneficial for one's health. Sony VAIO VGN-NS11M/S Battery

Danziger Goldwasser (German: Gold water of Danzig) or Goldwasser (English: Goldwater) is a traditional German herbal liqueur[25]produced in what is today Gda?sk,Poland, and Schwabach, Germany, and contains flakes of gold leaf. Sony VAIO VGN-NS11SR/S Battery

• There are also some expensive (~$1000) cocktails which contain flakes of gold leaf.[26] However, since metallic gold is inert to all body chemistry, it has no taste, it provides no nutrition, and it leaves the body unaltered.[27]

Gold solder is used for joining the components of gold jewelry by high-temperature hard soldering or brazing. Sony VAIO VGN-NS11S/S Battery

If the work is to be of hallmarking quality, gold solder must match the carat weight of the work, and alloy formulas are manufactured in most industry-standard carat weights to color match yellow and white gold. Gold solder is usually made in at least three melting-point ranges referred to as Easy, Medium and Hard. Sony VAIO VGN-NS11ZR/S Battery

• By using the hard, high-melting point solder first, followed by solders with progressively lower melting points, goldsmiths can assemble complex items with several separate soldered joints.
• Gold can be made into thread and used in embroidery.

Gold produces a deep, intense red color when used as a coloring agent in cranberry glass. Sony VAIO VGN-NS11Z/S Battery

In photography, gold toners are used to shift the color of silver bromide black-and-white prints towards brown or blue tones, or to increase their stability. Used on sepia-toned prints, gold toners produce red tones. Kodak published formulas for several types of gold toners, which use gold as the chloride.[28] Sony VAIO VGN-NS12M/S Battery

As gold is a good reflector of electromagnetic radiation such as infrared and visible light as well as radio waves, it is used for the protective coatings on many artificial satellites, in infrared protective faceplates in thermal protection suits and astronauts' helmets and in electronic warfare planes like the EA-6B Prowler. Sony VAIO VGN-NS12M/W Battery

• Gold is used as the reflective layer on some high-end CDs.
• Automobiles may use gold for heat dissipation. McLaren uses gold foil in the engine compartment of its F1 model.[29]

Gold can be manufactured so thin that it appears transparent. It is used in some aircraft cockpit windows for de-icing or anti-icing by passing electricity through it. Sony VAIO VGN-NS12S/S Battery

• The heat produced by the resistance of the gold is enough to deter ice from forming.[30]

Electronics

The concentration of free electrons in gold metal is 5.90×1022 cm?3. Gold is highly conductive to electricity, Sony VAIO VGN-NS21M/P Battery

and has been used forelectrical wiring in some high-energy applications (only silver and copper are more conductive per volume, but gold has the advantage of corrosion resistance). For example, gold electrical wires were used during some of the Manhattan Project's atomic experiments, but large high current silver wires were used in the calutron isotope separator magnets in the project.Sony VAIO VGN-NS21M/W Battery

Though gold is attacked by free chlorine, its good conductivity and general resistance to oxidation and corrosion in other environments (including resistance to non-chlorinated acids) has led to its widespread industrial use in the electronic era as a thin layer coatingelectrical connectors of all kinds, thereby ensuring good connection. Sony VAIO VGN-NS21S/S Battery

For example, gold is used in the connectors of the more expensive electronics cables, such as audio, video and USB cables. The benefit of using gold over other connector metals such as tin in these applications is highly debated. Gold connectors are often criticized by audio-visual experts as unnecessary for most consumers and seen as simply a marketing ploy. Sony VAIO VGN-NS21S/W Battery

However, the use of gold in other applications in electronic sliding contacts in highly humid or corrosive atmospheres, and in use for contacts with a very high failure cost (certain computers, communications equipment, spacecraft, jet aircraft engines) remains very common.[31] Sony VAIO VGN-NS21Z/S Battery

Besides sliding electrical contacts, gold is also used in electrical contacts because of its resistance to corrosion, electrical conductivity, ductility and lack of toxicity.[32] Switch contacts are generally subjected to more intense corrosion stress than are sliding contacts. Fine gold wires are used to connect semiconductor devices to their packages through a process known as wire bonding. Sony VAIO VGN-NS31M/P Battery

Commercial chemistry

Gold is attacked by and dissolves in alkaline solutions of potassium or sodium cyanide, to form the salt gold cyanide—a technique that has been used in extracting metallic gold from ores in the cyanide process. Sony VAIO VGN-NS31M/W Battery

Gold cyanide is the electrolyte used in commercialelectroplating of gold onto base metals and electroforming.

Gold chloride (chloroauric acid) solutions are used to make colloidal gold by reduction with citrate or ascorbate ions. Sony VAIO VGN-NS31S/S Battery

Gold chloride and gold oxide are used to make highly valued cranberry or red-colored glass, which, like colloidal gold suspensions, contains evenly sized spherical gold nanoparticles.[33]

Gold has been known and used by artisans since the Chalcolithic. Gold artifacts in the Balkans appear from the 4th millennium BC, such as those found in the Varna Necropolis, Bulgaria. Sony VAIO VGN-NS31Z/P Battery

Gold artifacts such as the golden hats and the Nebra disk appeared in Central Europe from the 2nd millennium BC Bronze Age.

Egyptian hieroglyphs from as early as 2600 BC describe gold, which king Tushratta of the Mitanni claimed was "more plentiful than dirt" in Egypt.[34] Sony VAIO VGN-NS31Z/S Battery

Egypt and especially Nubia had the resources to make them major gold-producing areas for much of history. The earliest known map is known as the Turin Papyrus Map and shows the plan of a gold mine in Nubia together with indications of the local geology. The primitive working methods are described by both Strabo and Diodorus Siculus, and included fire-setting. Sony VAIO VGN-NS31Z/W Battery

Large mines were also present across the Red Sea in what is now Saudi Arabia.

The legend of the golden fleece may refer to the use of fleeces to trap gold dust from placer deposits in the ancient world. Gold is mentioned frequently in the Old Testament, starting with Genesis 2:11 (at Havilah) and is included with the gifts of the magi in the first chapters of Matthew New Testament. Sony VAIO VGN-NS38M/P Battery

The Book of Revelation 21:21 describes the city of New Jerusalem as having streets "made of pure gold, clear as crystal". The south-east corner of the Black Sea was famed for its gold. Exploitation is said to date from the time of Midas, and this gold was important in the establishment of what is probably the world's earliest coinage in Lydia around 610 BC.[35] Sony VAIO VGN-NS38M/W Battery

From the 6th or 5th century BC, the Chu (state) circulated the Ying Yuan, one kind of square gold coin.

In Roman metallurgy, new methods for extracting gold on a large scale were developed by introducing hydraulic mining methods, especially in Hispania from 25 BC onwards and in Dacia from 106 AD onwards. Sony VAIO VGN-NS130E/L Battery

One of their largest mines was at Las Medulas in León (Spain), where seven long aqueducts enabled them to sluice most of a large alluvial deposit. The mines at Ro?ia Montan?in Transylvania were also very large, and until very recently, still mined by opencast methods. Sony VAIO VGN-NS130E/S Battery

They also exploited smaller deposits in Britain, such as placer and hard-rock deposits at Dolaucothi. The various methods they used are well described by Pliny the Elderin his encyclopedia Naturalis Historia written towards the end of the first century AD. Sony VAIO VGN-NS130E/W Battery

The Mali Empire in Africa was famed throughout the old world for its large amounts of gold. Mansa Musa, ruler of the empire (1312–1337) became famous throughout the old world for his great hajj to Mecca in 1324. Sony VAIO VGN-NS140E/L Battery

When he passed through Cairo in July 1324, he was reportedly accompanied by a camel train that included thousands of people and nearly a hundred camels. He gave away so much gold that it depressed the price in Egypt for over a decade.[36] A contemporary Arab historian remarked: Sony VAIO VGN-NS140E/S Battery

Gold was at a high price in Egypt until they came in that year. The mithqal did not go below 25 dirhams and was generally above, but from that time its value fell and it cheapened in price and has remained cheap till now. The mithqal does not exceed 22 dirhams or less. This has been the state of affairs for about twelve years until this day by reason of the large amount of gold which they brought into Egypt and spent there Sony VAIO VGN-NS140E/W Battery

—Chihab Al-Umari[37]

The European exploration of the Americas was fueled in no small part by reports of the gold ornaments displayed in great profusion byNative American peoples, especially in Central America, Peru, Ecuador and Colombia. Sony VAIO VGN-NS190J/L Battery

The Aztecs regarded gold as literally the product of the gods, calling it "god excrement" (teocuitlatl in Nahuatl).[38] However, for the indigenous peoples of North America, gold was considered useless, and they saw much greater value in other minerals, which were directly related to their utility, such as obsidian,flint, and slate.[39] Sony VAIO VGN-NS190J/S Battery

Although the price of some platinum group metals can be much higher, gold has long been considered the most desirable of precious metals, and its value has been used as the standard for many currencies (known as the gold standard) in history. Gold has been used as a symbol for purity, value, royalty, and particularly roles that combine these properties. Sony VAIO VGN-NS190J/W Battery

Gold as a sign of wealth and prestige was ridiculed by Thomas More in his treatise Utopia. On that imaginary island, gold is so abundant that it is used to make chains for slaves, tableware and lavatory-seats. When ambassadors from other countries arrive, dressed in ostentatious gold jewels and badges, the Utopians mistake them for menial servants, paying homage instead to the most modestly dressed of their party. Sony VAIO VGN-NS235J/L Battery

There is an age-old tradition of biting gold to test its authenticity. Although this is certainly not a professional way of examining gold, the bite test should score the gold because gold is a soft metal, as indicated by its score on the Mohs' scale of mineral hardness. The purer the gold the easier it should be to mark it. Sony VAIO VGN-NS235J/P Battery

Painted lead can cheat this test because lead is softer than gold (and may invite a small risk oflead poisoning if sufficient lead is absorbed by the biting).

Gold in antiquity was relatively easy to obtain geologically; however, 75% of all gold ever produced has been extracted since 1910.[40] Sony VAIO VGN-NS235J/S Battery

Sony VAIO VGN-NS235J/W Battery

It has been estimated that all gold ever refined would form a single cube 20 m (66 ft) on a side (equivalent to 8,000 m3).[40]

One main goal of the alchemists was to produce gold from other substances, such as lead — presumably by the interaction with a mythical substance called thephilosopher's stone. Sony VAIO VGN-NS240E/L Battery

Although they never succeeded in this attempt, the alchemists promoted an interest in what can be done with substances, and this laid a foundation for today's chemistry. Their symbol for gold was the circle with a point at its center (?), which was also the astrological symbol and the ancientChinese character for the Sun. Sony VAIO VGN-NS290J/L Battery

For modern creation of artificial gold by neutron capture, see gold synthesis.

During the 19th century, gold rushes occurred whenever large gold deposits were discovered. The first documented discovery of gold in the United States was at theReed Gold Mine near Georgeville, North Carolina in 1803.[41] Sony VAIO VGN-NS290J/S Battery

The first major gold strike in the United States occurred in a small north Georgia town calledDahlonega.[42] Further gold rushes occurred in California, Colorado, the Black Hills, Otago in New Zealand, Australia, Witwatersrand in South Africa, and theKlondike in Canada. Sony VAIO VGN-NS50B/L Battery

Because of its historically high value, much of the gold mined throughout history is still in circulation in one form or another.

Occurrence

Gold's atomic number of 79 makes it one of the higher atomic number elements which occur naturally. Sony VAIO VGN-NS50B/W Battery

Like all elements with atomic numbers larger than iron, gold is thought to have been formed from a supernova nucleosynthesis process. Their explosions scattered metal-containing dusts (including heavy elements like gold) into the region of space in which they later condensed into our solar system and the Earth.[43] Sony VAIO VGN-NS51B/L Battery

Because the Earth was molten when it was just formed, almost all of the gold present on Earth sank into the core. Most of the gold that is present today in the Earth's crust and mantle was delivered to Earth by asteroid impacts during the late heavy bombardment.[44]Sony VAIO VGN-NS51B/P Battery

On Earth, whenever elemental gold occurs, it appears most often as a metal solid solution of gold with silver, i.e. a gold silver alloy. Such alloys usually have a silver content of 8–10%. Electrum is elemental gold with more than 20% silver. Electrum's color runs from golden-silvery to silvery, dependent upon the silver content. Sony VAIO VGN-NS51B/W Battery

The more silver, the lower the specific gravity.

Gold is found in ores made up of rock with very small or microscopic particles of gold. This gold ore is often found together with quartz or sulfide minerals such as Fool's Gold, which is a pyrite.[45] These are called lode deposits. Sony VAIO VGN-NS52JB/L Battery

Native gold is also found in the form of free flakes, grains or larger nuggets that have been eroded from rocks and end up in alluvial deposits (called placer deposits). Such free gold is always richer at the surface of gold-bearing veins owing to the oxidation of accompanying minerals followed by weathering, Sony VAIO VGN-NS52JB/P Battery

and washing of the dust into streams and rivers, where it collects and can be welded by water action to form nuggets.

Gold sometimes occurs combined with tellurium as the minerals calaverite, krennerite, nagyagite, petzite and sylvanite, and as the rare bismuthide maldonite (Au2Bi) and antimonide aurostibite (AuSb2). Sony VAIO VGN-NS52JB/W Battery

Gold also occurs in rare alloys with copper, lead, andmercury: the minerals auricupride (Cu3Au), novodneprite (AuPb3) and weishanite ((Au, Ag)3Hg2).

Recent research suggests that microbes can sometimes play an important role in forming gold deposits, transporting and precipitating gold to form grains and nuggets that collect in alluvial deposits.[46] Sony VAIO VGN-NS70B/W Battery

The world's oceans contain gold. Measured concentrations of gold in the Atlantic and Northeast Pacific are 50–150 fmol/L or 10–30 parts per quadrillion (about 10–30 g/km3). In general, Au concentrations for Atlantic and Pacific samples are the same (~50 fmol/L) but less certain. Sony VAIO VGN-NS71B/W Battery

Mediterranean deep waters contain higher concentrations of Au (100–150 fmol/L) attributed to wind-blown dust and/or rivers. At 10 parts per quadrillion the Earth's oceans would hold 15,000 tons of gold.[47] These figures are three orders of magnitude less than reported in the literature prior to 1988, indicating contamination problems with the earlier data. Sony VAIO VGN-NS72JB/W Battery

A number of people have claimed to be able to economically recover gold from sea water, but so far they have all been either mistaken or acted in an intentional deception. A so-called reverend, Prescott Jernegan ran a gold-from-seawater swindle in theUnited States in the 1890s. A British fraudster ran the same scam in England in the early 1900s.[48] Sony VAIO VGN-NS90HS Battery

Fritz Haber (the German inventor of the Haber process) did research on the extraction of gold from sea water in an effort to help pay Germany's reparations following World War I.[49] Based on the published values of 2 to 64 ppb of gold in seawater a commercially successful extraction seemed possible. Sony VAIO VGN-NS92JS Battery

After analysis of 4,000 water samples yielding an average of 0.004 ppb it became clear that the extraction would not be possible and he stopped the project.[50] No commercially viable mechanism for performing gold extraction from sea water has yet been identified. Gold synthesis is not economically viable and is unlikely to become so in the foreseeable future. Sony VAIO VGN-NS92XS Battery

Production

Gold extraction is most economical in large, easily mined deposits. Ore grades as little as 0.5 mg/kg (0.5 parts per million, ppm) can be economical. Typical ore grades in open-pit mines are 1–5 mg/kg (1–5 ppm); ore grades in underground or hard rock mines are usually at least 3 mg/kg (3 ppm). Sony VAIO VGN-NW11S/S Battery

Because ore grades of 30 mg/kg (30 ppm) are usually needed before gold is visible to the naked eye, in most gold mines the gold is invisible.

Since the 1880s, South Africa has been the source for a large proportion of the world's gold supply, with about 50% of all gold ever produced having come from South Africa. Sony VAIO VGN-NW11S/T Battery

Production in 1970 accounted for 79% of the world supply, producing about 1,480 tonnes. 2008 production was 2,260 tonnes. In 2007 China (with 276 tonnes) overtook South Africa as the world's largest gold producer, the first time since 1905 that South Africa has not been the largest.[51] Sony VAIO VGN-NW11Z/S Battery

The city of Johannesburg located in South Africa was founded as a result of the Witwatersrand Gold Rush which resulted in the discovery of some of the largest gold deposits the world has ever seen. Sony VAIO VGN-NW11Z/T Battery

Gold fields located within the basin in the Free Stateand Gauteng provinces are extensive in strike and dip requiring some of the world's deepest mines, with the Savuka and TauTonamines being currently the world's deepest gold mine at 3,777 m. The Second Boer War of 1899–1901 between the British Empire and the Afrikaner Boers was at least partly over the rights of miners and possession of the gold wealth in South Africa. Sony VAIO VGN-NW21EF/S Battery

Other major producers are the United States, Australia, Russia and Peru. Mines in South Dakota and Nevada supply two-thirds of gold used in the United States. In South America, the controversial project Pascua Lama aims at exploitation of rich fields in the high mountains of Atacama Desert, at the border between Chile and Argentina. Sony VAIO VGN-NW21JF Battery

Today about one-quarter of the world gold output is estimated to originate from artisanal or small scale mining.[52]

After initial production, gold is often subsequently refined industrially by the Wohlwill process which is based onelectrolysis or by the Miller process, that is chlorination in the melt. Sony VAIO VGN-NW21MF Battery

The Wohlwill process results in higher purity, but is more complex and is only applied in small-scale installations.[53][54] Other methods of assaying and purifying smaller amounts of gold include parting and inquartation as well as cupellation, or refining methods based on the dissolution of gold in aqua regia.[55] Sony VAIO VGN-NW21MF/W Battery

At the end of 2009, it was estimated that all the gold ever mined totaled 165,000 tonnes.[2] This can be represented by a cube with an edge length of about 20.28 meters. At $1,600 per ounce, 165,000 tons of gold would have a value of $8.8 trillion. Sony VAIO VGN-NW21ZF Battery

The average gold mining and extraction costs were about US$317/oz in 2007, but these can vary widely depending on mining type and ore quality; global mine production amounted to 2,471.1 tonnes.[56]

Most of the gold used in manufactured goods, jewelry, and works of art is eventually recovered and recycled. Sony VAIO VGN-NW31EF/W Battery

Some gold used in spacecraft and electronic equipment cannot be profitably recovered, but it is generally used in these applications in the form of extremely thin layers or extremely fine wires so that the total quantity used (and lost) is small compared to the total amount of gold produced and stockpiled. Sony VAIO VGN-NW31JF Battery

Thus there is little true consumption of new gold in the economic sense; the stock of gold remains essentially constant (at least in the modern world) while ownership shifts from one party to another.[57] One estimate is that 85% of all the gold ever mined is still available in the world's easily recoverable stocks, with 15% having been lost, or used in non-recyclable industrial uses.[58] Sony VAIO VGN-NW320F/B Battery

Consumption

The consumption of gold produced in the world is about 50% in jewelry, 40% in investments, and 10% in industry.

India is the world's largest single consumer of gold, as Indians buy about 25% of the world's gold,[59] purchasing approximately 800 tonnes of gold every year, mostly for jewelry. Sony VAIO VGN-NW320F/TC Battery

India is also the largest importer of gold; in 2008, India imported around 400 tonnes of gold.[60] Indian households hold 18,000 tonnes of gold which represents 11 per cent of the global stock and worth more than $950 billion.[61]

Chemistry

Although gold is a noble metal, it forms many and diverse compounds. Sony VAIO VGN-NW35E Battery

The oxidation state of gold in its compounds ranges from ?1 to +5, but Au(I) and Au(III) dominate its chemistry. Au(I), referred to as the aurous ion, is the most common oxidation state with soft ligands such as thioethers, thiolates, and tertiary phosphines. Au(I) compounds are typically linear. Sony VAIO VGN-NW380F/S Battery

A good example isAu(CN)2?, which is the soluble form of gold encountered in mining. Curiously, aurous complexes of water are rare. The binary gold halides, such as AuCl, form zigzag polymeric chains, again featuring linear coordination at Au. Most drugs based on gold are Au(I) derivatives.[63] Sony VAIO VGN-NW380F/T Battery

Au(III) (auric) is a common oxidation state, and is illustrated by gold(III) chloride, Au2Cl6. The gold atom centers in Au(III) complexes, like other d8 compounds, are typically square planar, with chemical bonds that have both covalent and ionic character.

Aqua regia, a 1:3 mixture of nitric acid and hydrochloric acid, dissolves gold. Sony VAIO VGN-NW50JB Battery

Nitric acid oxidizes the metal to +3 ions, but only in minute amounts, typically undetectable in the pure acid because of the chemical equilibrium of the reaction. However, the ions are removed from the equilibrium by hydrochloric acid, forming AuCl4? ions, or chloroauric acid, thereby enabling further oxidation. Sony VAIO VGN-NW51FB/N Battery

Some free halogens react with gold.[64] Gold also reacts in alkaline solutions of potassium cyanide. With mercury, it forms anamalgam.

Less common oxidation states

Less common oxidation states of gold include ?1, +2, and +5. Sony VAIO VGN-NW51FB/W Battery

The ?1 oxidation state occurs in compounds containing the Au? anion, called aurides. Caesium auride (CsAu), for example, crystallizes in the caesium chloridemotif.[65] Other aurides include those of Rb+, K+, and tetramethylammonium (CH3)4N+.[66]Gold has the highest Pauling electronegativity of any metal, with a value of 2.54, making the auride anion relatively stable. Sony VAIO VGN-NW70JB Battery

Gold(II) compounds are usually diamagnetic with Au–Au bonds such as [Au(CH2)2P(C6H5)2]2Cl2. The evaporation of a solution of Au(OH)3 in concentrated H2SO4 produces red crystals of gold(II) sulfate, Au2(SO4)2. Originally thought to be a mixed-valence compound, it has been shown to contain Au4+
2 cations.[67][68] Sony VAIO VGN-NW71FB/N Battery

A noteworthy, legitimate gold(II) complex is the tetraxenonogold(II) cation, which contains xenon as a ligand, found in [AuXe4](Sb2F11)2.[69]

Gold pentafluoride and its derivative anion, AuF?
6, is the sole example of gold(V), the highest verified oxidation state.[70] Sony VAIO VGN-NW71FB/W Battery

Some gold compounds exhibit aurophilic bonding, which describes the tendency of gold ions to interact at distances that are too long to be a conventional Au–Au bond but shorter that van der Waals bonding. The interaction is estimated to be comparable in strength to that of a hydrogen bond. Sony VAIO VGN-NW91FS Battery

Mixed valence compounds

Well-defined cluster compounds are numerous.[66] In such cases, gold has a fractional oxidation state. A representative example is the octahedral species {Au(P(C6H5)3)}62+. Gold chalcogenides, such as gold sulfide, feature equal amounts of Au(I) and Au(III).Sony VAIO VGN-NW91GS Battery

Toxicity

Pure metallic (elemental) gold is non-toxic and non-irritating when ingested[71] and is sometimes used as a food decoration in the form of gold leaf. Metallic gold is also a component of the alcoholic drinks Goldschläger, Gold Strike, and Goldwasser. Sony VAIO VGN-NW91VS Battery

Metallic gold is approved as a food additive in the EU (E175 in the Codex Alimentarius). Although gold ion is toxic, the acceptance of metallic gold as a food additive is due to its relative chemical inertness, and resistance to being corroded or transformed into soluble salts (gold compounds) by any known chemical process which would be encountered in the human body. Sony VAIO VGN-SR11M Battery

Soluble compounds (gold salts) such as gold chloride are toxic to the liver and kidneys. Common cyanide salts of gold such as potassium gold cyanide, used in gold electroplating, are toxic by virtue of both their cyanide and gold content. There are rare cases of lethal gold poisoning from potassium gold cyanide.[72][73] Sony VAIO VGN-SR11MR Battery

Gold toxicity can be ameliorated with chelation therapy with an agent such as Dimercaprol.

Gold metal was voted Allergen of the Year in 2001 by the American Contact Dermatitis Society. Gold contact allergies affect mostly women.[74] Despite this, gold is a relatively non-potent contact allergen, in comparison with metals like nickel.[75] Sony VAIO VGN-SR140D Battery

Price

Like other precious metals, gold is measured by troy weight and by grams. When it is alloyed with other metals the term carator karat is used to indicate the purity of gold present, with 24 carats being pure gold and lower ratings proportionally less. Sony VAIO VGN-SR140D/B Battery

The purity of a gold bar or coin can also be expressed as a decimal figure ranging from 0 to 1, known as the millesimal fineness, such as 0.995 being very pure.

The price of gold is determined through trading in the gold and derivatives markets, but a procedure known as the Gold Fixingin London, originating in September 1919, Sony VAIO VGN-SR140D/P Battery

provides a daily benchmark price to the industry. The afternoon fixing was introduced in 1968 to provide a price when US markets are open.

Historically gold coinage was widely used as currency; when paper money was introduced, it typically was a receiptredeemable for gold coin or bullion. Sony VAIO VGN-SR140D/S Battery

In a monetary system known as the gold standard, a certain weight of gold was given the name of a unit of currency. For a long period, the United States government set the value of the US dollar so that one troy ounce was equal to $20.67 ($664.56/kg), but in 1934 the dollar was devalued to $35.00 per troy ounce ($1125.27/kg). Sony VAIO VGN-SR140E Battery

By 1961, it was becoming hard to maintain this price, and a pool of US and European banks agreed to manipulate the market to prevent further currency devaluationagainst increased gold demand.

On March 17, 1968, economic circumstances caused the collapse of the gold pool, Sony VAIO VGN-SR140E/B Battery

and a two-tiered pricing scheme was established whereby gold was still used to settle international accounts at the old $35.00 per troy ounce ($1.13/g) but the price of gold on the private market was allowed to fluctuate; this two-tiered pricing system was abandoned in 1975 when the price of gold was left to find its free-market level. Sony VAIO VGN-SR140E/P Battery

Central banks still hold historical gold reserves as a store of value although the level has generally been declining. The largest gold depository in the world is that of the U.S. Federal Reserve Bank in New York, which holds about 3%[76] of the gold ever mined, as does the similarly laden U.S. Bullion Depository at Fort Knox. Sony VAIO VGN-SR140E/S Battery

In 2005 the World Gold Council estimated total global gold supply to be 3,859 tonnes and demand to be 3,754 tonnes, giving a surplus of 105 tonnes.[77]

Since 1968 the price of gold has ranged widely, from a high of $850/oz ($27,300/kg) on January 21, 1980, to a low of $252.90/oz ($8,131/kg) on June 21, 1999 (London Gold Fixing).[78] Sony VAIO VGN-SR140N/S Battery

The period from 1999 to 2001 marked the "Brown Bottom" after a 20-year bear market.[79] Prices increased rapidly from 1991, but the 1980 high was not exceeded until January 3, 2008 when a new maximum of $865.35 per troy ounce was set.[80] Another record price was set on March 17, 2008 at $1023.50/oz ($32,900/kg).[80] Sony VAIO VGN-SR165E/B Battery

In late 2009, gold markets experienced renewed momentum upwards due to increased demand and a weakening US dollar. On December 2, 2009, Gold passed the important barrier of US$1200 per ounce to close at $1215.[81] Gold further rallied hitting new highs in May 2010 after the European Union debt crisis prompted further purchase of gold as a safe asset.[82][83] Sony VAIO VGN-SR165E/P Battery

On March 1, 2011, gold hit a new all-time high of $1432.57, based on investor concerns regarding ongoing unrest in North Africa as well as in the Middle East.[84]

Since April 2001 the gold price has more than quintupled in value against the US dollar, hitting a new all-time high of $1,913.50 on August 23, 2011,[85] Sony VAIO VGN-SR165E/S Battery

prompting speculation that this long secular bear market has ended and a bull market has returned.[86]

Symbolism

Gold has been highly valued in many societies throughout the ages. In keeping with this it has often had a strongly positive symbolic meaning closely connected to the values held in the highest esteem in the society in question. Sony VAIO VGN-SR190EBJ Battery

Gold may symbolize power, strength, wealth, warmth, happiness, love, hope, optimism, intelligence, justice, balance, perfection, summer, harvest and the sun.

Great human achievements are frequently rewarded with gold, in the form of gold medals, golden trophies and other decorations.Sony VAIO VGN-SR190EBQ Battery

Winners of athletic events and other graded competitions are usually awarded a gold medal (e.g., the Olympic Games). Many awards such as the Nobel Prize are made from gold as well. Other award statues and prizes are depicted in gold or are gold plated (such as the Academy Awards, the Golden Globe Awards, the Emmy Awards, the Palme d'Or, and the British Academy Film Awards). Sony VAIO VGN-SR190EEJ/C Battery

Aristotle in his ethics used gold symbolism when referring to what is now commonly known as the "golden mean". Similarly, gold is associated with perfect or divine principles, such as in the case of the "golden ratio".

Gold represents great value. Respected people are treated with the most valued rule, the "golden rule". Sony VAIO VGN-SR190NAB Battery

A company may give its most valued customers "gold cards" or make them "gold members". We value moments of peace and therefore we say: "silence is golden". In Greek mythology there was the "golden fleece".

Gold is further associated with the wisdom of aging and fruition. Sony VAIO VGN-SR190NBB Battery

The fiftieth wedding anniversary is golden. Our precious latter years are sometimes considered "golden years". The height of a civilization is referred to as a "golden age".

In Christianity gold has sometimes been associated with the extremities of utmost evil and the greatest sanctity. Sony VAIO VGN-SR190NDB Battery

In the Book of Exodus, the Golden Calf is a symbol of idolatry. In the Book of Genesis, Abraham was said to be rich in gold and silver, and Moses was instructed to cover the Mercy Seat of the Ark of the Covenant with pure gold. In Christian art the halos of Christ, Mary and the Christian saints are golden. Sony VAIO VGN-SR190NEB Battery

Medieval kings were inaugurated under the signs of sacred oil and a golden crown, the latter symbolizing the eternal shining light of heaven and thus a Christian king's divinely inspired authority. Wedding rings have long been made of gold. It is long lasting and unaffected by the passage of time and may aid in the ring symbolism of eternal vows before God and/or the sun and moon and the perfection the marriage signifies. Sony VAIO VGN-SR190NGB Battery

In Orthodox Christianity, the wedded couple is adorned with a golden crown during the ceremony, an amalgamation of symbolic rites.

In popular culture gold holds many connotations but is most generally connected to terms such as good or great, such as in the phrases: "has a heart of gold", "that's golden!", "golden moment", "then you're golden!" and "golden boy". Sony VAIO VGN-SR190PAB Battery

Gold also still holds its place as a symbol of wealth and through that, in many societies, success.

Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilverorhydrargyrum(from "hydr-" water and "argyros" silver). Sony VAIO VGN-SR190PCB Battery

A heavy, silvery d-block element, mercury is the only metal that is liquid at standard conditions for temperature and pressure; the only other element that is liquid under these conditions is bromine, and metals such as caesium, francium, gallium, and rubidium melt just above room temperature. Sony VAIO VGN-SR190PFB Battery

With a freezing point of ?38.83 °C and boiling pointof 356.73 °C, mercury has one of the narrowest ranges of its liquid state of any metal.[1][2][3]

Mercury occurs in deposits throughout the world mostly as cinnabar (mercuric sulfide). The red pigment vermilion is mostly obtained by reduction from cinnabar. Sony VAIO VGN-SR19VN Battery

Cinnabar is highly toxic by ingestion or inhalation of the dust. Mercury poisoning can also result from exposure to water-soluble forms of mercury (such as mercuric chloride ormethylmercury), inhalation of mercury vapor, or eating seafood contaminated with mercury. Sony VAIO VGN-SR19VN Battery

Mercury is used in thermometers, barometers, manometers, sphygmomanometers, float valves, some electrical switches, and other scientific apparatus, though concerns about the element's toxicity have led to mercury thermometers and sphygmomanometers being largely phased out in clinical environments in favor of alcohol-filled, galinstan-filled, digital, or thermistor-based instruments.Sony VAIO VGN-SR19VRN Battery

It remains in use in scientific research applications and in amalgammaterial for dental restoration. It is used in lighting: electricity passed through mercury vapor in a phosphor tube produces short-wave ultraviolet light which then causes the phosphor to fluoresce, making visible light. Sony VAIO VGN-SR19XN Battery

Physical properties

Mercury is a heavy, silvery-white metal. As compared to other metals, it is a poor conductor of heat, but a fair conductor of electricity.[4] Mercury has an exceptionally low melting temperature for a d-block metal. Sony VAIO VGN-SR19XN Battery

A complete explanation of this fact requires a deep excursion into quantum physics, but it can be summarized as follows: mercury has a unique electronic configuration where electrons fill up all the available 1s, 2s, 2p, 3s, 3p, 3d, 4s, 4p, 4d, 4f, 5s, 5p, 5d and 6s subshells. Sony VAIO VGN-SR210J/S Battery

As such configuration strongly resists removal of an electron, mercury behaves similarly to noble gas elements, which form weak bonds and thus easily melting solids. The stability of the 6s shell is due to the presence of a filled 4f shell. An f shell poorly screens the nuclear charge that increases the attractive Coulomb interaction of the 6s shell and the nucleus (seelanthanide contraction). Sony VAIO VGN-SR21M/S Battery

The absence of a filled inner f shell is the reason for the somewhat higher melting temperature of cadmium and zinc, although both these metals still melt easily and, in addition, have unusually low boiling points. Metals such as gold have atoms with one less 6s electron than mercury. Sony VAIO VGN-SR21RM/H Battery

Those electrons are more easily removed and are shared between the gold atoms forming relatively strong metallic bonds.[2][5] At its freezing point (?38.86 °C), the density of mercury is[6] 13.534 g/cm3. Sony VAIO VGN-SR21RM/S Battery

Chemical properties

Mercury does not react with most acids, such as dilute sulfuric acid, although oxidizing acids such as concentratedsulfuric acidand nitric acid or aqua regia dissolve it to give sulfate,nitrate , and chloride salts. Sony VAIO VGN-SR220J/B Battery

Like silver, mercury reacts with atmospherichydrogen sulfide. Mercury even reacts with solid sulfur flakes, which are used in mercury spill kits to absorb mercury vapors (spill kits also use activated carbon and powdered zinc).[7]

Amalgams

Mercury dissolves to form amalgams with gold, zinc and many other metals. Sony VAIO VGN-SR220J/H Battery

Because iron is an exception, iron flasks have been traditionally used to trade mercury. Other metals that do not form amalgams with mercury include tantalum, tungsten and platinum. Sodium amalgam is a common reducing agent in organic synthesis.

Mercury readily combines with aluminium to form a mercury-aluminium amalgam when the two pure metals come into contact.Sony VAIO VGN-SR240J/B Battery

Since the amalgam reacts with air to give aluminium oxide, small amounts of mercury corrode aluminium. For this reason, mercury is not allowed aboard an aircraft under most circumstances because of the risk of it forming an amalgam with exposed aluminium parts in the aircraft.[8] Sony VAIO VGN-SR240N/B Battery

Isotopes

There are seven stable isotopes of mercury with 202Hg being the most abundant (29.86%). The longest-livedradioisotopesare 194Hg with a half-life of 444 years, and 203Hg with a half-life of 46.612 days. Sony VAIO VGN-SR290JTH Battery

Most of the remaining radioisotopes have half-lives that are less than a day. 199Hg and 201Hg are the most often studied NMR-active nuclei, having spins of 1?2 and 3?2 respectively.[4]

In China and Tibet, mercury use was thought to prolong life, heal fractures, and maintain generally good health, Sony VAIO VGN-SR290JTJ Battery

although it is now known that exposure to mercury leads to serious adverse health effects.[10] One of China's emperors, Qín Sh? Huáng Dì — allegedly buried in a tomb that contained rivers of flowing mercury on a model of the land he ruled, representative of the rivers of China —Sony VAIO VGN-SR290JTQ Battery

was killed by drinking a mercury and powdered jade mixture formulated byQin alchemists (causing liver failure, mercury poisoning, and brain death) who intended to give him eternal life.[11][12]

The ancient Greeks used mercury in ointments; the ancient Egyptians and the Romans used it incosmetics which sometimes deformed the face. Sony VAIO VGN-SR290JVB/C Battery

In Lamanai, once a major city of the Maya civilization, a pool of mercury was found under a marker in a Mesoamerican ballcourt.[13][14] By 500 BC mercury was used to make amalgams (Medieval Latin amalgama, "alloy of mercury") with other metals.[15]

Alchemists thought of mercury as the First Matter from which all metals were formed. Sony VAIO VGN-SR290JVH/C Battery

They believed that different metals could be produced by varying the quality and quantity of sulfur contained within the mercury. The purest of these was gold, and mercury was called for in attempts at the transmutation of base (or impure) metals into gold, which was the goal of many alchemists.[16] Sony VAIO VGN-SR290NTB Battery

Hg is the modern chemical symbol for mercury. It comes from hydrargyrum, a Latinized form of the Greek word ?????????? (hydrargyros), which is a compound word meaning "water-silver" (hydr- = water, argyros = silver) — since it is liquid like water and shiny like silver. Sony VAIO VGN-SR29VN/S Battery

The element was named after the Roman godMercury, known for speed and mobility. It is associated with the planet Mercury; the astrological symbol for the planet is also one of the alchemical symbols for the metal; the Indian word for alchemy is Rasav?tamwhich means "the way of mercury".[17] Sony VAIO VGN-SR29XN/S Battery

Mercury is the only metal for which the alchemical planetary name became the common name.[16]

The mines in Almadén (Spain), Monte Amiata (Italy), and Idrija (now Slovenia) dominated the mercury production from the opening of the mine in Almadén 2500 years ago until new deposits were found at the end of the 19th century.[18] Sony VAIO VGN-SR2RVN/S Battery

Occurrence

Mercury is an extremely rare element in the Earth's crust, having an average crustal abundance by mass of only 0.08 parts per million (ppm).[19] However, because it does not blend geochemically with those elements that constitute the majority of the crustal mass, mercury ores can be extraordinarily concentrated considering the element's abundance in ordinary rock. Sony VAIO VGN-SR390NAB Battery

The richest mercury ores contain up to 2.5% mercury by mass, and even the leanest concentrated deposits are at least 0.1% mercury (12,000 times average crustal abundance). It is found either as a native metal (rare) or incinnabar, corderoite, livingstonite and other minerals, with cinnabar (HgS) being the most common ore.[20] Sony VAIO VGN-SR390NAH Battery

Mercury ores usually occur in very young orogenic belts where rock of high density are forced to the crust of the Earth, often in hot springs or other volcanic regions.[21]

Beginning in 1558, with the invention of the patio process to extract silver from ore using mercury, mercury became an essential resource in the economy of Spain and its American colonies. Sony VAIO VGN-SR41M/P Battery

Mercury was used to extract silver from the lucrative mines in New Spain and Peru. Initially, the Spanish Crown's mines in Almaden in Southern Spain supplied all the mercury for the colonies.[22]Mercury deposits were discovered in the New World, and more than 100,000 tons of mercury were mined from the region of Huancavelica, Peru, over the course of three centuries following the discovery of deposits there in 1563. Sony VAIO VGN-SR41M/S Battery

The patio process and later pan amalgamation process continued to create great demand for mercury to treat silver ores until the late 19th century.[23]

Former mines in Italy, the United States and Mexico which once produced a large proportion of the world supply have now been completely mined out or, in the case of Slovenia (Idrija) and Spain (Almadén), shut down due to the fall of the price of mercury. Sony VAIO VGN-SR49VN/H Battery

Nevada's McDermitt Mine, the last mercury mine in the United States, closed in 1992. The price of mercury has been highly volatile over the years and in 2006 was $650 per 76-pound (34.46 kg) flask.[24]

Mercury is extracted by heating cinnabar in a current of air and condensing the vapor. The equation for this extraction isSony VAIO VGN-SR51B/P Battery

HgS + O2 ? Hg + SO2

In 2005, China was the top producer of mercury with almost two-thirds global share followed by Kyrgyzstan.[25] Several other countries are believed to have unrecorded production of mercury from copper electrowinning processes and by recovery from effluents. Sony VAIO VGN-SR51B/S Battery

Because of the high toxicity of mercury, both the mining of cinnabar and refining for mercury are hazardous and historic causes of mercury poisoning.[26] In China, prison labor was used by a private mining company as recently as the 1950s to create new cinnabar mercury mines. Sony VAIO VGN-SR51MF Battery

Thousands of prisoners were used by the Luo Xi mining company to establish new tunnels.[27] In addition, worker health in functioning mines is at high risk.

The European Union directive calling for compact fluorescent bulbs to be made mandatory by 2012 has encouraged China to re-open deadly cinnabar mines to obtain the mercury required for CFL bulb manufacture. Sony VAIO VGN-SR51MF/P Battery

As a result, environmental dangers have been a concern, particularly in the southern cities of Foshan and Guangzhou, and in the Guizhou province in the south west.[27]

Abandoned mercury mine processing sites often contain very hazardous waste piles of roasted cinnabar calcines. Sony VAIO VGN-SR51MF/S Battery

Water run-off from such sites is a recognized source of ecological damage. Former mercury mines may be suited for constructive re-use. For example, in 1976 Santa Clara County, California purchased the historic Almaden Quicksilver Mine and created a county park on the site, after conducting extensive safety and environmental analysis of the property.[28] Sony VAIO VGN-SR51MF/W Battery

Chemistry

Mercury exists in two main oxidation states, I and II. Higher oxidation states are unimportant, but have been detected, e.g., mercury(IV) fluoride (HgF4) but only under extraordinary conditions.[29] Sony VAIO VGN-SR51MR Battery

Compounds of mercury(I)

Different from its lighter neighbors, cadmium and zinc, mercury forms simple stable compounds with metal-metal bonds. The mercury(I) compounds are diamagnetic and feature the dimeric cation, Hg2+
2. Stable derivatives include the chloride and nitrate. Sony VAIO VGN-SR59VG Battery

Treatment of Hg(I) compounds complexation with strong ligands such as sulfide, cyanide, etc. induces disproportionation to Hg2+and elemental mercury.[30] Mercury(I) chloride, a colorless solid also known as calomel, is really the compound with the formula Hg2Cl2, with the connectivity Cl-Hg-Hg-Cl. Sony VAIO VGN-SR59VG/H Battery

It is a standard in electrochemistry. It reacts with chlorine to give mercuric chloride, which resists further oxidation.

Indicative of its tendency to bond to itself, mercury forms mercury polycations, which consist of linear chains of mercury centers, capped with a positive charge. One example is Hg32+(AsF6–)2.[31] Sony VAIO VGN-SR70B/S Battery

Compounds of mercury(II)

Mercury(II) is the most common oxidation state and is the main one in nature as well. All four mercuric halides are known. The form tetrahedral complexes with other ligands but the halides adopt linear coordination geometry, somewhat like Ag+ does. Sony VAIO VGN-SR72B/P Battery

Best known is mercury(II) chloride, an easily sublimating white solid. HgCl2forms coordination complexes that are typically tetrahedral, e.g. HgCl42–.

Mercury(II) oxide, the main oxide of mercury, arises when the metal is exposed to air for long periods at elevated temperatures.Sony VAIO VGN-SR72B/S Battery

It reverts to the elements upon heating near 400 °C, as was demonstrated by Priestly in an early synthesis of pure oxygen.[7]Hydroxides of mercury are poorly characterized, as they are for its neighbors gold and silver.

Being a soft metal, mercury forms very stable derivatives with the heavier chalcogens. Sony VAIO VGN-SR73JB/S Battery

Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore cinnabar and is the brilliant pigment vermillion. Like ZnS, HgS crystallizes in two forms, the reddish cubic form and the black zinc blende form.[4] Mercury(II) selenide (HgSe) and mercury(II) telluride (HgTe) are also known, Sony VAIO VGN-SR74FB/S Battery

these as well as various derivatives, e.g. mercury cadmium telluride and mercury zinc telluridebeing semiconductors useful as infrared detectormaterials.[32]

Mercury(II) salts form a variety of complex derivatives with ammonia. These include Millon's base (Hg2N+), the one-dimensional polymer (salts of HgNH2+)n), and "fusible white precipitate" or [Hg(NH3)2]Cl2. Sony VAIO VGN-SR90FS Battery

Known as Nessler's reagent, potassium tetraiodomercurate(II) (HgI42–) is still occasionally used to test for ammonia owing to its tendency to form the deeply colored iodide salt of Millon's base.

Mercury fulminate, (a detonator widely used in explosives);[4] Sony VAIO VGN-SR90NS Battery

Compounds of mercury(IV)

Mercury(IV) is the rarest oxidation state of mercury which is known to exist. The only known mercury(IV) compound is mercury(IV) fluoride.

Organomercury compounds

Organic mercury compounds are historically important but are of little industrial value in the western world. Sony VAIO VGN-SR90S Battery

Mercury(II) salts are a rare examples of simple metal complexes that react directly with aromatic rings. Organomercury compounds are always divalent and usually two-coordinate and linear geometry. Unlike organocadmium and organozinc compounds, organomercury compounds do not react with water. Sony VAIO VGN-SR90US Battery

They usually have the formula HgR2, which are often volatile, or HgRX, which are often solids, where R is aryl or alkyl and X is usually halide or acetate. Methylmercury, a generic term for compounds with the formula CH3HgX is a dangerous family of compounds that is found in some a polluted water.[33] They arise by a process known as biomethylation. Sony VAIO VGN-SR91NS Battery

Applications

Mercury is used primarily for the manufacture of industrial chemicals or for electrical and electronic applications. It is used in some thermometers, especially ones which are used to measure high temperatures. Sony VAIO VGN-SR91PS Battery

A still increasing amount is used as gaseous mercury in fluorescent lamps, while most of the other applications are slowly phased out due to health and safety regulations and is in some applications replaced with less toxic but considerably more expensive Galinstan alloy. Sony VAIO VGN-SR91S Battery

Medicine

Mercury and its compounds have been used in medicine, although they are much less common today than they once were, now that the toxic effects of mercury and its compounds are more widely understood. The element mercury is an ingredient in dental amalgams. Sony VAIO VGN-SR91US Battery

Thiomersal (called Thimerosal in the United States) is an organic compound used as a preservative in vaccines, though this use is in decline.[34] Another mercury compound Merbromin (Mercurochrome) is a topical antiseptic used for minor cuts and scrapes is still in use in some countries. Sony VAIO VGN-SR92NS Battery

Since the 1930s some vaccines have contained the preservative thiomersal, which is metabolized or degraded to ethyl mercury. Although it was widely speculated that this mercury-based preservative can cause or trigger autism in children, scientific studies showed no evidence supporting any such link.[35] Sony VAIO VGN-SR92PS Battery

Nevertheless thiomersal has been removed from or reduced to trace amounts in all U.S. vaccines recommended for children 6 years of age and under, with the exception of inactivated influenza vaccine.[36]

Mercury in the form of one of its common ores, cinnabar, is used in various traditional medicines, especially in traditional Chinese medicine. Sony VAIO VGN-SR92S Battery

Review of its safety has found cinnabar can lead to significant mercury intoxication when heated, consumed in overdoseor taken long term, and can have adverse effects at therapeutic doses, though this is typically reversible at therapeutic doses. Although this form of mercury appears less toxic than others, its use in traditional Chinese medicine has not yet been justified as the therapeutic basis for the use of cinnabar is not clear.[37] Sony VAIO VGN-SR92US Battery

Today, the use of mercury in medicine has greatly declined in all respects, especially in developed countries. Thermometersandsphygmomanometers containing mercury were invented in the early 18th and late 19th centuries, respectively. In the early 21st century, their use is declining and has been banned in some countries, states and medical institutions.Sony VAIO VGN-SR93DS Battery

In 2002, the U.S. Senatepassed legislation to phase out the sale of non-prescription mercury thermometers. In 2003, Washington and Maine became the first states to ban mercury blood pressure devices.[38] Mercury compounds are found in some over-the-counter drugs, including topicalantiseptics, stimulant laxatives, diaper-rash ointment, eye drops, and nasal sprays.Sony VAIO VGN-SR93JS Batery

The FDA has "inadequate data to establish general recognition of the safety and effectiveness", of the mercury ingredients in these products.[39] Mercury is still used in some diuretics, although substitutes now exist for most therapeutic uses. Sony VAIO VGN-SR93PS Batttery

Production of chlorine and caustic soda

Chlorine is produced from sodium chloride (common salt, NaCl) using electrolysis to separate the metallic sodium from the chlorine gas. Usually the salt is dissolved in water to produce a brine. Sony VAIO VGN-SR93YS Battery

By-products of any such chloralkali process are hydrogen (H2) andsodium hydroxide (NaOH), which is commonly called caustic soda or lye. By far the largest use of mercury[40][41] in the late 20th century was in the mercury cell process (also called the Castner-Kellner process) where metallic sodium is formed as an amalgam at acathode made from mercury; Sony VAIO VGN-SR94FS Battery

this sodium is then reacted with water to produce sodium hydroxide.[42] Many of the industrial mercury releases of the 20th century came from this process, although modern plants claimed to be safe in this regard.[41] After about 1985, all new chloralkali production facilities that were built in the United States used either membrane cell or diaphragm cell technologies to produce chlorine. Sony VAIO VGN-SR94GS Battery

Laboratory uses

Some medical thermometers, especially those for high temperatures, are filled with mercury; however, they are gradually disappearing. In the United States, non-prescription sale of mercury fever thermometers has been banned since 2003.[43] Sony VAIO VGN-SR94HS Battery

Mercury is also found in liquid mirror telescopes. The mirror is formed by rotating liquid mercury on a disk, the parabolic form of the liquid thus formed reflecting and focusing incident light. Such telescopes are cheaper than conventional large mirror telescopes by up to a factor of 100, but the mirror cannot be tilted and always points straight up. Sony VAIO VGN-SR94VS Battery

Liquid mercury is a part of popular secondary reference electrode (called the calomel electrode) in electrochemistry as an alternative to the standard hydrogen electrode. The calomel electrode is used to work out the electrode potential of half cells.[47]Last, but not least, the triple point of mercury, ?38.8344 °C, is a fixed point used as a temperature standard for the International Temperature Scale (ITS-90).[4] Sony VAIO VGN-SZ35B/B Battery

Niche uses

Gaseous mercury is used in mercury-vapor lamps and some "neon sign" type advertising signs and fluorescent lamps. Those low-pressure lamps emit very spectrally narrow lines, which are traditionally used in optical spectroscopy for calibration of spectral position. Sony VAIO VGN-SZ54B/B Battery

Commercial calibration lamps are sold for this purpose; however simply reflecting some of the fluorescent-lamp ceiling light into a spectrometer is a common calibration practice.[48] Gaseous mercury is also found in some electron tubes, including ignitrons, thyratrons, and mercury arc rectifiers.[49] Sony VAIO VGN-SZ55B/B Battery

It is also used in specialist medical care lamps for skin tanning and disinfection (see pictures).[50] Gaseous mercury is added to cold cathode argon-filled lamps to increase the ionization andelectrical conductivity. An argon filled lamp without mercury will have dull spots and will fail to light correctly. Sony VAIO VGN-SZ55GN/B Battery

Lighting containing mercury can be bombarded/oven pumped only once. When added to neon filled tubes the light produced will be inconsistent red/blue spots until the initial burning-in process is completed; eventually it will light a consistent dull off-blue color.[51] Sony VAIO VGN-SZ56 Battery

Cosmetics

Mercury, as thiomersal, is widely used in the manufacture of mascara. In 2008, Minnesota became the first state in the US to ban intentionally added mercury in cosmetics, giving it a tougher standard than the federal government.[52] Sony VAIO VGN-SZ561N Battery

A study in geometric mean urine mercury concentration identified a previously unrecognized source of exposure (skin care products) to inorganic mercury among New York City residents. Population-based biomonitoring also showed that mercury concentration levels are higher in consumers of seafood and fish meals.[53] Sony VAIO VGN-SZ562N Battery

Historic uses

Many historic applications made use of the peculiar physical properties of mercury, especially as a dense liquid and a liquid metal:

In Islamic Spain, it was used for filling decorative pools. Later, the American artist Alexander Calder built a mercury fountainfor the Spanish Pavilion at the 1937 World Exhibition in Paris. Sony VAIO VGN-SZ57N Battery

• The fountain is now on display at the Fundació Joan Miróin Barcelona.[54]

Mercury was used inside wobbler lures. Its heavy, liquid form made it useful since the lures made an attractive irregular movement when the mercury moved inside the plug. Sony VAIO VGN-SZ58GN Battery

• Such use was stopped due to environmental concerns, but illegal preparation of modern fishing plugs has occurred.
• The Fresnel lenses of old lighthouses used to float and rotate in a bath of mercury which acted like a bearing.[55]

Mercury sphygmomanometers (blood pressure meter), barometers, diffusion pumps, coulometers, and many other laboratory instruments. Sony VAIO VGN-SZ58GN/C Battery

• As an opaque liquid with a high density and a nearly linear thermal expansion, it is ideal for this role.[56]

As an electrically conductive liquid, it was used in mercury switches (including home mercury light switches installed prior to 1970), tilt switches used in old fire detectors, and tilt switches in many modern home thermostats,[57] Sony VAIO VGN-SZ58N Battery

• Owing to its acoustic properties, mercury was used as the propagation medium in delay line memory devices used in early digital computers of the mid-20th century.

Experimental mercury vapor turbines were installed to increase the efficiency of fossil-fuel electrical power plants.[58] Sony VAIO VGN-SZ61MN/B Battery

The South Meadow power plant in Hartford, CT employed mercury as its working fluid, in a binary configuration with a secondary water circuit, or a number of years starting in the late 1920s in a drive to improve plant efficiency. Several other plants were built, including the Schiller Station in Portsmouth, NH, which went online in 1950. Sony VAIO VGN-SZ61VN/X Battery

• The idea did not catch on industry-wide due to the weight and toxicity of mercury, as well as the advent of supercritical steam plants in later years.[59][60]

Similarly, liquid mercury was used as a coolant for some nuclear reactors; however, sodium is proposed for reactors cooled with liquid metal, because the high density of mercury requires much more energy to circulate as coolant.[61] Sony VAIO VGN-SZ61WN/C Battery

Mercury was a propellant for early ion engines in electric space propulsion systems. Advantages were mercury's high molecular weight, low ionization energy, low dual-ionization energy, high liquid density and liquid storability at room temperature. Sony VAIO VGN-SZ640N/B Battery

Disadvantages were concerns regarding environmental impact associated with ground testing and concerns about eventual cooling and condensation of some of the propellant on the spacecraft in long-duration operations. The first spaceflight to use electric propulsion was a mercury-fueled ion thruster developed by NASA Lewis and flown on the Space Electric Rocket Test "SERT-1" spacecraft launched by NASA at its Wallops Flight Facility in 1964. Sony VAIO VGN-SZ645P3 Battery

The SERT-1 flight was followed up by the SERT-2 flight in 1970. Mercury and caesium were preferred propellants for ion engines until Hughes Research Laboratory performed studies finding xenon gas to be a suitable replacement. Xenon is now the preferred propellant for ion engines as it has a high molecular weightSony VAIO VGN-SZ650N/C Battery

• , little or no reactivity due to its noble gas nature, and has a high liquid density under mild cryogenic storage.[62][63]
• Mercury has been used to produce liquid mirror telescopes.[64]

Others applications made use of the chemical properties of mercury: Sony VAIO VGN-SZ660N/C Battery

Mercury was used for preserving wood, developing daguerreotypes, silvering mirrors, anti-fouling paints (discontinued in 1990), herbicides (discontinued in 1995), handheld maze games, cleaning, and road leveling devices in cars. Mercury compounds have been used in antiseptics, laxatives, antidepressants, and in antisyphilitics. Sony VAIO VGN-SZ670N/C Battery

• It was allegedly used by allied spies to sabotage Luftwaffe planes: a mercury paste was applied to bare aluminium, causing the metal to rapidly corrode; this would cause structural failures.[65]

Chloralkali process: The largest industrial use of mercury during the 20th century was in electrolysis for separating chlorine and sodium from brine; Sony VAIO VGN-SZ680ND Battery

mercury being the anode of the Castner-Kellner process. The chlorine was used for bleaching paper (hence the location of many of these plants near paper mills) while the sodium was used to make sodium hydroxide for soaps and other cleaning products. This usage has largely been discontinued, replaced with other technologies that utilize membrane cells.[66] Sony VAIO VGN-SZ691N/X Battery

• As electrodes in some types of electrolysis, batteries (mercury cells), sodium hydroxide and chlorine production, handheld games, catalysts, insecticides.
• Mercury was once used as a gun barrel bore cleaner.[67][68]

From the mid-18th to the mid-19th centuries, a process called "carroting" was used in the making of felt hats. Sony VAIO VGN-SZ71E/B Battery

Animal skins were rinsed in an orange solution (the term "carroting" arose from this color) of the mercury compound mercuric nitrate, Hg(NO3)2·2H2O.[69] This process separated the fur from the pelt and matted it together. This solution and the vapors it produced were highly toxic. Sony VAIO VGN-SZ71VN/X Battery

The United States Public Health Service banned the use of mercury in the felt industry in December 1941. The psychological symptoms associated with mercury poisoning are said by some to have inspired the phrase "mad as a hatter". Sony VAIO VGN-SZ71WN/C Battery

• Lewis Carroll's "Mad Hatter" in his book Alice's Adventures in Wonderland was a play on words based on the older phrase, but the character himself does not exhibit symptoms of mercury poisoning.[70]

Gold and silver mining. Historically, mercury was used extensively in hydraulic gold mining in order to help the gold to sink through the flowing water-gravel mixture. Sony VAIO VGN-SZ74B/B Battery

Thin mercury particles may form mercury-gold amalgam and therefore increase the gold recovery rates.[4] Large-scale use of mercury stopped in the 1960s. However, mercury is still used in small scale, often clandestine, gold prospecting. It is estimated that 45,000 metric tons of mercury used in California forplacer mininghave not been recovered.[71] Mercury was also used in silver mining.[72] Sony VAIO VGN-SZ750N/C Battery

Historic medicinal uses

Mercury(I) chloride (also known as calomel or mercurous chloride) has been used in traditional medicine as a diuretic, topical disinfectant, and laxative.Mercury(II) chloride (also known as mercuric chloride or corrosive sublimate) Sony VAIO VGN-SZ75B/B Battery

was once used to treat syphilis (along with other mercury compounds), although it is so toxic that sometimes the symptoms of its toxicity were confused with those of the syphilis it was believed to treat.[73] It is also used as a disinfectant. Blue mass, a pill or syrup in which mercury is the main ingredient, Sony VAIO VGN-SZ76 Battery

was prescribed throughout the 19th century for numerous conditions including constipation, depression, child-bearing and toothaches.[74] In the early 20th century, mercury was administered to children yearly as a laxative and dewormer, and it was used in teething powders for infants. Sony VAIO VGN-SZ770N/C Battery

The mercury-containing organohalide merbromin (sometimes sold as Mercurochrome) is still widely used but has been banned in some countries such as the U.S.[75]

Toxicity and safety

Mercury and most of its compounds are extremely toxic and must be handled with care; Sony VAIO VGN-SZ77N Battery

in cases of spills involving mercury (such as from certainthermometers or fluorescent light bulbs), specific cleaning procedures are used to avoid exposure and contain the spill.[76] Protocols call for physically merging smaller droplets on hard surfaces, combining them into a single larger pool for easier removal with an eyedropper, or for gently pushing the spill into a disposable container. Sony VAIO VGN-SZ780 Battery

Vacuum cleaners and brooms cause greater dispersal of the mercury and should not be used. Afterwards, fine sulfur, zinc, or some other powder that readily forms an amalgam (alloy) with mercury at ordinary temperatures is sprinkled over the area before itself being collected and properly disposed of. Sony VAIO VGN-SZ78N Battery

Cleaning porous surfaces and clothing is not effective at removing all traces of mercury and it is therefore advised to discard these kinds of items should they be exposed to a mercury spill.

Mercury can be inhaled and absorbed through the skin and mucous membranes, so containers of mercury are securely sealed to avoid spills and evaporation. Sony VAIO VGN-SZ791N/X Battery

Heating of mercury, or of compounds of mercury that may decompose when heated, is always carried out with adequate ventilation in order to avoid exposure to mercury vapor. The most toxic forms of mercury are its organic compounds, such as dimethylmercury and methylmercury. Sony VAIO VGN-SZ84NS Battery

However, inorganic compounds, such as cinnabar are also highly toxic by ingestion or inhalation.[77] Mercury can cause both chronic and acute poisoning.

Releases in the environment

Preindustrial deposition rates of mercury from the atmosphere may be about 4 ng /(1 L of ice deposit). Sony VAIO VGN-SZ84PS Battery

Although that can be considered a natural level of exposure, regional or global sources have significant effects. Volcanic eruptions can increase the atmospheric source by 4–6 times.[78]

Natural sources, such as volcanoes, are responsible for approximately half of atmospheric mercury emissions. Sony VAIO VGN-SZ84S Battery

The human-generated half can be divided into the following estimated percentages:[79][80][81]

65% from stationary combustion, of which coal-fired power plants are the largest aggregate source (40% of U.S. mercury emissions in 1999). This includes power plants fueled with gas where the mercury has not been removed. Sony VAIO VGN-SZ84US Battery

• Emissions from coal combustion are between one and two orders of magnitude higher than emissions from oil combustion, depending on the country.[79]

11% from gold production. The three largest point sources for mercury emissions in the U.S. are the three largest gold mines. Sony VAIO VGN-SZ85NS Battery

• Hydrogeochemical release of mercury from gold-mine tailings has been accounted as a significant source of atmospheric mercury in eastern Canada.[82]
• 6.8% from non-ferrous metal production, typically smelters.

6.4% from cement production. Sony VAIO VGN-SZ85S Battery

• 3.0% from waste disposal, including municipal and hazardous waste, crematoria, and sewage sludge incineration. This is a significant underestimate due to limited information, and is likely to be off by a factor of two to five.

3.0% from caustic soda production. Sony VAIO VGN-SZ85US Battery

• 1.4% from pig iron and steel production.
• 1.1% from mercury production, mainly for batteries.
• 2.0% from other sources.

The above percentages are estimates of the global human-caused mercury emissions in 2000, excluding biomass burning, an important source in some regions.[79] Sony VAIO VGN-SZ94NS Battery

Current atmospheric mercury contamination in outdoor urban air is (0.01–0.02 µg/m3) indoor concentrations are significantly elevated over outdoor concentrations, in the range 0.0065–0.523 µg/m3 (average 0.069 µg/m3).[83]

Mercury also enters into the environment through the improper disposal (e.g., land filling, incineration) of certain products. Sony VAIO VGN-SZ94PS Battery

Products containing mercury include: auto parts, batteries, fluorescent bulbs, medical products, thermometers, and thermostats.[84] Due to health concerns (see below), toxics use reduction efforts are cutting back or eliminating mercury in such products. For example, most thermometers now use pigmented alcohol instead of mercury, and galinstan alloy thermometers are also an option. Sony VAIO VGN-SZ94S Battery

Mercury thermometers are still occasionally used in the medical field because they are more accurate than alcohol thermometers, though both are commonly being replaced by electronic thermometers and less commonly by galinstan thermometers. Mercury thermometers are still widely used for certain scientific applications because of their greater accuracy and working range. Sony VAIO VGN-SZ94US Battery

The United States Clean Air Act, passed in 1990, put mercury on a list of toxic pollutants that need to be controlled to the greatest possible extent. Thus, industries that release high concentrations of mercury into the environment agreed to install maximum achievable control technologies (MACT). Sony VAIO VGN-SZ95NS Battery

In March 2005 EPA rule[85] added power plants to the list of sources that should be controlled and a national cap and trade rule was issued. States were given until November 2006 to impose stricter controls, and several States are doing so. The rule was being subjected to legal challenges from several States in 2005 and decision was made in 2008. Sony VAIO VGN-SZ95S Battery

The Clean Air Mercury Rule was struck down by a Federal Appeals Court on February 8, 2008. The rule was deemed not sufficient to protect the health of persons living near coal-fired power plants. The court opinion cited the negative impact on human health from coal-fired power plants' mercury emissions documented in the EPA Study Report to Congress of 1998.[86] Sony VAIO VGN-SZ95US Battery

Historically, one of the largest releases was from the Colex plant, a lithium-isotope separation plant at Oak Ridge. The plant operated in the 1950s and 1960s. Records are incomplete and unclear, but government commissions have estimated that some two million pounds of mercury are unaccounted for.[87] Sony VAIO VGN-TZ121 Battery

A serious industrial disasters was the dumping of mercury compounds into Minamata Bay, Japan. It is estimated that over 3,000 people suffered various deformities, severe mercury poisoning symptoms or death from what became known as Minamata disease.[88] Sony VAIO VGN-TZ13 Battery

Occupational exposure

Due to the health effects of mercury exposure, industrial and commercial uses are regulated in many countries. The World Health Organization, OSHA, and NIOSH all treat mercury as an occupational hazard, and have established specific occupational exposure limits. Sony VAIO VGN-TZ130N/B Battery

Environmental releases and disposal of mercury are regulated in the U.S. primarily by the United States Environmental Protection Agency.

Case control studies have shown effects such as tremors, impaired cognitive skills, and sleep disturbance in workers with chronic exposure to mercury vapor even at low concentrations in the range 0.7–42 ?g/m3.[89][90Sony VAIO VGN-TZ131 Battery

] A study has shown that acute exposure (4 – 8 hours) to calculated elemental mercury levels of 1.1 to 44 mg/m3resulted in chest pain, dyspnea, cough, hemoptysis, impairment of pulmonary function, and evidence of interstitial pneumonitis.[91] Acute exposure to mercury vapor has been shown to result in profound central nervous system effects, including psychotic reactions characterized by delirium, hallucinations, and suicidal tendency. Sony VAIO VGN-TZ132/N Battery

Occupational exposure has resulted in broad-ranging functional disturbance, including erethism, irritability, excitability, excessive shyness, and insomnia. With continuing exposure, a fine tremor develops and may escalate to violent muscular spasms. Tremor initially involves the hands and later spreads to the eyelids, lips, and tongue. Sony VAIO VGN-TZ132N Battery

Long-term, low-level exposure has been associated with more subtle symptoms of erethism, including fatigue, irritability, loss of memory, vivid dreams and depression.[92][93]

Treatment

Research on the treatment of mercury poisoning is limited. Currently available drugs for acute mercurial poisoning include chelators N-acetyl-D, L-penicillamine(NAP), Sony VAIO VGN-TZ150N/B Battery

British Anti-Lewisite (BAL), 2,3-dimercapto-1-propanesulfonic acid (DMPS), and dimercaptosuccinic acid (DMSA). In one small study including 11 construction workers exposed to elemental mercury, patients were treated with DMSA and NAP.[94] Chelation therapy with both drugs resulted in the mobilization of a small fraction of the total estimated body mercury. Sony VAIO VGN-TZ150N/N Battery

DMSA was able to increase the excretion of mercury to a greater extent than NAP.[95]

Fish

Fish and shellfish have a natural tendency to concentrate mercury in their bodies, often in the form of methylmercury, a highly toxic organic compound of mercury. Species of fish that are high on the food chain, such as shark, swordfish, king mackerel, albacore tuna, and tilefish contain higher concentrations of mercury than others. Sony VAIO VGN-TZ160CB Battery

As mercury and methylmercury are fat soluble, they primarily accumulate in the viscera, although they are also found throughout the muscle tissue.[96] When this fish is consumed by a predator, the mercury level is accumulated. Since fish are less efficient at depurating than accumulating methylmercury, fish-tissue concentrations increase over time. Sony VAIO VGN-TZ160N/B Battery

Thus species that are high on the food chain amass body burdens of mercury that can be ten times higher than the species they consume. This process is called biomagnification. Mercury poisoning happened this way in Minamata, Japan, now called Minamata disease.

Regulations

In the United States, the Environmental Protection Agency is charged with regulating and managing mercury contamination. Sony VAIO VGN-TZ16GN/B Battery

Several laws give the EPA this authority, including the Clean Air Act, the Clean Water Act, the Resource Conservation and Recovery Act, and the Safe Drinking Water Act. Additionally, the Mercury-Containing and Rechargeable Battery Management Act, passed in 1996, phases out the use of mercury in batteries, and provides for the efficient and cost-effective disposal of many types of used batteries.[97] Sony VAIO VGN-TZ16N Battery

North America contributed approximately 11% of the total global anthropogenic mercury emissions in 1995.[98]

In the European Union, the directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (see RoHS) bans mercury from certain electrical and electronic products, Sony VAIO VGN-TZ16N/B Battery

and limits the amount of mercury in other products to less than 1000 ppm.[99] There are restrictions for mercury concentration in packaging (the limit is 100 ppm for sum of mercury, lead, hexavalent chromium and cadmium) and batteries (the limit is 5 ppm).[100] In July 2007, the European Union also banned mercury in non-electrical measuring devices, such as thermometers and barometers. Sony VAIO VGN-TZ17/N Battery

The ban applies to new devices only, and contains exemptions for the health care sector and a two-year grace period for manufacturers of barometers. [101]

Norway enacted a total ban on the use of mercury in the manufacturing and import/export of mercury products, effective January 1, 2008.[102] Sony VAIO VGN-TZ170N/B Battery

In 2002, several lakes in Norway were found to have a poor state of mercury pollution, with an excess of 1 mg/g of mercury in their sediment. Sony VAIO VGN-TZ170N/N Battery,Sony VAIO VGN-TZ17GN/B Battery,Sony VAIO VGN-TZ17N Battery,Sony VAIO VGN-TZ18/N Battery,Sony VAIO VGN-TZ180N/RC Battery,Sony VAIO VGN-TZ185N/WC Battery

 

Rhenium,Osmium,Iridium,Platinum

Rhenium is a chemical element with the symbol Re and atomic number 75. It is a silvery-white, heavy, third-row transition metalin group 7 of the periodic table. With an average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. Sony VAIO VGN-CR11H/B Battery

The free element has the third-highestmelting point and highest boiling point of any element. Rhenium resembles manganese chemically and is obtained as a by-product of molybdenum and copper refinement. Rhenium shows in its compounds a wide variety of oxidation states ranging from ?1 to +7. Sony VAIO VGN-CR11S/L Battery

Discovered in 1925, rhenium was the last stable element to be discovered. It was named after the river Rhine in Europe.

Nickel-based superalloys for use in jet engines contain up to 6% rhenium, making jet engine construction the largest use for the element, with chemical industry catalytic uses being next-most important. Sony VAIO VGN-CR11H/B Battery

Because of the low availability relative to demand, rhenium is among the most expensive industrial metals, with an average price of approximately US$4,575 perkilogram, on 1 August 2011.[1]

Rhenium (Latin: Rhenus meaning: "Rhine")[2] was the last element to be discovered having a stable isotope (other new radioactive elements have been discovered in nature since then, such as neptunium and plutonium). Sony VAIO VGN-CR11S/L Battery

The existence of a yet undiscovered element at this position in the periodic table had been first predicted by Dmitry Mendeleev. Other calculated information was obtained by Henry Moseley in 1914.[4] It is generally considered to have been discovered byWalter Noddack, Ida Tacke, and Otto Berg in Germany. Sony VAIO VGN-CR11S/P Battery

In 1925 they reported that they detected the element in platinum ore and in the mineral columbite. They also found rhenium in gadolinite and molybdenite.[5] In 1928 they were able to extract 1 g of the element by processing 660 kg of molybdenite.[6] The process was so complicated and expensive that production was discontinued until early 1950 when tungsten-rhenium and molybdenum-rhenium alloys were prepared. Sony VAIO VGN-CR11S/W Battery

These alloys found important applications in industry that resulted in a great demand for the rhenium produced from the molybdenite fraction of porphyry copper ores.

In 1908, Japanese chemist Masataka Ogawa announced that he discovered the 43rd element and named it nipponium (Np) afterJapan (which is Nippon in Japanese). Sony VAIO VGN-CR11Z/R Battery

However, later analysis indicated the presence of rhenium (element 75), not element 43.[7] The symbol Np was later used for the element neptunium.

Characteristics

Rhenium is a silvery-white metal with one of the highest melting points of all elements, exceeded by only tungsten andcarbon. It is also one of the densest, exceeded only by platinum, iridium and osmium. Sony VAIO VGN-CR120E/L Battery

Sony VAIO VGN-CR120E/P Battery

Its usual commercial form is a powder, but this element can be consolidated by pressing and sintering in a vacuum orhydrogenatmosphere. This procedure yields a compact solid having a density above 90% of the density of the metal. Sony VAIO VGN-CR120E/R Battery

Whenannealed this metal is very ductile and can be bent, coiled, or rolled.[8] Rhenium-molybdenum alloys are superconductiveat 10 K; tungsten-rhenium alloys are also superconductive[9] around 4-8 K, depending on the alloy. Rhenium metal superconducts at 2.4 K.[10][11] Sony VAIO VGN-CR120E/W Battery

Rhenium has a stable isotope, rhenium-185, which nevertheless occurs in minority abundance, a situation found only in one other element (indium). Naturally occurring rhenium is 37.4% 185Re, which is stable, and 62.6% 187Re, which is unstablebut has a very long half-life (~1010 years). Sony VAIO VGN-CR125E/B Battery

This lifetime is affected by the charge state of rhenium atom.[12][13] Thebeta decay of 187Re is used for rhenium-osmium dating of ores. The available energy for this beta decay (2.6 keV) is one of the lowest known among all radionuclides. There are twenty-six other recognized radioactive isotopes of rhenium.[14] Sony VAIO VGN-CR13/B Battery

Compounds

Rhenium has nine known oxidation states: ?1, 0, +1, +2, +3, +4, +5, +6 and +7.[15] The oxidation states +7, +6, +4, and +2 are the most common.[15] Sony VAIO VGN-CR13/L Battery

The most common rhenium compounds are the oxides and the halides exhibiting a broad oxidation number spectrum: Re2O7, ReO3, Re2O5, ReO2, and Re2O3 are the known oxides, and ReF7, ReCl6, ReCl5, ReCl4 and ReCl3 are a few of the known halogen derivatives.[16] Known sulfides are ReS2 and Re2S7.[16] Sony VAIO VGN-CR13/P Battery

Reaction of rhenium with hydrogen produces the negatively charged hydride [ReH9]2? ion, which is isostructural with [TcH9]2?. It consists of a trigonal prism with Re atom in the center and six hydrogen atoms at the corners. Sony VAIO VGN-CR13/R Battery

Three more hydrogens make a triangle lying parallel to the base and crossing the prism in its center (see figure). Although those hydrogen atoms are not equivalent geometrically, their electronic structure is almost the same. The coordination number 9 in this complex is the highest for a rhenium complex. Sony VAIO VGN-CR13/W Battery

Sony VAIO VGN-CR131E/L Battery

Two protons in it can be replaced by sodium (Na+) or potassium (K+) ions.[17]

Rhenium is most available commercially as the sodium and ammonium perrhenates. It is also readily available as dirhenium decacarbonyl; these three compounds are common entry points to rhenium chemistry. Sony VAIO VGN-CR13G Battery

Various perrhenate salts may be easily converted to tetrathioperrhenate by the action of ammonium hydrosulfide.[18] It is possible to reduce the dirhenium decacarbonylRe2(CO)10 by reacting it with sodium amalgam to Na[Re(CO)5] with rhenium in the formal oxidation state ?1.[19Sony VAIO VGN-CR13G/B Battery

]Dirhenium decacarbonyl may be oxidatively cleaved with bromine to givebromopentacarbonylrhenium(I),[20] then reduced with zincand acetic acid topentacarbonylhydridorhenium:[21] Sony VAIO VGN-CR13G/L Battery

Re2(CO)10 + Br2 ? 2 Re(CO)5Br

Re(CO)5Br + Zn + HOAc ? Re(CO)5H + ZnBr(OAc)

Bromopentacarbonylrhenium(I) may be decarbonylated to give the rhenium tricarbonyl fragment either by refluxing in water:[22]Sony VAIO VGN-CR13G/P Battery

Re(CO)5Br + 3 H2O ? [Re(CO)3(H2O)3]Br + 2 CO

or by reacting with tetraethylammonium bromide:[23]

Re(CO)5Br + 2 NEt4Br ? [NEt4]2[Re(CO)3Br3] + 2 CO

Rhenium diboride (ReB2) is a hard compound having the hardness similar to that of tungsten carbide, silicon carbide, titanium diboride or zirconium diboride.[24] Sony VAIO VGN-CR13G/R Battery

Rhenium was originally thought to form the rhenide anion, Re?
, in which it has the ?1 oxidation state. This was based on the product of the reduction of perrhenatesalts, such as the reduction of potassium perrhenate (KReO4) by potassium metal.[25] "Sony VAIO VGN-CR13G/W Battery

Potassium rhenide" was shown to exist as a tetrahydrated complex, with the postulated chemical formula KRe·4H2O.[26] This compound exhibits strongly reducing properties, and slowly yields hydrogen gas when dissolved in water. The lithium and thallous salts were also reported. Sony VAIO VGN-CR13T/L Battery

Later rese

"Potassium rhenide" was shown to be in fact the nonahydridorhenate, K2ReH9, containing the ReH92? anion in which the oxidation state of rhenium is actually +7.[27][28] Other methods of reduction of perrhenate salts yield compounds containing other hydrido- complexes, including ReH3(OH)3(H2O)?. arch, however, indicates that the "rhenide" ion is actually a hydridorhenate complex. Sony VAIO VGN-CR13T/P Battery

Occurrence

Rhenium is one of the rarest elements in Earth's crust with an average concentration of 1 ppb;[16] other sources quote the number of 0.5 ppb making it the 77th most abundant element in Earth's crust.[30] Rhenium is probably not found free in nature (its possible natural occurrence is uncertain), but occurs in amounts up to 0.2%[1Sony VAIO VGN-CR13T/R Battery

6] in the mineral molybdenite (which is primarily molybdenum disulfide), the major commercial source, although single molybdenite samples with up to 1.88% have been found.[31]Chile has the world's largest rhenium reserves, part of the copper ore deposits, and was the leading producer as of 2005.[32] Sony VAIO VGN-CR13T/W Battery

It was only recently that the first rhenium mineral was found and described (in 1994), a rhenium sulfide mineral (ReS2) condensing from a fumaroleon Russia's Kudriavy volcano, Iturup island, in the Kurile Islands.[33] Kudryavy discharges up to 20–60 kg rhenium per year mostly in the form of rhenium disulfide. Sony VAIO VGN-CR15/B Battery

Named rheniite, this rare mineral commands high prices among collectors.[36]

Production

Commercial rhenium is extracted from molybdenum roaster-flue gas obtained from copper-sulfide ores. Some molybdenum ores contain 0.001% to 0.2% rhenium.[ Sony VAIO VGN-CR150E/B Battery

Rhenium(VII) oxide and perrhenic acid readily dissolve in water; they are leached from flue dusts and gasses and extracted by precipitating with potassium or ammonium chloride as the perrhenate salts, and purified byrecrystallization.[37] Total world production is between 40 and 50 tons/year; the main producers are in Chile, the United States, Peru, and Kazakhstan.[38] Sony VAIO VGN-CR190 Battery

Recycling of used Pt-Re catalyst and special alloys allow the recovery of another 10 tons per year. Prices for the metal rose rapidly in early 2008, from $1000–$2000 per kg in 2003-2006 to over $10,000 in February 2008.[39][40]The metal form is prepared by reducing ammonium perrhenate with hydrogen at high temperatures:[37] Sony VAIO VGN-CR190E/L Battery

2 NH4ReO4 + 7 H2 ? 2 Re + 8 H2O + 2 NH3

Applications

The F-15 engine uses rhenium-containing second-generation superalloys

Rhenium is added to high-temperature superalloys that are used to make jet engine parts, making 70% of the worldwide rhenium production.[41] Sony VAIO VGN-CR190E/P Battery

Another major application is in platinum-rhenium catalysts, which are primarily used in making lead-free, high-octane gasoline.[42]

Alloys

The nickel-based superalloys have improved creep strength with the addition of rhenium. The alloys normally contain 3% or 6% of rhenium.[43] Sony VAIO VGN-CR190E/R Battery

Second generation alloys contain 3%; these alloys were used in the engines of the F-16 and F-15, while the newer single-crystal third generation alloys contain 6% of rhenium; they are used in the F-22 and F-35 engines.[42][44] Rhenium is also used in the superalloys, such as CMSX-4 (2nd gen) and CMSX-10 (3rd gen) that are used in industrial gas turbine engines like the GE 7FA. Sony VAIO VGN-CR190E/W Battery

Rhenium can cause superalloys to become microstructurally unstable, forming undesirable TCP (topologically close packed)phases. In 4th and 5th generation superalloys, ruthenium is used to avoid this effect. Among others the new superalloys are EPM-102 (with 3 % Ru) and TMS-162 (with 6 % Ru), both containing 6 % rhenium,[45] as well as TMS-138[46] and TMS-174.[47][48] Sony VAIO VGN-CR19VN/B Battery

For 2006, the consumption is given as 28% for General Electric, 28% Rolls-Royce plc and 12% Pratt & Whitney, all for superalloys, while the use for catalysts only accounts for 14% and the remaining applications use 18%.[41] In 2006, 77% of the rhenium consumption in the United States was in alloys.[42] Sony VAIO VGN-CR19XN/B Battery

The rising demand for military jet engines and the constant supply made it necessary to develop superalloys with a lower rhenium content. For example the newer CFM International CFM56 high-pressure turbine (HPT) blades will use Rene N515 with a rhenium content of 1.5 % instead of Rene N5 with 3 %.[49][50] Sony VAIO VGN-CR20 Battery

Rhenium improves the properties of tungsten and is therefore the most important alloying material for tungsten. Tungsten-rhenium alloys are more ductile at low temperature making them easier to machine, while the high-temperature stability is also improved.Sony VAIO VGN-CR21/B Battery

The effect increases with the rhenium concentration, and therefore tungsten alloys are produced with up to 27% of Re, which is the solubility limit.[51] One application for the tungsten-rhenium alloys is X-ray sources. The high melting point of both compounds, together with the high atomic mass, makes them stable against the prolonged electron impact.[52] Sony VAIO VGN-CR21E/L Battery

Rhenium tungsten alloys are also applied as thermocouples to measure temperatures up to 2200 °C.[53]

The high temperature stability, low vapor pressure, good wear resistance and ability to withstand arc corrosion of rhenium are useful in self-cleaning electrical contacts. In particular, the discharge occurring during the switching oxidizes the contacts. Sony VAIO VGN-CR21E/P Battery

However, rhenium oxide Re2O7 has poor stability (sublimates at ~360 °C) and therefore is removed during the discharge.[41]

Rhenium has a high melting point and a low vapor pressure similar to tantalum and tungsten, however, rhenium forms no volatile oxides. Sony VAIO VGN-CR21E/W Battery

Therefore, rhenium filaments exhibit a higher stability if the filament is operated not in vacuum, but in oxygen-containing atmosphere.[54] Those filaments are widely used in mass spectrometers, in ion gauges.[55] and in photoflash lamps in photography.[56] Sony VAIO VGN-CR21S/L Battery

Catalysts

Rhenium in the form of rhenium-platinum alloy is used as catalyst for catalytic reforming, which is a chemical process to convert petroleum refinery naphthas with low octane ratings into high-octane liquid products. Sony VAIO VGN-CR21S/P Battery

Worldwide, 30% of catalysts used for this process contain rhenium.[57] The olefin metathesis is the other reaction for which rhenium is used as catalyst. Normally Re2O7on alumina is used for this process.[58] Rhenium catalysts are very resistant to chemical poisoningfrom nitrogen, sulfur and phosphorus, and so are used in certain kinds of hydrogenation reactions. Sony VAIO VGN-CR21S/W Battery

Other uses

188Re and 186Re isotopes are radioactive and are used for treatment of liver cancer. They both have similar penetration depth in tissue (5 mm for 186Re and 11 mm for188Re), but 186Re has advantage of longer lifetime (90 hours vs. 17 hours). Sony VAIO VGN-CR21Z/N Battery

Related by periodic trends, rhenium has a similar chemistry with technetium; work done to label rhenium onto target compounds can often be translated to technetium. This is useful for radiopharmacy, where it is difficult to work with technetium – especially the 99m isotope used in medicine – due to its expense and short half-life. Sony VAIO VGN-CR21Z/R Battery

Precaution

Very little is known about the toxicity of rhenium and its compounds because they are used in very small amounts. Soluble salts, such as the rhenium halides or perrhenates, could be hazardous due to elements other than rhenium or due to rhenium itself.[ Sony VAIO VGN-CR220E/R Battery

Only a few compounds of rhenium have been tested for their acute toxicity; two examples are potassium perrhenate and rhenium trichloride, which were injected as a solution into rats. The perrhenate had an LD50 value of 2800 mg/kg after seven days (this is very low toxicity, similar to that of table salt) and the rhenium trichloride showed LD50 of 280 mg/kg. Sony VAIO VGN-CR23/B Battery

Sony VAIO VGN-CR23/L Battery

Osmium is a chemical element with the symbol Os and atomic number 76. Osmium is a hard, brittle, blue-gray or blue-black transition metal in the platinum family, and is the densest natural element. Osmium is twice as dense as lead. Sony VAIO VGN-CR23/N Battery

The density of osmium is 22.59 g/cm3, slightly greater than that of iridium, the second densest element. Osmium is found in nature as an alloy, mostly in platinum ores. Osmium is also used in alloys, with platinum, iridium and other platinum group metals. Those alloys are employed in fountain pen tips, electrical contacts and in other applications where extreme durability and hardness are needed.[2] Sony VAIO VGN-CR23/P Battery

Physical properties

Osmium has a blue-gray tint and is the densest stable element, slightly denser thaniridium.[3] Calculations of density from the X-ray diffraction data may produce the most reliable data for these elements, giving a value of 22.562±0.009 g/cm3 for iridium versus 22.587±0.009 g/cm3 for osmium.[4] The high density of osmium is a consequence of the lanthanide contraction.[4][5] Sony VAIO VGN-CR23/R Battery

Osmium is a hard but brittle metal that remains lustrous even at high temperatures. It has a very low compressibility. Correspondingly, its bulk modulus is extremely high, reported between 395 and 462 GPa, which rivals that of diamond (443 GPa).Sony VAIO VGN-CR23/W Battery

The hardness of osmium is moderately high at 4 GPa.[6][7][8] Because of its hardness, brittleness, low vapor pressure (the lowest of the platinum group metals), and very high melting point (the fourth highest of all elements), solid osmium is difficult to machine, form or work. Sony VAIO VGN-CR240E/B Battery

Chemical properties

Osmium forms compounds with the oxidation states ranging from ?2 to +8. The most common oxidation states are +2, +3, +4, and +8. The +8 oxidation state is notable for being the highest attained by any chemical element, and aside from osmium, is encountered only inxenon, iron [9] and ruthenium.[10] Sony VAIO VGN-CR240N/B Battery

The oxidation state ?1 and ?2 represented by the two reactive compounds Na2[Os4(CO)13] and Na2[Os(CO)4] are used in the synthesis of osmiumcluster compounds.[11][12]

The most common compound exhibiting the +8 oxidation state is osmium tetroxide. Sony VAIO VGN-CR25G/N Battery

This toxic compound is formed when powdered osmium is exposed to air, and is a very volatile, water-soluble, pale yellow, crystalline solid with a strong smell. Therefore, osmium powder has a characteristic smell of osmium tetroxide.[13] Osmium tetroxide forms red osmates OsO4(OH)2?
2 upon reaction with a base. Sony VAIO VGN-CR290EAL Battery

With ammonia, it forms the nitrido-osmatesOsO3N?.[14][15][16] Osmium tetroxide boils at 130 °C and is a powerful oxidizing agent. By contrast, osmium dioxide (OsO2) is black, non-volatile, and much less reactive and toxic.

Only two osmium compounds have major applications: osmium tetroxide — for stainingtissue in electron microscopy and the non-volatile osmates for organic oxidation reactions.[17] Sony VAIO VGN-CR290EAN Battery

Osmium heptafluoride (OsF7) and osmium pentafluoride (OsF5) are known, but osmium trifluoride (OsF3) has not been synthesized yet. The lower oxidation states are stabilized by the larger halogens. Therefore, the trichloride, tribromide, triiodide and even osmium diiodide are known. Sony VAIO VGN-CR290EAP Battery

The oxidation state +1 is only known for the osmium iodide (OsI), whereas several carbonyl complexes of osmium, such as triosmium dodecacarbonyl (Os3(CO)12), represent the oxidation state 0.[14][15][18][19]

In general, the lower oxidation states of osmium are stabilized by ligands that are good ?-donors (such as amines) and ?-acceptors (heterocycles containing nitrogen).

The higher oxidation states are stabilized by strong ?- and ?-donors, such as O2? and N3?.[20]

Osmium has seven naturally occurring isotopes, six of which are stable: 184Os, 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. Sony VAIO VGN-CR290EAR Battery

186Os undergoes alpha decay with such long half-life ((2.0±1.1)×1015 years) that for practical purposes it can be considered stable. Alpha decay is predicted for all 7 naturally occurring isotopes, but due to very long half-lives, it was observed only for 186Os. It is predicted that 184Os and 192Os can undergo double beta decay but this radioactivity has not been observed yet.[21] Sony VAIO VGN-CR290EAW Battery

187Os is the daughter of 187Re (half-life 4.56×1010 yr) and is used extensively in dating terrestrial as well as meteoricrocks(see rhenium-osmium dating). It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. Sony VAIO VGN-CR29XN/B Battery

This decay is a reason why rhenium-rich minerals are abnormally rich in 187Os.[22] However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the K-T boundary that marks the extinction of thedinosaurs 65 million years ago.[23] Sony VAIO VGN-CR305E/RC Battery

Osmium (from Greek osme (????) meaning "smell") was discovered in 1803 by Smithson Tennant and William Hyde WollastoninLondon, England.[24] The discovery of osmium is intertwined with that of platinum and the other metals of the platinum group. Platinum reached Europe as platina ("small silver"), first encountered in the late 17th century in silver mines around the Chocó Department, in Colombia.[25] Sony VAIO VGN-CR31S/D Battery

The discovery that this metal was not an alloy, but a distinct new element, was published in 1748.[26]Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. They always observed a small amount of a dark, insoluble residue.[27] Sony VAIO VGN-CR323/W Battery

Joseph Louis Proustthought that the residue was graphite.[27]Victor Collet-Descotils, Antoine François, comte de Fourcroy, and Louis Nicolas Vauquelin also observed the black residue in 1803, but did not obtain enough material for further experiments.[27]

In 1803, Smithson Tennant analyzed the insoluble residue and concluded that it must contain a new metal. Sony VAIO VGN-CR33 Battery

Vauquelin treated the powder alternately with alkali and acids[28] and obtained a volatile new oxide, which he believed to be of this new metal—which he named ptene, from the Greek word ?????? (ptènos) for winged.[29][30] However, Tennant, who had the advantage of a much larger amount of residue, continued his research and identified two previously undiscovered elements in the black residue, iridium and osmium.[27][28] Sony VAIO VGN-CR382 Battery

He obtained a yellow solution (probably of cis–[Os(OH)2O4]2?) by reactions with sodium hydroxide at red heat. After acidification he was able to distill the formed OsO4.[29] He named osmium after Greek osme meaning "a smell", because of the ashen and smoky smell of the volatile osmium tetroxide.[31]Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.[27][32] Sony VAIO VGN-CR490EBL Battery

Uranium and osmium were early successful catalysts in the Haber process, the nitrogen fixation reaction of nitrogen andhydrogen to produce ammonia, giving enough yield to make the process economically successful. However, in 1908 cheaper catalysts based on iron and iron oxides were introduced for the first pilot plants.[33] Sony VAIO VGN-CR490EBN Battery

Nowadays, osmium is primarily obtained from the processing of platinum and nickel ores.[34]

Occurrence

Osmium is the least abundant stable element in the Earth's crust with an average mass fraction of 0.05 ppb in thecontinental crust.[35] Sony VAIO VGN-CR490EBP Battery

Osmium is found in nature as an uncombined element or in natural alloys; especially the iridium–osmium alloys, osmiridium(osmium rich), and iridiosmium (iridium rich).[28] In the nickel and copper deposits, the platinum group metals occur as sulfides(i.e., (Pt,Pd)S)), tellurides (e.g., PtBiTe), antimonides (e.g., PdSb), and arsenides (e.g., PtAs2); Sony VAIO VGN-CR490EBR Battery

in all these compounds platinum is exchanged by a small amount of iridium and osmium. As with all of the platinum group metals, osmium can be found naturally in alloys with nickel or copper.[36]

Within the Earth's crust, osmium, like iridium, is found at highest concentrations in three types of geologic structure: Sony VAIO VGN-CR490EBT Battery

igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the former structures. The largest known primary reserves are in the Bushveld igneous complex in South Africa,[37] though the large copper–nickel deposits nearNorilsk in Russia, and the Sudbury Basin in Canada are also significant sources of osmium. Sony VAIO VGN-CR490EBW Battery

Smaller reserves can be found in the United States.[37] The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum group metals. The second large alluvial deposit was found in the Ural Mountains, Russia, which is still mined.[34][38] Sony VAIO VGN-CR50B/W Battery

Production

Osmium is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copperand nickel, noble metals such as silver, gold and the platinum group metals, together with non-metallic elements such as seleniumand tellurium settle to the bottom of the cell as anode mud, which forms the starting material for their extraction. Sony VAIO VGN-CR51B/W Battery

In order to separate the metals, they must first be brought into solution. Several methods are available depending on the separation process and the composition of the mixture; two representative methods are fusion with sodium peroxide followed by dissolution inaqua regia, and dissolution in a mixture of chlorine with hydrochloric acid.[37][41] Sony VAIO VGN-CR520E/J Battery

Osmium, ruthenium, rhodium and iridium can be separated from platinum, gold and base metals by their insolubility in aqua regia, leaving a solid residue. Rhodium can be separated from the residue by treatment with molten sodium bisulfate. The insoluble residue, containing Ru, Os and Ir, is treated with sodium oxide, in which Ir is insoluble, producing water-soluble Ru and Os salts.Sony VAIO VGN-CR52B/W Battery

After oxidation to the volatile oxides,RuO4 is separated from OsO4 by precipitation of (NH4)3RuCl6 with ammonium chloride.

After it is dissolved, osmium is separated from the other platinum group metals by distillation or extraction with organic solvents of the volatile osmium tetroxide.[42] Sony VAIO VGN-CR590EBL Battery

The first method is similar to the procedure used by Tennant and Wollaston. Both methods are suitable for industrial scale production. In either case, the product is reduced using hydrogen, yielding the metal as a powder or sponge that can be treated using powder metallurgy techniques.[43] Sony VAIO VGN-CR590EBN Battery

Neither the producers nor the United States Geological Survey published any production amounts for osmium. Estimations of the United States consumption date published from 1971,[44] which gives a consumption in the United States of 2000 troy ounces(62 kg), would suggest that the production is still less than 1 ton per year. Sony VAIO VGN-CR590EBP Battery

Applications

Because of the volatility and extreme toxicity of its oxide, osmium is rarely used in its pure state, and is instead often alloyed with other metals. Those alloys are utilized in high-wear applications. Sony VAIO VGN-CR590EBR Battery

Osmium alloys such as osmiridium are very hard and, along with other platinum group metals, are used in the tips of fountain pens, instrument pivots, and electrical contacts, as they can resist wear from frequent operation. The stylus (needle) in early phonograph designs was also made of osmium, especially for 78-rpm records, until sapphire and synthetic diamond replaced the metal in later designs for 45-rpm and 33-rpmlong-playing records.[45] Sony VAIO VGN-CR590EBT Battery

Osmium tetroxide has been used in fingerprint detection[46] and in staining fattytissue for optical and electron microscopy. As a strong oxidant, it cross-links lipids mainly by reacting with unsaturated carbon-carbon bonds, and thereby both fixes biological membranes in place in tissue samples and simultaneously stains them. Sony VAIO VGN-CR590EBW Battery

Because osmium atoms are extremely electron dense, osmium staining greatly enhances image contrast in transmission electron microscopy (TEM) studies of biological materials. Those carbon materials have otherwise very weak TEM contrast (see image).[17]Another osmium compound, osmium ferricyanide (OsFeCN), exhibits similar fixing and staining action.[47] Sony VAIO VGN-CR60B/L Battery

An alloy of 90% platinum and 10% osmium is used in surgical implants such as pacemakers and replacement of pulmonaryvalves.[48]

The tetroxide and a related compound, potassium osmate, are important oxidants for chemical synthesis, despite being very poisonous. Sony VAIO VGN-CR60B/P Battery

For the Sharpless asymmetric dihydroxylation, which uses osmate for the conversion of a double bond into a vicinaldiol, Karl Barry Sharpless won the Nobel Prize in Chemistry in 2001.[49][50]

In 1898 an Austrian chemist, Auer von Welsbach, developed the Oslamp with a filament made of osmium, which he introduced commercially in 1902. Sony VAIO VGN-CR60B/R Battery

After only a few years, osmium was replaced by the more stable metal tungsten (also known as wolfram). Tungsten has the highest melting point of any metal, and using it in light bulbs increases the luminous efficacy and life of incandescent lamps.[29] Sony VAIO VGN-CR61B/L Battery

The light bulb manufacturer OSRAM (founded in 1906 when three German companies, Auer-Gesellschaft, AEG and Siemens & Halske, combined their lamp production facilities) derived its name from the elements of OSmium and wolfRAM.[53]

Like palladium, powdered osmium effectively absorbs hydrogen atoms. Sony VAIO VGN-CR61B/N Battery

This could make osmium a potential candidate for a metal hydride battery electrode. However, osmium is expensive and would react with potassium hydroxide, the most common battery electrolyte.[54]

Osmium has high reflectivity in the ultraviolet range of the electromagnetic spectrum; for example, at 600 Å osmium has a reflectivity twice that of gold.[55] Sony VAIO VGN-CR61B/P Battery

This high reflectivity is desirable in space-based UV spectrometers which have reduced mirror sizes due to space limitations. Osmium-coated mirrors were flown in several space missions aboard the Space Shuttle, but it soon became clear that the oxygen radicals in the low earth orbit are abundant enough to significantly deteriorate the osmium layer.[56] Sony VAIO VGN-CR61B/R Battery

Precautions

Finely divided metallic osmium is pyrophoric.[44] Osmium reacts with oxygen at room temperature forming volatile osmium tetroxide. Some osmium compounds are also converted to the tetroxide if oxygen is present.[44] This makes osmium tetroxide the main source of contact with the environment. Sony VAIO VGN-CR62B/L Battery

Osmium tetroxide is highly volatile and penetrates skin readily, and is very toxic by inhalation, ingestion, and skin contact.[57]Airborne low concentrations of osmium tetroxide vapor can cause lung congestion and skin or eye damage, and should therefore be used in a fume hood.[13] Sony VAIO VGN-CR62B/N Battery

Osmium tetroxide is rapidly reduced to relatively inert compounds by polyunsaturated vegetable oils, such as corn oil.[58]

Price

Osmium is usually sold as a 99% pure powder. Like other precious metals, it is measured by troy weight and by grams. Sony VAIO VGN-CR62B/P Battery

Its price at 2010 is about $400 per Troy ounce (or about $13 per gram), depending on the quantity and its supplier.[

Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. Sony VAIO VGN-CR62B/R Battery

A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element (after osmium) and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C. Although only certain molten salts andhalogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable. Sony VAIO VGN-CR70B/W Battery

Iridium was discovered in 1803 among insoluble impurities in natural platinum. Smithson Tennant, the primary discoverer, named the iridium for the goddess Iris, personification of the rainbow, because of the striking and diverse colors of its salts. Sony VAIO VGN-CR71B/W Battery

Iridium is one of the rarest elements in the Earth's crust, with annual production and consumption of only threetonnes. 191Ir and 193Ir are the only two naturally occurring isotopes of iridium as well as the only stable isotopes; the latter is the more abundant of the two. Sony VAIO VGN-CR72B/W Battery

The most important iridium compounds in use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in industrial catalysis, and in research. Iridium metal is employed when high corrosion resistance at high temperatures is needed, Sony VAIO VGN-CR90HS Battery

as in high-end spark plugs, crucibles for recrystallization of semiconductors at high temperatures, and electrodes for the production of chlorine in the chloralkali process. Iridium radioisotopes are used in some radioisotope thermoelectric generators. Sony VAIO VGN-CR90NS Battery

The unusually high abundance of iridium in the clay layer at the K–T geologic boundary gave rise to the Alvarez hypothesisthat the impact of a massive extraterrestrial object caused the extinction of dinosaurs and many other species 65 million years ago. Sony VAIO VGN-CR90S Battery

Iridium is found in meteorites with an abundance much higher than its average abundance in the Earth's crust. It is thought that the total amount of iridium in the planet Earth is much higher than that observed in crustal rocks, but as with other platinum group metals, the high density and tendency of iridium to bond with iron caused most iridium to descend below the crust when the planet was young and still molten. Sony VAIO VGN-CR92HS Battery

Physical properties

A member of the platinum group metals, iridium is white, resembling platinum, but with a slight yellowish cast. Because of its hardness, brittleness, and very high melting point (the ninth highest of all elements), solid iridium is difficult to machine, form, or work, and thus powder metallurgy is commonly employed instead. Sony VAIO VGN-CR92NS Battery

It is the only metal to maintain good mechanical properties in air at temperatures above 1600 °C.[4] Iridium has a very high boiling point (10th among all elements) and becomes a superconductor at temperatures below 0.14 K.[5]

Iridium's modulus of elasticity is the second highest among the metals, only being surpassed by osmium.[4] Sony VAIO VGN-CR92S Battery

This, together with a high modulus of rigidity and a very low figure for Poisson's ratio (the relationship of longitudinal to lateral strain), indicate the high degree of stiffness and resistance to deformation that have rendered its fabrication into useful components a matter of great difficulty. Sony VAIO VGN-CS118E/Q Battery

Despite these limitations and iridium's high cost, a number of applications have developed where mechanical strength is an essential factor in some of the extremely severe conditions encountered in modern technology.[4]

The measured density of iridium is only slightly lower (by about 0.12%) than that of osmium, the densest element known.[6][7] Sony VAIO VGN-CS118E/R Battery

There had been some ambiguity regarding which of the two elements was denser, due to the small size of the difference in density and difficulties in measuring it accurately,[8] but, with increased accuracy in factors used for calculating densityX-ray crystallographicdata yielded densities of 22.56 g/cm3 for iridium and 22.59 g/cm3 for osmium.[9] Sony VAIO VGN-CS118E/W Battery

Chemical properties

Iridium is the most corrosion-resistant metal known:[10] it is not attacked by almost any acid, aqua regia, molten metals or silicates at high temperatures. It can, however, be attacked by some molten salts, such as sodium cyanide and potassium cyanide,[10] as well as oxygen and the halogens (particularly fluorine)[11] at higher temperatures.[12] Sony VAIO VGN-CS11S/P Battery

Compounds

Iridium forms compounds in oxidation states between ?3 to +6; the most common oxidation states are +3 and +4.[3] Well-characterized examples of the highest oxidation state are rare, but includeIrF6 and two mixed oxides Sr2MgIrO6and Sr2CaIrO6.[3][13] Sony VAIO VGN-CS11S/Q Battery

In addition, it was reported in 2009 that iridium(VIII) tetroxide (IrO4) was prepared under matrix isolation conditions (6 K in Ar) by UV irradiation of an iridium-peroxo complex. This species, however, is not expected to be stable as a bulk solid at higher temperatures.[14] Sony VAIO VGN-CS11S/W Battery

Iridium dioxide, IrO2, a brown powder, is the only well-characterized oxide of iridium.[3] Asesquioxide, Ir2O3, has been described as a blue-black powder which is oxidized to IrO2 byHNO3.[11] The corresponding disulfides, diselenides, sesquisulfides and sesquiselenides are known and IrS3 has also been reported.[3] Sony VAIO VGN-CS11Z/R Battery

Iridium also forms iridates with oxidation states +4 and +5, such as K2IrO3 and KIrO3, which can be prepared from the reaction of potassium oxide or potassium superoxide with iridium at high temperatures.[15] Sony VAIO VGN-CS120J/P Battery

While no binary hydrides of iridium, IrxHy are known, complexes are known that contain IrH4?5 and IrH3?6, where iridium has the +1 and +3 oxidation states, respectively.[16] The ternary hydride Mg6Ir2H11 is believed to contain both the IrH4?
5 and the 18-electron IrH5?4 anion.[17] Sony VAIO VGN-CS120J/Q Battery

No monohalides or dihalides are known, whereas trihalides, IrX3, are known for all of the halogens.[3] For oxidation states +4 and above, only the tetrafluoride, pentafluoride and hexafluoride are known.[3] Iridium hexafluoride, IrF6, is a volatile and highly reactive yellow solid, composed of octahedral molecules. Sony VAIO VGN-CS120J/R Battery

It decomposes in water and is reduced to IrF4, a crystalline solid, by iridium black.[3] Iridium pentafluoride has similar properties but it is actually a tetramer, Ir4F20, formed by four corner-sharing octahedra.[3]

Hexachloroiridic(IV) acid, H2IrCl6, and its ammonium salt are the most important iridium compounds from an industrial perspective.[18] Sony VAIO VGN-CS190JTB Battery

They are involved in the purification of iridium and used as precursors for most other iridium compounds, as well as in the preparation of anode coatings. The IrCl2?
6 ion has an intense dark brown color, and can be readily reduced to the lighter-colored IrCl3?6 and vice versa.[18] Sony VAIO VGN-CS190JTP Battery

Iridium trichloride,IrCl3, which can be obtained in anhydrous form from direct oxidation of iridium powder bychlorine at 650 °C,[18] or in hydrated form by dissolving Ir2O3 in hydrochloric acid, is often used as a starting material for the synthesis of other Ir(III) compounds.[3] Sony VAIO VGN-CS190JTQ Battery

Another compound used as a starting material is ammonium hexachloroiridate(III), (NH4)3IrCl6. Iridium(III) complexes are diamagnetic (low-spin) and generally have an octahedral molecular geometry.[3]

Organoiridium compounds contain iridium–carbon bonds where the metal is usually in lower oxidation states. Sony VAIO VGN-CS190JTR Battery

For example, oxidation state zero is found in tetrairidium dodecacarbonyl, Ir4(CO)12, which is the most common and stable binary carbonylof iridium.[3] In this compound, each of the iridium atoms is bonded to the other three, forming a tetrahedral cluster. Some organometallic Ir(I) compounds are notable enough to be named after their discoverers. Sony VAIO VGN-CS190JTW Battery

One is Vaska's complex,IrCl(CO)[P(C6H5)3]2, which has the unusual property of binding to the dioxygen molecule, O2.[19] Another one is Crabtree's catalyst, a homogeneous catalyst for hydrogenation reactions.[20] These compounds are both square planar, d8complexes, with a total of 16 valence electrons, which accounts for their reactivity.[21] Sony VAIO VGN-CS190NAB Battery

Iridium has two naturally occurring, stable isotopes, 191Ir and 193Ir, with natural abundances of 37.3% and 62.7%, respectively.[22] At least 34 radioisotopes have also been synthesized, ranging in mass number from 164 to 199. 192Ir, which falls between the two stable isotopes, is the most stable radioisotope, with a half-lifeof 73.827 days, Sony VAIO VGN-CS190NAC Battery

and finds application in brachytherapy[23] and in industrial radiography, particularly for non-destructive testing of welds in steel in the oil and gas industries; iridium-192 sources have been responsible for a number of radiological accidents. Three other isotopes have half-lives of at least a day—188Ir,189Ir, 190Ir.[22] Sony VAIO VGN-CS190NAD Battery

Isotopes with masses below 191 decay by some combination of ?+ decay, ? decay, and proton emission, with the exceptions of 189Ir, which decays byelectron capture, and 190Ir, which decays by positron emission. Synthetic isotopes heavier than 191 decay by ??decay, although 192Ir also has a minor electron capture decay path.[22] Sony VAIO VGN-CS190NBB Battery

All known isotopes of iridium were discovered between 1934 and 2001; the most recent is 171Ir.[24]

At least 32 metastable isomers have been characterized, ranging in mass number from 164 to 197. Sony VAIO VGN-CS190NCA Battery

The most stable of these is 192m2Ir, which decays by isomeric transition with a half-life of 241 years,[22] making it more stable than any of iridium's synthetic isotopes in their ground states. The least stable isomer is190m3Ir with a half-life of only 2 µs.[22] The isotope 191Ir was the first one of any element to be shown to present a Mössbauer effect. Sony VAIO VGN-CS190NCB Battery

This renders it useful forMössbauer spectroscopy for research in physics, chemistry, biochemistry, metallurgy, and mineralogy.[25]

The discovery of iridium is intertwined with that of platinum and the other metals of the platinum group. Sony VAIO VGN-CS190NCC Battery

Native platinum used by ancient Ethiopians[26] and by South American cultures[27] always contained a small amount of the other platinum group metals, including iridium. Platinum reached Europe as platina ("small silver"), found in the 17th century by the Spanish conquerors in a region today known as the department of Chocó in Colombia.[ Sony VAIO VGN-CS50B/W Battery

The discovery that this metal was not an alloy of known elements, but instead a distinct new element, did not occur until 1748.[29]

Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. Sony VAIO VGN-CS51B/W Battery

Sony VAIO VGN-CS52JB/W Battery

They always observed a small amount of a dark, insoluble residue.[4] Joseph Louis Proust thought that the residue was graphite.[4]The French chemists Victor Collet-Descotils, Antoine François, comte de Fourcroy, and Louis Nicolas Vauquelin also observed the black residue in 1803, but did not obtain enough for further experiments.[4] Sony VAIO VGN-CS60B/P Battery

In 1803, British scientist Smithson Tennant (1761–1815) analyzed the insoluble residue and concluded that it must contain a new metal. Vauquelin treated the powder alternately with alkali and acids[10] and obtained a volatile new oxide, which he believed to be of this new metal—which he named ptene, from the Greek word?????? (ptènos) for winged.[30][31] Sony VAIO VGN-CS60B/Q Battery

Tennant, who had the advantage of a much greater amount of residue, continued his research and identified the two previously undiscovered elements in the black residue, iridium and osmium.[4][10] He obtained dark red crystals (probably of Na2[IrCl6]·nH2O) by a sequence of reactions withsodium hydroxide and hydrochloric acid.[31] Sony VAIO VGN-CS60B/R Battery

He named iridium after Iris (????), the Greek winged goddess of the rainbow and the messenger of the Olympian gods, because many of the salts he obtained were strongly colored.[note 2][32] Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.[4][33] Sony VAIO VGN-CS61B/P Battery

British scientist John George Children was the first to melt a sample of iridium in 1813 with the aid of "the greatest galvanic battery that has ever been constructed" (at that time).[4] The first to obtain high purity iridium was Robert Hare in 1842. He found that it had a density of around 21.8 g/cm3 and noted that the metal is nearly unmalleable and very hard. Sony VAIO VGN-CS61B/Q Battery

The first melting in appreciable quantity was done by Henri Sainte-Claire Deville and Jules Henri Debray in 1860. They required burning more than 300 L of pure O2and H2 for each kilogram of iridium.[4]

These extreme difficulties in melting the metal limited the possibilities for handling iridium. Sony VAIO VGN-CS61B/R Battery

John Isaac Hawkins was looking to obtain a fine and hard point for fountain pen nibs and in 1834 managed to create an iridium-pointed gold pen. In 1880 John Hollandand William Lofland Dudley were able to melt iridium by adding phosphorus and patented the process in the United States; Sony VAIO VGN-CS62JB/P Battery

British company Johnson Matthey later stated that they had been using a similar process since 1837 and had already presented fused iridium at a number of World Fairs.[4] The first use of an alloy of iridium with ruthenium in thermocouples was made by Otto Feussner in 1933. These allowed for the measurement of high temperatures in air up to 2000 °C.[4] Sony VAIO VGN-CS62JB/Q Battery

In 1957 Rudolf Mössbauer, in what has been called one of the "landmark experiments in twentieth century physics",[34] discovered the resonant and recoil-free emission and absorption of gamma rays by atoms in a solid metal sample containing only 191Ir.[35]Sony VAIO VGN-CS62JB/R Battery

This phenomenon, known as the Mössbauer effect (which has since been observed for other nuclei, such as 57Fe), and developed asMössbauer spectroscopy, has made important contributions to research in physics, chemistry, biochemistry, metallurgy, and mineralogy.[25] Mössbauer received the Nobel Prize in Physics in 1961, just three years after he published his discovery.[36] Sony VAIO VGN-CS71B/W Battery

Occurrence

The Willamette Meteorite, the sixth-largest meteorite found in the world, has 4.7 ppm iridium.[37]

Iridium is one of the least abundant elements in the Earth's crust, having an average mass fraction of 0.001 ppm in crustal rock; Sony VAIO VGN-CS72JB/W Battery

goldis 40 times more abundant, platinum is 10 times more abundant, and silver and mercury are 80 times more abundant.[3]Telluriumis about as abundant as iridium, and only three naturally occurring elements are less abundant: rhenium, ruthenium, andrhodium, iridium being 10 times more abundant than the last two.[3] Sony VAIO VGN-CS90HS Battery

In contrast to its low abundance in crustal rock, iridium is relatively common in meteorites, with concentrations of 0.5 ppm or more.[38] It is thought that the overall concentration of iridium on Earth is much higher than what is observed in crustal rocks, but because of the density and siderophilic ("iron-loving") character of iridium, it descended below the crust and into the Earth's core when the planet was still molten.[18] Sony VAIO VGN-CS90NS Battery

Iridium is found in nature as an uncombined element or in natural alloys; especially the iridium–osmium alloys, osmiridium(osmium rich), and iridiosmium (iridium rich).[10] In the nickel and copper deposits the platinum group metals occur as sulfides(i.e. (Pt,Pd)S), tellurides (i.e. PtBiTe), antimonides (PdSb), and arsenides (i.e. PtAs2). Sony VAIO VGN-CS90S Battery

In all of these compounds platinum is exchanged by a small amount of iridium and osmium. As with all of the platinum group metals, iridium can be found naturally in alloys with raw nickel or raw copper.[39]

Within the Earth's crust, iridium is found at highest concentrations in three types of geologic structure: Sony VAIO VGN-CS91HS Battery

igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the former structures. The largest known primary reserves are in the Bushveld igneous complex in South Africa,[40] though the large copper–nickel deposits near Norilsk inRussia, and the Sudbury Basin in Canada are also significant sources of iridium. Sony VAIO VGN-CS91NS Battery

Smaller reserves are found in the United States.[40] Iridium is also found in secondary deposits, combined with platinum and other platinum group metals in alluvialdeposits. The alluvial deposits used by pre-Columbian people in the Chocó Department of Colombia are still a source for platinum-group metals. As of 2003 the world reserves had not been estimated.[10]Sony VAIO VGN-CS91S Battery

K–T boundary presence

The K–T boundary of 65 million years ago, marking the temporal border between the Cretaceous and Tertiary periods of geological time, was identified by a thin stratum of iridium-rich clay.[41] Sony VAIO VGN-CS92DS Battery

A team led by Luis Alvarez proposed in 1980 an extraterrestrial origin for this iridium, attributing it to an asteroid or comet impact.[41] Their theory, known as the Alvarez hypothesis, is now widely accepted to explain the demise of the dinosaurs. A large buried impact crater structure with an estimated age of about 65 million years was later identified under what is now the Yucatán Peninsula (the Chicxulub crater).[42][43] Sony VAIO VGN-CS92JS Battery

Dewey M. McLean and others argue that the iridium may have been of volcanic origin instead, as the Earth's core is rich in iridium, and active volcanoes such as Piton de la Fournaise, in the island of Réunion, are still releasing iridium.[44][45] Sony VAIO VGN-CS92XS Battery

Production

Iridium is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copperand nickel, noble metals such as silver, gold and the platinum group metals as well as selenium and tellurium settle to the bottom of the cell as anode mud, which forms the starting point for their extraction. Sony VAIO VGN-FW11E Battery

In order to separate the metals, they must first be brought into solution. Several methods are available depending on the separation process and the composition of the mixture; two representative methods are fusion with sodium peroxide followed by dissolution in aqua regia, and dissolution in a mixture of chlorinewith hydrochloric acid.[18][40] Sony VAIO VGN-FW11L Battery

After it is dissolved, iridium is separated from the other platinum group metals by precipitating (NH4)2IrCl6 or by extracting IrCl2?
6with organic amines.[50] The first method is similar to the procedure Tennant and Wollaston used for their separation. Sony VAIO VGN-FW11M Battery

The second method can be planned as continuous liquid–liquid extraction and is therefore more suitable for industrial scale production. In either case, the product is reduced using hydrogen, yielding the metal as a powder or sponge that can be treated using powder metallurgytechniques.[51][52] Sony VAIO VGN-FW11S Battery

Annual production of iridium circa 2000 was around 3 tonnes or about 100,000 troy ounces (ozt).[note 3][10] The price of iridium as of 2007 was $440 USD/ozt,[46] but the price fluctuates considerably, as shown in the table. Sony VAIO VGN-FW11ZU Battery

The high volatility of the prices of the platinum group metals has been attributed to supply, demand, speculation, and hoarding, amplified by the small size of the market and instability in the producing countries.[53] Sony VAIO VGN-FW139E/H Battery

Applications

The global demand for iridium in 2007 was 119,000 troy ounces (3,700 kg), out of which 25,000 ozt (780 kg) were used for electrical applications such as spark plugs; 34,000 ozt (1,100 kg) for electrochemical applications such as electrodes for the chloralkali process; 24,000 ozt (750 kg) for catalysis; and 36,000 ozt (1,100 kg) for other uses.[54] Sony VAIO VGN-FW140AE Battery

Industrial and medical

The high melting point, hardness and corrosion resistance of iridium and its alloys determine most of its applications. Iridium and especially iridium–platinum alloys or osmium–iridium alloys have a low wear and are used, for example, for multi-pored spinnerets, through which a plastic polymer melt is extruded to form fibers, such as rayon.[55] Sony VAIO VGN-FW140D Battery

Osmium–iridium is used for compass bearings and for balances.[10]

Corrosion and heat resistance makes iridium an important alloying agent. Certain long-life aircraft engine parts are made of an iridium alloy and an iridium–titanium alloy is used for deep-water pipes because of its corrosion resistance.[10] Sony VAIO VGN-FW140E Battery

Iridium is also used as a hardening agent in platinum alloys. The Vickers hardness of pure platinum is 56 HV while platinum with 50% of iridium can reach over 500 HV.[56][57]

Devices that must withstand extremely high temperatures are often made from iridium. Sony VAIO VGN-FW140E/H Battery

For example, high-temperature cruciblesmade of iridium are used in the Czochralski process to produce oxide single-crystals (such as sapphires) for use in computer memory devices and in solid state lasers.[58][59] The crystals, such as gadolinium gallium garnet and yttrium gallium garnet, are grown by melting pre-sintered charges of mixed oxides under oxidizing conditions at temperatures up to 2100 °C.[4] Sony VAIO VGN-FW140E/W Battery

Its resistance to arc erosion makes iridium alloys ideal for electrical contacts for spark plugs.[59][60]

Iridium compounds are used as catalysts in the Cativa process for carbonylation of methanol to produce acetic acid.[61] Iridium itself is used as a catalyst in a type of automobile engine introduced in 1996 called the direct-ignition engine.[10] Sony VAIO VGN-FW140FE Battery

The radioisotope iridium-192 is one of the two most important sources of energy for use in industrial ?-radiography for non-destructive testing of metals.[62][63]Additionally, 192Ir is used as a source of gamma radiation for the treatment of cancer using brachytherapy, a form of radiotherapy where a sealed radioactive source is placed inside or next to the area requiring treatment. Sony VAIO VGN-FW140N Battery

Specific treatments include high dose rate prostate brachytherapy, bilary duct brachytherapy, and intracavitary cervix brachytherapy.[10]

Scientific

An alloy of 90% platinum and 10% iridium was used in 1889 to construct the International Prototype Meter and kilogram mass, kept by the International Bureau of Weights and Measures near Paris.[10] Sony VAIO VGN-FW140N/W Battery

The meter bar was replaced as the definition of the fundamental unit of length in 1960 by a line in the atomic spectrum of krypton,[note 4][64] but the kilogram prototype is still the international standard of mass.[65]

Iridium has been used in the radioisotope thermoelectric generators of unmanned spacecraft such as the Voyager, Viking, Pioneer,Cassini, Galileo, and New Horizons. Sony VAIO VGN-FW145E Battery

Iridium was chosen to encapsulate the plutonium-238 fuel in the generator because it can withstand the operating temperatures of up to 2000 °C and for its great strength.[4]

Another use concerns X-ray optics, especially X-ray telescopes.[66] The mirrors of the Chandra X-ray Observatory are coated with a layer of iridium 60 nm thick. Sony VAIO VGN-FW145E/W Battery

Iridium proved to be the best choice for reflecting X-rays after nickel, gold, and platinum were also tested. The iridium layer, which had to be smooth to within a few atoms, was applied by depositing iridium vapor under high vacuumon a base layer of chromium.[67] Sony VAIO VGN-FW160AE Battery

Iridium is used in particle physics for the production of antiprotons, a form of antimatter. Antiprotons are made by shooting a high-intensity proton beam at aconversion target, which needs to be made from a very high density material. Although tungsten may be used instead, iridium has the advantage of better stability under the shock waves induced by the temperature rise due to the incident beam.[68] Sony VAIO VGN-FW160D Battery

Carbon–hydrogen bond activation (C–H activation) is an area of research on reactions that cleave carbon–hydrogen bonds, which were traditionally regarded as unreactive. The first reported successes at activating C–H bonds in saturated hydrocarbons, published in 1982, used organometallic iridium complexes that undergo an oxidative addition with the hydrocarbon.[69][70] Sony VAIO VGN-FW160E Battery

Iridium complexes are being investigated as catalysts for asymmetric hydrogenation. These catalysts have been used in the synthesis of natural products and able to hydrogenate certain difficult substrates, such as unfunctionalized alkenes, enantioselectively (generating only one of the two possible enantiomers).[71][72]

Iridium forms a variety of complexes of fundamental interest in triplet harvesting.[73][74][75] Sony VAIO VGN-FW160E/H Battery

Historical

Iridium–osmium alloys were used to tip fountain pen nibs. The first major use of iridium was in 1834 in nibs mounted on gold.[4]Since 1944, the famous Parker 51 fountain pen was fitted with a nib tipped by a ruthenium and iridium alloy (with 3.8% iridium). Sony VAIO VGN-FW160F/E Battery

The tip material in modern fountain pens is still conventionally called "iridium," although there is seldom any iridium in it; other metals such as tungsten have taken its place.[76]

An iridium–platinum alloy was used for the touch holes or vent pieces of cannon. Sony VAIO VGN-FW170J/H Battery

According to a report of the Paris Exhibition of 1867, one of the pieces being exhibited by Johnson and Matthey "has been used in a Withworth gun for more than 3000 rounds, and scarcely shows signs of wear yet. Those who know the constant trouble and expense which are occasioned by the wearing of the vent-pieces of cannon when in active service, will appreciate this important adaptation".[77] Sony VAIO VGN-FW180AE Battery

The pigment iridium black, which consists of very finely divided iridium, is used for painting porcelain an intense black; it was said that "all other porcelain black colors appear grey by the side of it".[78]

Precautions

Iridium in bulk metallic form is not biologically important or hazardous to health due to its lack of reactivity with tissues; Sony VAIO VGN-FW180D Battery

there are only about 20 parts per trillion of iridium in human tissue.[10] However, finely divided iridium powder can be hazardous to handle, as it is an irritant and may ignite in air.[40] Very little is known about the toxicity of iridium compounds because they are used in very small amounts, but soluble salts, such as the iridium halides, could be hazardous due to elements other than iridium or due to iridium itself.[23] Sony VAIO VGN-FW180E Battery

However, most iridium compounds are insoluble, which makes absorption into the body difficult.[10]

A radioisotope of iridium, 192Ir, is dangerous like other radioactive isotopes. The only reported injuries related to iridium concern accidental exposure to radiation from 192Ir used in brachytherapy.[23] Sony VAIO VGN-FW180E/H Battery

High-energy gamma radiation from 192Ir can increase the risk of cancer. External exposure can cause burns, radiation poisoning, and death. Ingestion of 192Ir can burn the linings of the stomach and the intestines.[79] 192Ir, 192mIr, and 194mIr tend to deposit in the liver, and can pose health hazards from both gamma and beta radiation. Sony VAIO VGN-FW180FU Battery

Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River."[1]It is a dense, malleable, ductile, precious, gray-white transition metal. Sony VAIO VGN-FW190EBH Battery

Even though it has six naturally occurring isotopes, platinum is one of the rarest elements in the Earth's crust and has an average abundance of approximately 0.005 mg/kg. It is the least reactive metal. It occurs in some nickeland copper ores along with some native deposits, mostly in South Africa, which accounts for 80% of the world production. Sony VAIO VGN-FW190ECH Battery

As a member of the platinum group of elements, as well as of the group 10 of the periodic table of elements, platinum is generally non-reactive. It exhibits a remarkable resistance to corrosion, even at high temperatures, and as such is considered a noble metal. As a result, platinum is often found chemically uncombined as native platinum. Sony VAIO VGN-FW190EDH Battery

Because it occurs naturally in the alluvial sands of various rivers, it was first used by pre-Columbian South American natives to produce artifacts. It was referenced in European writings as early as 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian origin in 1748 that it became investigated by scientists. Sony VAIO VGN-FW190NAH Battery

Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry. Because only a few hundred tonnes are produced annually, it is a scarce material, and is highly valuable and is a major precious metal commodity. Sony VAIO VGN-FW190NBH Battery

Being a heavy metal, it leads to health issues upon exposure to its salts, but due to its corrosion resistance, it is not as toxic as some metals. Its compounds, most notablycisplatin, are applied in chemotherapy against certain types of cancer.[2]

Physical

As a pure metal, platinum is silvery-white, lustrous, ductile, and malleable.[ Sony VAIO VGN-FW190NCH Battery

Platinum is more ductile than gold, silver and copper, thus being the most ductile of pure metals, but gold is still more malleable than platinum [4] [5] It does not oxidize at any temperature, although it is corroded by halogens, cyanides, sulfur, and caustic alkalis. Platinum is insoluble in hydrochloricand nitric acid, but dissolves in aqua regia to form chloroplatinic acid, H2PtCl6.[6] Sony VAIO VGN-FW190NDH Battery

Platinum's resistance to wear and tarnish is well suited for making fine jewelry. The metal has an excellent resistance to corrosion and high temperature and has stable electrical properties. All of these characteristics have been used for industrial applications.[7]

Chemical

The most common oxidation states of platinum are +2 and +4. Sony VAIO VGN-FW190NEH Battery

The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) species. As is expected, tetracoordinate platinum(II) compounds tend to adopt 16-electronsquare planar geometries. While elemental platinum is generally unreactive, it dissolves in aqua regia to give soluble hexachloroplatinic acid ("H2PtCl6", formally (H3O)2PtCl6·nH2O ):[8]Sony VAIO VGN-FW198U/H Battery

Pt + 4 HNO3 + 6 HCl ? H2PtCl6 + 4 NO2 + 4 H2O

As a soft acid, platinum has a great affinity for sulfur, such as on dimethyl sulfoxide(DMSO); numerous DMSO complexes have been reported and care should be taken in the choice of reaction solvent.[9] Sony VAIO VGN-FW260J/B Battery

Platinum has six naturally occurring isotopes: 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt. The most abundant of these is195Pt, comprising 33.83% of all platinum. It is the only stable isotope with a non-zero spin; with a spin of 1/2, 195Pt satellite peaks are often observed in 1H and 31P NMR spectroscopy (i.e. Pt-phosphine and Pt-alkyl complexes). Sony VAIO VGN-FW280J/H Battery

190Pt is the least abundant at only 0.01%. Of the naturally occurring isotopes, only 190Pt is unstable, though it decays with a half-life of 6.5×1011 years. 198Pt undergoes alpha decay, but because its half-life is estimated at longer than 3.2×1014 years, it is considered stable. Sony VAIO VGN-FW290JRB Battery

Platinum also has 31 synthetic isotopes ranging in atomic mass from 166 to 202, making the total number of known isotopes 37. The least stable of these is 166Pt with a half-life of 300 µs, while the most stable is 193Pt with a half-life of 50 years. Most platinum isotopes decay by some combination of beta decay and alpha decay. 188Pt, 191Pt, and 193Pt decay primarily by electron capture. 190Pt and 198Pt have double beta decay paths.[10] Sony VAIO VGN-FW290JTB Battery

Occurrence

Platinum is an extremely rare metal,[11] occurring at a concentration of only 0.005 ppm in the Earth's crust.[12][13] It is sometimes mistaken for silver (Ag). Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium. Sony VAIO VGN-FW290JTH Battery

Most often the native platinum is found in secondary deposits; platinum is combined with the other platinum group metals in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department, Colombia are still a source for platinum group metals. Another large alluvial deposit is in the Ural Mountains, Russia, and it is still mined.[6] Sony VAIO VGN-FW290JTW Battery

In nickel and copper deposits, platinum group metals occur as sulfides (e.g., (Pt,Pd)S),tellurides (e.g., PtBiTe), antimonides (PdSb), and arsenides (e.g., PtAs2), and as end alloys with nickel or copper. Platinum arsenide, sperrylite (PtAs2), is a major source of platinum associated with nickel ores in the Sudbury Basin deposit in Ontario, Canada. Sony VAIO VGN-FW355J/H Battery

AtPlatinum, Alaska, about 545,000 troy ounces had been mined between 1927 and 1975. The mine ceased operations in 1990.[14]The rare sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with palladium and nickel. Cooperite occurs in theMerensky Reef within the Bushveld complex, Gauteng, South Africa.[15] Sony VAIO VGN-FW373J/B Battery

In 1865, chromites were identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906.[16]The largest known primary reserves are in the Bushveld complex in South Africa.[17] The large copper–nickel deposits nearNorilskin Russia, and the Sudbury Basin, Canada, are the two other large deposits. Sony VAIO VGN-FW30B Battery

In the Sudbury Basin, the huge quantities of nickel ore processed make up for the fact platinum is present as only 0.5 ppm in the ore. Smaller reserves can be found in the United States,[17]for example in the Absaroka Range in Montana.[18] In 2009, South Africa was the top producer of platinum, with an almost 80% share, followed by Russia at 11%.[19] Sony VAIO VGN-FW50B Battery

In 2010 July its been announced that Platinum is present in the state of Tamil nadu, India[20] and a MOU has been signed between Geological Survey of India with TAMIN - Tamilnadu Minerals Ltd.[21]

Platinum exists in higher abundances on the Moon and in meteorites. Sony VAIO VGN-FW51B/W Battery

Correspondingly, platinum is found in slightly higher abundances at sites of bolide impact on the Earth that are associated with resulting post-impact volcanism, and can be mined economically; the Sudbury Basin is one such example.[22] Sony VAIO VGN-FW51MF Battery

Compounds

Hexachloroplatinic acid mentioned above is probably the most important platinum compound, as it serves as the precursor for many other platinum compounds. By itself, it has various applications in photography, zinc etchings, indelible ink, plating, mirrors, porcelain coloring, and as a catalyst.[23] Sony VAIO VGN-FW51MF/H Battery

Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate,[8]which is relatively insoluble in ammonium solutions. Heating this ammonium salt in the presence of hydrogen reduces it to elemental platinum. Sony VAIO VGN-FW51ZF Battery

Potassium hexachloroplatinate is similarly insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by gravimetry.[24]

When hexachloroplatinic acid is heated, it decomposes through platinum(IV) chloride and platinum(II) chloride to elemental platinum, although the reactions do not occur stepwise:[25] Sony VAIO VGN-FW51ZF/H Battery

(H3O)2PtCl6·nH2O   PtCl4 + 2 HCl + (n + 2) H2O

PtCl4 PtCl2 + Cl2

PtCl2 Pt + Cl2

All three reactions are reversible. Platinum(II) and platinum(IV) bromides are known as well. Platinum hexafluoride is a strong oxidizer capable of oxidizing oxygen. Sony VAIO VGN-FW52JB Battery

Oxides

Platinum(IV) oxide, PtO2, also known as Adams' catalyst, is a black powder which is soluble in KOH solutions and concentrated acids.[26] PtO2 and the less common PtO both decompose upon heating.[3] Platinum(II,IV) oxide, Pt3O4, is formed in the following reaction: Sony VAIO VGN-FW54FB Battery

2 Pt2+ + Pt4+ + 4 O2? ? Pt3O4

Platinum also forms a trioxide, where it is present in the +4 oxidation state.

Other compounds

Unlike palladium acetate, platinum(II) acetate is not commercially available. Where a base is desired, the halides have been used in conjunction with sodium acetate.[9] The use of platinum(II) acetylacetonate has also been reported.[27] Sony VAIO VGN-FW70DB Battery

Several barium platinides have been synthesized in which platinum exhibits negative oxidation states ranging from ?1 to ?2. These include BaPt, Ba3Pt2, andBa2Pt.[28] Caesium platinide, Cs2Pt, a dark-red transparent crystalline compound[29] has been shown to contain Pt2?anions.[30] Sony VAIO VGN-FW71DB/W Battery

Platinum also exhibits negative oxidation states at surfaces reduced electrochemically.[31] The negative oxidation states exhibited by platinum are unusual for metallic elements, and they are attributed to the relativistic stabilization of the 6s orbitals.[30]

Zeise's salt, containing an ethylene ligand, was one of the first organometallic compounds discovered. Sony VAIO VGN-FW72JGB Battery

Dichloro(cycloocta-1,5-diene)platinum(II) is a commercially available olefin complex, which contains easily displaceable cod ligands ("cod" being an abbreviation of 1,5-cyclooctadiene). The cod complex and the halides are convenient starting points to platinum chemistry.[9] Sony VAIO VGN-FW73JGB Battery

Cisplatin, or cis-diamminedichloroplatinum(II) is the first of a series of square planar platinum(II)-containing chemotherapy drugs, including carboplatin andoxaliplatin. These compounds are capable of crosslinking DNA, and kill cells by similar pathways to alkylating chemotherapeutic agents.[32] Sony VAIO VGN-FW74FB Battery

Platinum occurs naturally in the alluvial sands of various rivers, though there is little evidence of its use by ancient people. However, the metal was used by pre-Columbian Americans near modern-day Esmeraldas, Ecuador to produce artifacts of a white gold-platinum alloy. Sony VAIO VGN-FW81HS Battery

The first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger as a description of an unknown noble metal found between Darién and Mexico, "which no fire nor any Spanish artifice has yet been able to liquefy."[33]

In 1741, Charles Wood, a British metallurgist, found various samples of Colombian platinum in Jamaica, which he sent to William Brownrigg for further investigation. Sony VAIO VGN-FW81NS Battery

Antonio de Ulloa, also credited with the discovery of platinum, returned to Spain from the French Geodesic Mission in 1746 after having been there for eight years. His historical account of the expedition included a description of platinum as being neither separable norcalcinable. Ulloa also anticipated the discovery of platinum mines. Sony VAIO VGN-FW81S Battery

After publishing the report in 1748, Ulloa did not continue to investigate the new metal. In 1758, he was sent to superintend mercury mining operations inHuancavelica.[33]

In 1750, after studying the platinum sent to him by Wood, Brownrigg presented a detailed account of the metal to the Royal Society, mentioning that he had seen no mention of it in any previous accounts of known minerals.[34Sony VAIO VGN-FW82DS Battery

Brownrigg also made note of platinum's extremely high melting point and refractoriness towardborax. Other chemists across Europe soon began studying platinum, including Torbern Bergman, Jöns Jakob Berzelius, William Lewis, and Pierre Macquer. In 1752, Henrik Scheffer published a detailed scientific description of the metal, which he referred to as "white gold", including an account of how he succeeded in fusing platinum ore with the aid of arsenic. Sony VAIO VGN-FW82JS Battery

Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosion.[33]

Carl von Sickingen researched platinum extensively in 1772. He succeeded in making malleable platinum by alloying it with gold, dissolving the alloy in aqua regia,

precipitating the platinum with ammonium chloride, igniting the ammonium chloroplatinate, and hammering the resulting finely divided platinum to make it cohere. Franz Karl Achard made the first platinum crucible in 1784. He worked with the platinum by fusing it with arsenic, then later volatilizing the arsenic.[33] Sony VAIO VGN-FW82XS Battery

Since the other platinum family members were not discovered yet (platinum was the first in the list), Scheffer and Sickingen made the false assumption that due to it's hardness -which is slightly more than for pure iron , platinum was a relatively non pliable material, even brittle at times, when in fact it's ductility and malleability are close to that of gold. Sony VAIO VGN-FW83DS Battery

Their assumptions could not be avoided since the platinum they experimented with was highly contaminated with minute amounts of the platinum family elements such as Osmium and Iridium amongst others, which embrittled the platinum alloy. Sony VAIO VGN-FW83JS Battery

Alloying this impure platinum residue called "plyoxen" with gold was the only solution at the time to obtain a pliable compound, but nowadays, very pure platinum is available and extremely long wire can be drawn from pure platinum, very easily, due to it's crystalline structure which is similar to that of many soft metals.[35] Sony VAIO VGN-FW83XS Battery

In 1786, Charles III of Spain provided a library and laboratory to Pierre-François Chabaneau to aid in his research of platinum. Chabaneau succeeded in removing various impurities from the ore, including gold, mercury, lead, copper, and iron. This led him to believe he was working with a single metal, but in truth the ore still contained the yet-undiscovered platinum group metals. Sony VAIO VGN-FW90HS Battery

Sony VAIO VGN-FW90NS Battery

This led to inconsistent results in his experiments. At times, the platinum seemed malleable, but when it was alloyed with iridium, it would be much more brittle. Sometimes the metal was entirely incombustible, but when alloyed with osmium, it would volatilize. After several months, Chabaneau succeeded in producing 23 kilograms of pure, malleable platinum by hammering and compressing the sponge form while white-hot. Sony VAIO VGN-FW90S Battery

Chabeneau realized the infusibility of platinum would lend value to objects made of it, and so started a business with Joaquín Cabezas producing platinum ingots and utensils. This started what is known as the "platinum age" in Spain.[33]

In 2007, Gerhard Ertl won the Nobel Prize in Chemistry for determining the detailed molecular mechanisms of the catalytic oxidation of carbon monoxide over platinum (catalytic converter).[36] Sony VAIO VGN-FW91NS Battery

Production

Platinum, along with the rest of the platinum metals, is obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper, noble metals such as silver, gold and the platinum group metals as well as seleniumand tellurium settle to the bottom of the cell as "anode mud", which forms the starting point for the extraction of the platinum group metals. Sony VAIO VGN-FW91S Battery

If pure platinum is found in placer deposits or other ores, it is isolated from them by various methods of subtracting impurities. Because platinum is significantly denser than many of its impurities, the lighter impurities can be removed by simply floating them away in a liquid. Platinum is also nonmagnetic, while nickel and iron are both magnetic. Sony VAIO VGN-FW92DS Battery

These two impurities are thus removed by running an electromagnet over the mixture. Because platinum has a higher melting point than most other substances, many impurities can be burned or melted away without melting the platinum. Finally, platinum is resistant to hydrochloric and sulfuric acids, while other substances are readily attacked by them. Sony VAIO VGN-FW92JS Battery

Metal impurities can be removed by stirring the mixture in either of the two acids and recovering the remaining platinum.[39]

One suitable method for purification for the raw platinum, which contains platinum, gold, and the other platinum group metals, is to process it with aqua regia, in which palladium, Sony VAIO VGN-FW93DS Battery

gold and platinum are dissolved, while osmium, iridium, ruthenium and rhodium stay unreacted. The gold is precipitated by the addition of iron(III) chloride and after filtering off the gold, the platinum is precipitated as ammonium chloroplatinate by the addition of ammonium chloride. Ammonium chloroplatinate can be converted to the metal by heating.[40] Sony VAIO VGN-FW93JS Battery

Applications

Of the 239 tonnes of platinum sold in 2006, 130 tonnes were used for vehicle emissions control devices, 49 tonnes for jewelry, 13.3 tonnes in electronics, and 11.2 tonnes in the chemical industry as a catalyst. The remaining 35.5 tonnes went to various other minor applications, such as electrodes, anticancer drugs, oxygen sensors, spark plugs and turbine engines.[41] Sony VAIO VGN-FW93XS Battery

Catalysis

The most common use of platinum is as a catalyst in chemical reactions, many times as platinum black. It has been employed in this application since the early 19th century, when platinum powder was used to catalyze the ignition of hydrogen. Sony VAIO VGN-FW94FS Battery

Its most important application is in automobiles as a catalytic converter, which allows the complete combustion of low concentrations of unburned hydrocarbons from the exhaust into carbon dioxide and water vapor. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, Sony VAIO VGN-FW94GS Battery

but especially in catalytic reforming of straight run naphthas into higher-octane gasoline which becomes rich in aromatic compounds. PtO2, also known as Adams' catalyst, is used as a hydrogenation catalyst, specifically for vegetable oils.[23] Platinum metal also strongly catalyzes the decomposition of hydrogen peroxide into water and oxygen gas.[42] Sony VAIO VGN-FW94HS Battery

Standard

From 1889 to 1960, the meter was defined as the length of a platinum-iridium (90:10) alloy bar, known as the International Prototype Meter bar. The previous bar was made of platinum in 1799. The International Prototype Kilogram remains defined by a cylinder of the same platinum-iridium alloy made in 1879.[43] Sony VAIO VGN-G118CN Battery

The standard hydrogen electrode also uses a platinized platinum electrode due to its corrosion resistance, and other attributes.[44]

Precious metal

Platinum is a precious metal commodity; its bullion has the ISO currency code of XPT. Coins, bars, and ingots are traded or collected. Sony VAIO VGN-G118GN/B Battery

Platinum finds use in jewelry, usually as a 90–95% alloy, due to its inertness and shine. Jewelry trade publications advise jewelers to present minute surface scratches (which they term patina) as a desirable feature.[45][46]

In watchmaking, Vacheron Constantin, Patek Philippe, Rolex, Breitling, and other companies use platinum for producing their limited edition watch series. Sony VAIO VGN-G118GN/T Battery

Watchmakers appreciate the unique properties of platinum, as it neither tarnishes nor wears out (relative to gold).[47]

Average price of platinum from 1991 to 2007 in US$ per troy ounce(~$20/g)[48]

The price of platinum, like other industrial commodities, is more volatile than that of gold. Sony VAIO VGN-G118TN/B Battery

In 2008, the price of platinum dropped from $2,252 to $774 per oz,[49] a loss of nearly 2/3 of its value. By contrast, the price of gold dropped from ~$1,000 to ~$700/ozt during the same time frame, a loss of only 1/3 of its value.

During periods of sustained economic stability and growth, the price of platinum tends to be as much as twice the price of gold, Sony VAIO VGN-G118TN/S Battery

whereas during periods of economic uncertainty,[50] the price of platinum tends to decrease due to reduced industrial demand, falling below the price of gold. Gold prices are more stable in slow economic times, as gold is considered a safe haven and gold demand is not driven by industrial uses. In the 18th century, platinum's rarity made King Louis XV of France declare it the only metal fit for a king.[51] Sony VAIO VGN-G11VN/T Battery

Other uses

In the laboratory, platinum wire is used for electrodes; platinum pans and supports are used in thermogravimetric analysisbecause of the stringent requirements of chemical inertness upon heating to high temperatures (~1000 °C). Sony VAIO VGN-G11VN/TC Battery

Platinum is used as an alloying agent for various metal products, including fine wires, noncorrosive laboratory containers, medical instruments, dental prostheses, electrical contacts, and thermocouples. Platinum-cobalt, an alloy of roughly three parts platinum and one part cobalt, is used to make relatively strong permanent magnets.[23] Sony VAIO VGN-G11XN/B Battery

Platinum-based anodes are used in ships, pipelines, and steel piers.[6]

Symbol of prestige

Platinum's rarity as a metal has caused advertisers to associate it with exclusivity and wealth. "Platinum" debit cards have greater privileges than do "gold" ones.[52] Sony VAIO VGN-G1AAPS Battery

"Platinum awards" are the second highest possible, ranking above "gold", "silver" and "bronze", but below diamond. For example, in the United States, a musical album that has sold more than 1 million copies, will be credited as "platinum", whereas an album that sold more than 10 million copies will be certified as "diamond".[53] Sony VAIO VGN-G1AAPSA Battery

Some products, such as blenders and vehicles, with a silvery-white color are identified as "platinum". Platinum is considered a precious metal, although its use is not as common as the use of gold or silver. The frame of the Crown of Queen Elizabeth the Queen Mother, manufactured for her coronation as Consort of King George VI, is made of platinum. It was the first British crown to be made of this particular metal.[54] Sony VAIO VGN-G1AAPSB Battery

Health issues

According to the Centers for Disease Control and Prevention, short-term exposure to platinum salts may cause irritation of the eyes, nose, and throat, and long-term exposure may cause both respiratory and skin allergies. The current OSHA standard is 2 micrograms per cubic meter of air averaged over an 8-hour work shift.[55] Sony VAIO VGN-G1AAPSC Battery

Certain platinum complexes are used in chemotherapy, and show good activity against some tumors. Cisplatin is particularly effective against testicular cancer; the cure rate was improved from 10% to 85%.[56] However, the side effects are severe. Cisplatin causes cumulative, irreversible kidney damage and deafness.[57] Sony VAIO VGN-G1ABNS Battery

As with other ototoxic agents, deafness may be secondary to interactions with melanin in the stria vascularis. Binding of platinum to RNA has been reviewed.Sony VAIO VGN-G1KBN Battery

As platinum is a catalyst in the manufacture of the silicone rubber and gel components of several types of medical implants (breast implants, joint replacement prosthetics, artificial lumbar discs, vascular access ports, etc.), the possibility platinum could enter the body and cause adverse effects has merited study. Sony VAIO VGN-G1KAP Battery

TheFood and Drug Administration and other institutions have reviewed the issue and found no evidence to suggest toxicity in vivo.Sony VAIO VGN-G1KBNA Battery,Sony VAIO VGN-G1LAP Battery,Sony VAIO VGN-G1LBN Battery,Sony VAIO VGN-G218LN/T Battery,Sony VAIO VGN-G218N/B Battery

 

Thulium,Ytterbium,Lutetium,Hafnium,Tantalum,Tungsten

Thulium is a chemical element that has the symbol Tm and atomic number 69. Thulium is the second least abundant of the lanthanides (promethium is only found in trace quantities on Earth). It is an easily workable metalwith a bright silvery-gray luster.Sony VAIO VGN-Z590UAB Battery

Despite its high price and rarity, thulium is used as the radiation source in portable X-ray devices and in solid-state lasers.

Physical properties

Pure thulium metal has a bright, silvery luster. It is reasonably stable in air, but should be protected from moisture. The metal is soft, malleable, and ductile.Thulium is ferromagnetic below 32 K, antiferromagnetic between 32 and 56 K andparamagnetic above 56 K.Sony VAIO VGN-Z591U/B Battery

Chemical properties

Thulium metal tarnishes slowly in air and burns readily at 150 °C to form thulium(III) oxide:

4 Tm + 3 O2 ? 2 Tm2O3

Thulium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form thulium hydroxide:Sony VAIO VGN-Z59G Battery

2 Tm (s) + 6 H2O (l) ? 2 Tm(OH)3 (aq) + 3 H2 (g)

Thulium reacts with all the halogens. Reactions are slow at room temperature, but are vigorous above 200 °C:

2 Tm (s) + 3 F2 (g) ? 2 TmF3 (s) [white]

2 Tm (s) + 3 Cl2 (g) ? 2 TmCl3 (s) [yellow]

2 Tm (s) + 3 Br2 (g) ? 2 TmBr3 (s) [white]

2 Tm (s) + 3 I2 (g) ? 2 TmI3 (s) [yellow]

Thulium dissolves readily in dilute sulfuric acid to form solutions containing the pale green Tm(III) ions, which exist as a [Tm(OH2)9]3+ complexes:Sony VAIO VGN-Z620D Battery

2 Tm (s) + 3 H2SO4 (aq) ? 2 Tm3+ (aq) + 3 SO2?

4 (aq) + 3 H2 (g)

Thulium reacts with various metallic and non-metallic elements forming a range of binary compounds, including TmN, TmS, TmC2, Tm2C3, TmH2, TmH3, TmSi2, TmGe3, TmB4, TmB6 and TmB12. In those compounds, thulium exhibits valence states +2, +3 and +4, however, the +3 state is most common and only this state has been observed in Tm solutions.Sony VAIO VGN-Z620N/B Battery

Naturally occurring thulium is composed of one stable isotope, Tm-169 (100% natural abundance). Thirty one radioisotopes have been characterized, with the most stable being Tm-171 with a half-life of 1.92 years, Tm-170 with a half-life of 128.6 days, Tm-168 with a half-life of 93.1 days, and Tm-167 with a half-life of 9.25 days.Sony VAIO VGN-Z650N/B Battery

All of the remaining radioactive isotopes have half-lives that are less than 64 hours, and the majority of these have half-lives that are less than 2 minutes. This element also has 14 meta states, with the most stable being Tm-164m (t½ 5.1 minutes), Tm-160m (t½ 74.5 seconds) and Tm-155m (t½ 45 seconds).Sony VAIO VGN-Z670N/B Battery

The isotopes of thulium range in atomic weight from 145.966 u (Tm-146) to 176.949 u (Tm-177). The primary decay mode before the most abundant stable isotope, Tm-169, is electron capture, and the primary mode after is beta emission. The primary decay products before Tm-169 are element 68 (erbium) isotopes, and the primary products after are element 70 (ytterbium) isotopes.Sony VAIO VGN-Z690CTO Battery

Thulium was discovered by Swedish chemist Per Teodor Cleve in 1879 by looking for impurities in the oxides of other rare earth elements (this was the same method Carl Gustaf Mosander earlier used to discover some other rare earth elements). Cleve started by removing all of the known contaminants of erbia (Er2O3).Sony VAIO VGN-Z690NAX Battery

Upon additional processing, he obtained two new substances; one brown and one green. The brown substance was the oxide of the element holmium and was named holmia by Cleve, and the green substance was the oxide of an unknown element. Cleve named the oxide thulia and its element thulium afterThule, Scandinavia.Sony VAIO VGN-Z690PAB Battery

Thulium was so rare that none of the early workers had enough of it to purify sufficiently to actually see the green color; they had to be content with spectroscopically observing the strengthening of the two characteristic absorption bands, as erbium was progressively removed.Sony VAIO VGN-Z690PCB Battery

The first researcher to obtain nearly pure thulium was Charles James, a British expatriate working on a large scale at New Hampshire College in Durham. In 1911 he reported his results, having used his discovered method of bromate fractional crystallization to do the purification. He famously needed 15,000 "operations" to establish that the material was homogeneous.Sony VAIO VGN-Z690PDB Battery

High-purity thulium oxide was first offered commercially in the late 1950s, as a result of the adoption of ion-exchangeseparation technology. Lindsay Chemical Division of American Potash & Chemical Corporation offered it in grades of 99% and 99.9% purity.Sony VAIO VGN-Z690PEB Battery

The price per kilogram has oscillated between US$4,600 and $13,300 in the period from 1959 to 1998 for 99.9% purity, and it was second highest for lanthanides behind lutetium.

Occurrence and production

The element is never found in nature in pure form, but it is found in small quantities in minerals with other rare earths. Its abundance in the Earth crust is 0.5 mg/kg.Sony VAIO VGN-Z690PFB Battery

Thulium is principally extracted from monazite (~0.007% thulium) ores found in river sands, through ion-exchange. Newer ion-exchange and solvent-extraction techniques have led to easier separation of the rare earths, which has yielded much lower costs for thulium production.Sony VAIO VGN-Z690YAD Battery

The principal sources today are the ion adsorption clays of southern China. In these, where about two-thirds of the total rare-earth content is yttrium, thulium is about 0.5% (or about tied with lutetium for rarity). The metal can be isolated through reduction of its oxide with lanthanummetal or by calcium reduction in a closed container.Sony VAIO VGN-Z691Y/B Battery

None of thulium's natural compounds are commercially important.

Applications

Rare and expensive, thulium has few applications:

Laser

Holmium-chromium-thulium triple-doped YAG (Ho:Cr:Tm:YAG, or Ho,Cr,Tm:YAG) is an active laser medium material with high efficiency.Sony VAIO VGN-Z691Y/X Battery

It lases at 2097 nm and is widely used in military, medicine, and meteorology. Single-element thulium-doped YAG (Tm:YAG) lasers operate between 1930 and 2040 nm. The wavelength of thulium-based lasers is very efficient for superficial ablation of tissue, with minimal coagulation depth in air or in water. This makes thulium lasers attractive for laser-based surgery.Sony VAIO VGN-Z698Y/X Battery

X-ray source

Despite its high cost, portable X-ray devices use thulium that has been bombarded in a nuclear reactor as a radiation source. These sources are available for about one year, as tools in medical and dental diagnosis, as well as to detect defects in inaccessible mechanical and electronic components.Sony VAIO VGN-Z699JAB Battery

Such sources do not need extensive radiation protection – only a small cup of lead.

Thulium-170 is gaining popularity as an X-ray source for cancer treatment via brachytherapy.[13] This isotope has a half-life of 128.6 days and five major emission lines of comparable intensity (7.4, 51.354, 52.389, 59.4 and 84.253 keV).Sony VAIO VGN-Z70B Battery

Others

Thulium has been used in high temperature superconductors similarly to yttrium. Thulium potentially has use in ferrites, ceramic magnetic materials that are used inmicrowave equipment.Thulium is also similar to scandium in that it is used in arc lighting for its unusual spectrum, in this case, its green emission lines, which are not covered by other elements.Sony VAIO VGN-Z71JB Battery

Biological role and precautions

Thulium has no known biological role, although it has been noted that it stimulates metabolism. Soluble thulium salts are regarded as slightly toxic if taken in large amounts, but the insoluble salts are non-toxic.Sony VAIO VGN-Z73FB Battery

Thulium is not taken up by plant roots to any extent and thus does not get into the human food chain. Vegetables typically contain only one milligram of thulium per tonne (dry weight).

Ytterbium is a chemical element with the symbol Yb and atomic number 70.Sony VAIO VGN-Z790DKX Battery

A soft silvery metallic element, ytterbium is a rare earth element of the lanthanide series and is found in the minerals gadolinite, monazite, andxenotime. The element is sometimes associated with yttrium or other related elements and is used in certain steels.Sony VAIO VGN-Z790DMR Battery

Natural ytterbium is a mix of seven stable isotopes. Ytterbium-169, an artificially produced isotope, is used as a gamma ray source.

Physical properties

Ytterbium is a soft, malleable and ductile chemical element that displays a bright silvery luster when in its pure form.Sony VAIO VGN-Z790DND Battery

It is a rare earth element, and it is readily attacked and dissolved by the strong mineral acids. It reacts slowly with coldwater and it oxidizes slowly in air.

Ytterbium has three allotropes labeled by the Greek letters alpha, beta and gamma; their transformation temperatures are ?13 °C and 795 °C.Sony VAIO VGN-Z820DB Battery

The beta allotrope exists at room temperature, and it has a face-centered cubic crystal structure. The high-temperature gamma allotrope has a body-centered cubic crystalline structure.

Normally, the beta allotrope has a metallic electrical conductivity, but it becomes a semiconductor when exposed to a pressure of about 16,000 atmospheres (1.6 GPa).Sony VAIO VGN-Z820G/B Battery

Its electrical resistivity increases ten times upon compression to 39,000 atmospheres (3.9 GPa), but then drops to about 10% of its room-temperature resistivity at about 40,000 atm (4.0 GPa).

In contrast with the other rare-earth metals, which usually have antiferromagnetic and/or ferromagnetic properties at lowtemperatures, ytterbium is paramagnetic at any temperatures above 1.0 kelvin.Sony VAIO VGN-Z890GLX Battery

With a melting point of 824 °C and a boiling point of 1196 °C ytterbium has a smaller range of liquid temperatures than any other metal.

Chemical properties

Ytterbium metal tarnishes slowly in air and burns readily at 200 °C to form ytterbium(III) oxide (Yb2O3) or less stable ytterbium monoxide (YbO)Sony VAIO VGN-Z890GMR Battery

Ytterbium is quite electropositive, and it reacts slowly with cold water and quite quickly with hot water to form ytterbium hydroxide:

2 Yb (s) + 6 H2O (l) ? 2 Yb(OH)3 (aq) + 3 H2 (g)

Ytterbium reacts with all the halogens:

2 Yb (s) + 3 F2 (g) ? 2 YbF3 (s) [white]

2 Yb (s) + 3 Cl2 (g) ? 2 YbCl3 (s) [white]

2 Yb (s) + 3 Br2 (g) ? 2 YbBr3 (s) [white]

2 Yb (s) + 3 I2 (g) ? 2 YbI3 (s) [white]Sony VAIO VGN-Z898H/X Battery

The ytterbium(III) ion absorbs light in the near infrared range of wavelengths, but not in visible light, so that the mineralytterbia, Yb2O3, is white in color, and the salts of ytterbium of colorless anions are also colorless. Ytterbium dissolves readily in dilute sulfuric acid to form solutions that contain the colorless Yb(III) ions, which exist as a [Yb(OH2)9]3+complexes:Sony VAIO VGN-Z90FS Battery

2 Yb (s) + 3 H2SO4 (aq) ? 2 Yb3+ (aq) + 3 SO2?

4 (aq) + 3 H2 (g)

Chemical compounds

The chemical behavior of ytterbium is similar to that of the rest of the lanthanides. Most ytterbium compounds are found in the oxidation state +3, and its salts in this oxidation state are nearly colorless.Sony VAIO VGN-Z90NS Battery

Like europium, samarium, and thulium, the trihalogens of ytterbium can be reduced by hydrogen or by the addition of the metal reduced to the dihalogens, in this case the for example YbCl2. The oxidation state +2 reacts in some ways similarly to the alkaline earth metal compounds, for example the Ytterbium(II) oxide (YbO) shows the same structure as calcium oxide (CaO).Sony VAIO VGN-Z90PS Battery

• Halides: YbCl2, YbBr3, YbCl3, YbF3
• Oxides: Yb2O3
• hydroxide: ytterbium hydroxide, Yb(OH)3

Natural ytterbium is composed of seven stable isotopes: 168Yb, 170Yb, 171Yb, 172Yb, 173Yb, 174Yb, and 176Yb, with 174Yb being the most abundant isotope, at 31.8% of the natural abundance).Sony VAIO VGN-Z90S Battery

27 radioisotopes have been observed, with the most stable ones being Yb-169 with a half-life of 32.0 days, 175Yb with a half-life of 4.18 days, and 166Yb with a half-life of 56.7 hours. All of its remaining radioactive isotopes have half-lives that are less than two hours, and the majority of these have half-lives that are less than 20 minutes.Sony VAIO VGN-Z90US Battery

Ytterbium also has 12 meta states, with the most stable being Yb-169m (t½ 46 seconds).

The isotopes of ytterbium range in atomic weight from 147.9674 atomic mass unit (u) for 148Yb to 180.9562 u for 181Yb. Its primary decay mode at weights lower than the most abundant stable isotope, 174Yb, is electron capture, and the primary decay mode above the atomic mass number of 174 is beta decay.Sony VAIO VGN-Z91DS Battery

The primary decay products at atomic masses lower than 174 arethulium isotopes, and the primary products from above 174 u are element (lutetium isotopes. Interestingly in modern quantum optics, the different isotopes of ytterbium follow either Bose-Einstein statistics or Fermi-Dirac statistics, leading to significant behavior in optical lattices.Sony VAIO VGN-Z91JS Battery

Ytterbium was discovered by the Swiss chemist Jean Charles Galissard de Marignac in the year 1878. Marignac found a new component in the earth then known as erbia, and he named it ytterbia, for Ytterby, the Swedish village near where he found the new component of erbium.Sony VAIO VGN-Z91PS Battery

Marignac suspected that ytterbia was a compound of a new element that he called "ytterbium".

In 1907, the French chemist Georges Urbain separated Marignac's ytterbia into two components: neoytterbia and lutecia. Neoytterbia would later become known as the element ytterbium, and lutecia would later be known as the element lutetium.Sony VAIO VGN-Z91YS Battery

Carl Auer von Welsbach independently isolated these elements from ytterbia at about the same time, but he called them aldebaranium and cassiopeium.

The chemical and physical properties of ytterbium could not be determined with any precision until 1953, when the first nearly pure ytterbium metal was produced by using ion-exchange processes.Sony VAIO VGN-Z92DS Battery

The price of ytterbium was relatively stable between 1953 and 1998 at about US$ 1,000/kg.

Occurrence

Ytterbium is found with other rare earth elements in several rare minerals. It is most often recovered commercially frommonazite sand (0.03% ytterbium). Sony VAIO VGN-Z92JS Battery

The element is also found in euxenite and xenotime. The main mining areas are China, United States, Brazil, India, Sri Lanka, and Australia; and reserves of ytterbium are estimated as one million tonnes. Ytterbium is normally difficult to separate from other rare earths,Sony VAIO VGN-Z92PS Battery

but ion-exchange and solvent extraction techniques developed in the mid to late 20th century have simplified separation. Known compounds of ytterbium are rare and have not yet been well characterized. The abundance of ytterbium in the Earth crust is about 3 mg/kg.Sony VAIO VGN-Z92YS Battery

The most important current (2008) sources of ytterbium are the ionic adsorption clays of southern China. The "High Yttrium" concentrate derived from some versions of these comprise about two thirds yttria by weight, and 3–4% ytterbia.Sony VAIO VGN-Z93FS Battery

As an even-numbered lanthanide, in accordance with the Oddo-Harkins rule, ytterbium is significantly more abundant than its immediate neighbors, thulium and lutetium, which occur in the same concentrate at levels of about 0.5% each. The world production of ytterbium is only about 50 tonnes per year, reflecting the fact that ytterbium has few commercial applications.Sony VAIO VGN-Z93GS Battery

Microscopic traces of ytterbium are used as a dopant in the ytterbium YAG laser, or Yb:YAG laser, a solid-state laser in which ytterbium is the element that undergoes stimulated emission of electromagnetic radiation.Sony VAIO VGN-Z93HS Battery

Production

Recovery of ytterbium from ores involves several processes which are common to most rare-earth elements: 1) processing, 2) separation of Yb from other rare earths, 3) preparation of the metal. If the starting ore is gadolinite, it is digested with hydrochloric or nitric acid which dissolves the rare-earth metals. Sony VAIO VGN-Z93VS Battery

The solution is treated with sodium oxalate or oxalic acid to precipitate rare earths as oxalates. For euxenite, ore is processed either by fusion with potassium bisulfate or withhydrofluoric acid. Monazite or xenotime are heated either with sulfuric acid or with caustic soda.Sony A1258274A Battery

Ytterbium is separated from other rare earths either by ion exchange or by reduction with sodium amalgam. In the latter method, a buffered acidic solution of trivalent rare earths is treated with molten sodium mercury alloy, which reduces and dissolves Yb3+. The alloy is treated with hydrochloric acid.Sony VGP-BPL10 Battery

The metal is extracted from the solution as oxalate and converted to oxide by heating. The oxide is reduced to metal by heating with lanthanum, aluminium, cerium or zirconium in high vacuum. The metal is purified by sublimation and collected over a condensed plate.Sony VGP-BPS10 Battery

Source of gamma rays

The 169Yb isotope has been used as a radiation source substitute for a portable X-ray machine when electricity was not available. Like X-rays, gamma rays pass through soft tissues of the body, but are blocked by bones and other dense materials. Thus, small 169Yb samples (which emit gamma rays) act like tiny X-ray machines useful for radiography of small objects.Sony VGP-BPS10/S Battery

Experiment shows that radiographs taken with 169Yb source are roughly equivalent to those taken with X-rays having energies between 250 and 350 keV.[9]

Doping of stainless steel

Ytterbium can also be used as a dopant to help improve the grain refinement, strength, and other mechanical properties of stainless steel. Some ytterbium alloys have rarely been used in dentistry.Sony VGP-BPS10A/B Battery

Yb as dopant of active media

Yb is used as dopant in optical materials, usually in the form of ions in active laser media. Several powerful double-clad fiber lasers and disk lasers use Yb3+ ions as dopant at concentration of several atomic percent. Glasses (optical fibers), crystals and ceramics with Yb3+ are used.Sony VGP-BPS10B Battery

Ytterbium is often used as a doping material (as Yb3+) for high power and wavelength-tunable solid state lasers. Yb lasers commonly radiate in the 1.06–1.12 µm band being optically pumped at wavelength 900 nm–1 µm, dependently on the host and application. Small quantum defect makes Yb prospective dopant for efficient lasers andpower scaling.Sony VGP-BPS10A Battery

The kinetic of excitations in Yb-doped materials is simple and can be described within concept of effective cross-sections; for the most of Yb-doped laser materials (as for many other optically pumped gain media), the McCumber relation holds,although the application to the Yb-doped composite materials was under discussion.Sony VGP-BPS11 Battery

Usually, low concentrations of Yb are used. At high concentration of excitations, the Yb-doped materials show photodarkening (glass fibers) or ever switch to the broadband emission  (crystals and ceramics) instead of the efficient laser action.Sony VGP-BPL11 Battery

This effect may be related with not only overheating, but also conditions of the charge compensation at high concentration of Yb ions.

Others

Ytterbium metal increases its electrical resistivity when subjected to high stresses. This property is used in stress gauges to monitor ground deformations from earthquakes and explosions.Sony VGP-BPL12 Battery

Precautions

Although ytterbium is fairly stable chemically, it should be stored in air-tight containers and in an inert atmosphere to protect the metal from air and moisture. All compounds of ytterbium should be treated as highly toxic although initial studies appear to indicate that the danger is minimal.Sony VGP-BPS12 Battery

Ytterbium compounds are, however, known to cause irritation to the skin and eye, and some might be teratogenic.[20] Metallic ytterbium dust poses a fire and explosion hazard.

Lutetium is a chemical element with the symbol Lu and atomic number 71.Sony VGP-BPL13 Battery

It is the last element in the lanthanide series, which, along with lanthanide contraction, explains several important properties of lutetium, such as it having the highest hardness or density among lanthanides. Unlike other lanthanides, the element lies in the d-block of the periodic table;Sony VGP-BPS13 Battery

however, lanthanum is sometimes placed on the d-block lanthanide position. Chemically, lutetium is a typical lanthanide: its only common oxidation state is +3, seen in its oxide, halides and other compounds. In an aqueous solution, like compounds of other late lanthanides, soluble lutetium compounds form a complex with nine water molecules.Sony VGP-BPS13/B Battery

Lutetium was independently discovered in 1907 by French scientist Georges Urbain, Austrian mineralogist Baron Carl Auer von Welsbach, and American chemist Charles James. All of these men found lutetium as an impurity in the mineral ytterbia, which was previously thought to consist entirely of ytterbium.Sony VGP-BPS13/S Battery

The dispute on the priority of the discovery occurred shortly after, with Urbain and von Welsbach accusing each other of publishing results influenced by the published research of the other; the naming honor went to Urbain as he published his results earlier. He chose the name lutecium for the new element but in 1949 the spelling of element 71 was changed to lutetium.Sony VGP-BPS13/S Battery

In 1909, the priority was finally granted to Urbain and his names were adopted as official ones; however, the name cassiopeium (or later cassiopium) for element 71 proposed by von Welsbach was used by many German scientists until the 1950s. Like other lanthanides, lutetium is one of the elements that traditionally were included in the classification "rare earths."Sony VGP-BPS13A/B Battery

Lutetium is rare and expensive; consequently, it has few specific uses. For example, a radioactive isotope lutetium-176 is used in nuclear technology to determine the age of meteorites. Lutetium usually occurs in association with the elementyttrium and is sometimes used in metal alloys and as a catalyst in various chemical reactions.Sony VGP-BPS13A/S Battery

Physical properties

A lutetium atom has 71 electrons, arranged in order [Xe]4f145d16s2.[2] When entering a chemical reaction, the atom loses its two outermost electrons and the only 5d-electron, which does not belong to an open subshell. Lutetium atoms are smaller than atoms of other lanthanides, due to the lanthanide contraction.Sony VGP-BPS13AS Battery

Lutetium is a silvery white corrosion-resistant trivalent metal. Many properties of lutetium metal relies on its last position of lanthanides and the lanthanide contraction — or, to be more accurate, the subsequent fact atomic radius of lutetium is the smallest among the lanthanides and is ? smaller than that of the biggest lanthanide, lanthanum.Sony VGP-BPS13B/B Battery

For example, lutetium (compared to other lanthanides) has the highest density, melting point, and hardness.

Chemical properties and compounds

Lutetium is a basic metal that always assumes +3 oxidation state in compounds.Sony VGP-BPS13B/Q Battery

However, it is common to name compounds both using and not using Stock nomenclature (for example, lutetium(III) chloride and lutetium chloride); once again, this is in accordance with other lanthanides.

Aqueous solutions of most lutetium salts are colorless and form white crystalline solids upon drying, with the common exception of the iodide.Sony VGP-BPS13B/S Battery

The soluble salts, such as nitrate, sulfate and acetate form hydrates upon crystallization. Theoxide, hydroxide, fluoride, carbonate, phosphate and oxalate are insoluble in water.

Lutetium metal is slightly instable in air at standard conditions, but it burns readily at 150 °C to form lutetium oxide.Sony VGP-BPS13Q Battery

The resulting compound is known to adsorb water and carbon dioxide, and may be used to remove vapors of these compounds from closed atmospheres. Similar observations are made during reaction between lutetium and water (slow when cold and fast when hot); lutetium hydroxide is formed in the reaction.Sony VGP-BPS13S Battery

Lutetium metal is known to react with four lightest halogens to form trihalides; all of them (except the fluoride) are soluble in water.

Lutetium dissolves readily in weak acids[6] and dilute sulfuric acid to form solutions containing the colorless lutetium ions, which exist as a [Lu(H2O)9]3+ complex:Sony VGP-BPL7 Battery

2 Lu + 3 H2SO4 + 18 H2O ? 2 [Lu(H2O)9]3+ + 3 SO2–4 + 3 H2?

Lutetium occurs on the Earth in form of two isotopes: lutetium-175 and lutetium-176. Out of these two, only the former is stable, making the element monoisotopic.Sony VGP-BPS7 Battery

The latter one, lutetium-176, decays via beta decay with a half-life of 3.78×1010years; it makes about one fortieth of the natural lutetium.[8] To date, 32 synthetic radioisotopes of the element have been characterized, ranging in mass from 149.973 (lutetium-150) to 183.961 (lutetium-184);Sony VGP-BPL8 Battery

the most stable such isotopes are lutetium-174 with a half-life of 3.31 years, and lutetium-173 with a half-life of 1.37 years.[8] All of the remainingradioactive isotopes have half-lives that are less than 9 days, and the majority of these have half-lives that are less than half an hour.Sony VGP-BPL8A Battery

Isotopes lighter than the stable lutetium-175 decay via electron capture (to produce isotopes of ytterbium), with some alpha and positron emission); the heavier isotopes decay primarily via beta decay, producing hafnium isotopes.[8]

The element also has 42 nuclear isomers, with masses of 150, 151, 153—162, 166—180 (not every mass number corresponds to only one isomer).Sony VGP-BPL8B Battery

The most stable of them are lutetium-177m, with half-life of 160.4 days and lutetium-174m, with half-life of 142 days; this is longer than half-lives of the ground states of all radioactive lutetium isotopes, except only for lutetium-173, 174, and 176.[8]

Lutetium (Latin: Lutetia meaning Paris) was independently discovered in 1907 by French scientist Georges Urbain,Sony VGP-BPS8 Battery

Austrian mineralogist Baron Carl Auer von Welsbach, and American chemist Charles James.[9] All of these men found lutetium as an impurity in the mineral ytterbia, which was thought by Swiss chemist Jean Charles Galissard de Marignac (and most others) to consist entirely of the element ytterbium.Sony VGP-BPS8A Battery

After the impurity was found out to consist of two different elements, the scientists proposed different names for the elements. Urbain chose the names neoytterbium and lutecium. Welsbach proposed the names cassiopeium for element 71 (after the constellation Cassiopeia)Sony VGP-BPS8B Battery

and aldebaranium for the new name of ytterbium but these naming proposals were rejected (although many German scientists in the 1950s called the element 71 cassiopium).[12] The dispute on the priority of the discovery is documented in two articles in which Urbain and von Welsbach accuse each other of publishing results influenced by the published research of the other.Sony VGP-BPL9 Battery

The Commission on Atomic Mass, which was responsible for the attribution of the names for the new elements, settled the dispute in 1909 by granting priority to Urbain and adopting his names as official ones. It is important that the separation of lutetium from Marignac's ytterbium was first described by Urbain rather than von Welsbach.Sony VGP-BPS9 Battery

An obvious problem with this decision was that Urbain was one of the four members of the commission.[13] After Urbain's names were recognized, the name neoytterbium was eventually reverted to ytterbium. Lutecium was the recognized name almost worldwide but in 1949 the spelling of element 71 was changed to lutetium.Sony VGP-BPS9/B Battery

Ironically, Charles James, who had modestly stayed out of the argument as to priority, worked on a much larger scale than the others, and undoubtedly possessed the largest supply of lutetium at the time.[14]

Only 46 years after its discovery, the lutetium metal was produced in 1953.Sony VGP-BPS9/S Battery

Occurrence and production

Found with almost all other rare-earth metals but never by itself, lutetium is very difficult to separate from other elements. The principal commercially viable ore of lutetium is the rare earth phosphate mineral monazite: (Ce,La,etc.)PO4 which contains 0.0001% of the element.Sony VGP-BPS9A Battery

The abundance of lutetium in the Earth crust is only about 0.5 mg/kg. The main mining areas are China,United States, Brazil, India, Sri Lanka and Australia. The world production of lutetium (in the form of oxide) is about 10 tonnes per year. Pure lutetium metal is very difficult to prepare.Sony VGP-BPS9A/B Battery

It is one of the rarest and most expensive of the rare earth metals with the price about US$10,000 per kilogram, or about one-fourth that of gold.

Crushed minerals are treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths.Sony VGP-BPS9A/S Battery

Thoriumprecipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate to convert rare earths into their insoluble oxalates. The oxalates are converted to oxides by annealing. The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO3.Sony VGP-BPS9B Battery

Several rare earth metals, including lutetium, are separated as a double salt with ammonium nitrate by crystallization. Lutetium is separated by ion exchange. In this process, rare-earth ions are sorbed onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin. Sony VGP-BPX11 Battery

Lutetium salts are then selectively washed out by suitable complexing agent. Lutetium metal is then obtained byreduction of anhydrous LuCl3 or LuF3 by either an alkali metal or alkaline earth metal.

2 LuCl3 + 3 Ca ? 2 Lu + 3 CaCl2Sony VGP-BPL18 Battery

Applications

Because of the rarity and high price, lutetium has very few commercial uses. However, stable lutetium can be used as catalysts in petroleum cracking in refineriesand can also be used in alkylation, hydrogenation, and polymerization applications.Sony VGP-BPS18 Battery

Lutetium aluminium garnet (Al5Lu3O12) has been proposed for use as a lens material in high refractive index immersion lithography.  Additionally, a tiny amount of lutetium is added as a dopant to gadolinium gallium garnet (GGG), which is used in magnetic bubble memory devices.Sony VGP-BPL20 Battery

Cerium-doped lutetium oxyorthosilicate (LSO) is currently the preferred compound for detectors in positron emission tomography (PET).[19][20] Lutetium is used as a phosphor in LED light bulbs.[21]

Aside from stable lutetium, its radioactive isotopes have several specific uses.Sony VGP-BPS20/B Battery

The suitable half-life and decay mode made lutetium-176 used as a pure beta emitter, using lutetium which has been exposed to neutron activation, and in lutetium–hafnium dating to date meteorites.  The synthetic isotope lutetium-177 bound to octreotate (a somatostatin analogue), is used experimentally in targeted radionuclide therapy for neuroendocrine tumors.Sony VGP-BPS20/S Battery

Lutetium tantalate (LuTaO4) is the densest known stable white material (density 9.81 g/cm3) and therefore is an ideal host for X-ray phosphors.  The only denser white material is thorium dioxide, with density of 10 g/cm3, but the thorium it contains is radioactive.Sony VGP-BPL21 Battery

Precautions

Like other rare-earth metals, lutetium is regarded as having a low degree of toxicity, but its compounds should be handled with care nonetheless: for example, lutetium fluoride inhalation is dangerous and the compound irritates skin.Sony VGP-BPS21 Battery

Lutetium nitrate may be dangerous as it may explode and burn once heated. Lutetium oxide powder is toxic as well if inhaled or ingested.[6]

Similarly to other group 3 elements and lanthanides, lutetium has no biological role, but it is found even in the highest known organism, the humans, concentrating in bones, and to a lesser extent in the liver and kidneys.Sony VGP-BPS21/S Battery

Lutetium salts are known to cause metabolism and they occur together with other lanthanide salts in nature; the element is the least abundant in the human body of all lanthanides. Human diets have not been monitored for lutetium content, so it is not known how much the average human takes in,Sony VGP-BPS21A Battery

but estimations show the amount is only about several micrograms per year, all coming from tiny amounts taken by plants. Soluble lutetium salts are mildly toxic, but insoluble ones are not.

Hafnium is a chemical element with the symbol Hf and atomic number 72.Sony VGP-BPS21A/B Battery

A lustrous, silvery gray,tetravalent transition metal, hafnium chemically resembles zirconium and is found in zirconium minerals. Its existence waspredicted by Dmitri Mendeleev in 1869. Hafnium was the penultimate stable isotope element to be discovered (rhenium was identified two years later).Sony VGP-BPS21B Battery

Hafnium is named for Hafnia, the Latin name for "Copenhagen", where it was discovered.

Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuitsat 45 nm and smaller feature lengths. Some superalloys used for special applications contain hafnium in combination withniobium, titanium, or tungsten.Sony VGP-BPL22 Battery

Hafnium's large neutron capture cross-section makes it a good material for neutron absorption in control rods in nuclear power plants, but at the same time requires that it be removed from the neutron-transparent corrosion-resistant zirconium alloys used in nuclear reactors.Sony VGP-BPS22 Battery

Physical characteristics

Hafnium is a shiny, silvery, ductile metal that is corrosion-resistant and chemically similar to zirconium (due to its having the same number of valence electrons and being in the same group). The physical properties of hafnium metal samples are markedly affected by zirconium impurities, especially the nuclear properties, as these two elements are among the most difficult to separate because of their chemical similarity.Sony VGP-BPS22/A Battery

A notable physical difference between these metals is their density, with zirconium having about one-half the density of hafnium. The most notable nuclear properties of hafnium are its high thermal neutron-capture cross-section and that the nuclei of several different hafnium isotopes readily absorb two or more neutrons apiece.Sony VGP-BPS22A Battery

In contrast with this, zirconium is practically transparent to thermal neutrons, and it is commonly used for the metal components of nuclear reactors – especially the claddings of their nuclear fuel rods.

Chemical characteristics

Hafnium reacts in air to form a protective film that inhibits further corrosion.Sony VGP-BPL23 Battery

The metal is not readily attacked by acids but can be oxidized with halogens or it can be burnt in air. Like its sister metal zirconium, finely divided hafnium can ignite spontaneously in air—similar to that obtained in Dragon's Breath.[3] The metal is resistant to concentrated alkalis.Sony VGP-BPS23 Battery

The chemistry of hafnium and zirconium is so similar that the two cannot be separated on the basis of differing chemical reactions. The melting points and boiling points of the compounds and the solubility in solvents are the major differences in the chemistry of these twin elements.Sony VGP-BPS23/B Battery

At least 34 isotopes of hafnium have been observed, ranging in mass number from 153 to 186. The five stable isotopes are in the range of 176 to 180. The radioactive isotopes' half-lives range from only 400 ms for 153Hf,[6] to 2.0 petayears (1015 years) for the most stable one, 174Hf.Sony VGP-BPS23/D Battery

The nuclear isomer 178m2Hf was at the center of a controversy for several years regarding its potential use as a weapon.

Occurrence

Hafnium is estimated to make up about 5.8 ppm of the Earth's upper crust by weight.Sony VGP-BPS23/G Battery

It does not exist as a free element in nature, but is found combined in solid solution for zirconium in natural zirconium compounds such as zircon, ZrSiO4, which usually has about 1 – 4 % of the Zr replaced by Hf. Rarely, the Hf/Zr ratio increases during crystallization to give the isostructural mineral 'hafnon' (Hf,Zr)SiO4, with atomic Hf > Zr.Sony VGP-BPS23/P Battery

An old (obsolete) name for a variety of zircon containing unusually high Hf content is alvite.

A major source of zircon (and hence hafnium) ores are heavy mineral sands ore deposits,pegmatites particularly in Brazil and Malawi, and carbonatite intrusions particularly the Crown Polymetallic Deposit at Mount Weld, Western Australia. Sony VGP-BPS23/W Battery

A potential source of hafnium is trachyte tuffs containing rare zircon-hafnium silicates eudialyte or armstrongite, atDubbo in New South Wales, Australia.[9]

Hafnium reserves are projected to last under 10 years if the world population increases and demand grows.Sony Limited Edition 007 Battery

Production

The heavy mineral sands ore deposits of the titanium ores ilmenite and rutile yield most of the mined zirconium, and therefore also most the hafnium.[11]

Zirconium is a good nuclear fuel-rod cladding metal, with the desirable properties of a very low neutron capture cross-section and good chemical stability at high temperatures.Sony VAIO VGC-LB15 Battery

However, because of hafnium's neutron-absorbing properties, hafnium impurities in zirconium would cause it to be far less useful for nuclear-reactor applications. Thus, a nearly complete separation of zirconium and hafnium is necessary for their use in nuclear power. The production of hafnium-free zirconium is the main source for hafnium.Sony VGN-AR Series Battery

The chemical properties of hafnium and zirconium are nearly identical, which makes the two difficult to separate.[12] The methods first used — fractional crystallization of ammonium fluoride salts[13] or the fractionated distillation of the chloride[14] — have not proven suitable for an industrial-scale production.Sony VGN-CR Series Battery

After zirconium was chosen as material for nuclear reactor programs in the 1940s, a separation method had to be developed. Liquid-liquid extraction processes with a wide variety of solvents were developed and are still used for the production of hafnium.[15]About half of all hafnium metal manufactured is produced as a by-product of zirconium refinement.Sony VIAO VGN-G Series Battery

The end product of the separation is hafnium(IV) chloride.[16] The purified hafnium(IV) chloride is converted to the metal by reduction with magnesium or sodium, as in the Kroll process.[17]

HfCl4 + 2 Mg (1100 °C) ? 2 MgCl2 + Hf

Further purification is effected by a chemical transport reaction developed by Arkel and de Boer:Sony VIAO VGN-G118 Battery

In a closed vessel, hafnium reacts with iodine at temperatures of 500 °C, forming hafnium(IV) iodide; at a tungsten filament of 1700 °C the reverse reaction happens, and the iodine and hafnium are set free. The hafnium forms a solid coating at the tungsten filament, and the iodine can react with additional hafnium, resulting in a steady turn over.Sony VIAO VGN-G118CN/B Battery

Hf + 2 I2 (500 °C) ? HfI4

HfI4 (1700 °C) ? Hf + 2 I2

Chemical compounds

Hafnium and zirconium form nearly identical series of chemical compounds. Hafnium tends to form inorganic compounds in the oxidation state of +4. Halogens react with it to form hafnium tetrahalides.Sony VIAO VGN-G118CN/T Battery

At higher temperatures, hafnium reacts withoxygen, nitrogen, carbon, boron, sulfur, and silicon.[19] Due to the lanthanide contraction of the elements in the sixth period, zirconium and hafnium have nearly identical ionic radii. The ionic radius of Zr4+ is 0.79 angstrom and that of Hf4+ is 0.78 angstrom.Sony VIAO VGN-G218 Battery

Hafnium(IV) chloride and hafnium(IV) iodide have some applications in the production and purification of hafnium metal. They are volatile solids with polymeric structures.[4] These tetrachlorides are precursors to various organohafnium compounds such as hafnocene dichloride and tetrabenzylhafnium.Sony VGN-TZ121 Battery

The white hafnium oxide (HfO2), with a melting point of 2812 °C and a boiling point of roughly 5100 °C, is very similar tozirconia, but slightly more basic.[4] Hafnium carbide is the most refractory binary compound known, with a melting point over 3890 °C, and hafnium nitride is the most refractory of all known metal nitrides, with a melting point of 3310 °C.Sony VGN-TZ13 Battery

This has led to proposals that hafnium or its carbides might be useful as construction materials that are subjected to very high temperatures. The mixed carbide tantalum hafnium carbide (Ta4HfC5) possesses the highest melting point of any currently known compound, 4215 °C.Sony VGN-TZ131 Battery

In his report on The Periodic Law of the Chemical Elements, in 1869, Dmitri Mendeleev had implicitly predicted the existence of a heavier analog of titanium and zirconium. At the time of his formulation in 1871, Mendeleev believed that the elements were ordered by their atomic masses and placed lanthanum (element 57) in the spot below zirconium.Sony VGN-TZ132N Battery

The exact placement of the elements and the location of missing elements was done by determining the specific weight of the elements and comparing the chemical and physical properties.

The X-ray spectroscopy done by Henry Moseley in 1914 showed a direct dependency between spectral line and effective nuclear charge.Sony VGN-TZ132/N Battery

This led to the nuclear charge, or atomic number of an element, being used to ascertain its place within the periodic table. With this method, Moseley determined the number of lanthanides and showed the gaps in the atomic number sequence at numbers 43, 61, 72, and 75.Sony VGN-TZ17N Battery

The discovery of the gaps led to an extensive search for the missing elements. In 1914, several people claimed the discovery after Henry Moseley predicted the gap in the periodic table for the then-undiscovered element 72.  Georges Urbain asserted that he found element 72 in the rare earth elements in 1907 and published his results on celtium in 1911.Sony VGN-TZ16N Battery

Neither the spectra nor the chemical behavior matched with the element found later, and therefore his claim was turned down after a long-standing controversy.  The controversy was partly because the chemists favored the chemical techniques which led to the discovery ofceltium,Sony VGN-TZ18N Battery

while the physicists relied on the use of the new X-ray spectroscopy method that proved that the substances discovered by Urbain did not contain element 72. By early 1923, several physicists and chemists such as Niels Bohr  and Charles R. Bury  suggested that element 72 should resemble zirconium and therefore was not part of the rare earth elements group.Sony VAIO VGN-AR47G/E1 Battery

These suggestions were based on Bohr's theories of the atom, the X-ray spectroscopy of Mosley, and the chemical arguments of Friedrich Paneth.

Encouraged by these suggestions and by the reappearance in 1922 of Urbain's claims that element 72 was a rare earth element discovered in 1911, Dirk Coster and Georg von Hevesy were motivated to search for the new element in zirconium ores.Sony VAIO VGN-AR520E Battery

Hafnium was discovered by the two in 1923 in Copenhagen, Denmark, validating the original 1869 prediction of Mendeleev. It was ultimately found in zircon in Norway through X-ray spectroscopy analysis. The place where the discovery took place led to the element being named for the Latin name for "Copenhagen", Hafnia, the home town of Niels Bohr.Sony VAIO VGN-AR53DB Battery

Today, the Faculty of Science of the University of Copenhagen uses in its seal a stylized image of the hafnium atom.

Hafnium was separated from zirconium through repeated recrystallization of the double ammonium or potassium fluorides by Valdemar Thal Jantzen and von Hevesey.Sony VAIO VGN-AR54DB Battery

Anton Eduard van Arkel and Jan Hendrik de Boer were the first to prepare metallic hafnium by passing hafnium tetra-iodide vapor over a heated tungsten filament in 1924. This process for differential purification of zirconium and hafnium is still in use today.Sony VAIO VGN-AR550E Battery

In 1923, four predicted elements were still missing from the periodic table: 43 (technetium) and 61 (promethium) are radioactive elements and are only present in trace amounts in the environment,  thus making elements 75 (rhenium) and 72 (hafnium) the last two unknown non-radioactive elements.Sony VAIO VGN-AR55DB Battery

Since rhenium was discovered in 1925,[37] hafnium was the next to last element with stable isotopes to be discovered.

Applications

Several details contribute to the fact that there are only a few technical uses for hafnium:Sony VAIO VGN-AR630E Battery

First, the close similarity between hafnium and zirconium makes it possible to use zirconium for most of the applications; second, hafnium was first available as pure metal after the use in the nuclear industry for hafnium-free zirconium in the late 1950s. Furthermore, the low abundance and difficult separation techniques necessary make it a scarce commodity.Sony VAIO VGN-AR64DB Battery

Most of the hafnium produced is used in the production of control rods for nuclear reactors.

Nuclear reactors

The nuclei of several hafnium isotopes can each absorb multiple neutrons. This makes hafnium a good material for use in the control rods for nuclear reactors. Its neutron-capture cross-section is about 600 times that of zirconium.Sony VAIO VGN-AR65DB Battery

(Other elements that are good neutron-absorbers for control rods are cadmium and boron.) Excellent mechanical properties and exceptional corrosion-resistance properties allow its use in the harsh environment of a pressurized water reactors.  The German research reactor FRM II uses hafnium as a neutron absorber.Sony VAIO VGN-AR660U Battery

Alloys

Hafnium is used in iron, titanium, niobium, tantalum, and other metal alloys. An alloy used for liquid rocket thruster nozzles, for example the main engine of the Apollo Lunar Modules is C103, which consists of 89% niobium, 10% hafnium and 1% titanium.Sony VAIO VGN-AR690U Battery

Small additions of hafnium increase the adherence of protective oxide scales on nickel based alloys. It improves thereby thecorrosion resistance especially under cyclic temperature conditions that tend to break oxide scales by inducing thermal stresses between the bulk material and the oxide layer.Sony VAIO VGN-AR71ZU Battery

Microprocessors

The electronics industry discovered that hafnium-based compound can be employed in gate insulators in the 45 nm generation ofintegrated circuits from Intel, IBM and others. Hafnium oxide-based compounds are practical high-k dielectrics, allowing reduction of the gate leakage current which improves performance at such scales.Sony VAIO VGN-AR730E/B Battery

Other uses

Due to its heat resistance and its affinity to oxygen and nitrogen, hafnium is a good scavenger for oxygen and nitrogen in gas-filled and incandescent lamps. Hafnium is also used as the electrode in plasma cutting because of its ability to shed electrons into air.Sony VAIO VGN-AR73DB Battery

The high energy content of 178m2Hf was the concern of a DARPA funded program in the US. This program determined the possibility of using a nuclear isomer of hafnium (the above mentioned 178m2Hf) to construct high yield weapons with X-ray triggering mechanisms—an application of induced gamma emission, was infeasible because of its expense. See Hafnium controversy.Sony VAIO VGN-AR74DB Battery

Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known astantalium, the name comes from Tantalus, a hero in Greek mythology.[3] Tantalum is a rare, hard, blue-gray, lustroustransition metal that is highly corrosion resistant. It is part of the refractory metals group, which are widely used as minor component in alloys.Sony VAIO VGN-AR75UDB Battery

The chemical inertness of tantalum makes it a valuable substance for laboratory equipment and a substitute for platinum, but its main use today is in tantalum capacitors in electronic equipment such as mobile phones, DVD players, video game systems and computers.Sony VAIO VGN-AR790U/B Battery

Tantalum, always together with the chemically similar niobium, occurs in theminerals tantalite, columbite and coltan (a mix of columbite and tantalite).

Tantalum was discovered in Sweden in 1802 by Anders Ekeberg. One year earlier, Charles Hatchett had discovered the elementcolumbium.Sony VAIO VGN-AR820E Battery

In 1809, the English chemist William Hyde Wollaston compared the oxides derived from both columbium—columbite, with a density 5.918 g/cm3, and tantalum—tantalite, with a density 7.935 g/cm3, and concluded that the two oxides, despite their difference in measured density, were identical. He decided to keep the name tantalum.Sony VAIO VGN-AR830E Battery

AfterFriedrich Wöhler confirmed these results, it was thought that columbium and tantalum were the same element. This conclusion was disputed in 1846 by the German chemist Heinrich Rose, who argued that there were two additional elements in the tantalite sample, and he named them after the children of Tantalus:Sony VAIO VGN-AR83S Battery

niobium (from Niobe, the goddess of tears), and pelopium (from Pelops). The supposed element "pelopium" was later identified as a mixture of tantalum and niobium, and it was found that the niobium was identical to the columbium already discovered in 1801 by Hatchett.Sony VAIO VGN-AR83US Battery

The differences between tantalum and niobium were demonstrated unequivocally in 1864 by Christian Wilhelm Blomstrand,[8]andHenri Etienne Sainte-Claire Deville, as well as by Louis J. Troost, who determined the empirical formulas of some of their compounds in 1865.Sony VAIO VGN-AR84S Battery

Further confirmation came from the Swiss chemist Jean Charles Galissard de Marignac,  in 1866, who proved that there were only two elements. These discoveries did not stop scientists from publishing articles about the so-called ilmenium until 1871.Sony VAIO VGN-AR84US Battery

De Marignac was the first to produce the metallic form of tantalum in 1864, when hereduced tantalum chloride by heating it in an atmosphere of hydrogen.[12] Early investigators had been only able to produce impure tantalum, and the first relatively pure ductile metal was produced by Werner von Bolton in 1903.Sony VAIO VGN-AR85S Battery

Wires made with metallic tantalum were used for light bulb filaments until tungsten replaced it in widespread use.

The name tantalum was derived from the name of the mythological Tantalus, the father of Niobe in Greek mythology.Sony VAIO VGN-AR85US Battery

In the story, he had been punished after death by being condemned to stand knee-deep in water with perfect fruit growing above his head, both of which eternally tantalized him. (If he bent to drink the water, it drained below the level he could reach, and if he reached for the fruit, the branches moved out of his grasp.)Sony VAIO VGN-AR870EA Battery

Ekeberg wrote "This metal I call tantalum … partly in allusion to its incapacity, when immersed in acid, to absorb any and be saturated."

For decades, the commercial technology for separating tantalum from niobium involved the fractional crystallization of potassium heptafluorotantalate away from potassium oxypentafluoroniobate monohydrate,Sony VAIO VGN-AR890U Battery

a process that was discovered by Jean Charles Galissard de Marignac in 1866. This method has been supplanted by solvent extraction from fluoride-containing solutions of tantalum.[9]

Physical properties

Tantalum is dark (blue-gray),[16] dense, ductile, very hard, easily fabricated, and highly conductive of heat and electricity.Sony VAIO VGN-AR93S Battery

The metal is renowned for its resistance to corrosion by acids; in fact, at temperatures below 150 °C tantalum is almost completely immune to attack by the normally aggressive aqua regia. It can be dissolved with hydrofluoric acid or acidic solutions containing the fluoride ion and sulfur trioxide, as well as with a solution of potassium hydroxide.Sony VAIO VGN-AR93US Battery

Tantalum's high melting point of 3017 °C (boiling point 5458 °C) is exceeded only by tungsten, rhenium and osmium for metals, and carbon.

Tantalum exists in two crystalline phases, alpha and beta. The alpha phase is relatively ductile and soft;Sony VAIO VGN-AR94S Battery

it has body-centered cubic structure (space group Im3m, lattice constant a = 0.33058 nm), Knoop hardness 200–400 HN and electrical resistivity 15–60 µ??cm. The beta phase is hard and brittle; its crystal symmetry is tetragonal (space group P42/mnm, a = 1.0194 nm, c = 0.5313 nm), Knoop hardness is 1000–1300 HN and electrical resistivity is relatively high at 170–210 µ??cm.Sony VAIO VGN-AR94US Battery

The beta phase is metastable and converts to the alpha phase upon heating to 750–775 °C. Bulk tantalum is almost entirely alpha phase, and the beta phase usually exists as thin films obtained by magnetron sputtering, chemical vapor deposition orelectrochemical deposition from an eutectic molten salt solution.Sony VAIO VGN-AR95S Battery

Chemical properties

Tantalum forms oxides with the oxidation states +5 (Ta2O5) and +4 (TaO2). The most stable oxidation state is +5, tantalum pentoxide.[18] Tantalum pentoxide is the starting material for several tantalum compounds.Sony VAIO VGN-AR95US Battery

The compounds are created by dissolving the pentoxide in basic hydroxide solutions or by melting it in another metal oxide. Such examples are lithium tantalate (LiTaO3) and lanthanum tantalate (LaTaO4). In the lithium tantalate, the tantalate ion TaO?
3 does not occur;Sony VAIO VGN-AW110J/H Battery

instead, this part of the formula represents linkage of TaO7?6 octahedra to form a three-dimensional perovskite framework; while the lanthanum tantalate contains lone TaO3?4 tetrahedral groups.

The fluorides of tantalum can be used for its separation from niobium.Sony VAIO VGN-AW11M/H Battery

Tantalum forms halogen compounds in the oxidation states of +5, +4, and +3 of the type TaX5, TaX4, and TaX3, although multi core complexes and substoichiometric compounds are also known.  Tantalum pentafluoride (TaF5) is a white solid with a melting point of 97.0 °C and tantalum pentachloride (TaCl5) is a white solid with a melting point of 247.4 °C.Sony VAIO VGN-AW11S/B Battery

Tantalum pentachloride is hydrolyzed by water and reacts with additional tantalum at elevated temperatures by forming the black and highly hygroscopic tantalum tetrachloride (TaCl4). While the trihalogen compounds can be obtained by reduction of the pentahalogenes with hydrogen, the dihalogen compounds do not exist.Sony VAIO VGN-AW11XU/Q Battery

A tantalum-tellurium alloy forms quasicrystals. Tantalum compounds with oxidation states as low as ?1 have been reported in 2008.

Similar to most other refractory metals, the hardest known compounds of tantalum are its stable nitrides and carbides.Sony VAIO VGN-AW11Z/B Battery

Tantalum carbide, TaC, like the more commonly used tungsten carbide, is a very hard ceramic that is used in cutting tools. Tantalum(III) nitride is used as a thin film insulator in some microelectronic fabrication processes. Chemists at theLos Alamos National Laboratory in the United States have developed a tantalum carbide-graphite composite material that is one of the hardest materials ever synthesized.Sony VAIO VGN-AW120J/H Battery

Korean researchers have developed an amorphous tantalum-tungsten-copper alloy that is more flexible and two to three times stronger than commonly used steel alloys.[23] There are two tantalum aluminides, TaAl3 and Ta3Al. These are stable, refractory, and reflective, and they have been proposed[24] as coatings for use in infrared wave mirrors.Sony VAIO VGN-AW150Y/H Battery

Natural tantalum consists of two isotopes: 180mTa (0.012%) and 181Ta (99.988%). 181Ta is a stable isotope. 180mTa (m denotes a metastable state) is predicted to decay in three ways: isomeric transition to the ground state of 180Ta, beta decay to 180W, or electron capture to 180Hf.Sony VAIO VGN-AW160J/Q Battery

However, radioactivity of this nuclear isomer has never been observed. Only a lower limit on its half life of over 1015 years has been set. The ground state of 180Ta has a half life of only 8 hours. 180mTa is the only naturally occurring nuclear isomer (excluding radiogenic and cosmogenic short-living nuclides).Sony VAIO VGN-AW170Y/Q Battery

It is also the rarest isotope in the Universe, taking into account the elemental abundance of tantalum and isotopic abundance of 180mTa in the natural mixture of isotopes (and again excluding radiogenic and cosmogenic short-living nuclides).Sony VAIO VGN-AW180Y/Q Battery

Tantalum has been examined theoretically as a "salting" material for nuclear weapons (cobalt is the better-known hypothetical salting material). An external shell of 181Ta would be irradiated by the intensive high-energy neutron flux from a hypothetical exploding nuclear weapon.Sony VAIO VGN-AW190JAH Battery

This would transmute the tantalum into the radioactive isotope 182Ta, which has a half-life of 114.4 days and produces gamma rays with approximately 1.12 million electron-volts (MeV) of energy apiece, which would significantly increase the radioactivity of the nuclear fallout from the explosion for several months.Sony VAIO VGN-AW190NAB Battery

Such "salted" weapons have never been built or tested, as far as is publicly known, and certainly never used as weapons.[26]

Occurrence

Tantalum is estimated to make up about 1 ppm[27] or 2 ppm[20] of the Earth's crust by weight.Sony VAIO VGN-AW190NBB Battery

There are many species of tantalum minerals, only some of which are so far being used by industry as raw materials: tantalite, microlite, wodginite, euxenite,polycrase. Tantalite (Fe,Mn) Ta2O6 is the most important mineral for tantalum extraction.Sony VAIO VGN-AW190NCB Battery

Tantalite has the same mineral structure as columbite (Fe,Mn) (Ta,Nb)2O6; when there is more Ta than Nb it is called tantalite and when there is more Nb than Ta is it called columbite (or niobite). The high density of tantalite and other tantalum containing minerals makes the use of gravitational separation the best method. Other minerals include samarskite and fergusonite.Sony VAIO VGN-AW190YAB Battery

The primary mining of tantalum is in Australia, where the largest producer, Global Advanced Metals, formerly known as Talison Minerals, operates two mines in Western Australia, Greenbushes in the Southwest and Wodgina in the Pilbara region. The Wodgina mine was reopened in January 2011 after mining at the site was suspended in late-2008 due to the global financial crisis.Sony VAIO VGN-AW190YBB Battery

This mine produces a primary tantalum concentrate which is further upgraded at the Greenbushes operation before being sold to customers.  Whereas the large-scale producers of niobium are in Brazil and Canada, the ore there also yields a small percentage of tantalum.Sony VAIO VGN-AW190YCB Battery

Some other countries such as China, Ethiopia, and Mozambique mine ores with a higher percentage of tantalum, and they produce a significant percentage of the world's output of it. Tantalum is also produced in Thailand and Malaysia as a by-product of the tin mining there.Sony VAIO VGN-AW190YDB Battery

During gravitational separation of the ores from placer deposits, not only is Cassiterite (SnO2) found, but a small percentage of tantalite also included. The slag from the tin smelters then contains economically useful amounts of tantalum, which is leached from the slag.Sony VAIO VGN-AW220J/B Battery

Future sources of supply of tantalum, in order of estimated size, are being explored in Saudi Arabia, Egypt, Greenland, China, Mozambique, Canada,Australia, the United States, Finland, and Brazil.

Coltan, the industrial name for a columbite–tantalite mineral from which columbium (i.e. niobium) and tantalum are extracted,Sony VAIO VGN-AW230J/H Battery

can also be found in Central Africa, which is why tantalum is being linked to the war in the Congo. According to an October 23, 2003 United Nations report, the smuggling and exportation of coltan has helped fuel the war in the Congo, a crisis that has resulted in approximately 5.4 million deaths since 1998– making it the world’s deadliest documented conflict since World War II.Sony VAIO VGN-AW235J/B Battery

Ethical questions have been raised about responsible corporate behavior, human rights, and endangering wildlife, due to the exploitation of resources such as coltan in the armed conflict regions of the Congo Basin.  However, although important for the local economy in Congo, the coltan mining in Congo is not important for the world supply of tantalum.Sony VAIO VGN-AW290JFQ Battery

The United States Geological Survey reports in its 2006 yearbook that this region produced a little less than 1% of the world's tantalum output for the past four years, peaking at 10% in 2000 and 2008.

Production and fabrication

Several steps are involved in the extraction of tantalum from tantalite.Sony VAIO VGN-AW41JF Battery

First, the mineral is crushed and concentrated by gravity separation. This is generally carried out near the mine site. Further processing by chemical separation is usually done by treating the ores with a mixture of hydrofluoric acid and sulfuric acidat over 90 °C.Sony VAIO VGN-AW41JF/H Battery

These reagents dissolve the tantalum and niobium oxides to give complex fluorides, which can be separated from impurities and from each other:

Ta2O5 + 14 HF ? 2 H2[TaF7] + 5 H2O

Nb2O5 + 10 HF ? 2 H2[NbOF5] + 3 H2OSony VAIO VGN-AW41MF Battery

The first industrial-scale separation, developed by de Marignac, used the difference in solubility between the complex niobium and tantalum fluorides K2[NbOF5]•H2O (potassium oxypentafluoroniobate monohydrate) and K2[TaF7] (potassium heptafluorotantalate) in water.Sony VAIO VGN-AW41MF/H Battery

Newer processes use the liquid extraction of the fluorides fromaqueous solution by organic solvents such as cyclohexanone. The complex niobium and tantalum fluorides are extracted separately from the organic solvent with water, and either precipitated by the addition of potassium fluoride to produce a potassium fluoride complex, or precipitated with ammonia as the pentoxide:Sony VAIO VGN-AW41XH Battery

H2[TaF7] + 2 KF ? K2[TaF7]? + 2 HF

2 H2[TaF7] + 14 NH4OH ? Ta2O5? + 14 NH4F + 9 H2O

The purified K2[TaF7] is generally treated by reduction with molten sodium to produce a coarse tantalum powder.Sony VAIO VGN-AW41XH/Q Battery

In terms of fabrication, all welding of tantalum must be done in an inert atmosphere of argon or helium in order to shield it from contamination with atmospheric gases. Tantalum is not solderable. Grinding tantalum is difficult, especially so for annealed tantalum. In the annealed condition, tantalum is extremely ductile and can be readily formed as metal sheets.Sony VAIO VGN-AW41ZF Battery

Electronics

The major use for tantalum, as the metal powder, is in the production of electronic components, mainly capacitors and some high-powerresistors. Tantalum electrolytic capacitors exploit the tendency of tantalum to form a protective oxide surface layer,Sony VAIO VGN-AW41ZF/B Battery

using tantalum powder, pressed into a pellet shape, as one "plate" of the capacitor, the oxide as the dielectric, and an electrolytic solution or conductive solid as the other "plate". Because the dielectric layer can be very thin (thinner than the similar layer in, for instance, an aluminium electrolytic capacitor), a high capacitance can be achieved in a small volume.Sony VAIO VGN-AW50DB/H Battery

Because of the size and weight advantages, tantalum capacitors are attractive for portable telephones, personal computers, and automotive electronics.

Alloys

Tantalum is also used to produce a variety of alloys that have high melting points, are strong and have good ductility.Sony VAIO VGN-AW51JGB Battery

Alloyed with other metals, it is also used in making carbide tools for metalworking equipment and in the production of superalloys for jet engine components, chemical process equipment, nuclear reactors, and missile parts. Because of its ductility, tantalum can be drawn into fine wires or filaments, which are used for evaporating metals such as aluminium.Sony VAIO VGN-AW52JGB Battery

Since it resists attack by body fluids and is nonirritating, tantalum is widely used in making surgical instruments and implants. For example, porous tantalum coatings are used in the construction of orthopedic implants due to tantalum's ability to form a direct bond to hard tissue.Sony VAIO VGN-AW53FB Battery

Tantalum is inert against most acids except hydrofluoric acid and hot sulfuric acid, also hot alkaline solutions cause tantalum to corrode. This property makes it an ideal metal for chemical reaction vessels and pipes for corrosive liquids. Heat exchanging coils for the steam heating of hydrochloric acid are made from tantalum.Sony VAIO VGN-AW70B/Q Battery

Tantalum was extensively used in the production of ultra high frequency electron tubes for radio transmitters. The tantalum is capable of capturing oxygen and nitrogen by forming nitrides and oxides and therefore helps to sustain the high vacuum needed for the tubes.Sony VAIO VGN-AW71JB Battery

Other uses

The oxide is used to make special high refractive index glass for camera lenses. The high melting point and oxidation resistance lead to the use of the metal in the production of vacuum furnace parts. Due to its high density, shaped charge and explosively formed penetrator liners have been constructed from tantalum.Sony VAIO VGN-AW72JB Battery

Tantalum greatly increases the armor penetration capabilities of a shaped charge due to its high density and high melting point. It is also occasionally used in precious watches e.g. from Audemars Piguet, Hublot, Montblanc and Panerai. Tantalum is also highly bioinert and is used as an orthopedic implant material.Sony VAIO VGN-AW73FB Battery

Precautions

Compounds containing tantalum are rarely encountered in the laboratory. The metal is highly biocompatible and is used for body implants and coatings, therefore attention may be focused on other elements or the physical nature of the chemical compound.Sony VAIO VGN-AW80NS Battery

A single study  is the only reference in literature linking tantalum to local sarcomas. The study was quoted in IARC Monograph vol. 74 which includes the following "Note to the reader": "Inclusion of an agent in the Monographs does not imply that it is a carcinogen, only that the published data have been examined."Sony VAIO VGN-AW80S Battery

Tungsten , also known as wolfram /?w?lfr?m/ (wuul-fr?m), is a chemical element with the chemical symbol W and atomic number 74.

A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds.Sony VAIO VGN-AW80US Battery

It was identified as a new element in 1781, and first isolated as a metal in 1783. Its important ores includewolframite and scheelite. The free element is remarkable for its robustness, especially the fact that it has the highestmelting point of all the non-alloyed metals and the second highest of all the elements after carbon.Sony VAIO VGN-AW81DS Battery

Also remarkable is its high density of 19.3 times that of water, comparable to that of uranium and gold, and much higher (about 1.7 times) than that of lead.[3] Tungsten with minor amounts of impurities is often brittle[4] and hard, making it difficult to work. However, very pure tungsten, though still hard, is more ductile, and can be cut with a hard-steel hacksaw.Sony VAIO VGN-AW81JS Battery

The unalloyed elemental form is used mainly in electrical applications. Tungsten's many alloys have numerous applications, most notably in incandescent light bulb filaments, X-ray tubes (as both the filament and target), and superalloys. Tungsten's hardness and high density give it military applications in penetrating projectiles.Sony VAIO VGN-AW81YS Battery

Tungsten compounds are most often used industrially as catalysts.

Tungsten is the only metal from the third transition series that is known to occur in biomolecules, where it is used in a few species of bacteria. It is the heaviest element known to be used by any living organism. However, tungsten interferes withmolybdenum and copper metabolism, and is somewhat toxic to animal life.Sony VAIO VGN-AW82DS Battery

In 1781, Carl Wilhelm Scheele discovered that a new acid, tungstic acid, could be made from scheelite (at the time named tungsten). Scheele and Torbern Bergman suggested that it might be possible to obtain a new metal by reducing this acid.[8] In 1783, José and Fausto Elhuyar found an acid made from wolframite that was identical to tungstic acid.Sony VAIO VGN-AW82JS Battery

Later that year, inSpain, the brothers succeeded in isolating tungsten by reduction of this acid with charcoal, and they are credited with the discovery of the element.

In World War II, tungsten played a significant role in background political dealings.Sony VAIO VGN-AW82YS Battery

Portugal, as the main European source of the element, was put under pressure from both sides, because of its deposits of wolframite ore at Panasqueira. Tungsten's resistance to high temperatures and its strengthening of alloys made it an important raw material for the arms industry.Sony VAIO VGN-AW83FS Battery

Etymology

The name "tungsten" (from the Nordic tung sten, meaning "heavy stone") is used in English, French, and many other languages as the name of the element. Tungsten was the old Swedish name for the mineral scheelite. The other name "wolfram" (or "volfram"),Sony VAIO VGN-AW83GS Battery

used for example in most European (especially Germanic and Slavic) languages, is derived from the mineralwolframite, and this is also the origin of its chemical symbol, W.[5] The name "wolframite" is derived from German "wolf rahm" ("wolf soot" or "wolf cream"), the name given to tungsten by Johan Gottschalk Wallerius in 1747.Sony VAIO VGN-AW83HS Battery

This, in turn, derives from "Lupi spuma", the name Georg Agricola used for the element in 1546, which translates into English as "wolf's froth" or "cream" (the etymology is not entirely certain), and is a reference to the large amounts of tin consumed by the mineral during its extraction.Sony VAIO VGN-AW90NS Battery

Physical properties

In tungsten's raw form, it is a hard steel-gray metal that is often brittle and hard to work. However, if made very pure, although tungsten retains its hardness (which exceeds that of many steels), it becomes malleable enough that it can be worked easily. It is worked by forging, drawing, extruding or sintering.Sony VAIO VGN-AW90S Battery

Of all metals in pure form, tungsten has the highest melting point (3,422 °C, 6,192 °F), lowest vapor pressure (at temperatures above 1,650 °C, 3,000 °F) and the highest tensile strength.[13] Tungsten has the lowest coefficient of thermal expansion of any pure metal.Sony VAIO VGN-AW90US Battery

The low thermal expansion and high melting point and strength of tungsten originate from strongcovalent bonds formed between tungsten atoms by the 5d electrons.[14] Alloying small quantities of tungsten with steel greatly increases its toughness.

Tungsten exists in two major crystalline forms: ? and ?. The former has a body-centered cubic structure and is the most stable form.Sony VAIO VGN-AW91CDS Battery

The structure of the ? phase is called A15 cubic; it is metastable, but can coexist with the ? phase at ambient conditions owing to non-equilibrium synthesis or stabilization by impurities. Contrary to the ? phase which crystallizes in isometric grains, the ? form exhibits a columnar habit.Sony VAIO VGN-AW91CJS Battery

The ? phase has a three times lower electrical resistivity  and a much lower superconducting transition temperature TC than the ? phase: ca. 0.015 K vs. 1–4 K; mixing the two phases allows obtaining intermedicate TC values. The TC value can also be raised by alloying tungsten with another metal (e.g. 7.9 K for W-Tc).Sony VAIO VGN-AW91CYS Battery

Such tungsten alloys are sometimes used in low-temperature superconducting circuits.

Naturally occurring tungsten consists of five isotopes whose half-lives are so long that they can be considered stable. Theoretically, all five can decay into isotopes of element 72 (hafnium) by alpha emission, but only 180W has been observed to do so with a half-life of (1.8 ± 0.2)×1018 years; on average, this yields about two alpha decays of 180W in one gram of natural tungsten per year.Sony VAIO VGN-AW91DS Battery

The other naturally occurring isotopes have not been observed to decay, constraining their half-lives to be 121.2 days, 185W with a half-life of 75.1 days, 188W with a half-life of 69.4 days, 178W with a half-life of 21.6 days, and187W with a half-life of 23.72 h. All of the remaining radioactive isotopes have half-lives of less than 3 hours, and most of these have half-lives below 8 minutes.Sony VAIO VGN-AW91JS Battery

Tungsten also has 4 meta states, the most stable being 179mW (T½ 6.4 minutes).

Chemical properties

Elemental tungsten resists attack by oxygen, acids, and alkalis.

The most common formal oxidation state of tungsten is +6, but it exhibits all oxidation states from ?2 to +6.Sony VAIO VGN-AW91YS Battery

Tungsten typically combines with oxygen to form the yellow tungstic oxide, WO3, which dissolves in aqueous alkaline solutions to form tungstate ions, WO2?4.

Tungsten carbides (W2C and WC) are produced by heating powdered tungsten with carbon. W2C is resistant to chemical attack, although it reacts strongly with chlorineto form tungsten hexachloride (WCl6).Sony VAIO VGN-AW92CDS Battery

In aqueous solution, tungstate gives the heteropoly acids and polyoxometalate anions under neutral and acidic conditions. As tungstate is progressively treated with acid, it first yields the soluble, metastable "paratungstate A" anion, W7O6–24, which over time converts to the less soluble "paratungstate B" anion, H2W12O10–42.Sony VAIO VGN-AW92CJS Battery

Further acidification produces the very soluble metatungstate anion, H2W12O6–40, after which equilibrium is reached. The metatungstate ion exists as a symmetric cluster of twelve tungsten-oxygen octahedra known as the Keggin anion. Many other polyoxometalate anions exist as metastable species.Sony VAIO VGN-AW92CYS Battery

The inclusion of a different atom such as phosphorus in place of the two central hydrogens in metatungstate produces a wide variety of heteropoly acids, such as phosphotungstic acid H3PW12O40.Tungsten trioxide can form intercalation compounds with alkali metals. These are known as bronzes; an example is sodium tungsten bronze.Sony VAIO VGN-AW92DS Battery

Occurrence

Tungsten is found in the minerals wolframite (iron-manganese tungstate, (Fe,Mn)WO4), scheelite (calcium tungstate, (CaWO4), ferberite (FeWO4) and hübnerite (MnWO4).China produced 51,000 tonnes of tungsten concentrate in 2009, which was 83% of the world output.Sony VAIO VGN-AW92JS Battery

Most of the remaining production originated from Russia (2,500 t),Canada (1,964 t), Bolivia (1,023 t), Austria (900 t), Portugal (900 t), Thailand (600 t), Brazil (500 t), Peru (500 t) and Rwanda (500 t).[27] Tungsten is also considered to be a conflict mineral due to the unethical mining practices observed in the Democratic Republic of the Congo.Sony VAIO VGN-AW92YS Battery

Biological role

Tungsten, at atomic number 74, is the heaviest element known to be biologically functional, with the next heaviest being iodine (Z = 53).Sony VAIO VGN-AW93FS Battery

not in eukaryotes, tungsten is used by some bacteria. For example, enzymes called oxidoreductases use tungsten similarly to molybdenum by using it in a tungsten-pterin complex withmolybdopterin (molybdopterin, despite its name, does not contain molybdenum, but may complex with either molybdenum or tungsten in use by living organisms).Sony VAIO VGN-AW93GS Battery

Tungsten-using enzymes typically reduce carboxylic acids to aldehydes.  However, the tungsten oxidoreductases may also catalyse oxidations. The first tungsten-requiring enzyme to be discovered also requires selenium, and in this case the tungsten-selenium pair may function analogously to the molybdenum-sulfur pairing of some molybdenum cofactor-requiring enzymes.Sony VAIO VGN-AW93HS Battery

One of the enzymes in the oxidoreductase family which sometimes employ tungsten (bacterial formate dehydrogenase H) is known to use a selenium-molybdenum version of molybdopterin. Although a tungsten-containing xanthine dehydrogenase from bacteria has been found to contain tungsten-molydopterin and also non-protein bound selenium, a tungsten-selenium molybdopterin complex has not been definitively described.Sony VAIO VGN-AW93ZFS Battery

In soil, tungsten metal oxidizes to the tungstate anion. It can be selectively or non-selectively imported by some prokaryotic organisms and may substitute formolybdate in certain enzymes. Its effect on the action of these enzymes is in some cases inhibitory and in others positive. It is thought that a tungstate-containing enzyme in eukaryotes would be inert.Sony VAIO VGN-AW93ZGS Battery

The soil's chemistry determines how the tungsten polymerizes; alkaline soils cause monomeric tungstates; acidic soils cause polymeric tungstates.

Sodium tungstate and lead have been studied for their effect on earthworms. Lead was found to be lethal at low levels and sodium tungstate was much less toxic, but the tungstate completely inhibited their reproductive ability.Sony VAIO VGN-AW93ZHS Battery

Tungsten has been studied as a biological copper metabolic antagonist, in a role similar to the action of molybdenum. It has been found that tetrathiotungstates may be used as biological copper chelation chemicals, similar to the tetrathiomolybdates.

About 61,300 tonnes of tungsten concentrates were produced in the year 2009.Sony VAIO VGN-BZ11EN Battery

Tungsten is extracted from its ores in several stages. The ore is eventually converted to tungsten(VI) oxide (WO3), which is heated with hydrogen or carbon to produce powdered tungsten.  Because of tungsten's high melting point, it is not commercially feasible to cast tungsten ingots.Sony VAIO VGN-BZ11MN Battery

Instead, powdered tungsten is mixed with small amounts of powdered nickel or other metals, andsintered. During the sintering process, the nickel diffuses into the tungsten, producing an alloy.

Tungsten can also be extracted by hydrogen reduction of WF6:Sony VAIO VGN-BZ11XN Battery

WF6 + 3 H2 ? W + 6 HF

or pyrolytic decomposition:

WF6 ? W + 3 F2 (?Hr = +)

Tungsten is not traded as a futures contract and cannot be tracked on exchanges like the London Metal Exchange. The price for pure metal is around $20,075 per tonne as of October 2008.Sony VAIO VGN-BZ12VN Battery

Applications

Approximately half of the tungsten is consumed for the production of hard materials — namely tungsten carbide — with the remaining major use being its use in alloys and steels. Less than 10% is used in chemical compounds.Sony VAIO VGN-BZ12XN Battery

Hard materials

Tungsten is mainly used in the production of hard materials based on tungsten carbide, one of the hardest carbides, with a melting point of 2770 °C. WC is an efficient electrical conductor, but W2C is less so. WC is used to make wear-resistantabrasives and cutters and knives for drills,Sony VAIO VGN-BZ31VT Battery

circular saws, milling and turning tools used by the metalworking, woodworking,mining, petroleum and construction industries and accounts for about 60% of current tungsten consumption.

The jewelry industry makes rings of sintered tungsten carbide, tungsten carbide/metal composites, and also simply metallic tungsten.Sony VAIO VGN-BZ31XT Battery

Sometimes manufacturers or retailers refer to tungsten carbide as a metal, but it is rather a ceramic. Because of tungsten carbide's hardness, rings made of this material are extremely abrasion resistant, and will hold a burnished finish much longer than rings made of metallic tungsten. Tungsten carbide rings are brittle, however, and may crack under a sharp blow.Sony VAIO VGN-BZ560 Battery

The hardness and density of tungsten are applied in obtaining heavy metal alloys. A good example is high speed steel, which can contain as much as 18% tungsten.Tungsten's high melting point makes tungsten a good material for applications like rocket nozzles, for example in the UGM-27 Polaris Submarine-launched ballistic missile.Sony VAIO VGN-BZ560N24 Battery

Superalloys containing tungsten, such asHastelloy and Stellite, are used in turbine blades and wear-resistant parts and coatings.

Armaments

Tungsten, usually alloyed with nickel and iron or cobalt to form heavy alloys, is used in kinetic energy penetrators as an alternative to depleted uranium,Sony VAIO VGN-BZ560N30 Battery

in applications where uranium's additional pyrophoric properties are not required (for example, in ordinary small arms bullets designed to penetrate body armor). Similarly, tungsten alloys have also been used in cannon shells, grenades and missiles, to create supersonic shrapnel.Sony VAIO VGN-BZ560P Battery

Tungsten has also been used in Dense Inert Metal Explosives, which use it as dense powder to reduce collateral damage while increasing the lethality of explosives within a small radius.

Chemical applications

Tungsten(IV) sulfide is a high temperature lubricant and is a component of catalysts for hydrodesulfurization.[47] MoS2 is more commonly used for such applications.Sony VAIO VGN-BZ560P20 Battery

Tungsten oxides are used in ceramic glazes and calcium/magnesium tungstates are used widely in fluorescent lighting. Crystal tungstates are used as scintillation detectors in nuclear physics and nuclear medicine. Other salts that contain tungsten are used in the chemical and tanning industries.Sony VAIO VGN-BZ560P22 Battery

oxide (WO3) is incorporated into selective catalytic reduction (SCR) catalysts found in coal-fired power plants. These catalysts convert nitrogen oxides(NOx) to nitrogen (N2) and water (H2O) using ammonia (NH3). The tungsten oxide helps with the physical strength of the catalyst and extends catalyst life.Sony VAIO VGN-BZ560P28 Battery

Niche uses

Applications requiring its high density include weights, counterweights, ballast keels for yachts, tail ballast for commercial aircraft, and as ballast in race cars for NASCAR and Formula One. It is an ideal material to use as a dolly for riveting, where the mass necessary for good results can be achieved in a compact bar.Sony VAIO VGN-BZ560P30 Battery

High-density alloys of tungsten with nickel, copper or iron are used in high-quality darts[50] (to allow for a smaller diameter and thus tighter groupings) or for fishing lures (tungsten beads allow the fly to sink rapidly). Some types of strings for musical instruments are wound with tungsten wires.Sony VAIO VGN-BZ560P34 Battery

Its density, similar to that of gold, allows tungsten to be used in jewelry as an alternative to gold or platinum. Metallic tungsten is harder than gold alloys (though not as hard as tungsten carbide), and is hypoallergenic, making it useful for rings that will resist scratching, especially in designs with a brushed finish.Sony VAIO VGN-BZ561 Battery

Electronics

Because it retains its strength at high temperatures and has a high melting point, elemental tungsten is used in many high-temperature applications,  such aslight bulb, cathode-ray tube, and vacuum tube filaments, heating elements, and rocket engine nozzles.Sony VAIO VGN-BZ561N20 Battery

Its high melting point also makes tungsten suitable for aerospace and high-temperature uses such as electrical, heating, and welding applications, notably in the gas tungsten arc welding process (also called tungsten inert gas (TIG) welding).

Because of its conductive properties and relative chemical inertia, tungsten is also used in electrodes, and in the emitter tips in electron-beam instruments that use field emission guns, such as electron microscopes.Sony VAIO VGN-BZ561P20 Battery

In electronics, tungsten is used as an interconnect material in integrated circuits, between the silicon dioxide dielectric material and the transistors. It is used in metallic films, which replace the wiring used in conventional electronics with a coat of tungsten (ormolybdenum) on silicon.Sony VAIO VGN-BZ562P Battery

The electronic structure of tungsten makes it one of the main sources for X-ray targets, and also for shielding from high-energy radiations (such as in theradiopharmaceutical industry for shielding radioactive samples of FDG). Tungsten powder is used as a filler material in plastic composites, which are used as a nontoxic substitute for lead in bullets, shot, and radiation shields.Sony VAIO VGN-BZ563P Battery

Since this element's thermal expansion is similar to borosilicate glass, it is used for making glass-to-metal seals.

Precautions

Because tungsten is rare and its compounds are generally inert, the effects of tungsten on the environment are limited.Sony VAIO VGN-BZAAFS Battery

The median lethal dose LD50 depends strongly on the animal and the method of administration and varies between 59 mg/kg (intravenous, rabbit)  and 5000 mg/kg (tungsten metal powder, intraperitoneal, rats).Sony VAIO VGN-BZAAHS Battery

Patent claim

Tungsten is unique amongst the elements in that it has been the subject of legal proceedings. In 1928, a US court rejected General Electric's attempt to patent it, overturning U.S. Patent 1,082,933 granted in 1913 to William D. Coolidge.Sony VAIO VGN-BZAANS Battery,Sony VAIO VGN-BZAAPS Battery

 

Praseodymium,Neodymium,Promethium,Samarium

Praseodymium is a chemical element that has the symbol Pr and atomic number 59. Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanide group. It is too reactive to be found in native form, and when artificially prepared, it slowly develops a green oxide coating.Sony VAIO VPCY11V9E/S Battery

The element was named for the color of its primary oxide. In 1841, Swedish chemist Carl Gustav Mosander extracted a rare earth oxide residue he called "didymium" from a residue he called "lantana," in turn separted from cerium salts. In 1885, the Austrian chemist baron Carl Auer von Welsbach separated didymium into two salts of different colors,Sony VAIO VPCY218EC/BI Battery

which he named praseodymium and neodymium. The name praseodymium comes from the Greek prasios (???????), meaning green, and didymos(???????), twin.

Like most rare earth elements, praseodymium most readily forms trivalent Pr(III) ions.Sony VAIO VPCY218EC/G Battery

These are yellow-green in water solution, and various shades of yellow-green when incorporated into glasses. Many of praseodymium's industrial uses involve its use to filter yellow light from light sources.

Physical properties

Praseodymium is a soft, silvery, malleable and ductile metal in the lanthanide group.Sony VAIO VPCY218EC/L Battery

It is somewhat more resistant tocorrosion in air than europium, lanthanum, cerium, or neodymium, but it does develop a green oxide coating that spalls off when exposed to air, exposing more metal to oxidation — a centimeter-sized sample of Pr completely oxidizes within a year.Sony VAIO VPCY218EC/P Battery

For this reason, praseodymium is usually stored under a light mineral oil or sealed in glass.

Unlike other rare-earth metals, which show antiferromagnetic or/and ferromagnetic ordering at low temperatures, Pr isparamagnetic at any temperature above 1 K.Sony VAIO VPCY21S1E/L Battery

Chemical properties

Praseodymium metal tarnishes slowly in air and burns readily at 150 °C to form praseodymium(III,IV) oxide:

12 Pr + 11 O2 ? 2 Pr6O11

Praseodymium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form praseodymium hydroxide:Sony VAIO VPCY21S1E/P Battery

2 Pr (s) + 6 H2O (l) ? 2 Pr(OH)3 (aq) + 3 H2 (g)

Praseodymium metal reacts with all the halogens:

2 Pr (s) + 3 F2 (g) ? 2 PrF3 (s) [green]

2 Pr (s) + 3 Cl2 (g) ? 2 PrCl3 (s) [green]

2 Pr (s) + 3 Br2 (g) ? 2 PrBr3 (s) [green]

2 Pr (s) + 3 I2 (g) ? 2 PrI3 (s) [green]Sony VAIO VPCY21S1E/SI Battery

Praseodymium dissolves readily in dilute sulfuric acid to form solutions containing green Pr(III) ions, which exist as a [Pr(OH2)9]3+complexes:[4]

2 Pr (s) + 3 H2SO4 (aq) ? 2 Pr3+(aq) + 3 SO2?4 (aq) + 3 H2 (g)Sony VAIO VPCCW2S5C CN1 Battery

Compounds

In its compounds, praseodymium occurs in oxidation states +2, +3 and/or +4. Praseodymium(IV) is a strong oxidant, instantly oxidizing water to elemental oxygen (O2), or hydrochloric acid to elemental chlorine. Thus, in aqueous solution, only the +3 oxidation state is encountered.Sony VAIO VPCEA20 Battery

Praseodymium(III) salts are yellow-green and, in solution, present a fairly simple absorption spectrum in the visible region, with a band in the yellow-orange at 589–590 nm (which coincides with the sodium emission doublet), and three bands in the blue/violet region, at 444, 468, and 482 nm, approximately.Sony VAIO VPCEB10 Battery

These positions vary slightly with the counter-ion. Praseodymium oxide, as obtained by the ignition of salts such as the oxalate or carbonate in air, is essentially black in color (with a hint of brown or green) and contains +3 and +4 praseodymium in a somewhat variable ratio, depending upon the conditions of formation. Its formula is conventionally rendered as Pr6O11.Sony VAIO VPCEB11FM Battery

Other praseodymium compounds include:

• Fluorides: PrF2, PrF3, PrF4
• Chlorides: PrCl3
• Bromides: PrBr3, Pr2Br5
• Iodides: PrI2, PrI3, Pr2I5
• Oxides: PrO2, Pr2O3, Pr6O11
• Sulfides: PrS, Pr2S3
• Sulfates: Pr2(SO4)3
• Selenides: PrSe
• Tellurides: PrTe, Pr2Te3
• Nitrides: PrN  Sony VAIO VPCEB11FM/BI Battery

Naturally occurring praseodymium is composed of one stable isotope, praseodymium-141,[5] which is of use in NMR and EPR   spectroscopy.[6] 38 radioisotopes have been characterized, with the most stable being praseodymium-143 with a half-life of 13.57 days and praseodymium-142 with a half-life of 19.12 hours.Sony VAIO VPCEB11FM/T Battery

All of the remaining radioactive isotopes have half-lives that are less than six hours, and the majority of these have half lives that are less than 10 minutes.[5] This element also has 15 nuclear isomers, with the longest-lived being praseodymium-138m, praseodymium-134m, and praseodymium-142m .Sony VAIO VPCEB11FM/WI Battery

The nuclei of nuclear isomers exist in a delicate equilibrium or metastability due to at least one nucleon having an excited energy state.

The isotopes of praseodymium range in mass number from 121 to 159 .Sony VAIO VPCEB11FX Battery

The most common decay mode of 20 isotopes with mass numbers lower than the most abundant stable isotope, praseodymium-141 is beta+ decay, primarily forming cerium isotopes (58 protons) as decay products.[5] The most common decay mode for 18 isotopes with mass numbers higher than praseodymium-141 isbeta- decay, primarily forming neodymium isotopes (60 protons) as decay products.Sony VAIO VPCEB11FX/BI Battery

In 1839 Mosander extracted an oxide he called "lantana" (see lanthana), which was the oxide of the newly discovered elementlanthanum, from a mixture of crude cerium nitrate. In 1841, Mosander went on to show that "lantana" was the most strongly basic of a mixture of rare earth element oxides and precipitated from acid solution when base was added.Sony VAIO VPCEB11FX/T Battery

The remaining rare earth(s) remained in solution, and Mosander called these remainder salts "didymium." In 1874, Per Teodor Cleve concluded that didymium was in fact two elements, and in 1879, Lecoq de Boisbaudran isolated a new earth, samarium, from "didymium" obtained from the mineral samarskite.Sony VAIO VPCEB11FX/WI Battery

Crude didymium actually contained three elements, and in 1885, the Austrian chemistbaron Carl Auer von Welsbach separated didymium into two elements, praseodymium and neodymium, which gave salts of differentcolors.

The name praseodymium comes from the Greek prasios (???????), meaning green, and didymos (???????), twin. Praseodymium is frequently misspelled as praseodynium.Sony VAIO VPCEB11GX Battery

Leo Moser (son of Ludwig Moser, founder of the Moser Glassworks in what is now Karlovy Vary, Bohemia, in the Czech Republic, not to be confused with Leo Moser, a mathematician) investigated the use of praseodymium in glass coloration in the late 1920s. The result was a yellow-green glass given the name "Prasemit".Sony VAIO VPCEB11GX/BI Battery

However, a similar color could be achieved with colorants costing only a minute fraction of what praseodymium cost in the late 1920s, such that the color was not popular, few pieces were made, and examples are now extremely rare. Moser also blended praseodymium with neodymium to produce "Heliolite" glass ("Heliolit" in German), which was more widely accepted.Sony VAIO VPCEB11GX/T Battery

The first enduring commercial use of purified praseodymium, which continues today, is in the form of a yellow-orange stain for ceramics, "Praseodymium Yellow", which is a solid-solution of praseodymium in the zirconium silicate (zircon) lattice. This stain has no hint of green in it. By contrast, at sufficiently high loadings, praseodymium glass is distinctly green, rather than pure yellow.Sony VAIO VPCEB11GX/WI Battery

Using classical separation methods, praseodymium was always difficult to purify. Much less abundant than the lanthanum and neodymium from which it was being separated (cerium having long since been removed by redox chemistry), praseodymium ended up being dispersed among a large number of fractions, and the resulting yields of purified material were low.Sony VAIO VPCEB12FX Battery

Praseodymium has historically been a rare earth whose supply has exceeded demand. This has occasionally led to its being offered more cheaply than the far more abundant neodymium. Unwanted as such, much praseodymium has been marketed as a mixture with lanthanum and cerium, or "LCP" for the first letters of each of the constituents,Sony VAIO VPCEB12FX/BI Battery

for use in replacing the traditional lanthanide mixtures that were inexpensively made from monazite or bastnäsite. LCP is what remains of such mixtures, after the desirable neodymium, and all the heavier, rarer and more valuable lanthanides have been removed, by solvent extraction.Sony VAIO VPCEB12FX/BIC Battery

However, as technology progresses, it has been found that praseodymium can be incorporated into neodymium-iron-boron magnets, thereby extending the supply of the much in demand neodymium[citation needed]. So LC is starting to replace LCP as a result.Sony VAIO VPCEB12FX/T Battery

Occurrence

Praseodymium is available in small quantities in Earth's crust (9.5 ppm). It is found in the rare earth minerals monazite andbastnäsite, typically comprising about 5% of the lanthanides contained therein, and can be recovered from these minerals by anion exchange process, or by counter-current solvent extraction.Sony VAIO VPCEB14FX Battery

Misch metal, used in making cigarette lighters, contains about 5% praseodymium metal.

Applications

Uses of praseodymium:

• As an alloying agent with magnesium to create high-strength metals that are used in aircraft engines. Sony VAIO VPCEB14FX/BI Battery

• Praseodymium forms the core of carbon arc lights which are used in the motion picture industry for studio lighting andprojector lights.
• Praseodymium compounds give glasses and enamels a yellow color.
• Praseodymium is used to color cubic zirconia yellow-green, to simulate the mineral peridot.Sony VAIO VPCEB14FX/T Battery

• Praseodymium is a component of didymium glass, which is used to make certain types of welder's and glass blower's goggles.
• Silicate crystals doped with praseodymium ions have been used to slow a light pulse down to a few hundred meters per second.Sony VAIO VPCEB14FX/WI Battery

• Praseodymium alloyed with nickel (PrNi5) has such a strong magnetocaloric effect that it has allowed scientists to approach within one thousandth of a degree of absolute zero.
• Doping praseodymium in fluoride glass allows it to be used as a single mode fiber optical amplifier.Sony VAIO VPCEB15FM Battery

• Praseodymium oxide in solid solution with ceria, or with ceria-zirconia, have been used as oxidation catalysts.
• Modern ferrocerium firesteel products, commonly referred to as "flint", used in lighters, torch strikers, "flint and steel" fire starters, etc., contain around 4% praseodymium.Sony VAIO VPCEB15FM/BI Battery

Neodymium is a chemical element with the symbol Nd and atomic number 60. It is a soft silvery metal that tarnishes in air. Neodymium was discovered in 1885 by the Austrian chemist Carl Auer von Welsbach. It is present in significant quantities in the ore minerals monazite and bastnäsite.Sony VAIO VPCEB15FM/T Battery

Neodymium is not found naturally in metallic form or unmixed with other lanthanides, and it is usually refined for general use. Although neodymium is classed as a "rare earth", it is no rarer than cobalt, nickel, and copper ore, and is widely distributed in the Earth's crust.[2]Most of the world's neodymium is mined in China.Sony VAIO VPCEB15FM/WI Battery

Neodymium compounds were first commercially used as glass dyes in 1927, and they remain a popular additive in glasses. The color of neodymium compounds—due to the Nd(III) ion—is often a reddish-purple but it changes with the type of lighting, due to fluorescent effects.Sony VAIO VPCEB15FX Battery

Some neodymium-doped glasses are also used in lasers that emit infrared light with wavelengthsbetween 1047 and 1062 nanometers. These have been used in extremely high power applications, such as experiments ininertial confinement fusion.Sony VAIO VPCEB15FX/BI Battery

Neodymium is also used with various other substrate crystals, such as yttrium aluminum garnet in the Nd:YAG laser. This laser usually emits infrared waves at a wavelength of about 1064 nanometers. The Nd:YAG laser is one of the most commonly used solid-state lasers.Sony VAIO VPCEB15FX/T Battery

Another chief use of neodymium is as the free pure element. It is used as a component in the alloys used to make high-strength neodymium magnets – the most powerful permanent magnets known. These magnets are widely used in such products as microphones, professional loudspeakers,Sony VAIO VPCEB15FX/WI Battery

in-ear headphones, and computer hard disks, where low magnet mass or volume, or strong magnetic fields are required. Larger neodymium magnets are used in high power versus weight electric motors (for example in hybrid cars) and generators (for example aircraft and wind turbine electric generators).Sony VAIO VPCEB16FX Battery

Physical properties

Neodymium, a rare earth metal, was present in the classical mischmetal at a concentration of about 18%. Metallic neodymium has a bright, silvery metallic luster, but as one of the more reactive lanthanide rare-earth metals, it quickly oxidizes in ordinary air.Sony VAIO VPCEB16FX/B Battery

The oxide layer that forms then peels off, and this exposes the metal to further oxidation. Thus a centimeter-sized sample of neodymium completely oxidizes within a year.

Neodymium exists in two allotropic forms, with a transformation from a double hexagonal to a body-centered cubic structure taking place at about 863 °C.Sony VAIO VPCEB16FX/G Battery

Chemical properties

Neodymium metal tarnishes slowly in air and it burns readily at about 150 °C to form the neodymium(III) oxide:

4 Nd + 3 O2 ? 2 Nd2O3

Neodymium is a quite electropositive element, and it reacts slowly with cold water, but quite quickly with hot water to form neodymium hydroxide:Sony VAIO VPCEB16FX/L Battery

2 Nd (s) + 6 H2O (l) ? 2 Nd(OH)3 (aq) + 3 H2 (g)

Neodymium metal reacts enthusiastically with all the halogens:

2 Nd (s) + 3 F2 (g) ? 2 NdF3 (s) [a violet substance]

2 Nd (s) + 3 Cl2 (g) ? 2 NdCl3 (s) [a mauve substance]

2 Nd (s) + 3 Br2 (g) ? 2 NdBr3 (s) [a violet substance]

2 Nd (s) + 3 I2 (g) ? 2 NdI3 (s) [a green substance]Sony VAIO VPCEB16FX/P Battery

Neodymium dissolves readily in dilute sulfuric acid to form solutions that contain the lilac Nd(III) ion. These exist as a [Nd(OH2)9]3+ complexes:[6]

2 Nd (s) + 3 H2SO4 (aq) ? 2 Nd3+ (aq) + 3 SO2?
4 (aq) + 3 H2 (g)Sony VAIO VPCEB16FX/W Battery

Compounds

Neodymium compounds include

• halides: neodymium(III) fluoride – NdF3;

neodymium(III) chloride – NdCl3; neodymium(III) bromide – NdBr3; neodymium(III) iodide – NdI3Sony VAIO VPCEB17FX Battery

• oxides: Nd2O3
• sulfides: neodymium(II) sulfide – NdS, neodymium(III) sulfide – Nd2S3
• nitrides: neodymium(III) nitride – NdN
• hydroxide: neodymium hydroxide Nd(OH)3
• phosphide: neodymium phosphide NdP Sony VAIO VPCEB17FX/B Battery
• carbide: neodymium carbide Nd4C3
• nitrate: neodymium nitrate Nd(NO3)3

And many more, since neodymium is a quite reactive element

Some neodymium compounds have colors which vary based upon the type of lighting.Sony VAIO VPCEB17FX/G Battery

Naturally occurring neodymium is a mixture of five stable isotopes, 142Nd, 143Nd, 145Nd, 146Nd and 148Nd, with 142Nd being the most abundant (27.2% of the natural abundance), and two radioisotopes, 144Nd and 150Nd. In all, 31 radioisotopes of neodymium have been detected as of 2010, with the most stable radioisotopes being the naturally occurring ones:Sony VAIO VPCEB17FX/L Battery

144Nd (alpha decay with a half-life (T½) of 2.29×1015 years) and 150Nd (double beta decay, T½ = 7×1018 years, approximately). All of the remaining radioactive isotopes have half-lives that are shorter than eleven days, and the majority of these have half-lives that are shorter than 70 seconds.Sony VAIO VPCEB17FX/P Battery

Neodymium also has 13 known meta states, with the most stable one being139mNd (T½ = 5.5 hours), 135mNd (T½ = 5.5 minutes) and 133m1Nd (T½ ~ 70 seconds).

The primary decay modes before the most abundant stable isotope, 142Nd, are electron capture and positron decay, and the primary mode after is beta minus decay.Sony VAIO VPCEB17FX/W Battery

The primary decay products before 142Nd are element Pr (praseodymium) isotopes and the primary products after are element Pm (promethium) isotopes.

Neodymium was discovered by Baron Carl Auer von Welsbach, an Austrian chemist, in Vienna in 1885.Sony VAIO VPCEB190X Battery

He separated neodymium, as well as the element praseodymium, from a material known as didymium by means of fractional crystallization of the double ammonium nitrate tetrahydrates from nitric acid, while following the separation byspectroscopic analysis; however, it was not isolated in relatively pure form until 1925.Sony VAIO VPCEB19FX Battery

The name neodymium is derived from the Greek words neos (????), new, anddidymos (???????), twin.

Double nitrate crystallization was the means of commercial neodymium purification until the 1950s. Lindsay Chemical Division was the first to commercialize large-scale ion-exchange purification of neodymium.Sony VAIO VPCEB19GX Battery

Starting in the 1950s, high purity (above 99%) neodymium was primarily obtained through an ion exchange process frommonazite, a mineral rich in rare earth elements. The metal itself is obtained through electrolysis of its halide salts. Currently, most neodymium is extracted from bastnäsite, (Ce,La,Nd,Pr)CO3F, and purified by solvent extraction.Sony VAIO VPCEB1AFX Battery

Ion-exchange purification is reserved for preparing the highest purities (typically >99.99 %). The evolving technology, and improved purity of commercially available neodymium oxide, was reflected in the appearance of neodymium glass that resides in collections today.Sony VAIO VPCEB1AFX/B Battery

Early neodymium glasses made in the 1930s have a more reddish or orange tinge than modern versions which are more cleanly purple, due to the difficulties in removing the last traces of praseodymium in the era when fractional crystallization technology had to be relied on.Sony VAIO VPCEB1AGX Battery

Occurrence and production

Neodymium is never found in nature as the free element, but rather it occurs in ores such as monazite and bastnäsite that contain small amounts of all the rare earth metals. The main mining areas are in China, the United States, Brazil, India, Sri Lanka, and Australia.Sony VAIO VPCEB1AGX/BI Battery

The reserves of neodymium are estimated at about eight million tonnes. Although it belongs to the rare earth metals, neodymium is not rare at all. Its abundance in the Earth crust is about 38 mg/kg, which is the second highest among rare-earth elements, following cerium. The world's production of neodymium was about 7,000 tonnes in 2004.Sony VAIO VPCEB1BGX Battery

The bulk of current production is from China, whose government has recently imposed strategic materials controls on the element, raising some concerns in consuming countries.

Neodymium is typically 10% to 18% of the rare earth content of commercial deposits of the light rare earth element minerals bastnasite and monazite.Sony VAIO VPCEB1BGX/BI Battery

With neodymium compounds being the most strongly colored for the trivalent lanthanides, that percentage of neodymium can occasionally dominate the coloration of rare earth minerals—when competing chromophores are absent. It usually gives a pink coloration.Sony VAIO VPCEB1CGX Battery

Outstanding examples of this include monazite crystals from the tin deposits in Llallagua, Bolivia, ancylite from Mont Saint-Hilaire, Quebec, or lanthanite from the Saucon Valley, Pennsylvania. As with neodymium glasses, such minerals change their colors under the differing lighting conditions.Sony VAIO VPCEB1CGX/BI Battery

The absorption bands of neodymium interact with the visible emission spectrum of mercury vapor, with the unfiltered shortwave UV light causing neodymium-containing minerals to reflect a distinctive green color. This can be observed with monazite-containing sands or bastnasite-containing ore.Sony VAIO VPCEB1DGX Battery

Applications

• Neodymium has an unusually large specific heat capacity at liquid-helium temperatures, so is useful in cryocoolers
• Probably because of similarities to Ca2+, Nd3+ has been reported to promote plant growth. Rare earth element compounds are frequently used in China asfertilizer.Sony VAIO VPCEB1DGX/BI Battery

• Samarium-neodymium dating is useful for determining the age relationships of rocks and meteorites.
• Size and strength of volcanic eruption can be predicted by scanning for neodymium isotopes. Small and large volcanic eruptions produce lava with different neodymium isotope composition.Sony VAIO VPCEB1EGX Battery

• From the composition of isotopes, scientists predict how big the coming eruption will be, and use this information to warn residents of the intensity of the eruption.

Magnets

Neodymium magnets are the strongest permanent magnets known – Nd2Fe14B.Sony VAIO VPCEB1EGX/BI Battery

A neodymium magnet of a few grams can lift a thousand times its own weight. These magnets are cheaper, lighter, and stronger than samarium-cobalt magnets. However, they are not superior in all ways, as neodymium-based magnets lose their magnetism at high temperatures and tend to rust, while samarium-cobalt magnets do not.Sony VAIO VPCEB1FGX Battery

Neodymium magnets appear in products such as microphones, professional loudspeakers, in-ear headphones, guitar and bass guitarpick-ups and computer hard disks where low mass, small volume, or strong magnetic fields are required.Sony VAIO VPCEB1FGX/BI Battery

Neodymium magnet electric motors have also been responsible for the development of purely electrical model aircraft within the first decade of the 21st century, to the point that these are displacing internal combustion powered models internationally. Likewise, due to this high magnetic capacity per weight, neodymium is used in the electric motors of hybrid and electric automobiles,Sony VAIO VPCEB1GGX Battery

and in the electricity generators of some designs of commercial wind turbines (only wind turbines with "permanent magnet" generators use neodymium). For example, drive electric motors of each Toyota Prius require one kilogram (2.2 pounds) of neodymium per vehicle.Sony VAIO VPCEB1GGX/BI Battery

Neodymium doped lasers

Neodymium ions in various types of ionic crystals, and also in glasses, act as a laser gain medium, typically emitting 1064 nm light from a particular atomic transition in the neodymium ion, after being "pumped" into excitation from an external source.Sony VAIO VPCEB1HGX Battery

Certain transparent materials with a small concentration of neodymiumions can be used in lasers as gain media for infrared wavelengths (1054–1064 nm), e.g. Nd:YAG (yttrium aluminium garnet), Nd:YLF(yttrium lithium fluoride), Nd:YVO4 (yttrium orthovanadate), and Nd:glass.Sony VAIO VPCEB1HGX/BI Battery

Neodymium-doped crystals (typically Nd:YVO4) generate high-powered infrared laser beams which are converted to green laser light in commercial DPSS hand-held lasers and laser pointers.

The current laser at the UK Atomic Weapons Establishment (AWE), the HELEN (High Energy Laser Embodying Neodymium) 1-terawatt neodymium-glass laser,Sony VAIO VPCEB1JFX Battery

can access the midpoints of pressure and temperature regions and is used to acquire data for modeling on how density, temperature and pressure interact inside warheads. HELEN can create plasmas of around 106 K, from which opacity and transmission of radiation are measured.Sony VAIO VPCEB1JFX/B Battery

Neodymium glass solid-state lasers are used in extremely high power (terawatt scale), high energy (megajoules) multiple beam systems for inertial confinement fusion. Nd:glass lasers are usually frequency tripled to the third harmonic at 351 nm in laser fusion devices.Sony VAIO VPCEB1JFX/G Battery

Neodymium glass for other applications

A neodymium glass light bulb, with the base and inner coating removed, under two different types of light: fluorescent on the left, and incandescent on the right.

Neodymium glass (Nd:glass) is produced by the inclusion of neodymium oxide (Nd2O3) in the glass melt.Sony VAIO VPCEB1JFX/L Battery

Usually in daylight orincandescent light neodymium glass appears lavender, but it appears pale blue under fluorescent lighting. Neodymium may be used to color glass in delicate shades ranging from pure violet through wine-red and warm gray.

The first commercial use of purified neodymium was in glass coloration, starting with experiments by Leo Moser in November 1927.Sony VAIO VPCEB1JFX/P Battery

The resulting "Alexandrite" glass remains a signature color of the Moser glassworks to this day. Neodymium glass was widely emulated in the early 1930s by American glasshouses, most notably Heisey, Fostoria ("wisteria"), Cambridge ("heatherbloom"), and Steuben ("wisteria"), and elsewhere (e.g. Lalique, in France, or Murano).Sony VAIO VPCEB1JFX/W Battery

Tiffin's "twilight" remained in production from about 1950 to 1980. Current sources include glassmakers in the Czech Republic, the United States, and China.

The sharp absorption bands of neodymium cause the glass color to change under different lighting conditions,Sony VAIO VPCEB1KGX Battery

being reddish-purple under daylight or yellow incandescent light, but blue under white fluorescent lighting, or greenish under trichromatic lighting. This color-change phenomenon is highly prized by collectors. In combination with gold or selenium, beautiful red colors result.Sony VAIO VPCEB1KGX/B Battery

Since neodymium coloration depends upon "forbidden" f-f transitions deep within the atom, there is relatively little influence on the color from the chemical environment, so the color is impervious to the thermal history of the glass. However, for the best color, iron-containing impurities need to be minimized in the silica used to make the glass. Sony VAIO VPCEB1KGX/W Battery

The same forbidden nature of the f-f transitions makes rare-earth colorants less intense than those provided by most d-transition elements, so more has to be used in a glass to achieve the desired color intensity. The original Moser recipe used about 5% of neodymium oxide in the glass melt, a sufficient quantity such that Moser referred to these as being "rare earth doped" glasses.Sony VAIO VPCEB1LFX Battery

Being a strong base, that level of neodymium would have affected the melting properties of the glass, and the lime content of the glass might have had to be adjusted accordingly.

Light transmitted through neodymium glasses shows unusually sharp absorption bands; the glass is used in astronomical work to produce sharp bands by which spectral lines may be calibrated.Sony VAIO VPCEB1LFX/BI Battery

Neodymium is also used to remove the green color caused by ironcontaminants from glass. Neodymium is a component of "didymium" (referring to mixture of salts of neodymium and praseodymium) used for coloring glass to make welder's and glass-blower's goggles; the sharp absorption bands obliterate the strong sodium emission at 589 nm.Sony VAIO VPCEB1LFX/WI Battery

Neodymium and didymium glass are used in color-enhancing filters in indoor photography, particularly in filtering out the yellow hues from incandescent lighting.

Similarly, neodymium glass is becoming widely used more directly in incandescent light bulbs. These lamps contain neodymium in the glass to filter out yellow light, resulting in a whiter light which is more like sunlight.Sony VAIO VPCEB1MFX Battery

Neodymium has been patented for use in automobile rear-view mirrors, to reduce the glare at night.

Similar to its use in glasses, neodymium salts are used as a colorant for enamels.

Precautions

Neodymium metal dust is a combustion and explosion hazard. Neodymium compounds, as with all rare earth metals, are of low to moderate toxicity; however its toxicity has not been thoroughly investigated.Sony VAIO VPCEB1MFX/BI Battery

Neodymium dust and salts are very irritating to the eyes and mucous membranes, and moderately irritating to skin. Breathing the dust can cause lung embolisms, and accumulated exposure damages the liver. Neodymium also acts as an anticoagulant, especially when given intravenously.Sony VAIO VPCEB1NFX Battery

Neodymium magnets have been tested for medical uses such as magnetic braces and bone repair, but biocompatibility issues have prevented widespread application. Commercially available magnets made from neodymium are exceptionally strong, and can attract each other from large distances.Sony VAIO VPCEB1NFX/B Battery

If not handled carefully, they come together very quickly and forcefully, causing injuries. For example, there is at least one documented case of a person losing a fingertip when two magnets he was using snapped together from 50 cm away.

Promethium is a chemical element with the symbol Pm and atomic number 61.Sony VAIO VPCEB1NFX/L Battery

It is notable for being the only exclusively radioactive element besides technetium that is followed by chemical elements with stable isotopes.

Prediction

The existence of promethium was first predicted by Bohuslav Brauner in 1902.Sony VAIO VPCEB1NFX/P Battery

During his research on the chemical properties of rare earth elements he found that the difference between neodymium and samarium is larger than between the otherlanthanides. This prediction was supported in 1914 by Henry Moseley who, having discovered that atomic number was an experimentally measurable property of elements, found that no known element had atomic number 61.Sony VAIO VPCEB1NFX/W Battery

With the knowledge of a gap in the periodic table several groups started to search for the predicted element among other rare earths in the natural environment.

Florentium and Illinium

The first claim of a discovery was published by Italian scientists Luigi Rolla and Lorenzo Fernandes from Florence.Sony VAIO VPCEB1PFX Battery

After separating a didymium nitrate concentrate from the Brazilian mineral monazite by fractionated crystallisation, they yielded a solution containing mostly samarium. This solution gave x-ray spectra attributed to samarium and element 61. In honor of their city they named element 61 Florentium.Sony VAIO VPCEB1PFX/B Battery

The results were published in 1926, but the scientists claimed that the experiments were done in 1924. ]

Also in 1926, a group of scientists from the University of Illinois at Urbana-Champaign, Smith Hopkins and Len Yntema published the discovery of element 61. They named it illinium, after the university.Sony VAIO VPCEB1QGX Battery

Both of these reported discoveries are now known to be erroneous because there are no stable or long-lived isotopes of promethium, hence there was none to be found in these sources.

True promethium

Promethium was first produced and characterized at Oak Ridge National Laboratory (ORNL) in 1945 by Jacob A. Marinsky,Sony VAIO VPCEB1QGX/BI Battery

Lawrence E. Glendenin and Charles D. Coryell by separation and analysis of the fission products of uranium fuel irradiated in the Graphite Reactor; however, being too busy with military-related research during World War II, they did not announce their discovery until 1947.Sony VAIO VPCEB1RGX Battery

The name promethium is derived from Prometheus, the Titan, in Greek mythology, who stole fire from Mount Olympus and brought it down to mankind. The name was suggested by Grace Mary Coryell, Charles Coryell's wife, who felt that they were stealing fire from the gods.Sony VAIO VPCEB1RGX/BI Battery

In 1963, ion-exchange methods were used at ORNL to prepare about ten grams of promethium from nuclear reactor fuel processing wastes.

Today, promethium is still recovered from the byproducts of uranium fission; it can also be produced by bombarding 146Nd withneutrons, turning it into 147Nd which decays into 147Pm through beta decay with a half-life of 11 days.Sony VAIO VPCEB20 Battery

Occurrence

Promethium can be formed in nature as a product of spontaneous fission of uranium-238 andalpha decay of europium-151. Only trace amounts can be found in naturally occurring ores: a sample of pitchblende has been found to contain promethium at a concentration of four parts per quintillion (1018) by mass.Sony VAIO VPCEC20 Battery

It was calculated that the equilibrium mass of promethium in the Earth's crust is about 560g due to uranium fission and about 12g due to the recently observed alpha decay of europium-151.

Promethium has also been identified in the spectrum of the star HR 465 in Andromeda, and possibly HD 101065 (Przybylski's star) and HD 965.Sony VAIO VPCEE20 Battery

Characteristics

Promethium is the only lanthanide and one of two elements among the first 82 that has no stable (or even long-lived) isotopes; this is a result of a rarely occurring effect of the liquid drop model and stabilities of neighbor element isotopes. The most stable isotope of the element is promethium-145, which has a half-life of 17.7 years.Sony VAIO VPCEF20 Battery

In other words, if a kilogram of pure promethium-145 could be created at a moment, only about 20 grams would be left after 100 years. Promethium is also the least stable element of the first 84. The primary decay products are neodymium and samariumisotopes (promethium-146 decays to both, the lighter generally to neodymium, and heavier to samarium).Sony VAIO VPCF112FX/B Battery

Exact promethium isotopes may decay to praseodymium or other promethium isotopes (in case of nuclear isomers).

Promethium is a lanthanide metal whose chemical properties mostly resemble those of other lanthanides. The melting point of the element was claimed to have been calculated to be around 1042 °C (1908 °F, 1315 K),Sony VAIO VPCF115FG/B Battery

well suiting in the general trend of its increase with atomic numbers in lanthanides. Pure promethium exists in two allotropic forms, and its chemistry is similar to other lanthanides. Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity.Sony VAIO VPCF116FGBI Battery

Chemical properties

Promethium metals tarnish slowly in air and burns readily at 150 °C to form promethium oxide:

4 Pm + 3 O2 ? 2 Pm2O3

Promethium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form promethium hydroxide:Sony VAIO VPCF117FJ/W Battery

2 Pm (s) + 6 H2O (l) ? 2 Pm(OH)3 (aq) + 3 H2 (g)

Promethium metal reacts with all the halogens:

2 Pm (s) + 3 F2 (g) ? 2 PmF3 (s)

2 Pm (s) + 3 Cl2 (g) ? 2 PmCl3 (s)

2 Pm (s) + 3 Br2 (g) ? 2 PmBr3 (s)

2 Pm (s) + 3 I2 (g) ? 2 PmI3 (s)

Promethium(III) iodide may also be synthesized by reacting PmX3 (X = Cl, Br) with hydrogen iodide at 400  °C:Sony VAIO VPCF117HG/BI Battery

2 PmX3(s) + 3HI(g) ? PmI3(s) + 3HX(g)

Promethium dissolves readily in dilute sulfuric acid to form solutions containing the pink Pm(III) ions, which exist as a [Pm(OH2)9]3+ complexes:

2 Pm(s) + 3 H2SO4 (aq) ? 2 Pm3+ (aq) + 3 (SO4)2- (aq) + 3 H2 (g)

Promethium(III) ions form an insoluble, hygroscopic oxalate when dissolved in aqueous H2C2O4:Sony VAIO VPCF118FJ/W Battery

2 Pm3+(aq) + C2O42- (aq) ? Pm2(C2O4)3•xH2O(s)

Applications

Uses for promethium include:

• As a beta radiation source for thickness gauges.
• As a light source for signals that require reliable, independent operation (using phosphor to absorb the beta radiation and produce light).Sony VAIO VPCF119FC Battery

• In particular, Promethium(III) chloride (PmCl3) mixed with zinc sulfide (ZnS) was used for a time as a major luminous paint for watches after radium was discontinued. This mixture is still occasionally used for some luminous paint applications (though most such uses requiring radioactive materials have switched to tritium for safety reasons).Sony VAIO VPCF119FC/BI Battery

• In an atomic battery in which cells convert the beta emissions into electric current, yielding a useful life of about five years, usingPm-147.
• Promethium has possible future uses in portable X-ray sources, and as auxiliary heat or power sources for space probes and satellites (although the alpha emitter plutonium-238 has become standard for most space-exploration related uses – see Radioisotope thermoelectric generators).Sony VAIO VPCF119FJ/BI Battery

]Precautions

Promethium must be handled with great care because of its high radioactivity. In particular, promethium can emit X-rays during its beta decay. It is expected to have biological toxicity comparable with beta emitters of similar half-life, for example iodine-131.Sony VAIO VPCF11AFJ Battery

It is not as hazardous as alpha emitters such as the transuranics, due to the far lower relative biological effectiveness of beta emitters over alpha emitters. Promethium has no biological role.

Samarium is a chemical element with the symbol Sm, atomic number 62 and atomic weight 150.36.Sony VAIO VPCF11AGJ Battery

It is a moderately hard silvery metal which readily oxidizes in air. Being a typical member of the lanthanide series, samarium usually assumes the oxidation state +3. Compounds of samarium(II) are also known, most notably monoxide SmO,monochalcogenides SmS, SmSe and SmTe, as well as samarium(II) iodide.Sony VAIO VPCF11AHJ Battery

The last compound is a common reducing agent inchemical synthesis. Samarium has no significant biological role and is only slightly toxic.

Samarium was discovered in 1879 by the French chemist Paul Émile Lecoq de Boisbaudran and named after the mineral samarskitefrom which it was isolated.Sony VAIO VPCF11JFX/B Battery

The mineral itself was earlier named after a Russian mine official, Colonel Vasili Samarsky-Bykhovets, who thereby became the first person to have a chemical element named after him, albeit indirectly. Although classified as a rare earth element, samarium is the 40th most abundant element in the Earth's crust and is more common than such metals as tin.Sony VAIO VPCF11M1E Battery

Samarium occurs with concentration up to 2.8% in several minerals including cerite, gadolinite,samarskite, monazite and bastnäsite, the last two being the most common commercial sources of the element. These minerals are mostly found in China, the USA, Brazil, India, Sri Lanka and Australia; China is by far the world leader in samarium mining and production.Sony VAIO VPCF11M1E/H Battery

The major commercial application of samarium is in samarium-cobalt magnets which have permanent magnetization second only toneodymium magnets; however, samarium compounds can withstand significantly higher temperatures, above 700 °C, without losing their magnetic properties.Sony VAIO VPCF11MFX/B Battery

Radioactive isotope samarium-153 is the major component of the drug samarium (153Sm) lexidronam(Quadramet) which kills cancer cells in the treatment of lung cancer, prostate cancer, breast cancer and osteosarcoma. Another isotope, samarium-149, is a strong neutron absorber and is therefore added to the control rods of nuclear reactors.Sony VAIO VPCF11S1E Battery

It is also formed as a decay product during the reactor operation and is one of the important factors considered in the reactor design and operation. Other applications of samarium include catalysis of chemical reactions, radioactive dating and an X-ray laser.

Physical properties

Samarium is a rare earth metal having the hardness and density similar to those of zinc.Sony VAIO VPCF11S1E/B Battery

With the boiling point of 1794 °C, samarium is the third most volatile lanthanide after ytterbium and europium; this property facilitates separation of samarium from the mineral ore. At ambient conditions, samarium normally assumes a trigonal structure (? form).Sony VAIO VPCF11Z1E Battery

Upon heating to 731 °C, its crystal symmetry changes into hexagonal close-packed (hcp), however the transition temperature depends on the metal purity. Further heating to 922 °C transforms the metal into a body-centered cubic (bcc) phase. Heating to 300 °C combined with compression to 40 kbar results in a double-hexagonal close-packed structure (dhcp).Sony VAIO VPCF11Z1E/BI Battery

Applying higher pressure of the order of hundreds or thousands of kilobars induces a series of phase transformations, in particular with a tetragonal phase appearing at about 900 kbar. In one study, the dhcp phase could be produced without compression, using a nonequilibrium annealing regime with a rapid temperature change between about 400 and 700 °C, confirming the transient character of this samarium phase. Sony VAIO VPCF11ZHJ Battery

Also, thin films of samarium obtained by vapor deposition may contain the hcp or dhcp phases at ambient conditions.

Samarium (and its sesquioxide) are paramagnetic at room temperature. Their corresponding effective magnetic moments, below 2µB, are the 3rd lowest among the lanthanides (and their oxides) after lanthanum and lutetium. The metal transforms to anantiferromagnetic state upon cooling to 14.8 K.Sony VAIO VPCF127HGBI Battery

Individual samarium atoms can be isolated by encapsulating them intofullerene molecules.They can also be doped between the C60molecules in the fullerene solid, rendering it superconductiveat temperatures below 8 K. Samarium doping of iron-based superconductors –Sony VAIO VPCF127HGBI Battery

the most recent class of high-temperature superconductors – allows to enhance their transition temperature to 56 K, which is the highest value achieved so far in this series.

Chemical properties

Freshly prepared samarium has a silvery luster. In air, it slowly oxidizes at room temperature and spontaneously ignites at 150 °C.Sony VAIO VPCF137HG/BI Battery

Even when stored under mineral oil, samarium gradually oxidizes and develops a grayish-yellow powder of theoxide-hydroxide mixture at the surface. The metallic appearance of a sample can be preserved by sealing it under an inert gas such as argon.

Samarium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form samarium hydroxide:Sony VAIO VPC-P111KX/B Battery

2 Sm (s) + 6 H2O (l) ? 2 Sm(OH)3 (aq) + 3 H2 (g)

Samarium dissolves readily in dilute sulfuric acid to form solutions containing the yellow to pale green Sm(III) ions, which exist as [Sm(OH2)9]3+ complexes: 2 Sm (s) + 3 H2SO4 (aq) ? 2 Sm3+ (aq) + 3 SO2?4 (aq) + 3 H2 (g)

Samarium is one of the few lanthanides that exhibit the oxidation state +2. The Sm2+ ions are blood-red in solutions.Sony VAIO VPC-P111KX/D Battery

Oxides

The most stable oxide of samarium is the sesquioxide Sm2O3. As many other samarium compounds, it exists in several crystalline phases. The trigonal form is obtained by slow cooling from the melt.Sony VAIO VPC-P111KX/G Battery

The melting point of Sm2O3 is rather high (2345 °C) and therefore melting is usually achieved not by direct heating, but with induction heating, through a radio-frequency coil. The Sm2O3 crystals of monoclinic symmetry can be grown by the flame fusion method (Verneuil process) from the Sm2O3 powder,Sony VAIO VPC-P111KX/P Battery

that yields cylindrical boules up to several centimeters long and about one centimeter in diameter. The boules are transparent when pure and defect-free and are orange otherwise. Heating the metastable trigonal Sm2O3 to 1900 °C converts it to the more stable monoclinic phase. Cubic Sm2O3 has also been described.Sony VAIO VPC-P111KX/W Battery

Samarium is one of the few lanthanides that form a monoxide, SmO. This lustrous golden-yellow compound was obtained by reducing Sm2O3 with samarium metal at elevated temperature (1000 °C) and pressure above 50 kbar; lowering the pressure resulted in an incomplete reaction. SmO has the cubic rock-salt lattice structure.Sony VAIO VPC-P112KX/B Battery

Chalcogenides

Samarium forms trivalent sulfide, selenide and telluride. Divalent chalcogenides SmS, SmSe and SmTe with cubic rock-salt crystal structure are also known. They are remarkable by converting from semiconducting to metallic state at room temperature upon application of pressure.Sony VAIO VPC-P112KX/D Battery

Whereas the transition is continuous and occurs at about 20–30 kbar in SmSe and SmTe, it is abrupt in SmS and requires only 6.5 kbar. This effect results in spectacular color change in SmS from black to golden yellow when its crystals of films are scratched or polished.Sony VAIO VPC-P112KX/G Battery

The transition does not change lattice symmetry, but there is a sharp decrease (~15%) in the crystal volume.[35] It shows hysteresis, that is when the pressure is released, SmS returns to the semiconducting state at much lower pressure of about 0.4 kbar.[8][36]

Halides

Samarium metal reacts with all the halogens X = F, Cl, Br or I, forming trihalides:Sony VAIO VPC-P112KX/P Battery

2 Sm (s) + 3 X2 (g) ? 2 SmX3 (s)

Their further reduction with samarium, lithium or sodium metals at elevated temperatures (about 700–900 °C) yields dihalides.[27]The diiodide can also be prepared by heating SmI3, or by reacting the metal with 1,2-diiodoethane in anhydrous tetrahydrofuran at room temperature:Sony VAIO VPC-P112KX/W Battery

Sm (s) + ICH2-CH2I ? SmI2 + CH2=CH2

In addition to dihalides, the reduction also produces numerous non-stoichiometric samarium halides with a well-defined crystal structure, such as Sm3F7, Sm14F33, Sm27F64,[26] Sm11Br24, Sm5Br11 and Sm6Br13Sony VAIO VPCP113KX/B Battery

As reflected in the table above, samarium halides change their crystal structures when one type of halide atoms is substituted for another, which is an uncommon behavior for most elements (e. g. actinides). Many halides have two major crystal phases for one composition, one being significantly more stable and another being metastable.Sony VAIO VPC-P113KX/B Battery

The latter is formed upon compression or heating, followed by quenching to ambient conditions. For example, compressing the usual monoclinic samarium diiodide and releasing the pressure results in a PbCl2-type orthorhombic structure (density 5.90 g/cm3), and similar treatment results in a new phase of samarium triiodide (density 5.97 g/cm3).Sony VAIO VPCP113KX/D Battery

Borides

Sintering powders of samarium oxide and boron, in vacuum, yields a powder containing several samarium boride phases, and their volume ratio can be controlled through the mixing proportion.Sony VAIO VPC-P113KX/D Battery

The powder can be converted into larger crystals of a certain samarium boride using arc melting or zone melting techniques, relying on the different melting/crystallization temperature of SmB6 (2580 °C), SmB4 (about 2300 °C) and SmB66 (2150 °C). All these materials are hard, brittle, dark-gray solids with the hardness increasing with the boron content.Sony VAIO VPCP113KX/G Battery

Samarium diboride is too volatile to be produced with these methods and requires high pressure (about 65 kbar) and low temperatures between 1140 and 1240 °C to stabilize its growth. Increasing the temperature results in the preferential formations of SmB6.Sony VAIO VPC-P113KX/G Battery

Samarium hexaboride is a typical intermediate-valence compound where samarium is present both as Sm2+ and Sm3+ ions at the ratio 3:7. It belongs to a class ofKondo insulators, that is at high temperatures (above 50 K), its properties are typical of a Kondo metal, with metallic electrical conductivity characterized by strong electron scattering, whereas at low temperatures, it behaves as a non-magnetic insulator with a narrow band gap of about 4–14 meV.Sony VAIO VPCP118JC/B Battery

The cooling-induced metal-insulator transition in SmB6 is accompanied by a sharp increase in the thermal conductivity, peaking at about 15 K. The reason for this increase is that electrons themselves do not contribute to the thermal conductivity at low temperatures, which is dominated by phonons, but the decrease in electron concentration reduced the rate of electron-phonon scattering.Sony VAIO VPCP118JC/P Battery

Other inorganic compounds

Samarium carbides are prepared by melting a graphite-metal mixture in an inert atmosphere. After the synthesis, they are unstable in air and are studied also under inert atmosphere. Samarium monophosphide SmP is a semiconductor with the bandgap of 1.10 eV, the same as in silicon, and high electrical conductivity of n-type.Sony VAIO VPCP118JC/W Battery

It can be prepared by annealing at 1100 °C an evacuated quartz ampoule containing mixed powders of phosphorus and samarium. Phosphorus is highly volatile at high temperatures and may explode, thus the heating rate has to be kept well below 1 °C/min. Similar procedure is adopted for the monarsenide SmAs, but the synthesis temperature is higher at 1800 °C.Sony VAIO VPC-P118KX/B Battery

A large number of crystalline binary compounds are known for samarium and one of the group-4, 5 or 6 element X, where X is Si, Ge, Sn, Pb, Sb or Te, and metallic alloys of samarium form another large group. They are all prepared by annealing mixed powders of the corresponding elements.Sony VAIO VPC-P118KX/D Battery

Many of the resulting compounds are non-stoichiometric and have nominal compositions SmaXb, where the b/a ratio varies between 0.5 and 3.

Organometallic compounds

Samarium forms a cyclopentadienide Sm(C5H5)3 and its chloroderivatives Sm(C5H5)2Cl and Sm(C5H5)Cl2.Sony VAIO VPC-P118KX/G Battery

They are prepared by reacting samarium trichloride with NaC5H5 intetrahydrofuran. Contrary to cyclopentadienides of most other lanthanides, in Sm(C5H5)3 some C5H5 rings bridge each other by forming ring vertexes ?1 or edges ?2toward another neighboring samarium atom, thereby creating polymeric chains.Sony VAIO VPC-P118KX/P Battery

The chloroderivative Sm(C5H5)2Cl has a dimer structure which is more accurately expressed as (?5-C5H5)2Sm(µ-Cl)2(?5-C5H5)2. There, the chlorine bridges can be replaced, for instance, by iodine, hydrogen or nitrogen atoms or by CN groups.

The (C5H5)– ion in samarium cyclopentadienides can be replaced by the indenide (C9H7)– or cyclooctatetraenide (C8H8)2– ring, resulting in Sm(C9H7)3 or KSm(?8-C8H8)2.Sony VAIO VPC-P118KX/W Battery

The latter compound has a similar structure to that of uranocene. There is also a cyclopentadienide of divalent samarium, Sm(C5H5)2 – a solid which sublimates at about 85 °C. Contrary to ferrocene, the C5H5 rings in Sm(C5H5)2 are not parallel but are tilted by 40°.Sony VAIO VPCP119JC Battery

Alkyls and aryls of samarium are obtained through a metathesis reaction in tetrahydrofuran or ether:[48]

SmCl3 + 3 LiR ? SmR3 + 3 LiCl

Sm(OR)3 + 3 LiCH(SiMe3)2 ? Sm{CH(SiMe3)2}3 + 3 LiOR

Here R is a hydrocarbon group and Me stands for methyl.Sony VAIO VPCP119JC/BI Battery

Naturally occurring samarium has a radioactivity of 128 Bq/g. It is composed of four stable isotopes: 144Sm, 150Sm, 152Sm and 154Sm, and three extremely long-livedradioisotopes, 147Sm (half-life t½ = 1.06×1011 years), 148Sm (7×1015 years) and 149Sm (>2×1015 years), with 152Sm being the most abundant (natural abundance26.75%).Sony VAIO VPCP11S1E/B Battery

149Sm is listed by various sources either as stable  or radioactive isotope.[52]

The long-lived isotopes,146Sm, 147Sm, and 148Sm, primarily decay by emission of alpha particles to isotopes of neodymium. Lighter unstable isotopes of samarium primarily decay by electron capture to isotopes of promethium, while heavier ones convert through beta decay to isotopes of europium.Sony VAIO VPC-P11S1E/B Battery

The alpha-decay of 147Sm to 143Nd with a half-life of 1.06×1011 years serve for samarium-neodymium dating

The half-lives of 151Sm and 145Sm are 90 years and 340 days, respectively. All of the remaining radioisotopes have half-lives that are less than 2 days, and the majority of these have half-lives that are less than 48 seconds.Sony VAIO VPCP11S1E/D Battery

Samarium also has five nuclear isomers with the most stable being 141mSm (half-life 22.6 minutes),143m1Sm (t½ = 66 seconds) and 139mSm (t½ = 10.7 seconds).

Detection of samarium and related elements was announced by several scientists in the second half of the 19th century; Sony VAIO VPC-P11S1E/D Battery

however, most sources give the priority to the French chemist Paul Émile Lecoq de Boisbaudran.[53][54] Boisbaudran isolated samarium oxide and/or hydroxide in Paris in 1879 from the mineral samarskite ((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16) and identified a new element in it via sharp optical absorption lines.Sony VAIO VPCP11S1E/G Battery

The Swiss chemist Marc Delafontaine announced a new element decipium (from Latin: decipiens meaning "deceptive, misleading") in 1878, but later in 1880–1881 demonstrated that it was a mixture of several elements, one being identical to the Boisbaudran's samarium.Sony VAIO VPC-P11S1E/G Battery

Although samarskite was first found in the remote Russian region of Urals, by the late 1870s its deposits had been located in other places making the mineral available to many researchers. In particular, it was found that the samarium isolated by Boisbaudran was also impure and contained comparable amount of europium.Sony VAIO VPCP11S1E/P Battery

The pure element was produced only in 1901 byEugène-Anatole Demarçay.

Boisbaudran named his element samaria after the mineral samarskite, which in turn honored Vasili Samarsky-Bykhovets (1803–1870). Samarsky-Bykhovets was the Chief of Staff of the Russian Corps of Mining Engineers who granted access for the German mineralogists, brothers Gustav Rose and Heinrich Rose, to study the mineral samples from the Urals.Sony VAIO VPCP11S1E/W Battery

In this sense samarium was the first chemical element to be named after a person. Later the name samaria used by Boisbaudran was transformed into samarium, to conform with other element names, and samaria nowadays is sometimes used to refer to samarium oxide, by analogy with yttria, zirconia, alumina,ceria, holmia, etc.Sony VAIO VPC-P11S1E/W Battery

The symbol Sm was suggested for samarium; however an alternative Sa was frequently used instead until the 1920s.

Prior to the advent of ion-exchange separation technology in the 1950s, samarium had no commercial uses in pure form.Sony VAIO VPCP11Z9E/B Battery

However, a by-product of the fractional crystallization purification of neodymium was a mixture of samarium and gadolinium that acquired the name of "Lindsay Mix" after the company that made it. This material is thought to have been used for nuclear control rods in some of the early nuclear reactors.Sony VAIO VPCS111FM/S Battery

Nowadays, a similar commodity product has the name "samarium-europium-gadolinium" (SEG) concentrate.[63] It is prepared by solvent extraction from the mixed lanthanides isolated from bastnäsite (or monazite). Since the heavier lanthanides have the greater affinity for the solvent used, they are easily extracted from the bulk using relatively small proportions of solvent.Sony VAIO VPCS115EC Battery

Not all rare earth producers who process bastnäsite do so on large enough scale to continue onward with the separation of the components of SEG, which typically makes up only one or two percent of the original ore. Such producers will therefore be making SEG with a view to marketing it to the specialized processors.Sony VAIO VPCS115FG Battery

In this manner, the valuable europium content of the ore is rescued for use in phosphor manufacture. Samarium purification follows the removal of the europium. Currently, being in oversupply, samarium oxide is less expensive on a commercial scale than its relative abundance in the ore might suggest.Sony VAIO VPCS117GG Battery

Occurrence and production

With the average concentration of about 8 parts per million (ppm), samarium is the 40th most abundant element in the Earth's crust. It is the fifth most abundant lanthanide and is more common than such element as tin. Samarium concentration in soils varies between 2 and 23 ppm, and oceans contain about 0.5–0.8 parts per trillion.Sony VAIO VPCS117GGB Battery

Distribution of samarium in soils strongly depends on its chemical state and is very inhomogeneous: in sandy soils, samarium concentration is about 200 times higher at the surface of soil particles than in the water trapped between them, and this ratio can exceed 1,000 in clays.Sony VAIO VPCS118EC Battery

Samarium is not found free in nature, but, like other rare earth elements, is contained in many minerals, including monazite,bastnäsite, cerite, gadolinite and samarskite; monazite (in which samarium occurs at concentrations of up to 2.8%)[9] and bastnäsite are mostly used as commercial sources.Sony VAIO VPCS119FJ/B Battery

World resources of samarium are estimated at two million tonnes; they are mostly located in China, US, Brazil, India, Sri Lanka and Australia, and the annual production is about 700 tonnes. Country production reports are usually given for all rare-earth metals combined.Sony VAIO VPCS119GC Battery

By far, China has the largest production with 120,000 tonnes mined per year; it is followed by the US (about 5,000 tonnes)[66] and India (2,700 tonnes). Samarium is usually sold as oxide, which at the price of about 30 USD/kg is one of the cheapest lanthanide oxides.Sony VAIO VPCS11AFJ Battery

Whereas mischmetal – a mixture of rare earth metals containing about 1% of samarium – has long been used, relatively pure samarium has been isolated only recently, through ion exchange processes, solvent extraction techniques, andelectrochemical deposition.Sony VAIO VPCS11AGJ Battery

The metal is often prepared by electrolysis of a molten mixture of samarium(III) chloride with sodium chloride or calcium chloride. Samarium can also be obtained by reducing its oxide with lanthanum. The product is then distilled to separate samarium (boiling point 1794 °C) and lanthanum (b. p. 3464 °C).Sony VAIO VPCS11AHJ Battery

Samarium-151 is produced in nuclear fission of uranium with the yield of about 0.4% of the total number of fission events. It is also synthesized upon neutron capture by samarium-149, which is added to the control rods of nuclear reactors. Consequently, samarium-151 is present in spent nuclear fuel and radioactive waste.Sony VAIO VPCS11AVJ Battery

Applications

One of the most important applications of samarium is in samarium-cobalt magnets, which have a nominal composition of SmCo5 or Sm2Co17. They have high permanent magnetization, which is about 10,000 times that of iron and is second only to that of neodymium magnets.Sony VAIO VPCS11J7E/B Battery

However, samarium-based magnets have higher resistance to demagnetization, as they are stable to temperatures above 700 °C (cf. 300–400 °C for neodymium magnets). These magnets are found in small motors, headphones, high-end magnetic pickups for guitars and related musical instruments.Sony VAIO VPCS11M1E/W Battery

For example, they are used in the motors of a solar-powered electric aircraft Solar Challenger and in the Samarium Cobalt Noiseless electric guitar and bass pickups.

Another important application of samarium and its compounds is as catalyst and chemical reagent.Sony VAIO VPCS11V9E Battery

Samarium catalysts assist decomposition of plastics, dechlorination of pollutants such as polychlorinated biphenyls (PCBs), as well as the dehydration anddehydrogenation of ethanol. Samarium(III) triflate (Sm(OTf)3, that is Sm(CF3SO3)3) is one of the most efficient Lewis acidcatalysts for a halogen-promoted Friedel–Crafts reaction with alkenes.Sony VAIO VPCS11V9E/B Battery

Samarium(II) iodide is a very common reducing and coupling agent in organic synthesis, for example in the desulfonylation reactions; annulation; Danishefsky, Kuwajima, Mukaiyamaand Holton Taxol total syntheses; strychnine total synthesis; Barbier reaction and other reductions with samarium(II) iodide.Sony VAIO VPCS11X9E/B Battery

In its usual oxidized form, samarium is added to ceramics and glasses where it increases absorption of infrared light. As a (minor) part of mischmetal, samarium is found in "flint" ignition device of many lighters and torches.

Radioactive samarium-153 is a beta emitter with a half-life of 46.3 hours.Sony VAIO VPCS123FGB Battery

It is used to kill cancer cells in the treatment oflung cancer, prostate cancer, breast cancer and osteosarcoma. For this purpose, samarium-153 is chelated with ethylene diamine tetramethylene phosphonate (EDTMP) and injected intravenously. The chelation prevents accumulation of radioactive samarium in the body that would result in excessive irradiation and generation of new cancer cells.Sony VAIO VPCS125EC Battery

The corresponding drug has several names including samarium (153Sm) lexidronam and its trade name is Quadramet.

Samarium-149 has high cross-section for neutron capture (41,000 barns) and is therefore used in the control rods of nuclear reactors.Sony VAIO VPCS128EC Battery

Its advantage compared to competing materials, such as boron and cadmium, is stability of absorption – most of the fusion and decay products of samarium-149 are other isotopes of samarium which are also good neutron absorbers. For example, the cross sections of samarium-151 is 15,000 barns, Sony VAIO VPCS129GC Battery

it is on the order of hundred barns for samarium-150, 152, 153, and is 6,800 barns for natural (mixed-isotope) samarium. Among the decay products in a nuclear reactor, samarium-149 is regarded as the second most important for the reactor design and operation after xenon-135.Sony VAIO VPCS12C7E/B Battery

Non-commercial and potential applications

Samarium-doped calcium fluoride crystals were used as an active medium in one of the first solid-state lasers designed and constructed by Peter Sorokin (co-inventor of the dye laser) and Mirek Stevenson at IBM research labs in early 1961.Sony VAIO VPCS12L9E/B Battery

This samarium laser emitted pulses of red light at 708.5 nm. It had to be cooled by liquid helium and thus did not find practical applications.

Another samarium-based laser became the first saturated X-ray laser operating at wavelengths shorter than 10 nanometers.Sony VAIO VPCS12V9E/B Battery

It provided 50-picosecond pulses at 7.3 and 6.8 nm suitable for applications in holography, high-resolution microscopy of biological specimens, deflectometry, interferometry and radiography of dense plasmas related to confinement fusion and astrophysics.Sony VAIO VPCW111XX/P Battery

Saturated operation meant that the maximum possible power was extracted from the lasing medium, resulting in the high peak energy of 0.3 mJ. The active medium was samarium plasma produced by irradiating samarium-coated glass with a pulsed infrared Nd-glass laser (wavelength ~1.05 µm).Sony VAIO VPCW111XX/PC Battery

The change in electrical resistivity in samarium monochalcogenides can be used in a pressure sensor or in a memory device triggered between a low-resistance and high-resistance state by external pressure,  and such devices are being developed commercially.Sony VAIO VPCW111XX/T Battery

Samarium monosulfide also generates electric voltage upon moderate heating to about 150 °C that can be applied in thermoelectric power converters.

The analysis of relative concentrations of samarium and neodymium isotopes 147Sm, 144Nd and 143Nd allows the determination of the age and origin of rocks and meteorites in samarium-neodymium dating.Sony VAIO VPCW111XX/W Battery

Both elements are lanthanides and have very similar physical and chemical properties. Therefore, Sm-Nd dating is either insensitive to partitioning of the marker elements during various geological processes, or such partitioning can well be understood and modeled from the ionic radiiof the involved elements.Sony VAIO VPCW111XXP Battery

Health issues

Samarium metal has no biological role in human body. Its salts stimulate metabolism, but it is unclear whether this is the effect of samarium or other lanthanides present with it. The total amount of samarium in adults is about 50 micrograms, mostly in liver and kidneys and with about 8 micrograms per liter being dissolved in the blood.Sony VAIO VPCW111XXT Battery

Samarium is not absorbed by plants to a measurable concentration and therefore is normally not a part of human diet. However, a few plants and vegetables may contain up to 1 part per million of samarium. Insoluble salts of samarium are non-toxic and the soluble ones are only slightly toxic.Sony VAIO VPCW111XXW Battery

When ingested, only about 0.05% of samarium salts is absorbed into the bloodstream and the remainder is excreted. From the blood, about 45% goes to the liver and 45% is deposited on the surface of the bones where it remains for about 10 years; the balance 10% is excreted.Sony VAIO VPCW115XG Battery,Sony VAIO VPCW115XGP Battery,Sony VAIO VPCW115XW/P Battery,Sony VAIO VPCW115XW/T Battery,Sony VAIO VPCW115XW/W Battery,Sony VAIO VPCW117XC/P Battery

 

Caesium,Barium,Lanthanum,Cerium

Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of 28 °C (82 °F), which makes it one of only five elemental metals that are liquid at (or near) room temperature.Sony VAIO VPCEB17FX/G Battery

Caesium is an alkali metal and has physical and chemical properties similar to those of rubidium and potassium. The metal is extremely reactive and pyrophoric, reacting with water even at ?116 °C (?177 °F). It is the least electronegative element that has stable isotopes, of which it has only one, caesium-133.Sony VAIO VPCEB17FX/L Battery

Caesium is mined mostly from pollucite, while the radioisotopes, especially caesium-137, a fission product, are extracted from waste produced by nuclear reactors.

Two German chemists, Robert Bunsen and Gustav Kirchhoff, discovered caesium in 1860 by the newly developed method of flame spectroscopy.Sony VAIO VPCEB17FX/P Battery

The first small-scale applications for caesium have been as a "getter" in vacuum tubes and in photoelectric cells. In 1967, a specific frequency from the emission spectrum of caesium-133 was chosen to be used in the definition of thesecond by the International System of Units. Since then, caesium has been widely used in atomic clocks.Sony VAIO VPCEB17FX/W Battery

Since the 1990s, the largest application of the element has been as caesium formate for drilling fluids. It has a range of applications in the production of electricity, in electronics, and in chemistry. The radioactive isotope caesium-137 has ahalf-life of about 30 years and is used in medical applications, industrial gauges, and hydrology.Sony VAIO VPCEB190X Battery

Although the element is only mildly toxic, it is a hazardous material as a metal and its radioisotopes present a high health risk in case of radiation leaks.

Physical properties

Caesium is a very soft (it has the lowest Mohs hardness of all elements (0.2)), veryductile, silvery-white metal, which develops a silvery-gold hue in the presence of trace amounts of oxygen.Sony VAIO VPCEB19FX Battery

It has a melting point of 28.4 °C (83.1 °F), making it one of the few elemental metals which are liquid near room temperature. Mercury is the only elemental metal with a known melting point lower than caesium. In addition, the metal has a rather low boiling point, 641 °C (1,186 °F), the lowest of all metals other than mercury. Its compounds burn with a blue color.Sony VAIO VPCEB19GX Battery

Caesium forms alloys with the other alkali metals as well as with gold, and amalgams with mercury. At temperatures below 650 °C (1,202 °F), it alloys with cobalt, iron,molybdenum, nickel, platinum, tantalum or tungsten. It forms well-defined intermetallic compounds with antimony, gallium, indium and thorium, which are photosensitive.Sony VAIO VPCEB1AFX Battery

It mixes with the other alkali metals (except with lithium), and the alloy with a molardistribution of 41% caesium, 47% potassium, and 12% sodium has the lowest melting point of any known metal alloy, at ?78 °C (?108 °F). A few amalgams have been studied:CsHg2is black with a purple metallic lustre, while CsHg is golden-coloured, also with a metallic lustre.Sony VAIO VPCEB1AFX/B Battery

Chemical properties

Caesium metal is highly reactive and very pyrophoric. In addition to igniting spontaneously in air, it reacts explosively with water even at low temperatures, more so than other members of the first group of the periodic table. The reaction with solid water occurs at temperatures as low as ?116 °C (?177 °F).Sony VAIO VPCEB1AGX Battery

Because of its high reactivity, the metal is classified as a hazardous material. It is stored and shipped in dry saturated hydrocarbons such as mineral oil. Similarly, it must be handled under inert atmosphere such as argon. It can be stored in vacuum-sealed borosilicate glass ampoules. In quantities of more than about 100 grams (3.5 oz), caesium is shipped in hermetically sealed stainless steel containers.Sony VAIO VPCEB1AGX/BI Battery

The chemistry of caesium is similar to that of other alkali metals, but is more closely similar to that of rubidium, the element above caesium in the periodic table. Some small differences arise from the fact that it has a higher atomic mass and is moreelectropositive than other (non-radioactive) alkali metals. Caesium is the most electropositive stable chemical element.Sony VAIO VPCEB1BGX Battery

The caesium ion is also larger and less "hard" than those of the lighter alkali metals.

Compounds

The vast majority of caesium compounds contain the element as the cation Cs+, which binds ionicallyto a wide variety of anions. One noteworthy exception is provided by the caeside anion (Cs?). Other exceptions include the several suboxides (see section on oxides below).Sony VAIO VPCEB1BGX/BI Battery

Returning to more normal compounds, salts of Cs+ are almost invariably colorless unless the anion itself is colored. Many of the simple salts are hygroscopic, but less so than the corresponding salts of the lighter alkali metals. The acetate, carbonate, halides, oxide, nitrate, and sulfatesalts are water-soluble.Sony VAIO VPCEB1CGX Battery

Double salts are often less soluble, and the low solubility of caesium aluminium sulfate is exploited in the purification of Cs from its ores. The double salt with antimony (such as CsSbCl4), bismuth, cadmium, copper, iron, and lead are also poorly soluble.

Caesium hydroxide (CsOH) is hygroscopic and a very strong base.Sony VAIO VPCEB1CGX/BI Battery

It rapidly etches the surface ofsemiconductors such as silicon. CsOH has been previously regarded by chemists as the "strongest base", reflecting the relatively weak attraction between the large Cs+ ion and OH–.;it is indeed the strongest Arrhenius base, but a number of compounds that cannot exist in aqueous solution, such as n-butyllithiumand sodium amide,are more basic.Sony VAIO VPCEB1DGX Battery

A stoichiometric mixture of caesium and gold will react to form caesium auride.

Complexes

Like all metal cations, Cs+ forms complexes with Lewis bases in solution. Because of its large size, Cs+ usually adopts coordination numbers greater than six-coordination, which is typical for the lighter alkali metal cations.Sony VAIO VPCEB1DGX/BI Battery

This trend is already apparent by the 8-coordination in CsCl, vs the halite motif adopted by the other alkali metal chlorides. Its high coordination number and softness (tendency to form covalent bonds) are the basis of the separation of Cs+ from other cations, as is practiced in the remediation of nuclear wastes, where 137Cs+ is separated from large amounts of non-radioactive K+.Sony VAIO VPCEB1EGX Battery

Halides

Caesium chloride (CsCl) crystallizes in the simple cubic crystal system. Also called the "caesium chloride structure", this structural motif is composed of aprimitive cubic lattice with a two-atom basis, each with an eightfold coordination; the chloride atoms lie upon the lattice points at the edges of the cube, while the caesium atoms lie in the holes in the center of the cubes.Sony VAIO VPCEB1EGX/BI Battery

This structure is shared with CsBr and CsI, and many other compounds that do not contain Cs. In contrast, most other alkaline halides adopt the sodium chloride (NaCl) structure.[16] The CsCl structure is preferred because Cs+ has an ionic radius of 174 pm andCl?181 pm.Sony VAIO VPCEB1FGX Battery

Oxides

More so than the other alkali metals, caesium forms numerous binary compounds with oxygen. When caesium burns in air, the superoxide CsO2 is the main product. The "normal" caesium oxide (Cs2O) forms yellow-orange hexagonal crystals, and is the only oxide of the anti-CdCl2 type.Sony VAIO VPCEB1FGX/BI Battery

It vaporizes at 250 °C (482 °F), and decomposes to caesium metal and the peroxide Cs2O2 at temperatures above 400 °C (752 °F).[25] Aside from the superoxide and the ozonide CsO3, several brightly colored suboxides have also been studied. These include Cs7O, Cs4O, Cs11O3, Cs3O (dark-green ), CsO, Cs3O2,[30] as well as Cs7O2.Sony VAIO VPCEB1GGX Battery

The latter may be heated under vacuum to generate Cs2O.[24] Binary compounds with sulfur,selenium, and tellurium also exist.

Caesium has a total of 39 known isotopes that range in their mass number (i.e. number of nucleons in its nucleus) from 112 to 151.Sony VAIO VPCEB1GGX/BI Battery

Several of these are synthesized from lighter elements by the slow neutron capture process (S-process) inside old stars, as well as inside supernova explosions (R-process). However, the onlystable isotope is 133Cs, which has 78 neutrons. Although it has a large nuclear spin (7/2+), nuclear magnetic resonance studies can be done with this isotope at a resonating frequency of 11.7 MHz.Sony VAIO VPCEB1HGX Battery

while 137Cs and 134Cs have half-lives of 30 and 2 years, respectively. 137Cs decomposes to a short-lived 137mBa by beta decay, and then to non-radioactive barium, while 134Cs transforms into 134Ba directly. The isotopes with mass numbers of 129, 131, 132 and 136, have half-times between a day and two weeks, while most of the other isotopes have half-lives from a few seconds to fractions of a second.Sony VAIO VPCEB1HGX/BI Battery

There are at least 21 metastable nuclear isomers. Other than 134mCs (with a half-life of just under 3 hours), all are very unstable and decay with half-lives of a few minutes or less.

The isotope 135Cs is one of the long-lived fission products of uranium which form in nuclear reactors.Sony VAIO VPCEB1JFX Battery

However, itsfission product yield is reduced in most reactors because its predecessor, 135Xe, is an extremely potent neutron poison and transmutes frequently to stable 136Xe before it can decay to 135Cs.

Because of its beta decay (to 137mBa), 137Cs is a strong emitter of gamma radiation.Sony VAIO VPCEB1JFX/B Battery

Its half-life makes it the principalmedium-lived fission product along with 90Sr—both are responsible for radioactivity of spent nuclear fuel after several years of cooling up to several hundred years after use. For example 137Cs together with 90Sr currently generate the largest source of radioactivity generated in the area around the Chernobyl disaster.Sony VAIO VPCEB1JFX/G Battery

It is not feasible to dispose of 137Cs through neutron capture (due to the low capture rate) and as a result it must be allowed to decay.

Almost all caesium produced from nuclear fission comes from beta decay of originally more neutron-rich fission products, passing through various isotopes of iodineand of xenon.Sony VAIO VPCEB1JFX/L Battery

Because iodine and xenon are volatile and can diffuse through nuclear fuel or air, radioactive caesium is often created far from the original site of fission.[46] With the commencement of nuclear weapons testing around 1945, 137Cs was released into the atmosphere and then returned to the surface of the earth as a component of radioactive fallout.Sony VAIO VPCEB1JFX/P Battery

Occurrence

Caesium is a relatively rare element as it is estimated to average approximately 3 parts per million in the Earth's crust. This makes it the 45th most abundant of all elements and the 36th of all the metals.Sony VAIO VPCEB1JFX/W Battery

Nevertheless, it is more abundant than such elements as antimony, cadmium, tin and tungsten, and two orders of magnitude more abundant than mercury or silver, but 30 times less abundant than rubidium—with which it is so closely chemically associated.

Due to its large ionic radius, caesium is one of the "incompatible elements."Sony VAIO VPCEB1KGX Battery

During magma crystallization, caesium is concentrated in the liquid phase and crystallizes last. Therefore the largest deposits of caesium are zone pegmatite ore bodies formed by this enrichment process. Because caesium does not substitute for potassium as readily as does rubidium, the alkali evaporite minerals sylvite (KCl) and carnallite (KMgCl3·6H2O) may contain only 0.002% caesium.Sony VAIO VPCEB1KGX/B Battery

Consequently, Cs is found in few minerals. Percent amounts of caesium may be found in beryl (Be3Al2(SiO3)6) and avogadrite ((K,Cs)BF4), up to 15 wt% Cs2O in the closely related mineral pezzottaite (Cs(Be2Li)Al2Si6O18), up to 8.4 wt% Cs2O in the rare mineral londonite ((Cs,K)Al4Be4(B,Be)12O28), and less in the more widespreadrhodizite.Sony VAIO VPCEB1KGX/W Battery

The only economically important source mineral for caesium is pollucite Cs(AlSi2O6), which is found in a few places around the world in zoned pegmatites, and is associated with the more commercially important lithium minerals lepidolite and petalite. Within the pegmatites, the large grain size and the strong separation of the minerals create high-grade ore for mining.Sony VAIO VPCEB1LFX Battery

One of the world's most significant and richest sources of the metal is the Tanco mine at Bernic Lake in Manitoba, Canada. The deposits there are estimated to contain 350,000 metric tons of pollucite ore, which represents more than two-thirds of the world's reserve base.Sony VAIO VPCEB1LFX/BI Battery

Although the stoichiometric content of caesium in pollucite is 42.6%, pure pollucite samples from this deposit contain only about 34% caesium, while the average content is 24 wt%. Commercial pollucite contains over 19% caesium. The Bikita pegmatite deposit in Zimbabwe is mined for its petalite but it also contains a significant amount of pollucite.Sony VAIO VPCEB1LFX/WI Battery

Notable amounts of pollucite are also mined in the Karibib Desert, Namibia.[50] At the present rate of world mine production of 5 to 10 metric tons per year, reserves will last for thousands of years.

Production

The mining of pollucite ore is a selective process and is conducted on a small scale in comparison with most metal mining operations.Sony VAIO VPCEB1MFX Battery

The ore is crushed, hand-sorted, but not usually concentrated, and then ground. Caesium is then extracted from pollucite mainly by three methods: acid digestion, alkaline decomposition, and direct reduction.

In the acid digestion, the silicate pollucite rock is dissolved with strong acids such as hydrochloric (HCl), sulfuric (H2SO4), hydrobromic (HBr), or hydrofluoric(HF).Sony VAIO VPCEB1MFX/BI Battery

With hydrochloric acid, a mixture of soluble chlorides is produced, and the insoluble chloride double salts of caesium are precipitated as caesium antimony chloride (Cs4SbCl7), caesium iodine chloride (Cs2ICl), or caesium hexachlorocerate (Cs2(CeCl6)). After separation, the pure precipitated double salt is decomposed, and pure CsCl is obtained after evaporating the water.Sony VAIO VPCEB1NFX Battery

The method using sulfuric acid yields the insoluble double salt directly as caesium alum (CsAl(SO4)2·12H2O). The aluminium sulfate in it is converted to the insoluble aluminium oxide by roasting the alum with carbon, and the resulting product is leached with water to yield a Cs2SO4 solution.Sony VAIO VPCEB1NFX/B Battery

The roasting of pollucite with calcium carbonate and calcium chloride yields insoluble calcium silicates and soluble caesium chloride. Leaching with water or diluteammonia (NH4OH) yields then a dilute chloride (CsCl) solution. This solution can be evaporated to produce caesium chloride or transformed into caesium alum or caesium carbonate.Sony VAIO VPCEB1NFX/L Battery

Albeit not commercially feasible, direct reduction of the ore with potassium, sodium or calcium in vacuum can produce caesium metal directly.

Most of the mined caesium (as salts) is directly converted into caesium formate (HCOO?Cs+) for applications such as oil drilling.Sony VAIO VPCEB1NFX/P Battery

To supply the developing market,Cabot Corporation built a production plant in 1997 at the Tanco Mine near Bernic Lake in Manitoba, Canada, with a capacity of 12,000 barrels (1,900 m3) per year of caesium formate solution.[53] The primary smaller-scale commercial compounds of caesium are caesium chloride and its nitrate.Sony VAIO VPCEB1NFX/W Battery

Alternatively, caesium metal may be obtained from the purified compounds derived from the ore. Caesium chloride, and the other caesium halides as well, can be reduced at 700 to 800 °C (1,292 to 1,472 °F) with calcium or barium, followed by distillation of the caesium metal.Sony VAIO VPCEB1PFX Battery

In the same way, the aluminate, carbonate, or hydroxide may be reduced by magnesium.[7] The metal can also be isolated by electrolysis of fused caesium cyanide (CsCN). Exceptionally pure and gas-free caesium can be made by the thermal decomposition at 390 °C (734 °F) of caesium azide CsN3, which is produced from aqueous caesium sulfate and barium azide.Sony VAIO VPCEB1PFX/B Battery

In vacuum applications, caesium dichromate can be reacted with zirconium forming pure caesium metal without other gaseous products.

Cs2Cr2O7 + 2 Zr ? 2 Cs + 2 ZrO2+ Cr2O3

The price of 99.8% pure caesium (metal basis) in 2009 was about US$10 per gram ($280 per ounce), but its compounds are significantly cheaper.Sony VAIO VPCEB1QGX Battery

In 1860, Robert Bunsen and Gustav Kirchhoff discovered caesium in the mineral water from Dürkheim, Germany. Due to the bright blue lines in its emission spectrum, they chose a name derived from the Latin word caesius, meaning sky-blue. Caesium was the first element to be discovered spectroscopically, only one year after the invention of the spectroscope by Bunsen and Kirchhoff.Sony VAIO VPCEB1QGX/BI Battery

To obtain a pure sample of caesium, 44,000 litres (9,700 imp gal; 12,000 US gal) of mineral water had to be evaporated to yield 240 kilograms (530 lb) of concentrated salt solution. The alkaline earth metals were precipitated either as sulfates or oxalates, leaving the alkali metal in the solution.Sony VAIO VPCEB1RGX Battery

After conversion to the nitrates and extraction with ethanol, a sodium-free mixture was obtained. From this mixture, the lithium was precipitated by ammonium carbonate. Potassium, rubidium and caesium form insoluble salts with chloroplatinic acid, but these salts show a slight difference in solubility in hot water.Sony VAIO VPCEB1RGX/BI Battery

Therefore, the less-soluble caesium and rubidium hexachloroplatinate ((Cs,Rb)2PtCl6) could be obtained by fractional crystallization. After reduction of the hexachloroplatinate with hydrogen, caesium and rubidium could be separated by the difference in solubility of their carbonates in alcohol.Sony VAIO VPCEB20 Battery

The process yielded 9.2 grams (0.32 oz) of rubidium chloride and 7.3 grams (0.26 oz) of caesium chloride from the initial 44,000 liters of mineral water.

The two scientists used the caesium chloride thus obtained to estimate the atomic weight of the new element at 123.35 (compared to the currently accepted one of 132.9).Sony VAIO VPCEC20 Battery

They tried to generate elemental caesium by electrolysis of molten caesium chloride, but instead of a metal, they obtained a blue homogenous substance which "neither under the naked eye nor under the microscope" showed the slightest trace of metallic substance;" as a result, they assigned it as a subchloride (Cs2Cl).Sony VAIO VPCEE20 Battery

In reality, the product was probably a colloidal mixture of the metal and caesium chloride.[58] The electrolysis of the aqueous solution of chloride with a mercury anode produced a caesium amalgam which readily decomposed under the aqueous conditions.Sony VAIO VPCEF20 Battery

The pure metal was eventually isolated by the German chemist Carl Setterberg while working on his doctorate with Kekulé and Bunsen. In 1882 he produced caesium metal by electrolyzing caesium cyanide, and thus avoiding the problems with the chloride.Sony VAIO VPCF112FX/B Battery

Historically, the most important use for caesium has been in research and development, primarily in chemical and electrical fields. Very few applications existed for caesium until the 1920s when it became used in radio vacuum tubes. It had two functions: as a getter it removed excess oxygen after manufacture, and as a coating on the heated cathode, it increased its electrical conductivity.Sony VAIO VPCF115FG/B Battery

Caesium did not become recognized as a high-performance industrial metal until the 1950s. Applications of non-radioactive caesium included photoelectric cells, photomultiplier tubes, optical components of infrared spectrophotometers, catalysts for several organic reactions, crystals for scintillation counters, and in magnetohydrodynamic power generators.Sony VAIO VPCF116FGBI Battery

Since 1967, the International System of Measurements has based its unit of time, the second, on the properties of caesium. The International System of Units (SI) defines the second as 9,192,631,770 cycles of the radiation, which corresponds to the transition between two hyperfine energy levels of the ground state of the caesium-133 atom.Sony VAIO VPCF117FJ/W Battery

The 13th General Conference on Weights and Measures of 1967 defined a second as: "the duration of 9,192,631,770 cycles of microwave light absorbed or emitted by the hyperfine transition of caesium-133 atoms in their ground state undisturbed by external fields".Sony VAIO VPCF117HG/BI Battery

Petroleum exploration

The largest current end-use of non-radioactive caesium is in caesium formate-based drilling fluids for the extractive oil industry. Aqueous solutions of caesium formate (HCOO–Cs+)—made by reacting caesium hydroxide with formic acid—were developed in the mid-1990s for use as oil well drilling and completion fluids.Sony VAIO VPCF118FJ/W Battery

The function of caesium formate as a drilling fluid is to lubricate drill bits, to bring rock cuttings to the surface, and to maintain pressure on the formation during drilling of the well. As completion fluid, which assists the emplacement of control hardware after drilling but prior to production, the function of caesium formate is to maintain the pressure.Sony VAIO VPCF119FC Battery

The high density of the caesium formate brine (up to 2.3 g·cm?3, or 19.2 pounds per gallon), coupled with the relatively benign nature of most caesium compounds, reduces the requirement for toxic high-density suspended solids in the drilling fluid—a significant technological, engineering and environmental advantage.Sony VAIO VPCF119FC/BI Battery

Unlike the components of many other heavy liquids, caesium formate is relatively environment-friendly.The caesium formate brine can be blended with potassium and sodium formates to decrease the density of the fluids down to that of water (1.0 g·cm?3, or 8.3 pounds per gallon).Sony VAIO VPCF119FJ/BI Battery

Furthermore, it is biodegradable and reclaimable, and may be recycled, which is important in view of its high cost (about $4,000 per barrel in 2001). Alkali formates are safe to handle and do not damage the producing formation or downhole metals as their corrosive alternative, high-density brines (such as zinc bromide ZnBr2 solutions),sometimes do; they also require less cleanup and disposal costs.Sony VAIO VPCF11AFJ Battery

Atomic clocks

Caesium-based atomic clocks observe electromagnetic transitions in the hyperfine structure of caesium-133 atoms and use it as a reference point. The first accurate caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.Sony VAIO VPCF11AGJ Battery

Since then, they have been improved repeatedly over the past half-century, and form the basis for standards-compliant time and frequency measurements. These clocks measure frequency with an error of 2 to 3 parts in 1014, which would correspond to a time measurement accuracy of 2 nanoseconds per day, or one second in 1.4 million years.Sony VAIO VPCF11AHJ Battery

The latest versions are accurate to better than 1 part in 1015, which means they would be off by about 2 seconds since the extinction of the dinosaurs 65 million years ago,[7] and has been regarded as "the most accurate realization of a unit that mankind has yet achieved.Sony VAIO VPCF11JFX/B Battery

Caesium clocks are also used in networks that oversee the timing of cell phone transmissions and the information flow on the Internet.

Electric power and electronics

Caesium vapor thermionic generators are low-power devices that convert heat energy to electrical energy.Sony VAIO VPCF11M1E Battery

In the two-electrodevacuum tube converter, it neutralizes the space charge that builds up near the cathode, and in doing so, it enhances the current flow.

Caesium is also important for its photoemissive properties by which light energy is converted to electron flow.Sony VAIO VPCF11M1E/H Battery

It is used inphotoelectric cells because caesium-based cathodes such as the intermetallic compound K2CsSb have low threshold voltage for emission of electrons.[67] The range of photoemissive devices using caesium include optical character recognition devices,photomultiplier tubes, and video camera tubes.Sony VAIO VPCF11MFX/B Battery

Nevertheless, germanium, rubidium, selenium, silicon, tellurium, and several other elements can substitute caesium in photosensitive materials.

Caesium iodide (CsI), bromide (CsBr) and caesium fluoride (CsF) crystals are employed for scintillators in scintillation counterswidely used in mineral exploration and particle physics research as they are well suited for the detection of gamma and x-rayradiation.Sony VAIO VPCF11S1E Battery

Caesium, being a heavy element, provides good stopping power contributing to better detectivity. Caesium compounds may also provide a faster response (CsF) and be less hygroscopic (CsI).

Caesium vapor is used in many common magnetometers.[70] The element is also used as an internal standard in spectrophotometry.Sony VAIO VPCF11S1E/B Battery

Like other alkali metals, caesium has a great affinity for oxygen and is used as a "getter" in vacuum tubes.[72] Other uses of the metal include high-energy lasers,vapor glow lamps, and vapor rectifiers.[7]

Centrifugation fluids

Because of their high density, solutions of caesium chloride (CsCl), sulfate (Cs2SO4), and trifluoroacetate (Cs(O2CCF3)) are commonly used in molecular biology for density gradient ultracentrifugation.Sony VAIO VPCF11Z1E Battery

This technology is primarily applied to the isolation of viral particles, sub-cellular organelles and fractions, andnucleic acids from biological samples.[74]

Chemical and medical use

Relatively few chemical applications exist for caesium.Sony VAIO VPCF11Z1E/BI Battery

Doping with caesium compounds is used to enhance the effectiveness of several metal-ion catalysts used in the production of chemicals, such as acrylic acid, anthraquinone, ethylene oxide, methanol,phthalic anhydride, styrene, methyl methacrylate monomers, and various olefins. Sony VAIO VPCF11ZHJ Battery

It is also used in the catalytic conversion ofsulfur dioxide into sulfur trioxide in the production of sulfuric acid.

Caesium fluoride enjoys niche use in organic chemistry as a base, or as an anhydrous source of fluoride ion. Caesium salts sometimes replace potassium or sodium salts in organic synthesis, such as cyclization, esterification, and polymerization.Sony VAIO VPCF127HGBI Battery

Nuclear and isotope applications

Caesium-137 is a very common radioisotope used as a gamma-emitter in industrial applications. Its advantages include a half-life of roughly 30 years, its availability from the nuclear fuel cycle, and having 137Ba as stable end product. The high water solubility is a disadvantage which makes it incompatible with irradiation of food and medical supplies.Sony VAIO VPCF137HG/BI Battery

It has been used in agriculture, cancer treatment, and the sterilization of food, sewage sludge, and surgical equipment. Radioactive isotopes of caesium in radiation devices were used in the medical field to treat certain types of cancer, but emergence of better alternatives and the use of water-soluble caesium chloride in the sources, which could create wide-ranging contamination, gradually put some of these caesium sources out of use.Sony VAIO VPC-P111KX/B Battery

Caesium-137 has been employed in a variety of industrial measurement gauges, including moisture, density, leveling, and thickness gauges. It has also been used in well logging devices for measuring the electron density of the rock formations, which is analogous to the bulk density of the formations.Sony VAIO VPC-P111KX/D Battery

Isotope 137 has also been used in hydrologic studies analogous to those using tritium. It is a daughter product of nuclear fission reactions. With the commencement of nuclear testing around 1945, and continuing through the mid-1980s, caesium-137 was released into the atmosphere where it is absorbed readily into solution.Sony VAIO VPC-P111KX/G Battery

Known year-to-year variation within that period allows correlation with soil and sediment layers. Caesium-134, and to a lesser extent caesium-135, have also been used in hydrology as a measure of caesium output by the nuclear power industry. While they are less prevalent than either caesium-133 or caesium-137, these isotopes have the advantage of being produced solely from anthropogenic sources.Sony VAIO VPC-P111KX/P Battery

Other uses

Caesium and mercury were used as a propellant in early ion engines designed for spacecraft propulsion on very long interplanetary or extraplanetary missions. The ionization method was to strip the outer electron from the propellant upon contact with a tungsten electrode that had voltage applied.Sony VAIO VPC-P111KX/W Battery

Concerns about the corrosive action of caesium on spacecraft components have pushed development in the direction of use of inert gas propellants such as xenon; this is easier to handle in ground-based tests and has less potential to interfere with the spacecraft. Eventually, xenon was used in the experimental spacecraft Deep Space 1 launched in 1998.Sony VAIO VPC-P112KX/B Battery

Nevertheless, field emission electric propulsion thrusters which use a simple system of accelerating liquid metal ions such as of caesium to create thrust have been built.

Caesium nitrate is used as an oxidizer and pyrotechnic colorant to burn silicon in infrared flares such as the LUU-19 flare, because it emits much of its light in the near infrared spectrum.Sony VAIO VPC-P112KX/D Battery

Caesium has been used to reduce the radar signature of exhaust plumes in the SR-71 Blackbird military aircraft.Caesium, along with rubidium, has been added as a carbonate to glass because it reduces electrical conductivity and improves stability and durability offiber optics and night vision devices.Sony VAIO VPC-P112KX/G Battery

Caesium fluoride or caesium aluminium fluoride are used in fluxes formulated for the brazing of aluminium alloys that contain magnesium.

Prognostications

Magnetohydrodynamic (MHD) power-generating systems were researched but failed to gain widespread acceptance.Sony VAIO VPC-P112KX/P Battery

Caesium metal has also been considered as the working fluid in high-temperature Rankine cycle turboelectric generators. Caesium salts have been evaluated as antishock reagents to be used following the administration of arsenical drugs. Because of their effect on heart rhythms, however, they are less likely to be used than potassium or rubidium salts. They have also been used to treat epilepsy.Sony VAIO VPC-P112KX/W Battery

Health and safety hazards

The portion of the total radiation dose (in air) contributed by each isotope versus time after the Chernobyl disaster depicting caesium-137 becoming the largest source of radiation about 200 days after the accident.Sony VAIO VPCP113KX/B Battery

Caesium compounds are rarely encountered by most people, but most caesium compounds are mildly toxic because of chemical similarity of caesium to potassium. Exposure to large amounts of caesium compounds can causehyperirritability and spasms, but as such amounts would not ordinarily be encountered in natural sources, caesium is not a major chemical environmental pollutant.Sony VAIO VPC-P113KX/B Battery

The median lethal dose (LD50) value for caesium chloride in mice is 2.3 g per kilogram, which is comparable to the LD50 values of potassium chloride and sodium chloride.

Caesium metal is one of the most reactive elements and is highly explosive when it comes in contact with water.Sony VAIO VPCP113KX/D Battery

The hydrogen gas produced by the reaction is heated by the thermal energy released at the same time, causing ignition and a violent explosion. This can occur with other alkali metals, but caesium is so potent that this explosive reaction can even be triggered by cold water.Sony VAIO VPC-P113KX/D Battery

The metal is highly pyrophoric, and ignites spontaneously in air to form caesium hydroxide and various oxides. Caesium hydroxide is a very strong base, and can rapidly corrode glass.

The isotopes 134 and 137 (present in the biosphere in small amounts from radiation leaks) represent a radioactivity burden which varies depending on location.Sony VAIO VPCP113KX/G Battery

Radiocaesium does not accumulate in the body as effectively as many other fission products (such as radioiodine and radiostrontium). As with other alkali metals, radiocaesium washes out of the body relatively quickly in sweat and urine. However, radiocaesium follows potassium and tends to accumulate in plant tissues, including fruits and vegetables.Sony VAIO VPC-P113KX/G Battery

It is also well-documented that mushrooms from contaminated forests accumulate radiocaesium (caesium-137) in their fungalsporocarps. Accumulation of caesium-137 in lakes has been a high concern after the Chernobyl disaster. Experiments with dogs showed that a single dose of 3.8 millicuries (140 MBq, 4.1 ?g of caesium-137) per kilogram is lethal within three weeks;Sony VAIO VPCP113KX/P Battery

smaller amounts may cause infertility and cancer. TheInternational Atomic Energy Agency and other sources have warned that radioactive materials, such as caesium-137, could be used in radiological dispersion devices, or "dirty bombs".

Barium is a chemical element with the symbol Ba and atomic number 56.Sony VAIO VPC-P113KX/P Battery

It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivitywith air. Its oxide is historically known as baryta but it reacts with water and carbon dioxide and is not found as a mineral.Sony VAIO VPCP113KX/W Battery

The most common naturally occurring minerals are the very insoluble barium sulfate, BaSO4 (barite), and barium carbonate, BaCO3(witherite). Barium's name originates from Greek barys (?????), meaning "heavy", describing the high density of some common barium-containing ores.Sony VAIO VPC-P113KX/W Battery

Barium has few industrial applications, but the metal has been historically used to scavenge air in vacuum tubes. Barium compounds impart a green color to flames and have been used in fireworks. Barium sulfate is used for its density, insolubility, and X-ray opacity.Sony VAIO VPC-P114KX/B Battery

It is used as an insoluble heavy mud-like paste when drilling oil wells, and in purer form, as an X-ray radiocontrast agent for imaging the human gastrointestinal tract. Soluble barium compounds are poisonous due to release of the soluble barium ion, and have been used as rodenticides.Sony VAIO VPC-P114KX/D Battery

New uses for barium continue to be sought. It is a component of some "high temperature" YBCO superconductors, and electroceramics.

Physical properties

Barium is a soft, silvery white alkali earth metal, which quickly oxidizes in air.It crystallizes in body centered cubic lattices. It burns with a green to pale green flame, resulting from emission at 524.2 and 513.7 nm.Sony VAIO VPC-P114KX/G Battery

Its simple compounds are notable for their relatively high (for an alkaline earth element) specific gravity. This high density is true of the most common barium-bearing mineral, barite (BaSO4), also called 'heavy spar' due to the high density (4.5 g/cm³).

Chemical properties

Barium, as for other alkali earth (group II) metals, is highly reducing.Sony VAIO VPC-P114KX/P Battery

It reacts exothermically with oxygen at room temperature to form barium oxide and peroxide. Because of its sensitivity to air, samples are generally stored under protective oils. The reaction is violent if barium is powdered. The metal is readily attacked in most acids, with the notable exception of sulfuric acid, as passivation stops the reaction by forming the insoluble barium sulfate.Sony VAIO VPC-P114KX/W Battery

It also reacts violently with water according to the reaction:

Ba + 2 H2O ? Ba(OH)2 + H2?

Barium combines with several metals, including aluminium, zinc, lead and tin, forming intermetallic phases and alloys.Sony VAIO VPCP115JC Battery

Naturally occurring barium is a mix of seven stable isotopes, the most abundant being 138Ba (71.7 %). 22 isotopes are known, but most of these are highly radioactive and have half-lives in the several millisecond to several day range. The only notable exceptions are 133Ba which has a half-life of 10.51 years, and 137mBa (2.55 minutes).Sony VAIO VPCP115JC/B Battery

133Ba is a standard calibrant for gamma-ray detectors in nuclear physics studies.

Occurrence

The abundance of barium is 0.0425 % in the Earth's crust and 13 µg/L in sea water. It occurs in the minerals barite (as the sulfate) and witherite (as the carbonate).Sony VAIO VPCP115JC/D Battery

Although witherite deposits were mined from the 17th century till 1969[4] in northern England, for example in the Settlingstones Mine near Newbrough,[5] today nearly all barium is mined as barite.

Large deposits of barite are found in China, Germany, India, Morocco, and in the United States.[6] A rare gem containing barium is known, called benitoite.Sony VAIO VPCP115JC/G Battery

Production

Because barium quickly oxidizes in air, it is difficult to obtain the free metal and it is never found free in nature. The metal is primarily found in, and extracted from, barite. Because barite is so insoluble, it cannot be used directly for the preparation of other barium compounds, or barium metal.Sony VAIO VPCP115JC/P Battery

Instead, the ore is heated with carbon to reduce it tobarium sulfide:

BaSO4 + 2 C ? BaS + 2 CO2

The barium sulfide is then hydrolyzed or treated with acids to form other barium compounds, such as the chloride, nitrate, and carbonate.Sony VAIO VPCP115JC/W Battery

Barium is commercially produced through the electrolysis of molten barium chloride (BaCl2):

(cathode) Ba2+ + 2 e?? Ba

(anode) 2 Cl– ? Cl2 + 2 e?
Barium metal is also obtained by the reduction of barium oxide with finely divided aluminium at temperatures between 1100 and 1200 °C:Sony VAIO VPCP115KG Battery

4 BaO + 2 Al ? BaO·Al2O3 + 3 Ba

The barium vapor is cooled and condensed to give the solid metal, which can be cast into rods or extruded into wires. Being a flammable solid, it is packaged under argon in steel containers or plastic bags.

Compounds

Ba2+ is the dominant oxidation state throughout the chemistry of barium.Sony VAIO VPCP116KG Battery

Its properties generally resemble those of other alkaline earth ions such as strontium and calcium. All halides, pseudohalides and chalcogenides are known, usually as colourless solids. The sulfate is famously insoluble. BaO forms a peroxide when heated in air. The oxide is basic and reacts with acids to give salts. Barium reduces oxides, chlorides and sulfides of less active metals.Sony VAIO VPC-P116KX/B Battery

For example:

Ba + CdO ? BaO + Cd

Ba + ZnCl2 ? BaCl2 + Zn

3 Ba + Al2S3 ? 3 BaS + 2 Al

At elevated temperatures, barium combines with nitrogen and hydrogen to produce the nitride Ba3N2 and hydride BaH2, respectively. When heated with nitrogen and carbon, it forms the cyanide:Sony VAIO VPC-P116KX/D Battery

Ba + N2 + 2 C ? Ba(CN)2

Barium's name originates from Greek ????? barys, meaning "heavy", describing the density of some common barium-containing ores. Alchemists in the early Middle Ages knew about some barium minerals. Smooth pebble-like stones of mineral barite found in Bologna, Italy were known as "Bologna stones".Sony VAIO VPC-P116KX/G Battery

Witches and alchemists were attracted to them because after exposure to light they would glow for years.

Carl Scheele identified barite as containing a new element in 1774, but could not isolate barium, only barium oxide. Johan Gottlieb Gahn also isolated barium oxide two years later in similar studies. Oxidized barium was at first called barote, byGuyton de Morveau, a name which was changed by Antoine Lavoisier to baryta.Sony VAIO VPC-P116KX/P Battery

Also in the 18th century, English mineralogistWilliam Withering noted a heavy mineral in the lead mines of cumberland, now known to be Witherite. Barium was first isolated by electrolysis of molten barium salts in 1808, by Sir Humphry Davy in England. Davy, by analogy with calcium named "barium" after baryta, with the "-ium" ending signifying a metallic element.Sony VAIO VPC-P116KX/W Battery

Robert Bunsen and Augustus Matthiessen yielded pure barium by electrolysis of a molten mixture of barium chloride and ammonium chloride.

The production of pure oxygen in the Brin process was a large scale application of barium peroxide before electrolysis and fractionally distill liquefied air became the dominant ways to produce oxygen. Sony VAIO VPCP118JC Battery

In this process the barium oxide reacts at 500–600°C with air to form barium peroxide which decomposes at above 700°C by releasing oxygen.

2 BaO + O2 ? 2 BaO2

Applications

The dominating application of elemental barium is as a scavenger or "getter" removing the last traces of oxygen and other gases in electronic vacuum tubes such as television cathode ray tubes.Sony VAIO VPCP118JC/B Battery

An alloy of barium with nickel is commonly used in automobile ignitions.

Applications of barium sulfate

Barium sulfate (the mineral barite, BaSO4) is important to the petroleum industry, for example, as drilling mud, a weighting agent in drilling new oil wells.Sony VAIO VPCP118JC/P Battery

It is also a filler in a variety of products such as rubber. Taking advantage of its opacity to X-rays, the sulfate is used as a radiocontrast agent for X-ray imaging of the digestive system ("barium meals" and "barium enemas").[6] Lithopone, a pigment that contains barium sulfate and zinc sulfide, is a permanent white that has good covering power, and does not darken when exposed to sulfides.Sony VAIO VPCP118JC/W Battery

Applications of other barium compounds

Aside from the sulfate, other compounds of barium find only niche applications. Applications are limited by the toxicity of Ba2+ions (Barium carbonate is a rat poison), which is not a problem for the insoluble BaSO4.Sony VAIO VPC-P118KX/B Battery

• Barium oxide is used in a coating for the electrodes of fluorescent lamps, which facilitates the release of electrons.
• Barium carbonate is also used in glassmaking. Being a heavy element, barium increases the refractive index and luster of the glass.Sony VAIO VPC-P118KX/D Battery

• Barium, commonly as barium nitrate, is used to give green colors in fireworks. The species responsible for the brilliant green is barium monochloride; in the absence of a source of chlorine a yellow or "apple" green is produced instead.
• Barium peroxide can be used as a catalyst to start an aluminothermic reaction when welding rail tracks together. It can also be used in green tracer ammunition and as a bleaching agent.Sony VAIO VPC-P118KX/G Battery

• Barium titanate is a promising electroceramic.
• Barium fluoride is used for optics in infrared applications, since it is transparent from about 0.15 to 12 micrometres.

Precautions

Soluble barium compounds are poisonous.Sony VAIO VPC-P118KX/P Battery

At low doses, barium acts as a muscle stimulant, whereas higher doses affect the nervous system, causing cardiac irregularities, tremors, weakness, anxiety, dyspnea and paralysis. This may be due to its ability to block potassium ion channels which are critical to the proper function of the nervous system.Sony VAIO VPC-P118KX/W Battery

However, individual responses to barium salts vary widely, with some being able to handle barium nitrate casually without problems, and others becoming ill from working with it in small quantities. For example, barium acetate was used by Marie Robards to poison her father in 1993.Sony VAIO VPCP119JC Battery

Non-toxicity of barium sulfate

Because it is highly insoluble in water as well as stomach acids, barium sulfate can be taken orally. It is eliminated completely from the digestive tract. Unlike other heavy metals, barium does not bioaccumulate. However, inhaled dust containing barium compounds can accumulate in the lungs, causing a benign condition called baritosis.Sony VAIO VPCP119JC/BI Battery

Lanthanum is a chemical element with the symbol La and atomic number 57. Lanthanum is a silvery white metallic element that belongs to group 3 of the periodic table and is the first element of the lanthanide series. It is found in some rare-earth minerals, usually in combination with cerium and other rare earth elements.Sony VAIO VPCP11S1E/B Battery

Lanthanum is a malleable, ductile, and soft metal that oxidizes rapidly when exposed to air. It is produced from the minerals monazite andbastnäsite using a complex multistage extraction process. Lanthanum compounds have numerous applications as catalysts, additives in glass, carbon lighting for studio lighting and projection,Sony VAIO VPC-P11S1E/B Battery

ignition elements in lighters and torches, electron cathodes, scintillators, and others. Lanthanum carbonate (La2(CO3)3) was approved as a medication against renal failure.

Physical properties

Lanthanum is a soft, malleable, silvery white metal which has hexagonal crystal structure at room temperature.Sony VAIO VPCP11S1E/D Battery

At 310 °C, lanthanum changes to a face-centered cubic structure, and at 865 °C into a body-centered cubic structure. Lanthanum easily is oxidized (a centimeter-sized sample will completely oxidize within a year) and is therefore used as in elemental form only for research purposes.Sony VAIO VPC-P11S1E/D Battery

For example, single La atoms have been isolated by implanting them intofullerene molecules.[4] If carbon nanotubes are filled with those lanthanum-encapsulated fullerenes and annealed, metallic nanochains of lanthanum are produced inside carbon nanotubes.Sony VAIO VPCP11S1E/G Battery

Chemical properties

Lanthanum exhibits two oxidation states, +3 and +2, the former being much more stable. For example, LaH3 is more stable than LaH2.Lanthanum burns readily at 150 °C to form lanthanum(III) oxide:

4 La + 3 O2 ? 2 La2O3

However, when exposed to moist air at room temperature, lanthanum oxide forms a hydrated oxide with a large volume increase.Sony VAIO VPC-P11S1E/G Battery

Lanthanum is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form lanthanum hydroxide:

2 La (s) + 6 H2O (l) ? 2 La(OH)3 (aq) + 3 H2 (g)

Lanthanum metal reacts with all the halogens. The reaction is vigorous if conducted at above 200 °C:Sony VAIO VPCP11S1E/P Battery

2 La (s) + 3 F2 (g) ? 2 LaF3 (s)

2 La (s) + 3 Cl2 (g) ? 2 LaCl3 (s)

2 La (s) + 3 Br2 (g) ? 2 LaBr3 (s)

2 La (s) + 3 I2 (g) ? 2 LaI3 (s)

Lanthanum dissolves readily in dilute sulfuric acid to form solutions containing the La(III) ions, which exist as [La(OH2)9]3+complexes:Sony VAIO VPCP11S1E/W Battery

2 La(s) + 3 H2SO4 (aq) ? 2 La3+(aq) + 3 SO2?

4 (aq) + 3 H2 (g)

Lanthanum combines with nitrogen, carbon, sulfur, phosphorus, boron, selenium, silicon and arsenic at elevated temperatures, forming binary compounds.Sony VAIO VPC-P11S1E/W Battery

Naturally occurring lanthanum is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance). 38 radioisotopes have been characterized with the most stable being 138La with a half-life of 1.05×1011 years, and 137La with a half-life of 60,000 years.Sony VAIO VPCP11Z9E/B Battery

Most of the remaining radioactive isotopes have half-lives that are less than 24 hours, and the majority of these have half-lives less than 1 minute. This element also has three meta states.

The isotopes of lanthanum range in atomic weight from 117 u (117La) to 155 u (155La).Sony VAIO VPCS111FM/S Battery

The word lanthanum comes from the Greek ??????? [lanthan?] = to lie hidden. Lanthanum was discovered in 1839 bySwedish chemist Carl Gustav Mosander, when he partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute nitric acid.Sony VAIO VPCS115EC Battery

From the resulting solution, he isolated a new rare earth he called lantana. Lanthanum was isolated in relatively pure form in 1923.

Lanthanum is the most strongly basic of all the trivalent lanthanides, and this property is what allowed Mosander to isolate and purify the salts of this element.Sony VAIO VPCS115FG Battery

Basicity separation as operated commercially involved the fractional precipitation of the weaker bases (such as didymium) from nitrate solution by the addition of magnesium oxide or dilute ammonia gas. Purified lanthanum remained in solution. (The basicity methods were only suitable for lanthanum purification; didymium could not be efficiently further separated in this manner.)Sony VAIO VPCS117GG Battery

The alternative technique of fractional crystallization was invented by Dmitri Mendeleev, in the form of the double ammonium nitrate tetrahydrate, which he used to separate the less-soluble lanthanum from the more-soluble didymium in the 1870s. This system was used commercially in lanthanum purification until the development of practical solvent extraction methods that started in the late 1950s.Sony VAIO VPCS117GGB Battery

(A detailed process using the double ammonium nitrates to provide 99.99% pure lanthanum, neodymium concentrates and praseodymium concentrates is presented in Callow 1967, at a time when the process was just becoming obsolete.) As operated for lanthanum purification, the double ammonium nitrates were recrystallized from water.Sony VAIO VPCS118EC Battery

When later adapted by Carl Auer von Welsbach for the splitting of didymium, nitric acid was used as a solvent to lower the solubility of the system. Lanthanum is relatively easy to purify, since it has only one adjacent lanthanide, cerium, which itself is very readily removed due to its potential tetravalency.Sony VAIO VPCS119FJ/B Battery

The fractional crystallization purification of lanthanum as the double ammonium nitrate was sufficiently rapid and efficient, that lanthanum purified in this manner was not expensive. The Lindsay Chemical Division of American Potash and Chemical Corporation, for a while the largest producer of rare earths in the world,Sony VAIO VPCS119GC Battery

in a price list dated October 1, 1958 priced 99.9% lanthanum ammonium nitrate (oxide content of 29%) at $3.15 per pound, or $1.93 per pound in 50-pound quantities. The corresponding oxide (slightly purer at 99.99%) was priced at $11.70 or $7.15 per pound for the two quantity ranges. The price for their purest grade of oxide (99.997%) was $21.60 and $13.20, respectively.Sony VAIO VPCS11AFJ Battery

Occurrence

Although lanthanum belongs to the element group called rare earth metals, it is not rare at all. Lanthanum is available in relatively large quantities (32 ppm in Earth’s crust). "Rare earths" got their name because they were indeed rare as compared to the "common" earths such as lime or magnesia, and historically only a few deposits were known.Sony VAIO VPCS11AGJ Battery

Monazite (Ce, La, Th, Nd, Y)PO4, and bastnäsite (Ce, La, Y)CO3F, are the principal ores in which lanthanum occurs, in percentages of up to 25 to 38 percent of the total lanthanide content. In general, there is more lanthanum in bastnäsite than in monazite. Until 1949, bastnäsite was a rare and obscure mineral, not even remotely contemplated as a potential commercial source for lanthanides.Sony VAIO VPCS11AHJ Battery

In that year, the large deposit at the Mountain Pass rare earth mine in California was discovered. This discovery alerted geologists to the existence of a new class of rare earth deposit, the rare-earth bearingcarbonatite, other examples of which soon surfaced, particularly in Africa and China.Sony VAIO VPCS11AVJ Battery

Production

Lanthanum is most commonly obtained from monazite and bastnäsite. The mineral mixtures are crushed and ground. Monazite, because of its magnetic properties, can be separated by repeated electromagnetic separation. After separation, it is treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths.Sony VAIO VPCS11J7E/B Battery

The acidic filtrates are partially neutralized with sodium hydroxide to pH 3-4. Thorium precipitates out of solution as hydroxide and is removed. After that, the solution is treated with ammonium oxalate to convert rare earths to their insoluble oxalates. The oxalates are converted to oxides by annealing.Sony VAIO VPCS11M1E/W Battery

The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose oxide is insoluble in HNO3. Lanthanum is separated as a double salt with ammonium nitrate by crystallization. This salt is relatively less soluble than other rare earth double salts and therefore stays in the residue.Sony VAIO VPCS11V9E Battery

The most efficient separation routine for lanthanum salt from the rare-earth salt solution is, however, ion exchange. In this process, rare-earth ions are adsorbed onto suitable ion-exchange resin by exchange with hydrogen, ammonium or cupric ions present in the resin.Sony VAIO VPCS11V9E/B Battery

The rare earth ions are then selectively washed out by a suitable complexing agent, such as ammonium citrate or nitrilotriacetate. Lanthanum can also be separated from a solution of rare earth nitrates by liquid-liquid extraction with a suitable organic liquid, such as tributyl phosphalate.Sony VAIO VPCS11X9E/B Battery

Currently, the most widely used extractant for the purification of lanthanum and the other lanthanides is the 2-ethylhexyl ester of 2-ethylhexylphosphonic acid; this has better handling characteristics than the previously used bis-2-ethylhexyl phosphate.

Lanthanum metal is obtained from its oxide by heating it with ammonium chloride or fluoride and hydrofluoric acid at 300-400 °C to produce the chloride or fluoride:Sony VAIO VPCS123FGB Battery

La2O3 + 6 NH4Cl ? 2 LaCl3 + 6 NH3 + 3 H2O

This is followed by reduction with alkali or alkaline earth metals in vacuum or argon atmosphere:

LaCl3 + 3 Li ? La + 3 LiCl

Also, pure lanthanum can be produced by electrolysis of molten mixture of anhydrous LaCl3 and NaCl or KCl at elevated temperatures.Sony VAIO VPCS125EC Battery

Applications

The first historical application of lanthanum was in gas lantern mantles. Carl Auer von Welsbach used a mixture of 60% magnesium oxide, 20% lanthanum oxide and 20% yttrium oxide which he called Actinophor, and patented in 1885.Sony VAIO VPCS128EC Battery

The original mantles gave a green-tinted light and were not very successful, and his first company, which established a factory in Atzgersdorf in 1887, failed in 1889.

Modern uses of lanthanum include:Sony VAIO VPCS129GC Battery

• One material used for anodic material of nickel-metal hydride batteries is La(Ni3.6Mn0.4Al0.3Co0.7. Due to high cost to extract the other lanthanides a mischmetal with more than 50% of lanthanum is used instead of pure lanthanum. The compound is an intermetalliccomponent of the AB5 type.Sony VAIO VPCS12C7E/B Battery

As most hybrid cars use nickel-metal hydride batteries, massive quantities of lanthanum are required for the production of hybrid automobiles. A typical hybrid automobile battery for aToyota Prius requires 10 to 15 kg (22-33 lb) of lanthanum. As engineers push the technology to increase fuel mileage, twice that amount of lanthanum could be required per vehicle.Sony VAIO VPCS12L9E/B Battery

• Hydrogen sponge alloys can contain lanthanum. These alloys are capable of storing up to 400 times their own volume of hydrogen gas in a reversible adsorption process. Heat energy is released every time they do so; therefore these alloys have possibilities in energy conservation systems.Sony VAIO VPCS12V9E/B Battery

• Mischmetal, a pyrophoric alloy used in lighter flints, contains 25% to 45% lanthanum.
• Lanthanum oxide and the boride are used in electronic vacuum tubes as hot cathode materials with strong emissivity ofelectrons. Crystals of LaB6 are used in high brightness, extended life, thermionic electron emission sources for electron microscopes and Hall effect thrusters.Sony VAIO VPCW111XX/P Battery

• Lanthanum fluoride (LaF3) is an essential component of a heavy fluoride glass named ZBLAN. This glass has superior transmittance in the infrared range and is therefore used for fiber-optical communication systems.
• Cerium doped lanthanum bromide and lanthanum chloride are the recent inorganic scintillators which have a combination of high light yield, best energy resolution and fast response.Sony VAIO VPCW111XX/PC Battery

• Their high yield converts into superior energy resolution; moreover, the light output is very stable and quite high over a very wide range of temperatures, making it particularly attractive for high temperature applications. These scintillators are already widely used commercially in detectors of neutrons or gamma rays.Sony VAIO VPCW111XX/T Battery

• Carbon arc lamps use a mixture of rare earth elements to improve the light quality. This applications, especially by themotion picture industry for studio lighting and projection, consumed about 25% of the rare-earth compounds produced until the phase out of Carbon arc lamps.Sony VAIO VPCW111XX/W Battery

• Lanthanum(III) oxide (La2O3) improves the alkali resistance of glass, and is used in making special optical glasses, such as infrared-absorbing glass, as well as camera and telescope lenses, because of the high refractive index and low dispersion of rare-earth glasses.Sony VAIO VPCW111XXP Battery

• Lanthanum oxide is also used as a grain growth additive during the liquid phase sintering of silicon nitride and zirconium diboride.
• Small amounts of lanthanum added to steel improves its malleability, resistance to impact and ductility. Whereas addition of lanthanum to molybdenum decreases its hardness and sensitivity to temperature variations.Sony VAIO VPCW111XXT Battery

• Small amounts of lanthanum are present in many pool products to remove the phosphates that feed algae.[19]
• Lanthanum oxide additive to tungsten is used in gas tungsten arc welding electrodes, as a substitute for radioactive thorium.Sony VAIO VPCW111XXW Battery

• Various compounds of lanthanum and other rare-earth elements (oxides, chlorides, etc.) are components of various catalysis, such as petroleum crackingcatalysts.
• Lanthanum-barium radiometric dating is used to estimate age of rocks and ores, though the technique has limited popularity.Sony VAIO VPCW115XG Battery

• Lanthanum carbonate was approved as a medication (Fosrenol, Shire Pharmaceuticals) to absorb excess phosphate in cases of end-stage renal failure.
• Lanthanum fluoride is used in phosphor lamp coatings. Mixed with europium fluoride, it is also applied in the crystal membrane of fluoride ion-selective electrodes.Sony VAIO VPCW115XGP Battery

• Like horseradish peroxidase, lanthanum is used as an electron-dense tracer in molecular biology.

Biological role

Lanthanum has no known biological role. The element is very poorly absorbed after oral administration and when injected its elimination is very slow. Lanthanum carbonate was approved as a medication named Fosrenol to absorb excess phosphate in cases of end-stage renal failure.Sony VAIO VPCW115XW/P Battery

While lanthanum has pharmacological effects on several receptors and ion channels, its specificity for the GABA receptor is unique among divalent cations. Lanthanum acts at the same modulatory site on the GABA receptor as zinc- a known negative allosteric modulator.Sony VAIO VPCW115XW/T Battery

The Lanthanum cation La3+ is a positive allosteric modulator at native and recombinant GABA receptors, increasing open channel time and decreasing desensitization in a subunit configuration dependent manner.

Precautions

Lanthanum has a low to moderate level of toxicity and should be handled with care. In animals, the injection of lanthanum solutions produces hyperglycaemia, low blood pressure, degeneration of the spleen and hepatic alterations.Sony VAIO VPCW115XW/W Battery

The application in carbon arc light led to the exposure of people to rare earth element oxides and fluorides, sometimes led to pneumoconiosis.

Cerium /?s??ri?m/ is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air.Sony VAIO VPCW117XC/P Battery

Cerium was named after the dwarf planet Ceres (itself named for the Roman goddess of agriculture). Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight. It is found in a number of minerals, the most important being monazite and bastnasite.Sony VAIO VPCW117XC/T Battery

Commercial applications of cerium are numerous. They include catalysts, additives to fuel to reduce emissions and to glass and enamels to change their color. Cerium oxideis an important component of glass polishing powders and phosphors used in screens and fluorescent lamps.Sony VAIO VPCW117XC/W Battery

Physical properties

Cerium is a silvery metal, belonging to the lanthanide group. It resembles iron in color and luster, but is soft, and both malleable and ductile. Cerium has the third-longest liquid range of any element: 2648 C° (795 °C to 3443 °C) or 4766 F° (1463 °F to 6229 °F). (Neptunium and Thorium have the longer liquid ranges.)Sony VAIO VPCW119XJ Battery

Cerium is especially interesting because of its variable electronic structure. The energy of the inner 4f level is nearly the same as that of the outer or valence electrons, and only small energy is required to change the relative occupancy of these electronic levels. This gives rise to dual valency states.Sony VAIO VPCW119XJ/P Battery

For example, a volume change of about 10% occurs when cerium is subjected to high pressures or low temperatures. It appears that the valence changes from about 3 to 4 when it is cooled or compressed. The low temperature behavior of cerium is complex. Four allotropic modifications are thought to exist: cerium at room temperature and at atmospheric pressure is known as ? cerium.Sony VAIO VPCW119XJ/W Battery

Upon cooling to –16 °C, ? cerium changes to ? cerium. The remaining ? cerium starts to change to ? cerium when cooled to –172 °C, and the transformation is complete at –269 °C. ? Cerium has a density of 8.16; ? cerium exists above 726 °C. At atmospheric pressure, liquid cerium is more dense than its solid form at the melting point.Sony VAIO VPCW11AXJ Battery

Chemical properties

Cerium metal tarnishes slowly in air and burns readily at 150 °C to form cerium(IV) oxide:

Ce + O2 ? CeO2

Cerium is quite electropositive and reacts slowly with cold water and quite quickly with hot water to form cerium hydroxide:Sony VAIO VPCW11S1E/P Battery

2 Ce (s) + 6 H2O (l) ? 2 Ce(OH)3 (aq) + 3 H2 (g)

Cerium metal reacts with all the halogens:

2 Ce (s) + 3 F2 (g) ? 2 CeF3 (s) [white]

2 Ce (s) + 3 Cl2 (g) ? 2 CeCl3 (s) [white]

2 Ce (s) + 3 Br2 (g) ? 2 CeBr3 (s) [white]

2 Ce (s) + 3 I2 (g) ? 2 CeI3 (s) [yellow]

Cerium dissolves readily in dilute sulfuric acid to form solutions containing the colorless Ce(III) ions, which exist as a [Ce(OH2)9]3+complexes:Sony VAIO VPCW11S1E/T Battery

2 Ce (s) + 3 H2SO4 (aq) ? 2 Ce3+ (aq) + 3 SO2?4 (aq) + 3 H2 (g)

Compounds

Cerium(IV) (ceric) salts are orange red or yellowish, whereas cerium(III) (cerous) salts are usually white or colorless. Both oxidation states absorb ultraviolet light strongly.Sony VAIO VPCW11S1E/W Battery

Cerium(III) can be used to make glasses that are colorless, yet absorb ultraviolet light almost completely. Cerium can be readily detected in rare earth mixtures by a very sensitive qualitative test: addition of ammonia and hydrogen peroxide to an aqueous solution of lanthanides produces a characteristic dark brown color if cerium is present.Sony VAIO VPCW121AX Battery

Cerium exhibits three oxidation states, +2, +3 and +4. The +2 state is rare and is observed in CeH2, CeI2 and CeS. The most common compound of cerium is cerium(IV) oxide (CeO2), which is used as "Jeweller's rouge" as well as in the walls of some self-cleaning ovens.Sony VAIO VPCW126AG Battery

Two common oxidizing agents used in titrations are ammonium cerium(IV) sulfate (ceric ammonium sulfate, (NH4)2Ce(SO4)3) and ammonium cerium(IV) nitrate (ceric ammonium nitrate or CAN, (NH4)2Ce(NO3)6). Cerium also forms a chloride, CeCl3or cerium(III) chloride, used to facilitate reactions at carbonyl groupsin organic chemistry.Sony VAIO VPCW127JC/P Battery

Other compounds include cerium(III) carbonate (Ce2(CO3)3), cerium(III) fluoride (CeF3), cerium(III) oxide (Ce2O3), as well as cerium(IV) sulfate (ceric sulfate, Ce(SO4)2) and cerium(III) triflate (Ce(OSO2CF3)3).

The two oxidation states of cerium differ enormously in basicity: cerium(III) is a strong base, comparable to the other trivalent lanthanides, but cerium(IV) is weak.Sony VAIO VPCW127JC/T Battery

This difference has always allowed cerium to be by far the most readily isolated and purified of all the lanthanides, otherwise a notoriously difficult group of elements to separate. A wide range of procedures have been devised over the years to exploit the difference. Among the better ones:Sony VAIO VPCW127JC/W Battery

1. Leaching the mixed hydroxides with dilute nitric acid: the trivalent lanthanides dissolve in cerium-free condition, and tetravalent cerium remains in the insoluble residue as a concentrate to be further purified by other means. A variation on this uses hydrochloric acid and the calcined oxides from bastnasite, but the separation is less sharp.Sony VAIO VPCW127JC/WZ Battery

1. Precipitating cerium from a nitrate or chloride solution using potassium permanganate and sodium carbonate in a 1:4 molar ratio.
2. Boiling rare-earth nitrate solutions with potassium bromate and marble chips.Sony VAIO VPCW12AAJ Battery

Formerly used commercially was a method whereby a solution of cerium(IV) in nitric acid would be added to dilute sulfuric acid. This caused cerium(IV) to largely precipitate as a basic salt, leaving trivalent lanthanide in solution. However, the finely divided precipitate was difficult to filter from the highly corrosive medium.Sony VAIO VPCW12AKJ Battery

Using the classical methods of rare-earth separation, there was a considerable advantage to a strategy of removing cerium from the mixture at the beginning. Cerium typically comprised 45% of the cerite or monazite rare earths, and removing it early greatly reduced the bulk of what needed to be further processed (or the cost of reagents to be associated with such processing).Sony VAIO VPCW12AVJ Battery

However, not all cerium purification methods relied on basicity. Ceric ammonium nitrate [ammonium hexanitratocerate(IV)] crystallization from nitric acid was one purification method. Cerium(IV) nitrate (hexanitratoceric acid) was more readily extractable into certain solvents (e.g. tri-n-butyl phosphate) than the trivalent lanthanides.Sony VAIO VPCW12S1E/P Battery

However, modern practice in China seems to be to do purification of cerium by counter-current solvent extraction, in its trivalent form, just like the other lanthanides.

Cerium(IV) is a strong oxidant under acidic conditions, but stable under alkaline conditions, when it is cerium(III) that becomes a strong reductant, easily oxidized by atmospheric oxygen (O2).Sony VAIO VPCW12S1E/T Battery

This ease of oxidation under alkaline conditions leads to the occasional geochemical parting of the ways between cerium and the trivalent light lanthanides under supergeneweathering conditions, leading variously to the "negative cerium anomaly" or to the formation of the mineral cerianite.Sony VAIO VPCW12S1E/W Battery

Air-oxidation of alkaline cerium(III) is the most economical way to get to cerium(IV), which can then be handled in acid solution.

Naturally occurring cerium is composed of 4 stable isotopes; 136
Ce, 138
Ce, 140
Ce, and 142
Ce, with 140
Ce being the most abundant (88.48% natural abundance).Sony VAIO VPCW213AG/L Battery

136

Ce and 142
Ce are predicted to be double beta active but no signs of activity were ever observed (for 142
Ce, the lower limit on half-life is 5×1016 yr). 26 radioisotopes have been characterized, with the most long-lived being 144
Ce with a half-life of 284.893 days, 139
Ce with a half-life of 137.640 days, and 141
Ce with a half-life of 32.501 days.Sony VAIO VPCW213AG/P Battery

All of the remaining radioactive isotopes have half-lives that are less than 4 days and the majority of these have half-lives that are less than10 minutes. This element also has 2 meta states.

The known isotopes of cerium range in atomic weight from 123 u (123Ce) to 152 u (152Ce).Sony VAIO VPCW213AG/T Battery

144

Ce is a high-yield product of nuclear fission; the ORNL Fission Product Pilot Plant separated substantial quantities of 144
Ce from reactor waste, and it was used in the Aircraft Nuclear Propulsion and SNAP programs.Sony VAIO VPCW213AG/W Battery

Cerium was discovered in Bastnäs in Sweden by Jöns Jakob Berzelius and Wilhelm Hisinger, and independently in Germany by Martin Heinrich Klaproth, both in 1803. Cerium was named by Berzelius after the dwarf planet Ceres, discovered two years earlier (1801). As originally isolated, cerium was in the form of its oxide, and was named ceria, a term that is still used.Sony VAIO VPCW215AG/L Battery

The metal itself was too electropositive to be isolated by then-current smelting technology, a characteristic of rare earth metals in general. After the development of electrochemistry by Humphry Davy five years later, the earths soon yielded the metals they contained.Sony VAIO VPCW217JC Battery

Ceria, as isolated in 1803, contained all of the lanthanides present in the cerite ore from Bastnäs, Sweden, and thus only contained about 45% of what is now known to be pure ceria. It was not until Carl Gustaf Mosander succeeded in removing lanthana and "didymia" in the late 1830s, that ceria was obtained pure.Sony VAIO VPCW217JC/L Battery

Wilhelm Hisinger was a wealthy mine owner and amateur scientist, and sponsor of Berzelius. He owned or controlled the mine at Bastnäs, and had been trying for years to find out the composition of the abundant heavy gangue rock (the "Tungstein of Bastnäs"), now known as cerite, that he had in his mine.Sony VAIO VPCW217JC/P Battery

Mosander and his family lived for many years in the same house as Berzelius, and Mosander was undoubtedly persuaded by Berzelius to investigate ceria further.

When the rare earths were first discovered, since they were strong bases like the oxides of calcium or magnesium, they were thought to be divalent.Sony VAIO VPCW217JC/T Battery

Thus, "ceric" cerium was thought to be trivalent, and the oxidation state ratio was therefore thought to be 1.5. Berzelius was annoyed to keep on getting the correct ratio 1.33. He was after all one of the finest analytical chemists in Europe.

In the late 1950s, the Lindsay Chemical Division of American Potash and Chemical Corporation of West Chicago,Sony VAIO VPCW217JC/W Battery

Illinois, then the largest producer of rare earths in the world, was offering cerium compounds in two purity ranges, "commercial" at 94-97% purity, and "purified", at a reported 99.9+% purity. In their October 1, 1958 price list, one-pound quantities of the oxides were priced at $3.30 or $8.10 respectively for the two purities;Sony VAIO VPCW218JC Battery

the per-pound price for 50-pound quantities were respectively $1.95 or $4.95 for the two grades. Cerium salts were proportionately cheaper, reflecting their lower net content of oxide.

Occurrence

Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight.Sony VAIO VPCW218JC/L Battery

It is found in a number of minerals including allanite (also known as orthite)—(Ca,Ce,La,Y)2(Al,Fe)3(SiO4)3(OH), monazite (Ce,La,Th,Nd,Y)PO4,bastnasite (Ce,La,Y)CO3F, hydroxylbastnasite (Ce,La,Nd)CO3(OH,F), rhabdophane (Ce,La,Nd)PO4-H2O, zircon (ZrSiO4), and synchysiteCa(Ce,La,Nd,Y)(CO3)2F.Sony VAIO VPCW218JC/P Battery

Monazite and bastnasite are presently the two most important sources of cerium. Large deposits of monazite,allanite, and bastnasite will supply cerium, thorium, and other rare-earth metals for many years to come.

Production

The mineral mixtures are crushed, ground and treated with hot concentrated sulfuric acid to produce water-soluble sulfates of rare earths.Sony VAIO VPCW218JC/T Battery

The acidic filtrates are partially neutralized with sodium hydroxide to pH 3–4. Thorium precipitates out of solution as hydroxide and is removed. After that the solution is treated with ammonium oxalate to convert rare earths in to their insoluble oxalates. The oxalates are converted to oxides by annealing.Sony VAIO VPCW218JC/W Battery

The oxides are dissolved in nitric acid that excludes one of the main components, cerium, whose salts are insoluble in HNO3. Metallic cerium is prepared by metallothermic reduction techniques, such as by reducing cerium fluoride or chloride with calcium, or by electrolysis of molten cerous chloride or other cerous halides. The metallothermic technique is used to produce high-purity cerium.Sony VAIO VPCW219AJ/L Battery

Applications

A major technological application for Cerium(III) oxide is a catalytic converter for the reduction of CO emissions in the exhaust gases from motor vehicles. In particular, cerium oxide is added into Diesel fuels. Another important use of the cerium oxide is a hydrocarbon catalyst in self cleaning ovens, incorporated into oven walls and as a petroleum cracking catalyst in petroleum refining.Sony VAIO VPCW219AJ/P Battery

Cerium(IV) oxide is considered one of the most efficient agents for precision polishing of optical components. Cerium compounds are also used in the manufacture ofglass, both as a component and as a decolorizer. For example, cerium(IV) oxide in combination with titanium(IV) oxide gives a golden yellow color to glass;Sony VAIO VPCW219AJ/W Battery

it also allows for selective absorption of ultraviolet light in glass. Cerium oxide has high refractive index and is added to enamel to make it more opaque.

Cerium(IV) oxide is used in incandescent gas mantles, such as the Welsbach mantle, where it was combined with thorium, lanthanum, magnesium or yttrium oxides.Sony VAIO VPCW21AAJ Battery

Doped with other rare earth oxides, it has been investigated as a solid electrolyte in intermediate temperature solid oxide fuel cells: The cerium(IV) oxide-cerium(III) oxide cycle or CeO2/Ce2O3 cycle is a two step thermochemical process based on cerium(IV) oxide and cerium(III) oxide for hydrogen production.Sony VAIO VPCW21AKJ Battery

The photostability of pigments can be enhanced by addition of cerium. It provides pigments with light fastness and prevents clear polymers from darkening in sunlight. Television glass plates are subject to electron bombardment, which tends to darken them by creation of F-center color centers.Sony VAIO VPCW21AVJ Battery

This effect is suppressed by addition of cerium oxide. Cerium is also an essential component of phosphors used in TV screens and fluorescent lamps.

A traditional use of cerium was in the pyrophoric mischmetal alloy used for light flints. Because of the high affinity of cerium to sulfur and oxygen, it is used in various aluminium alloys, and iron alloys.Sony VAIO VPCY115FGS Battery

In steels, cerium degasifies and can help reduce sulfides and oxides, and it is a precipitation hardening agent instainless steel. Adding cerium to cast irons opposes graphitization and produces a malleable iron. Addition of 3–4% of cerium to magnesium alloys, along with 0.2 to 0.6% zirconium, helps refine the grain and give sound casting of complex shapes. It also adds heat resistance to magnesium castings.Sony VAIO VPCY115FX/BI Battery

Cerium alloys are used in permanent magnets and in tungsten electrodes for gas tungsten arc welding. Cerium is used in carbon-arc lighting, especially in the motion picture industry. Cerium oxalate is an anti-emetic drug. Cerium(IV) sulfate is used extensively as a volumetric oxidizing agent in quantitative analysis.Sony VAIO VPCY115FXBI Battery

Ceric ammonium nitrate is a useful one-electron oxidant in organic chemistry, used to oxidatively etch electronic components, and as a primary standard for quantitative analysis.

Precautions

Cerium, like all rare-earth metals, is of low to moderate toxicity. Cerium is a strong reducing agent and ignites spontaneously in air at 65 to 80 °C. Fumes from cerium fires are toxic.Sony VAIO VPCY118EC Battery

Water should not be used to stop cerium fires, as cerium reacts with water to produce hydrogen gas. Workers exposed to cerium have experienced itching, sensitivity to heat, and skin lesions. Animals injected with large doses of cerium have died due to cardiovascular collapse.Sony VAIO VPCY118GX/BI Battery

Cerium(IV) oxide is a powerful oxidizing agent at high temperatures and will react with combustible organic materials. While cerium is not radioactive, the impure commercial grade may contain traces of thorium, which is radioactive. Cerium serves no known biological function.Sony VAIO VPCY119FJ/S Battery,Sony VAIO VPCY11AFJ Battery,Sony VAIO VPCY11AGJ Battery,Sony VAIO VPCY11AHJ Battery,Sony VAIO VPCY11AVJ Battery,Sony VAIO VPCY11M1E/S Battery,Sony VAIO VPCY11S1E Battery

 

Tellurium,Iodine,Xenon

Tellurium is a chemical element that has the symbol Te and atomic number 52. A brittle, mildly toxic, rare, silver-white metalloid which looks similar to tin, tellurium is chemically related toselenium and sulfur. It is occasionally found in native form, as elemental crystals. Tellurium is far more common in the universe than on Earth.Sony VAIO VGN-SZ58GN/C Battery

Its extreme rarity in the Earth's crust, comparable to that of platinum, is partly due to its high atomic number, but also due to its formation of a volatile hydride which caused the element to be lost to space as a gas during the hot nebular formation of the planet.Sony VAIO VGN-SZ58N Battery

Tellurium was discovered in Transylvania (today part of Romania) in 1782 by Franz-Joseph Müller von Reichenstein in a mineral containing tellurium and gold. Martin Heinrich Klaproth named the new element in 1798 after the Latin word for "earth", tellus. Gold telluride minerals (responsible for the name of Telluride, Colorado) are the most notable natural gold compounds.Sony VAIO VGN-SZ61MN/B Battery

However, they are not a commercially significant source of tellurium itself, which is normally extracted as by-product of copper and lead production.

Tellurium is commercially primarily used in alloys, foremost in steel and copper to improve machinability. Applications in solar panels and as a semiconductor material also consume a considerable fraction of tellurium production.Sony VAIO VGN-SZ61VN/X Battery

Tellurium has no biological function, although fungi can incorporate it in place of sulfur and selenium into amino acidssuch as telluro-cysteine and telluro-methionine.[3] In humans, tellurium is partly metabolized into dimethyl telluride, (CH3)2Te, a gas with a garlic-like odor which is exhaled in the breath of victims of tellurium toxicity or exposure.Sony VAIO VGN-SZ61WN/C Battery

Physical properties

When crystalline, tellurium is silvery-white and when it is in pure state it has a metallic luster. It is a brittle and easily pulverized metalloid. Amorphous tellurium is found by precipitating it from a solution of tellurous or telluricacid (Te(OH)6).Sony VAIO VGN-SZ640N/B Battery

ellurium is a semiconductor that shows a greater electrical conductivity in certain directions which depends on atomic alignment; the conductivity increases slightly when exposed to light (photoconductivity).[5] When in its molten state, tellurium is corrosive to copper, iron and stainless steel.Sony VAIO VGN-SZ645P3 Battery

Chemical properties

Tellurium adopts a polymeric structure, consisting of zig-zag chains of Te atoms. This gray material resists oxidation by air and is nonvolatile.

Naturally occurring tellurium has eight isotopes. Four of those isotopes, 122Te, 124Te, 125Te and 126Te, are stable.Sony VAIO VGN-SZ650N/C Battery

The other four, 120Te, 123Te, 128Te and 130Te, have been observed to be radioactive.[6][7] The stable isotopes make up only 33.2 % of the naturally occurring tellurium; this is possible due to the long half-lives of the unstable isotopes. They are in the range from 1013 to 2.2 1024 years (for 128Te).Sony VAIO VGN-SZ660N/C Battery

This makes 128Te the isotope with the longest half life among allradionuclides.,[8] which is approximately 160 trillion (1012) times the age of known universe.

There are 38 known nuclear isomers of tellurium with atomic masses that range from 105 to 142.Sony VAIO VGN-SZ670N/C Battery

Tellurium is among the lightest elements known to undergo alpha decay, with isotopes 106Te to 110Te being able to undergo this mode of decay.[6]The atomic mass of tellurium (127.60 g·mol?1) exceeds that of the following element iodine (126.90 g·mol?1).Sony VAIO VGN-SZ680ND Battery

Occurrence

With an abundance in the Earth's crust comparable to that of platinum, tellurium is one of the rarest stable solid elements in the Earth's crust. Its abundance is about 1 µg/kg.[10] In comparison, even the rarest of the lanthanides have crustal abundances of 500 µg/kg (see Abundance of the chemical elements).Sony VAIO VGN-SZ691N/X Battery

The extreme rarity of tellurium in the Earth's crust is not a reflection of its cosmic abundance, which is in fact greater than that of rubidium, even though rubidium is ten thousand times more abundant in the Earth's crust. The extraordinarily low abundance of tellurium on Earth is rather thought to be due to conditions in the Earth's formation,Sony VAIO VGN-SZ71E/B Battery

when the stable form of certain elements, in the absence of oxygen andwater, was controlled by the reductive power of free hydrogen. Under this scenario, certain elements such as tellurium which form volatile hydrides were severely depleted during the formation of the Earth's crust, through evaporation of these hydrides.Sony VAIO VGN-SZ71VN/X Battery

Tellurium and selenium are the heavy elements most depleted in the Earth's crust by this process.

Tellurium is sometimes found in its native (elemental) form, but is more often found as the tellurides of gold (calaverite, krennerite, petzite, sylvanite and others). Tellurium compounds are the most common chemical compounds of gold found in nature (rare non-tellurides such as gold aurostibite and bismuthide are known).Sony VAIO VGN-SZ71WN/C Battery

Tellurium is also found combined with elements other than gold, in salts of other metals. In contrast to selenium, tellurium is not able to replace sulfur in its minerals. This is due to the large difference in ion radius of sulfur and tellurium. In consequence, many sulfide minerals contain considerable amounts of selenium, but only traces of tellurium.Sony VAIO VGN-SZ74B/B Battery

In the gold rush of 1893, diggers in Kalgoorlie discarded a pyritic material which got in their way as they searched for pure gold. The Kalgoorlie waste was thus used to fill in potholes or as part of sidewalks. Three years passed before it was realized that this waste was calaverite, a telluride of gold that had not been recognized. This led to a second gold rush in 1896 which included mining the streets.Sony VAIO VGN-SZ750N/C Battery

Production

The principal source of tellurium is from anode sludges produced during the electrolytic refining of blister copper. It is a component of dusts from blast furnace refining of lead. Treatment of 500 tons of copper ore typically yields one pound (0.45 kg) of tellurium.Sony VAIO VGN-SZ75B/B Battery

Tellurium is produced mainly in the United States, Peru, Japan and Canada.[14] For the year 2006 the British Geological Survey gives the following numbers: United States 50 t, Peru 37 t, Japan 24 t and Canada 11 t.[15]

The anode sludges contain the selenides and tellurides of the noble metals in compounds with the formula M2Se or M2Te (M = Cu, Ag, Au).Sony VAIO VGN-SZ76 Battery

At temperatures of 500 °C the anode sludges are roasted with sodium carbonate under air. The metal ions are reduced to the metals, while the telluride is converted to sodium tellurite.

M2Te + O2 + Na2CO3 ? Na2TeO3 + 2 M + CO2

Tellurites can be leached from the mixture with water and are normally present as hydrotellurites HTeO3– in solution.Sony VAIO VGN-SZ770N/C Battery

Selenites are also formed during this process, but they can be separated by adding sulfuric acid. The hydrotellurites are converted into the insoluble tellurium dioxide while the selenites stay in solution.

HTeO3– + OH– + H2SO4 ? TeO2 + 2 SO42? + 2 H2O

The reduction to the metal is done either by electrolysis or by reacting the tellurium dioxide with sulfur dioxide in sulfuric acid.Sony VAIO VGN-SZ77N Battery

TeO2 + 2 SO2 + 2H2O ? Te + SO42? + 4 H+

Commercial-grade tellurium is usually marketed as 200-mesh powder but is also available as slabs, ingots, sticks, or lumps. The year-end price for tellurium in 2000 was US$14 per pound. In recent years, the tellurium price was driven up by increased demand and limited supply, reaching as high as US$100 per pound in 2006.Sony VAIO VGN-SZ780 Battery

Despite an expected doubling in production due to improved extraction methods, the United States Department of Energy (DoE) anticipates a supply shortfall of tellurium by 2025.

Compounds

Tellurium belongs to the same chemical family as oxygen, sulfur, selenium and polonium: the chalcogen family. Tellurium and selenium compounds are similar.Sony VAIO VGN-SZ78N Battery

It exhibits the oxidation states ?2, +2, +4 and +6, with the +4 state being most common.

Tellurides

Reduction of Te metal produces the tellurides and polytellurides, Ten2–. The ?2 oxidation state is exhibited in binary compounds with many metals, such as zinc telluride, ZnTe, formed by heating tellurium with zinc.Sony VAIO VGN-SZ791N/X Battery

Decomposition of ZnTe with hydrochloric acid yields hydrogen telluride (H2Te), a highly unstable analogue of the other chalcogen hydrides, H2O, H2S and H2Se:

ZnTe + 2 HCl ? ZnCl2 + H2Te

H2Te is unstable, whereas salts of its conjugate base [TeH]– are stable.Sony VAIO VGN-SZ84NS Battery

Halides

The +2 oxidation state is exhibited by the dihalides, TeCl2, TeBr2 and TeI2. The dihalides have not been obtained in pure form,although they are known decomposition products of the tetrahalides in organic solvents, and their derived tetrahalotellurates are well-characterized:Sony VAIO VGN-SZ84PS Battery

Te + X2 + 2 X? ? TeX2?4

where X is Cl, Br, or I. These anions are square planar in geometry. Polynuclear anionic species also exist, such as the dark brown Te2I2?6,[21]:283 and the black Te4I2?14.[21]:285Sony VAIO VGN-SZ84S Battery

Fluorine forms two halides with tellurium: the mixed-valence Te2F4 and TeF6. In the +6 oxidation state, the –OTeF5 structural group occurs in a number of compounds such as HOTeF5, B(OTeF5)3, Xe(OTeF5)2, Te(OTeF5)4 and Te(OTeF5)6.[22] The square antiprismatic anion TeF2?8 is also attested.Sony VAIO VGN-SZ84US Battery

The other halogens do not form halides with tellurium in the +6 oxidation state, but only tetrahalides (TeCl4, TeBr4 and TeI4) in the +4 state, and other lower halides (Te3Cl2, Te2Cl2, Te2Br2, Te2I and two forms of TeI). In the +4 oxidation state, halotellurate anions are known, such as TeCl2?6 and Te2Cl2?10. Halotellurium cations are also attested, including TeI+3, found in TeI3AsF6.Sony VAIO VGN-SZ85NS Battery

Oxocompounds

Tellurium monoxide was first reported in 1883 as a black amorphous solid formed by the heat decomposition of TeSO3 in vacuum, disproportionating into tellurium dioxide, TeO2 and elemental tellurium upon heating.Sony VAIO VGN-SZ85S Battery

Since then, however, some doubt has been cast on its existence in the solid phase, although it is known as a vapor phase fragment; the black solid may be merely an equimolar mixture of elemental tellurium and tellurium dioxide.

Tellurium dioxide is formed by heating tellurium in air, causing it to burn with a blue flame.Sony VAIO VGN-SZ85US Battery

Tellurium trioxide, ?-TeO3, is obtained by thermal decomposition of Te(OH)6. The other two forms of trioxide reported in the literature, the ?- and ?- forms, were found not to be true oxides of tellurium in the +6 oxidation state, but a mixture of Te4+, OH?and O?2. Tellurium also exhibits mixed-valence oxides, Te2O5 and Te4O9.Sony VAIO VGN-SZ94NS Battery

The tellurium oxides and hydrated oxides form a series of acids, including tellurous acid (H2TeO3), orthotelluric acid (Te(OH)6) and metatelluric acid ((H2TeO4)n).[26] The two forms of telluric acid form tellurate salts containing the TeO2–4 and TeO6?6 anions, respectively.Sony VAIO VGN-SZ94PS Battery

Tellurous acid forms tellurite salts containing the anion TeO2?3. Other tellurium cations include TeF2+8, which consists of two fused tellurium rings and the polymeric TeF2+7.

Zintl cations

When tellurium is treated with concentrated sulfuric acid, it forms red solutions containing the Zintl ion, Te2+4.Sony VAIO VGN-SZ94S Battery

The oxidation of tellurium by AsF5 in liquid SO2also produces this square planar cation, as well as with the trigonal prismatic, yellow-orange Te4+6:4 Te + 3 AsF5 ? Te2+4(AsF?6)2 + AsF36 Te + 6 AsF5 ? Te4+6(AsF?6)4 + 2 AsF3 Other tellurium Zintl cations include the polymeric Te2+7 and the blue-black Te2+8, which consists of two fused 5-membered tellurium rings. The latter cation is formed by the reaction of tellurium with tungsten hexachloride:Sony VAIO VGN-SZ94US Battery

8 Te + 2 WCl6 ? Te2+8(WCl?6)2

Interchalcogen cations also exist, such as Te2Se2+6 (distorted cubic geometry) and Te2Se2+8. These are formed by oxidizing mixtures of tellurium and selenium with AsF5or SbF5.Sony VAIO VGN-SZ95NS Battery

Organotellurium compounds

Tellurium does not readily form analogues of alcohols and thiols, with the functional group –TeH and are called tellurols. The –TeH functional group is also attributed to using the prefix tellanyl-.Like H2Te, these species are unstable with respect to loss of hydrogen. Telluraethers (R-Te-R) are more stable as aretelluroxides.Sony VAIO VGN-SZ95S Battery

Tellurium (Latin tellus meaning "earth") was discovered in the 18th century in a gold ore from the mines in Zlatna, near what is now Sibiu, Transylvania. This ore was known as "Faczebajer weißes blättriges Golderz" (white leafy gold ore from Faczebaja) orantimonalischer Goldkies (antimonic gold pyrite), and, according to Anton von Rupprecht, was Spießglaskönig (argent molybdique), containing native antimony.Sony VAIO VGN-SZ95US Battery

In 1782 Franz-Joseph Müller von Reichenstein, who was then serving as the Austrian chief inspector of mines in Transylvania, concluded that the ore did not contain antimony, but that it was bismuth sulfide. The following year, he reported that this was erroneous and that the ore contained mostly gold and an unknown metal very similar to antimony.Sony VAIO VGN-TZ121 Battery

After a thorough investigation which lasted for three years and consisted of more than fifty tests, Müller determined the specific gravity of the mineral and noted the radish-like odor of the white smoke which passed off when the new metal was heated, the red color which the metal imparts to sulfuric acid, and the black precipitate which this solution gives when diluted with water.Sony VAIO VGN-TZ13 Battery

Nevertheless, he was not able to identify this metal and gave it the names aurum paradoxium and metallum problematicum, as it did not show the properties predicted for the expected antimony.

In 1789, another Hungarian scientist, Pál Kitaibel, also discovered the element independently in an ore from Deutsch-Pilsen which had been regarded as argentiferous molybdenite, but later he gave the credit to Müller.Sony VAIO VGN-TZ130N/B Battery

In 1798, it was named by Martin Heinrich Klaproth who earlier isolated it from the mineral calaverite. The 1960s brought growth in thermoelectric applications for tellurium (as bismuth telluride), as well as its use in free-machining steel, which became the dominant use.Sony VAIO VGN-TZ131 Battery

Metallurgy

The largest consumer of tellurium is metallurgy, where it is used in iron, copper and lead alloys. When added to stainless steel and copper it makes these metals more machinable. It is alloyed into cast iron for promoting chill for spectroscopic purposes, as the presence of electrically conductive free graphite tends to deleteriously affect spark emission testing results.Sony VAIO VGN-TZ132/N Battery

In lead it improves strength and durability and decreases the corrosive action of sulfuric acid.

Semiconductor and electronic industry uses

Tellurium is used in cadmium telluride (CdTe) solar panels. National Renewable Energy Laboratory lab tests using this material achieved some of the highest efficiencies for solar cell electric power generation.Sony VAIO VGN-TZ132N Battery

Massive commercial production of CdTe solar panels by First Solar in recent years has significantly increased tellurium demand. If some of the cadmium in CdTe is replaced by zinc then (Cd,Zn)Te is formed which is used in solid-state X-ray detectors.

Alloyed with both cadmium and mercury, to form mercury cadmium telluride, an infrared sensitive semiconductor material is formed.Sony VAIO VGN-TZ150N/B Battery

Organotellurium compounds such as dimethyl telluride, diethyl telluride, diisopropyl telluride, diallyl telluride andmethyl allyl telluride are used as precursors for metalorganic vapor phase epitaxy growth of II-VI compound semiconductors. Diisopropyl telluride (DIPTe) is employed as the preferred precursor for achieving the low-temperature growth of CdHgTe byMOVPE.Sony VAIO VGN-TZ150N/N Battery

For these processes highest purity metalorganics of both selenium and tellurium are used. The compounds for semiconductor industry and are prepared by adduct purification.

Tellurium as a tellurium suboxide is used in the media layer of several types of rewritable optical discs, including ReWritable Compact Discs (CD-RW), ReWritable Digital Video Discs (DVD-RW) and ReWritable Blu-ray Discs.Sony VAIO VGN-TZ160CB Battery

Tellurium is used in the new phase change memory chips.[49] developed by Intel.[50] Bismuth telluride (Bi2Te3) and lead telluride are working elements ofthermoelectric devices. Lead telluride is used in far-infrared detectors.

Other uses

• Used to color ceramics.Sony VAIO VGN-TZ160N/B Battery

• The strong increase in optical refraction upon the addition of selenides and tellurides into glass is used in the production of glass fibers for telecommunications. These chalcogenide glasses are widely used.
• Mixtures of selenium and tellurium are used with barium peroxide as oxidizer in the delay powder of electric blasting caps.Sony VAIO VGN-TZ16GN/B Battery

• Organic tellurides have been employed as initiators for living radical polymerization and electron-rich mono- and di-tellurides possess antioxidant activity.
• Rubber can be vulcanized with tellurium instead of sulfur or selenium. The rubber produced in this way shows improved heat resistance.Sony VAIO VGN-TZ16N Battery

• Tellurite agar is used to identify member of the corynebacterium genus, most typically Corynebacterium diphtheriae, the pathogen responsible for diphtheria.Biological role

Tellurium has no known biological function, although fungi can incorporate it in place of sulfur and selenium into amino acids such as telluro-cysteine and telluro-methionine.Sony VAIO VGN-TZ16N/B Battery

Organisms have shown a highly variable tolerance to tellurium compounds. Most organisms metabolize tellurium partly to form dimethyl telluride although dimethyl ditelluride is also formed by some species. Dimethyl telluride has been observed in hot springs at very low concentrations.Sony VAIO VGN-TZ17/N Battery

Precautions

Tellurium and tellurium compounds are considered to be mildly toxic and need to be handled with care, although acute poisoning is rare.[61] Tellurium is not reported to be carcinogenic.[61]

Humans exposed to as little as 0.01 mg/m3 or less in air develop "tellurium breath", which has a garlic-like odor.Sony VAIO VGN-TZ170N/B Battery

The garlic odor that is associated with human intake of tellurium compounds is caused from the tellurium being metabolized by the body. When the body metabolizes tellurium in any oxidation state, the tellurium is converted into dimethyl telluride, (CH3)2Te, which is volatile and is the cause of the garlic-like smell.Sony VAIO VGN-TZ170N/N Battery

Even though the metabolic pathways of tellurium are not known, it is generally assumed that they resemble those of the more extensively studied selenium, because the final methylated metabolic products of the two elements are similar.

Iodine is a chemical element with the symbol I and atomic number 53.Sony VAIO VGN-TZ17GN/B Battery

The name is pronounced  in both American[2] and British[3] English.[4] The name is from the Greek:????? iodes, meaning violet or purple, due to the color of elemental iodine vapor.

Iodine and its compounds are primarily used in nutrition, and industrially in the production of acetic acid and certain polymers.Sony VAIO VGN-TZ17N Battery

Iodine's relatively high atomic number, low toxicity, and ease of attachment to organic compounds have made it a part of many X-ray contrast materials in modern medicine. Iodine has only one stable isotope. A number of iodine radioisotopes are also used in medical applications.Sony VAIO VGN-TZ18/N Battery

Iodine is found on Earth mainly as the highly water-soluble iodide I-, which concentrates it in oceans and brine pools. Like the other halogens, free iodine occurs mainly as a diatomic molecule I2, and then only momentarily after being oxidized from iodide by an oxidant like free oxygen.Sony VAIO VGN-TZ180N/RC Battery

In the universe and on Earth, iodine's high atomic number makes it a relatively rare element, ranking 47th in abundance. However, its presence in ocean water has given it a role in biology. It is the heaviest essential element utilized widely by life in biological functions (only tungsten, employed in enzymes by a few species of bacteria, is heavier).Sony VAIO VGN-TZ185N/WC Battery

Iodine's rarity in many soils, due to initial low abundance as a crust-element, and also leaching of soluble iodide by rainwater, has led to many deficiency problems in land animals and inland human populations. Iodine deficiency affects about two billion people and is the leading preventable cause ofintellectual disabilities.Sony VAIO VGN-TZ18GN/X Battery

Iodine is required by higher animals, which use it to synthesize thyroid hormones, which contain the element. Because of this function, radioisotopes of iodine are concentrated in the thyroid gland along with nonradioactive iodine. The radioisotope iodine-131, which has a high fission product yield, concentrates in the thyroid, and is one of the mostcarcinogenic of nuclear fission products.Sony VAIO VGN-TZ18N Battery

Characteristics

Iodine under standard conditions is a bluish-black solid. It can be seen apparently sublimating at standard temperatures into a violet-pink gas that has an irritating odor. This halogen forms compounds with many elements, but is less reactive than the other members of its Group VII (halogens) and has some metallic light reflectance.Sony VAIO VGN-TZ190N/B Battery

Elemental iodine dissolves easily in most organic solvents such as hexane or chloroform owing to its lack of polarity, but is only slightly soluble in water. However, the solubility of elemental iodine in water can be increased by the addition of potassium iodide.Sony VAIO VGN-TZ190N/BC Battery

The molecular iodine reacts reversibly with the negative ion, generating the triiodide anion I3? inequilibrium, which is soluble in water. This is also the formulation of some types of medicinal (antiseptic) iodine, although tincture of iodine classically dissolves the element in aqueousethanol.Sony VAIO VGN-TZ191N/XC Battery

The colour of solutions of elemental iodine changes depending on the polarity of the solvent. In non-polar solvents like hexane, solutions are violet; in moderately polar dichloromethane, the solution is dark crimson, and, in strongly polar solvents such as acetone or ethanol, it appears orange or brown. This effect is due to the formation of adducts.Sony VAIO VGN-TZ195N/XC Battery

Iodine melts at the relatively low temperature of 113.7 °C, although the liquid is often obscured by a dense violet vapor of gaseous iodine.

Occurrence

Iodine is rare in the solar system and Earth's crust (47th in abundance); however, iodide salts are often very soluble in water.Sony VAIO VGN-TZ198N/RC Battery

Iodine occurs in slightly greater concentrations in seawaterthan in rocks, 0.05 vs 0.04 ppm. Minerals containing iodine include caliche, found in Chile. The brown algae Laminaria and Fucus found in temperate zones of the Northern Hemisphere contain 0.028–0.454 dry weight percent of iodine.Sony VAIO VGN-TZ250N/B Battery

Aside from tungsten, iodine is the heaviest element to be essential in living organisms, and iodine is the heaviest element thought to be needed by higher animals. About 19,000 tonnes are produced annually from natural sources.

Organoiodine compounds are produced by marine life forms, the most notable being iodomethane(commonly called methyl iodide).Sony VAIO VGN-TZ250N/N Battery

The total iodomethane that is produced by the marine environment, by microbial activity in rice paddies and by the burning of biological material is estimated to be 214 kilotonnes/year.[7] The volatile iodomethane is broken up in the atmosphere as part of a global iodine cycle.Sony VAIO VGN-TZ250N/P Battery

Structure and bonding

Iodine normally exists as a diatomic molecule with a I-I bond length of 270 pm,  one of the longest single bonds known. The I2molecules tend to interact via the weak van der Waals force called the London Forces, and this interaction is responsible for the higher melting point compared to more compact halogens, which are also diatomic. Since the atomic size of Iodine is larger, its melting point is higher.Sony VAIO VGN-TZ27/N Battery

The solid crystallizes as orthorhombic crystals. The crystal motif in the Hermann–Mauguin notation is Cmca (No 64), Pearson symbol oS8. The I-I bond is relatively weak, with a bond dissociation energy of 36 kcal/mol. In fact, most bonds to iodine tend to be weaker than for the lighter halides. One consequence of this weak bonding is the relatively high tendency of I2 molecules to dissociate into atomic iodine.Sony VAIO VGN-TZ270N/B Battery

Production

Of the several places in which iodine occurs in nature, only two sources are useful commercially: the caliche, found in Chile, and the iodine-containing brines of gas and oil fields, especially in Japan and the United States. The caliche, found in Chile, contains sodium nitrate, which is the main product of the mining activities and small amounts of sodium iodate and sodium iodide.Sony VAIO VGN-TZ27N Battery

In the extraction of sodium nitrate, the sodium iodate and sodium iodide are extracted.[10] The high concentration of iodine in the caliche and the extensive mining made Chile the largest producer of iodine in 2007.

Most other producers use natural occurring brine for the production of iodine.Sony VAIO VGN-TZ28/N Battery

The Japanese Minami Kanto gas field east of Tokyoand the American Anadarko Basin gas field in northwest Oklahoma are the two largest sources for iodine from brine. The brine has a temperature of over 60°C owing to the depth of the source. The brine is first purified and acidified using sulfuric acid, then the iodide present is oxidized to iodine with chlorine.Sony VAIO VGN-TZ285N/RC Battery

An iodine solution is produced, but is dilute and must be concentrated.Air is blown into the solution, causing the iodine to evaporate, then it is passed into an absorbing tower containing acid wheresulfur dioxide is added to reduce the iodine. The hydrogen iodide (HI) is reacted with chlorine to precipitate the iodine. After filtering and purification the iodine is packed.Sony VAIO VGN-TZ28N Battery

2 HI + Cl2 ? I2? + 2 HCl

I2 + 2 H2O + SO2 ? 2 HI + H2SO4

2 HI + Cl2 ? I2? + 2 HCl

The production of iodine from seawater via electrolysis is not used owing to the sufficient abundance of iodine-rich brine. Another source of iodine was kelp, used in the 18th and 19th centuries, but it is no longer economically viable.Sony VAIO VGN-TZ290EAB Battery

Commercial samples often contain high concentrations of impurities, which can be removed by sublimation. The element may also be prepared in an ultra-pure form through the reaction of potassium iodide with copper(II) sulfate, which gives copper(II) iodide initially. That decomposes spontaneously to copper(I) iodide and iodine:

Cu2+ + 2 I– ? CuI2

2 CuI2 ? 2 CuI + I2

There are also other methods of isolating this element in the laboratory, for example, the method used to isolate other halogens: Oxidation of the iodide in hydrogen iodide (often made in situ with an iodide and sulfuric acid) by manganese dioxide (see below in Descriptive chemistry).Sony VAIO VGN-TZ290EAN Battery

Isotopes and their applications

Of the 37 known (characterized) isotopes of iodine, only one, 127I, is stable.

The longest-lived radioisotope, 129I, has a half-life of 15.7 million years. This is long enough to make it a permanent fixture of the environment on human time scales, but far too short for it to exist as a primordial isotope today.Sony VAIO VGN-TZ290EAP Battery

Instead, iodine-129 is an extinct radionuclide, and its presence in the early solar system is inferred from the observation of an excess of its daughter xenon-129. This nuclide is also newly-made by cosmic rays and as a byproduct of human nuclear fission, which it is used to monitor as a very long-lived environmental contaminant.Sony VAIO VGN-TZ295N/XC Battery

The next-longest-lived radioisotope, iodine-125, has a half-life of 59 days. It is used as a convenient gamma-emitting tag for proteins in biological assays, and a few nuclear medicine imaging tests where a longer half-life is required. It is also commonly used in brachytherapy implanted capsules, which kill tumors by local short-range gamma radiation (but where the isotope is never released into the body).Sony VAIO VGN-TZ298N/XC Battery

Iodine-123 (half-life 13 hours) is the isotope of choice for nuclear medicine imaging of the thyroid gland, which naturally accumulates all iodine isotopes.

Iodine-131 (half-life 8 days) is a beta-emitting isotope, which is a common nuclear fission product.Sony VAIO VGN-TZ33/B Battery

It is preferably administered to humans only in very high doses which destroy all tissues that accumulate it (usually the thyroid), which in turn prevents these tissues from developing cancer from a lower dose (paradoxically, a high dose of this isotope appears safer for the thryoid than a low dose).Sony VAIO VGN-TZ33/N Battery

Like other radioiodines, I-131 accumulates in the thyroid gland, but unlike the others, in small amounts it is highly carcinogenic there, it seems, owing to the high local cell mutation due to damage from beta decay. Because of this tendency of 131I to cause high damage to cells that accumulate it and other cells near them (0.6 to 2 mm away, the range of the beta rays),Sony VAIO VGN-TZ33/W Battery

it is the only iodine radioisotope used as direct therapy, to kill tissues such as cancers that take up artificially iodinated molecules (example, the compound iobenguane, also known as MIBG). For the same reason, only the iodine isotope I-131 is used to treat Grave's disease and those types of thyroid cancers (sometimes in metastatic form) where the tissue that requires destruction, still functions to naturally accumulate iodide.Sony VAIO VGN-TZ350N/B Battery

Nonradioactive ordinary potassium iodide (iodine-127), in a number of convenient forms (tablets or solution) may be used to saturate the thyroid gland's ability to take up further iodine, and thus protect against accidental contamination from iodine-131 generated by nuclear fission accidents,Sony VAIO VGN-TZ350N/N Battery

such as the Chernobyl disaster and more recently the Fukushima I nuclear accidents, as well as from contamination from this isotope in nuclear fallout from nuclear weapons.

Iodine was discovered by Bernard Courtois in 1811. He was born to a manufacturer of saltpeter (a vital part of gunpowder).Sony VAIO VGN-TZ350N/P Battery

At the time of the Napoleonic Wars,France was at war and saltpeter was in great demand. Saltpeter produced from French niter beds required sodium carbonate, which could be isolated from seaweedcollected on the coasts of Normandy and Brittany. To isolate the sodium carbonate, seaweed was burned and the ash washed with water.Sony VAIO VGN-TZ370N/B Battery

The remaining waste was destroyed by adding sulfuric acid. Courtois once added excessive sulfuric acid and a cloud of purple vapor rose. He noted that the vapor crystallized on cold surfaces, making dark crystals. Courtois suspected that this was a new element but lacked funding to pursue it further.Sony VAIO VGN-TZ37N/G Battery

Courtois gave samples to his friends, Charles Bernard Desormes (1777–1862) and Nicolas Clément (1779–1841), to continue research. He also gave some of the substance to chemist Joseph Louis Gay-Lussac (1778–1850), and to physicist André-Marie Ampère (1775–1836). On 29 November 1813, Dersormes and Clément made public Courtois's discovery.Sony VAIO VGN-TZ37N/P Battery

They described the substance to a meeting of the Imperial Institute of France. On December 6, Gay-Lussac announced that the new substance was either an element or a compound of oxygen. It was Gay-Lussac who suggested the name "iode", from the Greek word ????? (iodes) for violet (because of the color of iodine vapor).Sony VAIO VGN-TZ37N/R Battery

Ampère had given some of his sample to Humphry Davy (1778–1829). Davy did some experiments on the substance and noted its similarity to chlorine.[18] Davy sent a letter dated December 10 to the Royal Society of London stating that he had identified a new element.Sony VAIO VGN-TZ37N/X Battery

Arguments erupted between Davy and Gay-Lussac over who identified iodine first, but both scientists acknowledged Courtois as the first to isolate the element.

Catalysis

The major application of iodine is as a co-catalyst for the production of acetic acid by the Monsanto and Cativa processes.Sony VAIO VGN-TZ38N/X Battery

In these technologies, which support the world's demand for acetic acid, hydroiodic acid converts the methanol feedstock into methyl iodide, which undergoes carbonylation. Hydrolysis of the resulting acetyl iodide regenerates hydroiodic acid and gives acetic acid.Sony VAIO VGN-TZ398U/XC Battery

Animal feed

The production of ethylenediammonium diiodide (EDDI) consumes a large fraction of available iodine. EDDI is provided to livestock as a nutritional supplement.[6]

Disinfectant and water treatment

Elemental iodine is used as a disinfectant in various forms.Sony VAIO VGN-TZ50B Battery

The iodine exists as the element, or as the water-soluble triiodide anion I3- generated in situ by adding iodide to poorly water-soluble elemental iodine (the reverse chemical reaction makes some free elemental iodine available for antisepsis). In alternative fashion, iodine may come from iodophors, which contain iodine complexed with a solubilizing agent (iodide ion may be thought of loosely as the iodophor in triiodide water solutions).Sony VAIO VGN-TZ90HS Battery

Examples of such preparations include:

• Tincture of iodine: iodine in ethanol, or iodine and sodium iodide in a mixture of ethanol and water.
• Lugol's iodine: iodine and iodide in water alone, forming mostly triiodide. Unlike tincture of iodine, Lugol's has a minimized amount of the free iodine (I2) component.
• Povidone iodine (an iodophor)Sony VAIO VGN-TZ90NS Battery

Health, medical, and radiological use

In most countries, table salt is iodized. Iodine is required for the essential thyroxin hormones produced by and concentrated in the thyroid gland.

Potassium iodide has been used as an expectorant, although this use is increasingly uncommon. Sony VAIO VGN-TZ90S Battery

In medicine, potassium iodide is used to treat acute thyrotoxicosis, usually as a saturated solution of potassium iodide (SSKI). It is also used to block uptake of iodine-131 in the thyroid gland (see isotopes section above), when this isotope is used as part of radiopharmaceuticals (such as iobenguane) that are not targetted to the thyroid or thyroid type tissues.Sony VAIO VPC CW2MFX/PU Battery

Iodine-131 (in the chemical form of iodide) is a component of nuclear fallout and a particularly dangerous one owing to the thyroid gland's propensity to concentrate ingested iodine, where it is kept for periods longer than this isotope's radiological half-life of eight days.Sony VAIO VPC S11V9E/B Battery

For this reason, if people are expected to be exposed to a significant amount of environmental radioactive iodine (iodine-131 in fallout), they may be instructed to take non-radioactive potassium iodide tablets. The typical adult dose is one 130 mg tablet per 24 hours, supplying 100 mg (100,000 micrograms) iodine, as iodide ion.Sony VAIO VPCB119GJ/B Battery

(Note: typical daily dose of iodine to maintain normal health is of order 100 micrograms; see "Dietary Intake" below.) By ingesting this large amount of non-radioactive iodine, radioactive iodine uptake by the thyroid gland is minimized. See the main article above for more on this topic.Sony VAIO VPCB11AGJ Battery

Radiocontrast agent

Iodine, as a heavy element, is quite radio-opaque. Organic compounds of a certain type (typically iodine-substituted benzene derivatives) are, thus, used in medicine as X-ray radiocontrast agents for intravenous injection. This is often in conjunction with advanced X-ray techniques such as angiography and CT scanning. At present, all water-soluble radiocontrast agents rely on iodine.Sony VAIO VPCB11AVJ Battery

Other uses

Inorganic iodides find specialized uses. Hafnium, zirconium, titanium are purified by the van Arkel Process, which involves the reversible formation of the tetraiodides of these elements. Silver iodide is a major ingredient to traditional photographic film. Thousands of kilograms of silver iodide are consumed annually for cloud seeding.Sony VAIO VPCB11V9E Battery

The organoiodine compound erythrosine is an important food coloring agent. Perfluoroalkyl iodides are precursors to important surfactants, such as perfluorooctanesulfonic acid.

Iodine chemistry

Iodine adopts a variety of oxidation states, commonly ranging from (formally) I7+ to I-, and including the intermediate states of I5+, I3+ and I+.Sony VAIO VPCB11X9E Battery

Practically, only the 1- oxidation state is of significance, being the form found in iodide salts and organoiodine compounds.

Solubility

Being a nonpolar molecule, iodine is highly soluble in nonpolar organic solvents, including ethanol (20.5 g/100 ml at 15 °C, 21.43 g/100 ml at 25 °C), diethyl ether (20.6 g/100 ml at 17 °C, 25.20 g/100 ml at 25 °C), chloroform, acetic acid, glycerol,Sony VAIO VPCCW18FJ/P Battery

benzene (14.09 g/100 ml at 25 °C), carbon tetrachloride(2.603 g/100 ml at 35 °C), and carbon disulfide (16.47 g/100 ml at 25 °C). Elemental iodine is poorly soluble in water, with one gram dissolving in 3450 ml at 20 °C and 1280 ml at 50 °C. Aqueous and ethanol solutions are brown reflecting the role of these solvents as Lewis bases. Solutions in chloroform, carbon tetrachloride, and carbon disulfide are violet, the color of iodine vapor.Sony VAIO VPCCW18FJ/R Battery

One of the most distinctive properties of iodine is the way that its solubility in water is enhanced by the presence of iodide ions. The dissolution of iodine in aqueous solutions containing iodide (e.g., from hydroiodic acid, potassium iodide, etc.) results from the formation of the I3? ion. Dissolved bromides also improve water solubility of iodine.Sony VAIO VPCCW18FJ/W Battery

Redox reactions

In everyday life, iodides are slowly oxidized by atmospheric oxygen in the atmosphere to give free iodine. Evidence for this conversion is the yellow tint of certain aged samples of iodide salts and some organoiodine compounds.Sony VAIO VPCCW19FJ/W Battery

The oxidation of iodide to iodine in air is also responsible for the slow loss of iodide content iniodized salt if exposed to air.[23] Some salts use iodate to prevent the loss of iodine.

Iodine is easily oxidized and easily reduced. Most common is the interconversion of I- and I2. Molecular iodine can be prepared by oxidizing iodides with chlorine:Sony VAIO VPCCW1AFJ Battery

2 I? + Cl2 ? I2 + 2 Cl?

or with manganese dioxide in acid solution:

2 I? + 4 H+ + MnO2 ? I2 + 2 H2O + Mn2+

Iodine is reduced to hydroiodic acid by hydrogen sulfide and hydrazine:Sony VAIO VPCCW1AHJ Battery

8 I2 + 8 H2S ? 16 HI + S8

2 I2 + N2H4 ? 4 HI + N2

When dissolved in fuming sulfuric acid (65% oleum), iodine forms an intense blue solution. The blue color is due to I+
2 cation, the result of iodine being oxidized bySO3:

2 I2 + 2 SO3 + H2SO4 ? 2 I+2 + SO2 + 2 HSO?
4

The I+
2 cation is also formed in the oxidation of iodine by SbF5 or TaF5.Sony VAIO VPCCW1S1E Battery

The resulting I+2Sb2F?11 or I+2Ta2F?11 can be isolated as deep blue crystals. The solutions of these salts turn red when cooled below ?60°C, owing to the formation of the I2+4 cation:

2 I+2   I2+4

Under slightly more alkaline conditions, I2+4 disproportionates into I+3 and an iodine(III) compound. Excess iodine can then react with I+3 to form I+5 (green) and I3+15(black).Sony VAIO VPCCW1S1E/B Battery

Oxides of iodine

The best-known oxides are the anions, IO3– and IO4–, but several other oxides are known, such as the strong oxidant iodine pentoxide.

By contrast with chlorine, the formation of the hypohalite ion (IO–) in neutral aqueous solutions of iodine is negligible.Sony VAIO VPCCW1S1E/L Battery

I2 + H2O   H+ + I? + HIO   (K = 2.0×10?13)[24] In basic solutions (such as aqueous sodium hydroxide), iodine converts in a two stage reaction to iodide andiodate:

I2 + 2 OH? ? I? + IO? + H2O		(K = 30)
3 IO? ? 2 I? + IO3?		(K = 1020)

Organic derivatives of hypoiodate (2-Iodoxybenzoic acid, and Dess-Martin periodinane) are used in organic chemistry.Sony VAIO VPCCW1S1E/P Battery

Iodic acid (HIO3), periodic acid (HIO4) and their salts are strong oxidizers and are of some use in organic synthesis. Iodine is oxidized to iodate by nitric acid as well as by chlorates:

I2 + 10 HNO3 ? 2 HIO3 + 10 NO2 + 4 H2O

I2 + 2 ClO3? ? 2 IO3? + Cl2 Sony VAIO VPCCW1S1E/R Battery

Inorganic iodine compounds

Iodine forms compounds with all the elements except for the noble gases. From the perspective of commercial applications, an important compound is hydroiodic acid, used as a co-catalyst in the Cativa process for the production of acetic acid. Titanium and aluminium iodides are used in the production of butadiene, a precursor to rubber tires.Sony VAIO VPCCW1S1E/W Battery

Alkali metal salts are common colourless solids that are highly soluble in water. Potassium iodide is a convenient source of the iodide anion; it is easier to handle than sodium iodide because it is not hygroscopic. Both salts are mainly used in the production of iodized salt.Sony VAIO VPCCW21FX/B Battery

Sodium iodide is especially useful in the Finkelstein reaction, because it is soluble in acetone, whereas potassium iodide is less so. In this reaction, an alkyl chloride is converted to an alkyl iodide. This relies on the insolubility of sodium chloride in acetone to drive the reaction:Sony VAIO VPCCW21FX/L Battery

R-Cl (acetone) + NaI (acetone) ? R-I (acetone) + NaCl (s)

Despite having the lowest electronegativity of the common halogens, iodine reacts violently with some metals, such as aluminium:

3 I2 + 2 Al ? 2 AlI3

This reaction produces 314 kJ per mole of aluminum, comparable to thermite's 425 kJ. Yet the reaction initiates spontaneously, and if unconfined, causes a cloud of gaseous iodine due to the high temperature.Sony VAIO VPCCW21FX/R Battery

Interhalogen compounds

Interhalogen compounds are well known; examples include iodine monochloride and trichloride; iodine pentafluoride and heptafluoride.

Organic compounds

Many organoiodine compounds exist; the simplest is iodomethane, approved as a soil fumigant. Iodinated organic compounds are used as synthetic reagents.Sony VAIO VPCCW21FX/W Battery

Organic synthesis

Organoiodine compounds can be made in many ways. For example, methyl iodide can be prepared from methanol, red phosphorus, and iodine.[28] The iodinating reagent isphosphorus triiodide that is formed in situ:Sony VAIO VPCCW26EC Battery

3 CH3OH + PI3 ? 3 CH3I + [[H3PO3|Phosphorous acid]]

The iodoform test uses an alkaline solution of iodine to react with methyl ketones to give the labile triiodomethide leaving group, forming iodoform, which precipitates.Sony VAIO VPCCW26FX/B Battery

Aryl and alkyl iodides both form Grignard reagents. Iodine is sometimes used to activate magnesium when preparing Grignard reagents. Alkyl iodides such as iodomethane are good alkylating agents. Some drawbacks to use of organoiodine compounds in chemical synthesis are:

Sony AIO VPCCW28EC Battery

• iodine compounds tend to be more expensive than the corresponding bromides and chlorides, in that order
• iodides tend to be much stronger alkylating agents, and so are more toxic (e.g., methyl iodide is very toxic (T+).Sony VAIO VPCCW28FJ/P Battery

• low-molecular-weight iodides tend to have a much higher equivalent weight, compared to other alkylating agents (e.g., methyl iodide versus dimethyl carbonate), owing to the atomic mass of iodine.

Analytical chemistry and bioanalysis

Iodine is a common general stain used in thin-layer chromatography. In particular, iodine forms an intense blue complex with the glucose polymers starch and glycogen. Several analytical methods rely on this property:Sony VAIO VPCCW28FJ/R Battery

• Iodometry. The concentration of an oxidant can be determined by adding it to an excess of iodide, to destroy elemental iodine/triiodide as a result of oxidation by the oxidant. A starch indicator is then used as the indicator close to the end-point, in order to increase the visual contrast (dark blue becomes colorless, instead of the yellow of dilute triiodide becoming colorless).Sony VAIO VPCCW28FJ/W Battery

• An Iodine test may be used to test a sample substance for the presence of starch. The Iodine clock reaction is an extension of the techniques in iodometry.
• Iodine solutions are used in counterfeit banknote detection pens; the premise being that counterfeit banknotes made using commercially available paper contain starch.Sony VAIO VPCCW29FJ/W Battery

• Starch-iodide paper are used to test for the presence of oxidants such as peroxides. The oxidants convert iodide to iodine, which shows up as blue. A solution of starch and iodide can perform the same function.
• During colposcopy, Lugol's iodine is applied to the vagina and cervix.Sony VAIO VPCCW2AFJ Battery

• Normal vaginal tissue stains brown owing to its high glycogen content (a color-reaction similar to that with starch), while abnormal tissue suspicious for cancer does not stain, and thus appears pale compared to the surrounding tissue. Biopsy of suspicious tissue can then be performed. This is called a Schiller's Test.Sony VAIO VPCCW2AHJ Battery

Clandestine synthetic chemical use

In the United States, the Drug Enforcement Agency (DEA) regards iodine and compounds containing iodine (ionic iodides, iodoform, ethyl iodide, and so on) as reagents useful for the clandestine manufacture of methamphetamine.Sony VAIO VPCCW2S1E Battery

Biological role

Iodine is an essential trace element for life, the heaviest element commonly needed by living organisms. Only tungsten, a component of a few bacterial enzymes, has a higher atomic number and atomic weight.

Thyroxines are iodine-containing hormones that justify the widespread use of iodised salt.Sony VAIO VPCCW2S1E/B Battery

Iodine's main role in animal biology is as a constituent of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). These are made from addition condensation products of the amino acid tyrosine, and are stored prior to release in an iodine-containingprotein called thyroglobulin. T4 and T3 contain four and three atoms of iodine per molecule, respectively.Sony VAIO VPCCW2S1E/L Battery

The thyroid glandactively absorbs iodide from the blood to make and release these hormones into the blood, actions that are regulated by a second hormone TSH from the pituitary. Thyroid hormones are phylogenetically very old molecules that are synthesized by mostmulticellular organisms, and that even have some effect on unicellular organisms.Sony VAIO VPCCW2S1E/P Battery

Thyroid hormones play a basic role in biology, acting on gene transcription to regulate the basal metabolic rate.[citation needed]The total deficiency of thyroid hormones can reduce basal metabolic rate up to 50%, while in excessive production of thyroid hormones the basal metabolic rate can be increased by 100%.Sony VAIO VPCCW2S1E/R Battery

T4 acts largely as a precursor to T3, which is (with minor exceptions) the biologically active hormone.

Iodine has a nutritional relationship with selenium. A family of selenium-dependent enzymes called deiodinases converts T4 to T3 (the active hormone) by removing an iodine atom from the outer tyrosine ring.Sony VAIO VPCCW2S1E/W Battery

These enzymes also convert T4 to reverse T3 (rT3) by removing an inner ring iodine atom, and convert T3 to 3,3'-diiodothyronine (T2) also by removing an inner ring atom. Both of the latter are inactivated hormones that are ready for disposal and have, in essence, no biological effects.Sony VAIO VPCCW2S5C CN1 Battery

A family of non-selenium-dependent enzymes then further deiodinates the products of these reactions.

Iodine accounts for 65% of the molecular weight of T4 and 59% of the T3. Fifteen to 20 mg of iodine is concentrated in thyroid tissue and hormones, but 70% of the body's iodine is distributed in other tissues, including mammary glands, eyes, gastric mucosa, the cervix, and salivary glands.Sony VAIO VPCF112FX/B Battery

In the cells of these tissues, iodide enters directly by sodium-iodide symporter (NIS). Its role in mammary tissue is related to fetal and neonatal development, but its role in the other tissues is unknown.

Dietary intake

The daily Dietary Reference Intake recommended by the United States Institute of Medicine is between 110 and 130 µg for infants up to 12 months,Sony VAIO VPCF115FG/B Battery

90 µg for children up to eight years, 130 µg for children up to 13 years, 150 µg for adults, 220 µg for pregnant women and 290 µg for lactating mothers.[34] The Tolerable Upper Intake Level (UL) for adults is 1,100 ?g/day (1.1 mg/day).[35] The tolerable upper limit was assessed by analyzing the effect of supplementation on thyroid-stimulating hormone.Sony VAIO VPCF116FGBI Battery

The thyroid gland needs no more than 70 micrograms /day to synthesize the requisite daily amounts of T4 and T3. The higher recommended daily allowance levels of iodine seem necessary for optimal function of a number of body systems, including lactating breast, gastric mucosa, salivary glands, oral mucosa, thymus, epidermis, choroid plexus, etc.Sony VAIO VPCF117FJ/W Battery

The high iodide-concentration of thymus tissue in particular suggests an anatomical rationale for this role of iodine in the immune system.[39] The trophic, antioxidant and apoptosis-inductor actions and the presumed anti-tumour activity of iodides has been suggested to also be important for prevention of oral and salivary glands diseases.Sony VAIO VPCF117HG/BI Battery

Natural sources of iodine include sea life, such as kelp and certain seafood, as well as plants grown on iodine-rich soil. Iodized salt is fortified with iodine.

As of 2000, the median intake of iodine from food in the United States was 240 to 300 ?g/day for men and 190 to 210 ?g/day for women.Sony VAIO VPCF118FJ/W Battery

In Japan, consumption is much higher, owing to the frequent consumption of seaweed or kombu kelp.

After iodine fortification programs (e.g., iodized salt) have been implemented, some cases of iodine-induced hyperthyroidism have been observed (so called Jod-Basedow phenomenon). The condition seems to occur mainly in people over forty, and the risk appears higher when iodine deficiency is severe and the initial rise in iodine intake is high.Sony VAIO VPCF119FC Battery

It should also be noted that information processing, fine motor skills, and visual problem solving are improved by iodine repletion in moderately iodine-deficient children.

Deficiency

In areas where there is little iodine in the diet, typically remote inland areas and semi-arid equatorial climates where no marine foods are eaten, iodine deficiency gives rise to hypothyroidism, symptoms of which are extreme fatigue, goitre, mental slowing, depression, weight gain, and low basal body temperatures.Sony VAIO VPCF119FC/BI Battery

Iodine deficiency is the leading cause of preventable mental retardation, a result that occurs primarily when babies or small children are rendered hypothyroidic by a lack of the element. The addition of iodine to table salt has largely eliminated this problem in the wealthier nations, but, as of March 2006, iodine deficiency remained a serious public health problem in the developing world.Sony VAIO VPCF119FJ/BI Battery

Iodine deficiency is also a problem in certain areas of Europe.

Other possible health effects being investigated as being related to deficiency include:

• Breast cancer. The breast strongly and actively concentrates iodine into breast-milk for the benefit of the developing infant, and may develop a goiter-like hyperplasia, sometimes manifesting as fibrocystic breast disease, when iodine level are low.Sony VAIO VPCF11AFJ Battery

• Studies indicate that iodine deficiency, either dietary or pharmacologic, can lead to breast atypia and increased incidence of malignancy in animal models, while iodine treatment can reverse dysplasia . The role of iodide in breast dysplasia and development of breast cancer is an area of active research.Sony VAIO VPCF11AGJ Battery

• Stomach cancer. Some researchers have found an epidemiologic correlation between iodine deficiency, iodine-deficient goitre and gastric cancer. A decrease of the incidence of death rate from stomach cancer after implementation of the effective iodine-prophylaxis has been reported also.Sony VAIO VPCF11AHJ Battery

Precautions and toxicity of elemental iodine

Elemental iodine is an oxidizing irritant and direct contact with skin can cause lesions, so iodine crystals should be handled with care. Solutions with high elemental iodine concentration such as tincture of iodine and Lugol's solution are capable of causing tissue damage if use for cleaning and antisepsis is prolonged.Sony VAIO VPCF11JFX/B Battery

Elemental iodine (I2) is poisonous if taken orally in larger amounts; 2–3 grams of it is a lethal dose for an adult human.

Iodine vapor is very irritating to the eye, to mucous membranes, and in the respiratory tract. Concentration of iodine in the air should not exceed 1 mg/m3 (eight-hour time-weighted average).Sony VAIO VPCF11M1E Battery

Toxicity of iodide ion

Excess iodine has symptoms similar to those of iodine deficiency. Commonly encountered symptoms are abnormal growth of the thyroid gland and disorders in functioning and growth of the organism as a whole. Iodides are similar in toxicity to bromides.Sony VAIO VPCF11M1E/H Battery

Excess iodine can be more cytotoxic in the presence of selenium deficiency. Iodine supplementation in selenium-deficient populations is, in theory, problematic, partly for this reason.

Iodine sensitivity

Some people develop a sensitivity to iodine. Application of tincture of iodine can cause a rash. Some cases of reaction to Povidone-iodine (Betadine) have been documented to be a chemical burn.Sony VAIO VPCF11MFX/B Battery

Eating iodine-containing foods can cause hives. Medical use of iodine (i.e. as a contrast agent, see above) can causeanaphylactic shock in highly iodine-sensitive patients. Some cases of sensitivity to iodine can be formally classified as iodine allergies. Iodine sensitivity is rare but has a considerable effect given the extremely widespread use of iodine-based contrast media.Sony VAIO VPCF11S1E Battery

Xenon is a chemical element with the symbol Xe and atomic number 54. The element name is pronounced  A colorless, heavy, odorless noble gas, xenon occurs in the Earth's atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized.Sony VAIO VPCF11S1E/B Battery

Naturally occurring xenon consists of nine stable isotopes. There are also over 40 unstable isotopes that undergo radioactive decay. The isotope ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced from iodine-135 as a result ofnuclear fission, and it acts as the most significant neutron absorber in nuclear reactors.Sony VAIO VPCF11Z1E Battery

Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser design used a xenon dimer molecule (Xe2) as its lasing medium, and the earliest laser designs used xenon flash lamps as pumps. Xenon is also being used to search for hypothetical weakly interacting massive particles and as the propellant for ion thrusters in spacecraft.Sony VAIO VPCF11Z1E/BI Battery

Xenon was discovered in England by William Ramsay and Morris Travers on July 12, 1898, shortly after their discovery of the elements krypton and neon. They found it in the residue left over from evaporating components of liquid air. Ramsay suggested the name xenon for this gas from theGreek word ????? [xenon], neuter singular form of ????? [xenos], meaning 'foreign(er)', 'strange(r)', or 'guest'.Sony VAIO VPCF11ZHJ Battery

In 1902, Ramsay estimated the proportion of xenon in the Earth's atmosphere as one part in 20 million.

During the 1930s, engineer Harold Edgerton began exploring strobe light technology for high speed photography. This led him to the invention of the xenon flash lamp, in which light is generated by sending a brief electrical current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method.Sony VAIO VPCF127HGBI Battery

In 1939, Albert R. Behnke Jr. began exploring the causes of "drunkenness" in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, and discovered that this caused the divers to perceive a change in depth. From his results, he deduced that xenon gas could serve as ananesthetic.Sony VAIO VPCF137HG/BI Battery

Although Lazharev, in Russia, apparently studied xenon anesthesia in 1941, the first published report confirming xenon anesthesia was in 1946 by J. H. Lawrence, who experimented on mice. Xenon was first used as a surgical anesthetic in 1951 by Stuart C. Cullen, who successfully operated on two patients.Sony VAIO VPCS111FM/S Battery

Xenon and the other noble gases were for a long time considered to be completely chemically inert and not able to form compounds. However, while teaching at the University of British Columbia, Neil Bartlett discovered that the gas platinum hexafluoride (PtF6) was a powerful oxidizing agent that could oxidize oxygen gas (O2) to form dioxygenyl hexafluoroplatinate (O2+[PtF6]–).Sony VAIO VPCS115EC Battery

Since O2 and xenon have almost the same first ionization potential, Bartlett realized that platinum hexafluoride might also be able to oxidize xenon. On March 23, 1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate.Sony VAIO VPCS115FG Battery

Bartlett thought its composition to be Xe+[PtF6]–, although later work has revealed that it was probably a mixture of various xenon-containing salts. Since then, many other xenon compounds have been discovered,  along with some compounds of the noble gases argon, krypton, and radon, including argon fluorohydride (HArF), krypton difluoride (KrF2), and radon fluoride. By 1971, more than 80 xenon compounds were known.Sony VAIO VPCS117GG Battery

Characteristics

Xenon has atomic number 54; that is, its nucleus contains 54 protons. Atstandard temperature and pressure, pure xenon gas has a density of 5.761 kg/m3, about 4.5 times the surface density of the Earth's atmosphere, 1.217 kg/m3. As a liquid, xenon has a density of up to 3.100 g/mL, with the density maximum occurring at the triple point.Sony VAIO VPCS117GGB Battery

Under the same conditions, the density of solid xenon, 3.640 g/cm3, is higher than the average density of granite, 2.75 g/cm3. Using gigapascals of pressure, xenon has been forced into a metallic phase.

Solid xenon changes from face-centered cubic (fcc) to hexagonal close packed(hcp) crystal phase under pressure and begins to turn metallic at about 140 GPa, with no noticeable volume change in the hcp phase.Sony VAIO VPCS118EC Battery

It is completely metallic at 155 GPa. When metalized, xenon looks sky blue because it absorbs red light and transmits other visible frequencies. Such behavior is unusual for a metal and is explained by the relatively small widths of the electron bands in metallic xenon.

Xenon is a member of the zero-valence elements that are called noble or inert gases.Sony VAIO VPCS119FJ/B Battery

It is inert to most common chemical reactions (such as combustion, for example) because the outer valence shellcontains eight electrons. This produces a stable, minimum energy configuration in which the outer electrons are tightly bound. However, xenon can be oxidized by powerful oxidizing agents, and many xenon compounds have been synthesized.Sony VAIO VPCS119GC Battery

In a gas-filled tube, xenon emits a blue or lavenderish glow when the gas is excited by electrical discharge. Xenon emits a band of emission lines that span the visual spectrum,[45] but the most intense lines occur in the region of blue light, which produces the coloration.Sony VAIO VPCS11AFJ Battery

Occurrence and production

Xenon is a trace gas in Earth's atmosphere, occurring at 87±1 parts per billion (nL/L), or approximately 1 part per 11.5 million,[47]and is also found in gases emitted from some mineral springs.

Xenon is obtained commercially as a byproduct of the separation of air into oxygen and nitrogen.Sony VAIO VPCS11AGJ Battery

After this separation, generally performed by fractional distillation in a double-column plant, the liquid oxygen produced will contain small quantities of krypton and xenon. By additional fractional distillation steps, the liquid oxygen may be enriched to contain 0.1–0.2% of a krypton/xenon mixture, which is extracted either via adsorption onto silica gel or by distillation.Sony VAIO VPCS11AHJ Battery

Finally, the krypton/xenon mixture may be separated into krypton and xenon via distillation.  Extraction of a liter of xenon from the atmosphere requires 220 watt-hours of energy.[50] Worldwide production of xenon in 1998 was estimated at 5,000–7,000 m3.Sony VAIO VPCS11AVJ Battery

Because of its low abundance, xenon is much more expensive than the lighter noble gases—approximate prices for the purchase of small quantities in Europe in 1999 were 10 €/L for xenon, 1 €/L for krypton, and 0.20 €/L for neon.

Within the Solar System, the nucleon fraction of xenon is 1.56 × 10?8, for an abundance of one part in 64 million of the total mass.Sony VAIO VPCS11J7E/B Battery

Xenon is relatively rare in the Sun's atmosphere, on Earth, and in asteroids and comets. The planet Jupiter has an unusually high abundance of xenon in its atmosphere; about 2.6 times as much as the Sun. This high abundance remains unexplained and may have been caused by an early and rapid buildup of planetesimals—small, subplanetary bodies—before the presolar disk began to heat up.Sony VAIO VPCS11M1E/W Battery

(Otherwise, xenon would not have been trapped in the planetesimal ices.) The problem of the low terrestrial xenon may potentially be explained by covalent bonding of xenon to oxygen within quartz, hence reducing the outgassing of xenon into the atmosphere.Sony VAIO VPCS11V9E Battery

Unlike the lower mass noble gases, the normal stellar nucleosynthesis process inside a star does not form xenon. Elements more massive than iron-56 have a net energy cost to produce through fusion, so there is no energy gain for a star when creating xenon.Sony VAIO VPCS11V9E/B Battery

Instead, xenon is formed during supernova explosions, by the slow neutron capture process (s-process) of red giant stars that have exhausted the hydrogen at their cores and entered the asymptotic giant branch,  in classicalnovae explosions and from the radioactive decay of elements such as iodine, uranium and plutonium.Sony VAIO VPCS11X9E/B Battery

Isotopes and isotopic studies

Naturally occurring xenon is made of nine stable isotopes, the most of any element with the exception of tin, which has ten. Xenon and tin are the only elements to have more than seven stable isotopes.The isotopes 124Xe, 134Xe and 136Xe are predicted to undergo double beta decay, but this has never been observed so they are considered to be stable.Sony VAIO VPCS123FGB Battery

Besides these stable forms, there are over 40 unstable isotopes that have been studied. 129Xe is produced by beta decay of 129I, which has a half-life of 16 million years, while 131mXe, 133Xe, 133mXe, and 135Xe are some of the fission products of both 235U and 239Pu, and therefore used as indicators of nuclear explosions.Sony VAIO VPCS125EC Battery

Nuclei of two of the stable isotopes of xenon, 129Xe and 131Xe, have non-zero intrinsic angular momenta (nuclear spins, suitable for nuclear magnetic resonance). The nuclear spins can be aligned beyond ordinary polarization levels by means of circularly polarized light and rubidium vapor.Sony VAIO VPCS128EC Battery

The resulting spin polarization of xenon nuclei can surpass 50% of its maximum possible value, greatly exceeding the equilibrium value dictated by the Boltzmann distribution (typically 0.001% of the maximum value at room temperature, even in the strongest magnets). Such non-equilibrium alignment of spins is a temporary condition, and is called hyperpolarization.Sony VAIO VPCS129GC Battery

The process of hyperpolarizing the xenon is called optical pumping (although the process is different from pumping a laser).

Because a 129Xe nucleus has a spin of 1/2, and therefore a zero electric quadrupole moment, the 129Xe nucleus does not experience any quadrupolar interactions during collisions with other atoms,Sony VAIO VPCS12C7E/B Battery

and thus its hyperpolarization can be maintained for long periods of time even after the laser beam has been turned off and the alkali vapor removed by condensation on a room-temperature surface. Spin polarization of 129Xe can persist from several seconds for xenon atoms dissolved in blood to several hours in the gas phase and several days in deeply frozen solid xenon.Sony VAIO VPCS12L9E/B Battery

In contrast, 131Xe has a nuclear spin value of 3/2 and a nonzero quadrupole moment, and has T1 relaxation times in the millisecond and second ranges.

Some radioactive isotopes of xenon, for example, 133Xe and 135Xe, are produced by neutron irradiation of fissionable material within nuclear reactors.Sony VAIO VPCS12V9E/B Battery

135Xe is of considerable significance in the operation of nuclear fission reactors. 135Xe has a huge cross section for thermal neutrons, 2.6×106 barns,  so it acts as aneutron absorber or "poison" that can slow or stop the chain reaction after a period of operation. This was discovered in the earliest nuclear reactors built by the American Manhattan Project for plutonium production.Sony VAIO VPCY115FGS Battery

Fortunately the designers had made provisions in the design to increase the reactor's reactivity (the number of neutrons per fission that go on to fission other atoms of nuclear fuel).[69] 135Xe reactor poisoning played a major role in the Chernobyl disaster.[70] A shutdown or decrease of power of a reactor can result in buildup of 135Xe and getting the reactor into the iodine pit.Sony VAIO VPCY115FX/BI Battery

Under adverse conditions, relatively high concentrations of radioactive xenon isotopes may be found emanating from nuclear reactors due to the release of fission products from cracked fuel rods, or fissioning of uranium in cooling water.

Because xenon is a tracer for two parent isotopes, xenon isotope ratios in meteorites are a powerful tool for studying the formation of the solar system.Sony VAIO VPCY115FXBI Battery

The iodine-xenon method of dating gives the time elapsed between nucleosynthesis and the condensation of a solid object from the solar nebula. In 1960, physicist John H. Reynolds discovered that certain meteorites contained an isotopic anomaly in the form of an overabundance of xenon-129. He inferred that this was a decay product of radioactive iodine-129.Sony VAIO VPCY118EC Battery

This isotope is produced slowly by cosmic ray spallation and nuclear fission, but is produced in quantity only in supernova explosions. As the half-life of 129I is comparatively short on a cosmological time scale, only 16 million years, this demonstrated that only a short time had passed between the supernova and the time the meteorites had solidified and trapped the 129I.Sony VAIO VPCY118GX/BI Battery

These two events (supernova and solidification of gas cloud) were inferred to have happened during the early history of the Solar System, as the 129I isotope was likely generated before the Solar System was formed, but not long before, and seeded the solar gas cloud with isotopes from a second source. This supernova source may also have caused collapse of the solar gas cloud.Sony VAIO VPCY119FJ/S Battery

In a similar way, xenon isotopic ratios such as 129Xe/130Xe and 136Xe/130Xe are also a powerful tool for understanding planetary differentiation and early outgassing. For example, The atmosphere of Mars shows a xenon abundance similar to that of Earth: 0.08 parts per million, however Mars shows a higher proportion of 129Xe than the Earth or the Sun.Sony VAIO VPCY11AFJ Battery

As this isotope is generated by radioactive decay, the result may indicate that Mars lost most of its primordial atmosphere, possibly within the first 100 million years after the planet was formed. In another example, excess 129Xe found in carbon dioxide well gases fromNew Mexico was believed to be from the decay of mantle-derived gases soon after Earth's formation.Sony VAIO VPCY11AGJ Battery

Compounds

After Neil Bartlett's discovery in 1962 that xenon can form chemical compounds, a large number of xenon compounds have been discovered and described. Almost all known xenon compounds contain the electronegative atoms fluorine or oxygen.Sony VAIO VPCY11AHJ Battery

Halides

Three fluorides are known: XeF2, XeF4, and XeF6. The fluorides are the starting point for the synthesis of almost all xenon compounds.

The solid, crystalline difluoride XeF2 is formed when a mixture of fluorine and xenon gases is exposed to ultraviolet light.Sony VAIO VPCY11AVJ Battery

Ordinary daylight is sufficient.Long-term heating of XeF2 at high temperatures under an NiF2 catalyst yields XeF6.[82]Pyrolysis of XeF6 in the presence of NaF yields high-purity XeF4.

The xenon fluorides behave as both fluoride acceptors and fluoride donors, forming salts that contain such cations as XeF+ and Xe2F3+, and anions such as XeF5?, XeF7?, and XeF82?.Sony VAIO VPCY11M1E/S Battery

The green, paramagnetic Xe2+ is formed by the reduction of XeF2 by xenon gas.

XeF2 is also able to form coordination complexes with transition metal ions. Over 30 such complexes have been synthesized and characterized.

Whereas the xenon fluorides are well-characterized, the other halides are not known, the only exception being the dichloride,XeCl2.Sony VAIO VPCY11S1E Battery

Xenon dichloride is reported to be an endothermic, colorless, crystalline compound that decomposes into the elements at 80°C, formed by the high-frequency irradiation of a mixture of xenon, fluorine, and silicon or carbon tetrachloride. However, doubt has been raised as to whether XeCl2 is a real compound and not merely a van der Waals molecule consisting of weakly bound Xe atoms and Cl2 molecules.Sony VAIO VPCY11V9E/S Battery

Theoretical calculations indicate that the linear molecule XeCl2 is less stable than the van der Waals complex.

Oxides and oxohalides

Three oxides of xenon are known: xenon trioxide (XeO3) and xenon tetroxide (XeO4), both of which are dangerously explosive and powerful oxidizing agents. Xenon dioxide (XeO2) was reported in 2011 with a coordination number of four.Sony VAIO VPCY218EC/BI Battery

XeO2 forms when xenon fluoride is poured over ice. Its crystal structure may allow it to replace silicon in silicate minerals. XeOO+cation has been identified by infrared spectroscopy in solid argon.

Xenon does not react with oxygen directly; the trioxide is formed by the hydrolysis of XeF6:Sony VAIO VPCY218EC/G Battery

XeF6 + 3 H2O ? XeO3 + 6 HF

XeO3 is weakly acidic, dissolving in alkali to form unstable xenate salts containing the HXeO?
4 anion. These unstable salts easilydisproportionate into xenon gas and perxenate salts, containing the XeO4?
6 anion.[91]

Barium perxenate, when treated with concentrated sulfuric acid, yields gaseous xenon tetroxide:Sony VAIO VPCY218EC/L Battery

Ba2XeO6 + 2 H2SO4 ? 2 BaSO4 + 2 H2O + XeO4

To prevent decomposition, the xenon tetroxide thus formed is quickly cooled to form a pale-yellow solid. It explodes above ?35.9 °C into xenon and oxygen gas.

A number of xenon oxyfluorides are known, including XeOF2, XeOF4, XeO2F2, and XeO3F2. XeOF2 is formed by the reaction of OF2with xenon gas at low temperatures.Sony VAIO VPCY218EC/P Battery

It may also be obtained by the partial hydrolysis of XeF4. It disproportionates at ?20 °C into XeF2 and XeO2F2. XeOF4 is formed by the partial hydrolysis ofXeF6,[93] or the reaction of XeF6 with sodium perxenate, Na4XeO6. The latter reaction also produces a small amount of XeO3F2.Sony VAIO VPCY21S1E/L Battery

XeOF4 reacts with CsF to form the XeOF?5anion, while XeOF3 reacts with the alkali metal fluorides KF, RbF and CsF to form the XeOF?4 anion.

Other compounds

Recently, there has been an interest in xenon compounds where xenon is directly bonded to a less electronegative element than fluorine or oxygen, particularlycarbon.Sony VAIO VPCY21S1E/P Battery

Electron-withdrawing groups, such as groups with fluorine substitution, are necessary to stabilize these compounds.[91] Numerous such compounds have been characterized, including:

• C6F5–Xe+–N?C–CH3, where C6F5 is the pentafluorophenyl group.
• [C6F5]2Xe
• C6F5–Xe–X, where X is CN, F, or Cl.
• R–C?C–Xe+, where R is C2F?
  5 or tert-butyl.
• C6F5–XeF+
  2
• (C6F5Xe)2Cl+

Other compounds containing xenon bonded to a less electronegative element include F–Xe–N(SO2F)2 and F–Xe–BF2. The latter is synthesized from dioxygenyltetrafluoroborate, O2BF4, at ?100 °C.Sony VAIO VPCY21S1E/SI Battery

An unusual ion containing xenon is the tetraxenonogold(II) cation, AuXe2+

4, which contains Xe–Au bonds.[99] This ion occurs in the compound AuXe4(Sb2F11)2, and is remarkable in having direct chemical bonds between two notoriously unreactive atoms, xenon and gold, with xenon acting as a transition metal ligand.Sony VAIO VPCCW2S5C CN1 Battery

In 1995, M. Räsänen and co-workers, scientists at the University of Helsinki in Finland, announced the preparation of xenon dihydride (HXeH), and later xenon hydride-hydroxide (HXeOH), hydroxenoacetylene (HXeCCH), and other Xe-containing molecules.Sony VAIO VPCEA20 Battery

In 2008, Khriachtchev et al. reported the preparation of HXeOXeH by the photolysis of water within a cryogenic xenon matrix. Deuterated molecules, HXeOD and DXeOH, have also been produced.

Clathrates and excimers

In addition to compounds where xenon forms a chemical bond, xenon can form clathrates—substances where xenon atoms are trapped by the crystalline lattice of another compound.Sony VAIO VPCEB10 Battery

An example is xenon hydrate (Xe·5.75 H2O), where xenon atoms occupy vacancies in a lattice of water molecules. This clathrate has a melting point of 24 °C.The deuterated version of this hydrate has also been produced. Such clathrate hydrates can occur naturally under conditions of high pressure, such as in Lake Vostok underneath the Antarctic ice sheet.Sony VAIO VPCEB11FM Battery

Clathrate formation can be used to fractionally distill xenon, argon and krypton.

Xenon can also form endohedral fullerene compounds, where a xenon atom is trapped inside a fullerene molecule. The xenon atom trapped in the fullerene can be monitored via 129Xe nuclear magnetic resonance (NMR) spectroscopy.Sony VAIO VPCEB11FM/BI Battery

Using this technique, chemical reactions on the fullerene molecule can be analyzed, due to the sensitivity of the chemical shift of the xenon atom to its environment. However, the xenon atom also has an electronic influence on the reactivity of the fullerene.

While xenon atoms are at their ground energy state, they repel each other and will not form a bond.Sony VAIO VPCEB11FM/T Battery

When xenon atoms becomes energized, however, they can form anexcimer (excited dimer) until the electrons return to the ground state. This entity is formed because the xenon atom tends to fill its outermost electronic shell, and can briefly do this by adding an electron from a neighboring xenon atom.Sony VAIO VPCEB11FM/WI Battery

The typical lifetime of a xenon excimer is 1–5 ns, and the decay releases photons withwavelengths of about 150 and 173 nm. Xenon can also form excimers with other elements, such as the halogens bromine, chlorine and fluorine.

Applications

Although xenon is rare and relatively expensive to extract from the Earth's atmosphere, it has a number of applications.Sony VAIO VPCEB11FX Battery

Gas-discharge lamps

Xenon is used in light-emitting devices called xenon flash lamps, which are used in photographic flashes and stroboscopic lamps; to excite the active medium inlasers which then generate coherent light; and, occasionally, in bactericidal lamps. The first solid-state laser, invented in 1960, was pumped by a xenon flash lamp, and lasers used to power inertial confinement fusion are also pumped by xenon flash lamps.Sony VAIO VPCEB11FX/BI Battery

Continuous, short-arc, high pressure xenon arc lamps have a color temperature closely approximating noon sunlight and are used insolar simulators. That is, the chromaticity of these lamps closely approximates a heated black body radiator that has a temperature close to that observed from the Sun.Sony VAIO VPCEB11FX/T Battery

After they were first introduced during the 1940s, these lamps began replacing the shorter-lived carbon arc lamps in movie projectors.[13] They are employed in typical 35mm and IMAX film projection systems, automotive HID headlights, high-end "tactical" flashlights and other specialized uses.Sony VAIO VPCEB11FX/WI Battery

These arc lamps are an excellent source of short wavelength ultraviolet radiation and they have intense emissions in the near infrared, which is used in some night visionsystems.

The individual cells in a plasma display use a mixture of xenon and neon that is converted into a plasma using electrodes.Sony VAIO VPCEB11GX Battery

The interaction of this plasma with the electrodes generates ultraviolet photons, which then excite the phosphor coating on the front of the display.

Xenon is used as a "starter gas" in high pressure sodium lamps. It has the lowest thermal conductivity and lowest ionization potential of all the non-radioactive noble gases.Sony VAIO VPCEB11GX/BI Battery

As a noble gas, it does not interfere with the chemical reactions occurring in the operating lamp. The low thermal conductivity minimizes thermal losses in the lamp while in the operating state, and the low ionization potential causes the breakdown voltage of the gas to be relatively low in the cold state, which allows the lamp to be more easily started.Sony VAIO VPCEB11GX/T Battery

Lasers

In 1962, a group of researchers at Bell Laboratories discovered laser action in xenon, and later found that the laser gain was improved by adding helium to the lasing medium. The first excimer laser used a xenon dimer (Xe2) energized by a beam of electrons to produce stimulated emission at an ultraviolet wavelength of 176 nm.Sony VAIO VPCEB11GX/WI Battery

Xenon chloride and xenon fluoride have also been used in excimer (or, more accurately, exciplex) lasers. The xenon chloride excimer laser has been employed, for example, in certain dermatological uses.

Anesthesia

Xenon has been used as a general anesthetic. Although it is expensive, anesthesia machines that can deliver xenon are about to appear on the European market, because advances in recovery and recycling of xenon have made it economically viable.Sony VAIO VPCEB12FX Battery

Two physiological mechanisms for xenon anesthesia have been proposed. The first one involves the inhibition of the calcium ATPase pump—the mechanism cells use to remove calcium (Ca2+)—in the cell membrane of synapses. This results from a conformational change when xenon binds to nonpolar sites inside the protein.Sony VAIO VPCEB12FX/BI Battery

The second mechanism focuses on the non-specific interactions between the anesthetic and the lipid membrane.

Xenon has a minimum alveolar concentration (MAC) of 72% at age 40, making it 44% more potent than N2O as an anesthetic. Thus it can be used in concentrations with oxygen that have a lower risk of hypoxia.Sony VAIO VPCEB12FX/BIC Battery

Unlike nitrous oxide (N2O), xenon is not a greenhouse gas and so it is also viewed as environmentally friendly. Xenon vented into the atmosphere is being returned to its original source, so no environmental impact is likely.

Neuroprotectant

Xenon is finding application in treating brain injuries, since it is an antagonist of N-methyl-d-aspartate receptors (NMDA receptors).Sony VAIO VPCEB12FX/T Battery

These receptors exacerbate the damage from oxygen deprivation and xenon performs better as a neuroprotectant than either ketamine or nitrous oxide, which have undesired side-effects. Xenon gas was added as an ingredient of the ventilation mix for a newborn baby at St. Michael's Hospital, Bristol, England, whose life chances were otherwise very compromised, and was successful, leading to the authorisation of clinical trials for similar cases.Sony VAIO VPCEB14FX Battery

The treatment is done simultaneously with cooling the body temperature to 33.5 °C.

Imaging

Gamma emission from the radioisotope 133Xe of xenon can be used to image the heart, lungs, and brain, for example, by means of single photon emission computed tomography. 133Xe has also been used to measure blood flow.Sony VAIO VPCEB14FX/BI Battery

Xenon, particularly hyperpolarized 129Xe, is a useful contrast agent for magnetic resonance imaging (MRI). In the gas phase, it can be used to image empty space such as cavities in a porous sample or alveoli in lungs. Hyperpolarization renders 129Xe much more detectable via magnetic resonance imaging and has been used for studies of the lungs and other tissues.Sony VAIO VPCEB14FX/T Battery

It can be used, for example, to trace the flow of gases within the lungs. Because xenon is soluble in water and also in hydrophobic solvents, it can be used to image various soft living tissues.

NMR spectroscopy

Because of the atom's large, flexible outer electron shell, the NMR spectrum changes in response to surrounding conditions, and can therefore be used as a probe to measure the chemical circumstances around the xenon atom.Sony VAIO VPCEB14FX/WI Battery

For instance xenon dissolved in water, xenon dissolved in hydrophobic solvent, and xenon associated with certain proteins can be distinguished by NMR.

Hyperpolarized xenon can be used by surface-chemists. Normally, it is difficult to characterize surfaces using NMR,Sony VAIO VPCEB15FM Battery

because signals from the surface of a sample will be overwhelmed by signals from the far-more-numerous atomic nuclei in the bulk. However, nuclear spins on solid surfaces can be selectively polarized, bytransferrering spin polarization to them from hyperpolarized xenon gas. This makes the surface signals strong enough to measure, and distinguishes them from bulk signals.Sony VAIO VPCEB15FM/BI Battery

Other

In nuclear energy applications, xenon is used in bubble chambers, probes, and in other areas where a high molecular weight and inert nature is desirable. A by-product of nuclear weapon testing is the release of radioactive xenon-133 and xenon-135. The detection of these isotopes is used to monitor compliance with nucleartest ban treaties, as well as to confirm nuclear test explosions by states such as North Korea.Sony VAIO VPCEB15FM/T Battery

Liquid xenon is being used in calorimeters for measurements of gamma rays as well as a medium for detecting hypotheticalweakly interacting massive particles, or WIMPs. When a WIMP collides with a xenon nucleus, it should, theoretically, strip an electron and create a primary scintillation.Sony VAIO VPCEB15FM/WI Battery

By using xenon, this burst of energy could then be readily distinguished from similar events caused by particles such as cosmic rays. However, the XENON experiment at the Gran Sasso National Laboratory in Italy and the ZEPLIN-II and ZEPLIN-III experiments at the Boulby Underground Laboratory in the UK have thus far failed to find any confirmed WIMPs.Sony VAIO VPCEB15FX Battery

Even if no WIMPs are detected, the experiments will serve to constrain the properties of dark matter and some physics models. The current detector at the Gran Sasso facility has demonstrated sensitivity comparable to that of the best cryogenic detectors, and the sensitivity was expected to be increased by an order of magnitude in 2009.Sony VAIO VPCEB15FX/BI Battery

Xenon is the preferred propellant for ion propulsion of spacecraft because of its low ionization potential per atomic weight, and its ability to be stored as a liquid at near room temperature (under high pressure) yet be easily converted back into a gas to feed the engine.Sony VAIO VPCEB15FX/T Battery

The inert nature of xenon makes it environmentally friendly and less corrosive to an ion engine than other fuels such as mercury or caesium. Xenon was first used for satellite ion engines during the 1970s. It was later employed as a propellant for Europe's SMART-1 spacecraft and for the three ion propulsion engines on NASA's Dawn Spacecraft.Sony VAIO VPCEB15FX/WI Battery

Chemically, the perxenate compounds are used as oxidizing agents in analytical chemistry. Xenon difluoride is used as an etchant for silicon, particularly in the production of microelectromechanical systems (MEMS). The anticancer drug 5-fluorouracil can be produced by reacting xenon difluoride with uracil.Sony VAIO VPCEB16FX Battery

Xenon is also used in protein crystallography. Applied at pressures from 0.5 to 5 MPa (5 to 50 atm) to a protein crystal, xenon atoms bind in predominantly hydrophobic cavities, often creating a high quality, isomorphous, heavy-atom derivative, which can be used for solving the phase problem.Sony VAIO VPCEB16FX/B Battery

Precautions

Many oxygen-containing xenon compounds are toxic due to their strong oxidative properties, and explosive due to their tendency to break down into elemental xenon plus diatomic oxygen (O2), which contains much stronger chemical bonds than the xenon compounds.Sony VAIO VPCEB16FX/G Battery

Xenon gas can be safely kept in normal sealed glass or metal containers at standard temperature and pressure. However, it readily dissolves in most plastics and rubber, and will gradually escape from a container sealed with such materials. Xenon is non-toxic, although it does dissolve in blood and belongs to a select group of substances that penetrate the blood-brain barrier, causing mild to full surgical anesthesia when inhaled in high concentrations with oxygen.Sony VAIO VPCEB16FX/L Battery

At 169 m/s, the speed of sound in xenon gas is slower than that in air due to the slower average speed of the heavy xenon atoms compared to nitrogen and oxygen molecules. Hence, xenon lowers the resonant frequencies of the vocal tract when inhaled. This produces a characteristic lowered voice timbre, an effect opposite to the high-timbred voice caused by inhalation of helium.Sony VAIO VPCEB16FX/P Battery

Like helium, xenon does not satisfy the body's need for oxygen. Xenon is both a simple asphyxiant and an anesthetic more powerful than nitrous oxide; consequently, many universities no longer allow the voice stunt as a general chemistry demonstration. As xenon is expensive, the gas sulfur hexafluoride, which is similar to xenon in molecular weight (146 versus 131), is generally used in this stunt, and is an asphyxiant without being anesthetic.Sony VAIO VPCEB16FX/W Battery

It is possible to safely breathe heavy gases such as xenon or sulfur hexafluoride when they are in a mixture with oxygen; the oxygen comprising at least 20% of the mixture. Xenon at 80% concentration along with 20% oxygen rapidly produces the unconsciousness of general anesthesia (and has been used for this, as discussed above).Sony VAIO VPCEB17FX Battery

Breathing mixes gases of different densities very effectively and rapidly so that heavier gases are purged along with the oxygen, and do not accumulate at the bottom of the lungs. There is, however, a danger associated with any heavy gas in large quantities: it may sit invisibly in a container, and if a person enters a container filled with an odorless, colorless gas, they may find themselves breathing it unknowingly. Sony VAIO VPCEB17FX/B Battery

Xenon is rarely used in large enough quantities for this to be a concern, though the potential for danger exists any time a tank or container of xenon is kept in an unventilated space.Sony VAIO VPCEB17FX/G Battery,Sony VAIO VPCEB17FX/L Battery,Sony VAIO VPCEB17FX/P Battery,Sony VAIO VPCEB17FX/W Battery,Sony VAIO VPCEB190X Battery,Sony VAIO VPCEB19FX Battery,Sony VAIO VPCEB19GX Battery

 

Cadmium,Indium,Tin,Antimony

Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, bluish-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Similar to zinc, it prefersoxidation state +2 in most of its compounds and similar to mercury it shows a low melting point compared to transition metals.Sony VAIO VGN-G118CN Battery

Cadmium and its congeners are not always considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states. The average concentration of cadmium in the Earth's crust is between 0.1 and 0.5 parts per million (ppm).Sony VAIO VGN-G118GN/B Battery

It was discovered in 1817 simultaneously by Stromeyer and Hermann, both in Germany, as an impurity in zinc carbonate.

Cadmium occurs as a minor component in most zinc ores and therefore is a byproduct of zinc production. It was used for a long time as a pigment and for corrosion resistant plating on steel while cadmium compounds were used to stabilizeplastic.Sony VAIO VGN-G118GN/T Battery

With the exception of its use in nickel–cadmium batteries and cadmium telluride solar panels, the use of cadmium is generally decreasing in its other applications. These declines have been due to competing technologies, cadmium’stoxicity in certain forms and concentration and resulting regulations.Sony VAIO VGN-G118TN/B Battery

Although cadmium has no known biological function in higher organisms, a cadmium-dependent carbonic anhydrase has been found in marine diatoms.

Physical properties

Cadmium is a soft, malleable, ductile, bluish-white divalent metal. It is similar in many respects to zinc but formscomplex compounds.Sony VAIO VGN-G118TN/S Battery

Unlike other metals, cadmium is resistant to corrosion and as a result it is used as a protective layer when deposited on other metals. As a bulk metal, cadmium is insoluble in water and is not flammable; however, in its powdered form it may burn and release toxic fumes.Sony VAIO VGN-G11VN/T Battery

Chemical properties

Although cadmium usually has an oxidation state of +2, it also exists in the +1 state. Cadmium and its congeners are not always considered transition metals, in that they do not have partly filled d or f electron shells in the elemental or common oxidation states.Sony VAIO VGN-G11VN/TC Battery

Cadmium burns in air to form brown amorphous cadmium oxide (CdO); the crystalline form of this compound is a dark red which changes color when heated, similar to zinc oxide. Hydrochloric acid, sulfuric acid and nitric acid dissolve cadmium by forming cadmium chloride (CdCl2), cadmium sulfate (CdSO4), or cadmium nitrate (Cd(NO3)2).Sony VAIO VGN-G11XN/B Battery

The oxidation state +1 can be reached by dissolving cadmium in a mixture of cadmium chloride and aluminium chloride, forming the Cd22+ cation, which is similar to the Hg22+ cation in mercury(I) chloride.

Naturally occurring cadmium is composed of 8 isotopes. Two of them are naturally radioactive, and three are expected to decay but have not been experimentally confirmed to do so.Sony VAIO VGN-G1AAPS Battery

The two natural radioactive isotopes are 113Cd (beta decay, half-life is 7.7 × 1015 years) and 116Cd (two-neutrino double beta decay, half-life is 2.9 × 1019 years). The other three are 106Cd, 108Cd (both double electron capture), and114Cd (double beta decay); only lower limits on their half-life times have been set.Sony VAIO VGN-G1AAPSA Battery

At least three isotopes – 110Cd, 111Cd, and 112Cd – are stable. Among the isotopes that do not occur naturally, the most long-lived are 109Cd with a half-life of 462.6 days, and 115Cd with a half-life of 53.46 hours. All of the remaining radioactive isotopes have half-lives that are less than 2.5 hours, and the majority of these have half-lives that are less than 5 minutes.Sony VAIO VGN-G1AAPSB Battery

Cadmium has 8 known meta states, with the most stable being 113mCd (t½ = 14.1 years), 115mCd (t½ = 44.6 days), and 117mCd (t½= 3.36 hours).

The known isotopes of cadmium range in atomic mass from 94.950 u (95Cd) to 131.946 u (132Cd).Sony VAIO VGN-G1AAPSC Battery

For isotopes lighter than 112 u, the primary decay mode is electron capture and the dominant decay product is element 47 (silver). Heavier isotopes decay mostly through beta emission producing element 49 (indium).

One isotope of cadmium, 113Cd, absorbs neutrons with very high probability if they have an energy below the cadmium cut-off and transmits them otherwise.Sony VAIO VGN-G1ABNS Battery

The cadmium cut-off is about 0.5 eV. Neutrons with energy below the cutoff are deemed slow neutrons, distinguishing them from intermediate and fast neutrons.

Cadmium is created via the long s-process in low-medium mass stars with masses of 0.6 to 10 solar masses, which lasts thousands of years. It requires a silver atom to capture a neutron and then undergo beta decay.Sony VAIO VGN-G1KAP Battery

Cadmium (Latin cadmia, Greek ??????? meaning "calamine", a cadmium-bearing mixture of minerals, which was named after the Greek mythological character, ?????? Cadmus, the founder of Thebes) was discovered simultaneously in 1817 by Friedrich Stromeyer and Karl Samuel Leberecht Hermann, both in Germany, as an impurity in zinc carbonate.Sony VAIO VGN-G1KBN Battery

Stromeyer found the new element as an impurity in zinc carbonate (calamine), and, for 100 years, Germany remained the only important producer of the metal. The metal was named after the Latin word for calamine, since the metal was found in this zinc compound.Sony VAIO VGN-G1KBNA Battery

Stromeyer noted that some impure samples of calamine changed color when heated but pure calamine did not. He was persistent in studying these results and eventually isolated cadmium metal by roasting and reduction of the sulfide. The possibility to use cadmium yellow as pigment was recognized in the 1840s but the lack of cadmium limited this application.Sony VAIO VGN-G1LAP Battery

Even though cadmium and its compounds may be toxic in certain forms and concentrations, theBritish Pharmaceutical Codex from 1907 states that cadmium iodide was used as a medication to treat "enlarged joints, scrofulous glands, and chilblains".

In 1927, the International Conference on Weights and Measures redefined the meter in terms of a red cadmium spectral line (1 m = 1,553,164.13 wavelengths). This definition has since been changed (see krypton).Sony VAIO VGN-G1LBN Battery

After the industrial scale production of cadmium started in the 1930s and 1940s, the major application of cadmium was the coating of iron and steel to prevent corrosion; in 1944, 62% and in 1956, 59% of the cadmium in the United States was for coating.Sony VAIO VGN-G218LN/T Battery

In 1956, 24% of the cadmium used within the United States was used for the second application, which was for red, orange and yellow pigments based on sulfides and selenides of cadmium. The stabilizing effect of cadmium-containing chemicals like the carboxylates cadmium laureate and cadmium stearate on PVC led to an increased use of those compounds in the 1970s and 1980s.Sony VAIO VGN-G218N/B Battery

The use of cadmium in applications such as pigments, coatings, stabilizers and alloys declined due to environmental and health regulations in the 1980s and 1990s; in 2006, only 7% of total cadmium consumption was used for plating and coating and only 10% was used for pigments.Sony VAIO VGN-G21XP/B Battery

The decrease in consumption in other applications was made up by a growing demand of cadmium in nickel-cadmium batteries, which accounted for 81% of the cadmium consumption in the United States in 2006.

Occurrence

Cadmium makes up about 0.1 ppm of the Earth's crust. Compared with the more abundant zinc with 65 ppm cadmium is rare.Sony VAIO VGN-G2AANS Battery

No significant deposits of cadmium-containing ores are known. Greenockite (CdS), the only cadmium mineral of importance, is nearly always associated with sphalerite (ZnS). This association is caused by the geochemical similarity between zinc and cadmium which makes geological separation unlikely.Sony VAIO VGN-G2AAPS Battery

As a consequence, cadmium is produced mainly as a byproduct from mining, smelting, and refining sulfidic ores of zinc, and, to a lesser degree, lead and copper. Small amounts of cadmium, about 10% of consumption, are produced from secondary sources, mainly from dust generated by recycling iron and steel scrap.Sony VAIO VGN-G2AAPSA Battery

Production in the United States began in 1907, but it was not until after World War I that cadmium came into wide use. One place where metallic cadmium can be found is the Vilyuy River basin in Siberia.

Rocks mined to produce phosphate fertilizers contain varying amounts of cadmium, leading to a cadmium concentration of up to 300 mg/kg in the produced phosphate fertilizers and thus in the high cadmium content in agricultural soils.Sony VAIO VGN-G2AAPSB Battery

Coal can contain significant amounts of cadmium, which ends up mostly in the flue dust.

Production

The British Geological Survey reports that in 2001, China was the top producer of cadmium, producing almost one-sixth of the world share, closely followed by South Korea and Japan.Sony VAIO VGN-G2AAPSC Battery

Cadmium is a common impurity in zinc ores, and it is most often isolated during the production of zinc. Some zinc ores concentrates from sulfidic zinc ores contain up to 1.4% of cadmium. In 1970s, the output of cadmium was 6.5 pounds per ton of zinc.Zinc sulfide ores are roasted in the presence of oxygen, converting the zinc sulfide to the oxide.Sony VAIO VGN-G2KAN Battery

Zinc metal is produced either by smelting the oxide with carbon or by electrolysis in sulfuric acid. Cadmium is isolated from the zinc metal by vacuum distillation if the zinc is smelted, or cadmium sulfate is precipitated out of the electrolysis solution.

Applications

Cadmium has many common industrial uses as it is a key component in battery production, is present in cadmium pigments,coatings, and is commonly used in electroplating.Sony VAIO VGN-G2KANA Battery

Batteries

In 2009, 86% of cadmium was used in batteries, predominantly in rechargeable nickel-cadmium batteries. Nickel-cadmium cells have a nominal cell potential of 1.2 V. The cell consists of a positive nickel hydroxide electrode and a negative cadmium electrode plate separated by an alkaline electrolyte (potassium hydroxide) . Sony VAIO VGN-G2KBNA Battery

The European Union banned the use of cadmium in electronics in 2004 with several exceptions but reduced the allowed content of cadmium in electronics to 0.002%.

Electroplating

Cadmium electroplating, consuming 6% of the global production, can be found in the aircraft industry due to the ability to resistcorrosion when applied to steel components.Sony VAIO VGN-NR160E/S Battery

This coating is passivated by the usage of chromate salts. A limitation of cadmium plating is hydrogen embrittlement of high-strength steels caused by the electroplating process. Therefore, steel parts heat-treated to tensile strength above 1300 MPa (200 ksi) should be coated by an alternative method (such as special low-embrittlement cadmium electroplating processes or physical vapor deposition).Sony VAIO VGN-NR160E/T Battery

In addition, titanium embrittlement caused by cadmium-plated tool residues resulted in banishment of these tools (along with routine tool testing programs to detect any cadmium contamination) from the A-12/SR-71 and U-2 programs, and subsequent aircraft programs using titanium.Sony VAIO VGN-NR160E/W Battery

Nuclear fission

Cadmium is used as a barrier to control neutrons in nuclear fission. The pressurized water reactor designed by Westinghouse Electric Company uses an alloy consisting of 80% silver, 15% indium, and 5% cadmium.

Compounds

Cadmium oxide is used in black and white television phosphors and in the blue and green phosphors for color television picture tubes.Sony VAIO VGN-NR180E/S Battery

Cadmium sulfide (CdS) is used as a photoconductive surface coating for photocopier drums.

In paint pigments, cadmium forms various salts, with CdS being the most common. This sulfide is used as a yellow pigment. Cadmium selenide can be used as red pigment, commonly called cadmium red.Sony VAIO VGN-NR180E/T Battery

To painters who work with the pigment, cadmium yellows, oranges, and reds are the most brilliant and long-lasting colors to use. In fact, during production, these colors are significantly toned down before they are ground with oils and binders, or blended into watercolors, gouaches, acrylics, and other paint and pigment formulations.Sony VAIO VGN-NR290E/S Battery

Since these pigments are potentially toxic, it is recommended to use a barrier cream on the hands to prevent absorption through the skin when working with them even though the amount of cadmium absorbed into the body through the skin is usually reported to be less than 1%.Sony VAIO VGN-NR290E/T Battery

In PVC, cadmium was used as heat, light, and weathering stabilizers. Currently, cadmium stabilizers have been completely replaced with barium-zinc, calcium-zinc and organo-tin stabilizers. Cadmium is used in many kinds of solder and bearing alloys, due to a low coefficient of friction and fatigue resistance.Sony VAIO VGN-NR298E/S Battery

It is also found in some of the lowest-melting alloys, such asWood's metal.

Laboratory uses

Helium–cadmium lasers are a common source of blue-ultraviolet laser light. They operate at either 325 or 422 nm and are used influorescence microscopes and various laboratory experiments.Cadmium selenide quantum dots emit bright luminescence under UV excitation (He-Cd laser, for example).Sony VAIO VGN-NR460E/L Battery

The color of this luminescence can be green, yellow or red depending on the particle size. Colloidal solutions of those particles are used for imaging of biological tissues and solutions with a fluorescence microscope.

Cadmium is a component of some compound semiconductors, such as cadmium sulfide, cadmium selenide, and cadmium telluride, which can be used for light detection or solar cells.Sony VAIO VGN-NR460E/P Battery

HgCdTe is sensitive to infrared light and therefore may be utilized as an infrared detector or switch for example in remote control devices.

In molecular biology, cadmium is used to block voltage-dependent calcium channels from fluxing calcium ions, as well as inhypoxia research to stimulate proteasome-dependent degradation of Hif-1?.Sony VAIO VGN-NR498E/L Battery

Biological role

Cadmium has no known useful role in higher organisms. A role for cadmium in lower life-forms has recently been found. A cadmium-dependent carbonic anhydrase has been found in marine diatoms. Cadmium performs the same function as zinc in other anhydrases, but the diatoms live in environments with very low zinc concentrations and thus they utilize cadmium to perform functions normally carried out by zinc.Sony VAIO VGN-NR498E/S Battery

The discovery relied on the use of X-ray absorption fluorescence spectroscopy (XAFS).

The highest concentration of cadmium has been found to be absorbed in the kidneys of humans, and up to about 30 mg of cadmium is commonly inhaled throughout childhood and adolescence.

Cadmium can be used to block calcium channels in chicken neurons.Sony VAIO VGN-NR498E/T Battery

Safety

The most dangerous form of occupational exposure to cadmium is inhalation of fine dust and fumes, or ingestion of highly soluble cadmium compounds. Inhalation of cadmium-containing fumes can result initially in metal fume fever but may progress to chemical pneumonitis, pulmonary edema, and death.Sony VAIO VGN-NR498E/W Battery

Cadmium is also an environmental hazard. Human exposures to environmental cadmium are primarily the result of fossil fuel combustion, phosphate fertilizers, natural sources, iron and steel production, cement production and related activities, nonferrous metals production, and municipal solid waste incineration.Sony VAIO VGN-NR50 Battery

However, there have been a few instances of general population toxicity as the result of long-term exposure to cadmium in contaminated food and water. In the decades leading up toWorld War II, Japanese mining operations contaminated the Jinz? River with cadmium and traces of other toxic metals.Sony VAIO VGN-NR50B Battery

As a consequence, cadmium accumulated in the rice crops growing along the riverbanks downstream of the mines. Some members of the local agricultural communities consuming the contaminated rice developed itai-itai disease and renal abnormalities, including proteinuria and glucosuria.Sony VAIO VGN-NR51 Battery

The victims of this poisoning were almost exclusively post-menopausal women with low iron and other mineral body stores. Similar general population cadmium exposures in other parts of the world have not resulted in the same health problems because the populations maintained sufficient iron and other mineral levels.Sony VAIO VGN-NR51B Battery

Thus, while cadmium is a major factor in the itai-itai disease in Japan, most researchers have concluded that it was one of several factors. Cadmium is one of six substances banned by the European Union's Restriction on Hazardous Substances (RoHS) directive, which bans certain hazardous substances in electrical and electronic equipment but allows for certain exemptions and exclusions from the scope of the law.Sony VAIO VGN-NR52 Battery

Although some studies linked exposure to cadmium with lung and prostate cancer, there is still a substantial controversy about the carcinogenicity of cadmium. More recent studies suggest that arsenic rather than cadmium may lead to the increased lung cancer mortality rates.Sony VAIO VGN-NR52B Battery

Furthermore, most data regarding the carcinogenicity of cadmium rely on research confounded by the presence of other carcinogenic substances.

Tobacco smoking is the most important single source of cadmium exposure in the general population. It has been estimated that about 10% of the cadmium content of a cigarette is inhaled through smoking.Sony VAIO VGN-NR71B Battery

The absorption of cadmium from the lungs is much more effective than that from the gut, and as much as 50% of the cadmium inhaled via cigarette smoke may be absorbed.

On average, smokers have 4–5 times higher blood cadmium concentrations and 2–3 times higher kidney cadmium concentrations than non-smokers.Sony VAIO VGN-NR71B2 Battery

Despite the high cadmium content in cigarette smoke, there seems to be little exposure to cadmium from passive smoking. No significant effect on blood cadmium concentrations has been detected in children exposed to environmental tobacco smoke.

Cadmium exposure is a risk factor associated with early atheroslcerosis and hypertension, which can both lead to cardiovascular disease.Sony VAIO VGN-NR72B Battery

Regulations

Due to the adverse effects on the environment and human health, the supply and use of cadmium is restricted in Europe under the REACH Regulation.

Product recalls

In May 2006, a sale of the seats from Arsenal F.C.'s old stadium, Highbury in London, England was cancelled after the seats were discovered to contain trace amounts of cadmium.Sony VAIO VGN-NS10E/S Battery

Reports of high levels of cadmium use in children's jewelry in 2010 led to a US Consumer Product Safety Commission investigation.The U.S. CPSC issued specific recall notices for cadmium content applying to jewelry sold by Claire's and Wal-Mart stores. Sony VAIO VGN-NS10J/S Battery

In June 2010 McDonald's voluntarily recalled more than 12 million promotional "Shrek Forever After 3D" Collectable Drinking Glasses due to concerns over cadmium levels in paint pigments used on the glassware. The glasses were manufactured by Arc International, of Millville, NJ, USA.Sony VAIO VGN-NS10L/S Battery

Indium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two.Sony VAIO VGN-NS110E/L Battery

Indium was discovered in 1863 and named for the indigo blue line in its spectrum that was the first indication of its existence in zinc ores, as a new and unknown element. The metal was first isolated in the following year. Zinc ores continue to be the primary source of indium, where it is found in compound form.Sony VAIO VGN-NS110E/S Battery

Very rarely the element can be found as grains of native (free) metal, but these are not of commercial importance.

Indium's current primary application is to form transparent electrodes from indium tin oxide in liquid crystal displays andtouchscreens, and this use largely determines its global mining production.Sony VAIO VGN-NS110E/W Battery

It is widely used in thin-films to form lubricated layers (during World War II it was widely used to coat bearings in high-performance aircraft). It is also used for making particularly low melting point alloys, and is a component in some lead-free solders.

Indium is not known to be used by any organism.Sony VAIO VGN-NS115N/S Battery

In a similar way to aluminium salts, indium(III) ions can be toxic to the kidney when given by injection, but oral indium compounds do not have the chronic toxicity of salts of heavy metals, probably due to poor absorption in basic conditions. Radioactive indium-111 (in very small amounts on a chemical basis) is used innuclear medicine tests, as a radiotracer to follow the movement of labeled proteins and white blood cells in the body.Sony VAIO VGN-NS11ER/S Battery

Physical

Indium is a very soft, silvery-white, relatively rare true metal with a bright luster. When it is bent, indium emits a high-pitched "cry".Like gallium, indium is able to wetglass. Indium has a low melting point, compared to those of most other metals, 156.60 °C (313.88 °F);Sony VAIO VGN-NS11E/S Battery

it is higher than that of its lighter homologue, gallium, but lower than that of the heavier homologue, thallium. Its boiling point is, however, moderate, being 2072 °C (3762 °F), which is higher than that of thallium, but lower than that of gallium, showing opposition to melting points trend.Sony VAIO VGN-NS11J/S Battery

The density of indium, 7.31 g·cm?3, is also higher than that of gallium, but lower than that of thallium.

Indium atom has 49 electrons, having electronic configuration [Kr]4d105s25p1. In its compounds, indium most often loses its three outermost electrons, becoming indium(III) ions, In3+, but in some cases the pair of 5s-electrons can stay within the atom,Sony VAIO VGN-NS11L/S Battery

indium thus oxidized only to indium(I), In+. This happens due to inert pair effect, which occurs because of stabilization of 5s-orbital due to relativistic effects, which are stronger closer to the bottom of the periodic table. Thallium shows an even stronger effect, making oxidation to thallium(I) more likely than to thallium(III), making +1 the more likely oxidation state.Sony VAIO VGN-NS11MR/S Battery

A number of standard electrode potentials, depending on the reaction under study, is reported for indium:

Indium is a post-transition metal and chemically, is the intermediate element between its group 13 neighbors gallium andthallium.Sony VAIO VGN-NS11M/S Battery

It shows two main oxidation states, which are +1 and +3, with latter being more stable, where as the only common oxidation state of gallium is +3 and thallium shows +1 more likely than +3, with thallium(III) being a moderately strongoxidizing agent, while indium(III) is stable and indium(I) is a powerful reducing agent.Sony VAIO VGN-NS11SR/S Battery

Indium does not react with water, but it is oxidized by stronger oxidizing agents, such as halogens or oxalic acid, to give indium(III) compounds. It does not react with boron, silicon or carbon, and the corresponding boride, silicide or carbide are not known. Similarly, reaction between indium and hydrogen has not been observed, but both indium(I) and indium(III) hydridesare known.Sony VAIO VGN-NS11S/S Battery

Indium(III) oxide is formed at hot temperatures during reaction between indium and oxygen, with blue flame. It is amphoteric, i. e. it can react with both acids and bases. Its reaction with water results in insoluble indium(III) hydroxide, which is also amphoteric, reacting with alkalies to give indates(III) and with acids to give indium(III) salts:Sony VAIO VGN-NS11ZR/S Battery

In(OH)3 + 2 NaOH ? 2 Na[InO2] + H2O

In(OH)3 + 3 HCl ? InCl3 + 3 H2O

The hydrolysis of sodium indate(III) gives weak indic acid, HInO2. Out of common indium(III) salts, chloride, sulfate and nitrate are soluble.Sony VAIO VGN-NS11Z/S Battery

In water solutions, In3+ and [InO2]- ions are hydrolyzed to give InOH2+ and HInO2 due to generally amphoteric character of indium(III) ions. Indium(III) compounds are not well-soluble, similarly to thallium(III) compounds; however, indium(III) salts of strong acids, such as chloride, sulfate and nitrate are soluble, hydrolyzing in water solutions.Sony VAIO VGN-NS12M/S Battery

The In3+ ion is colorless in solution because of the absence of unpaired electrons in the d- and f-electron shells.

Indium(I) compounds are not as common as indium(III) ones; only chloride, bromide, iodide, sulfide and cyclopentadienyl are well-characterized. Indium(I) sulfide is the product of reaction between indium and sulfur or indium and hydrogen sulfide, and can be received at 700—1000 °C.Sony VAIO VGN-NS12M/W Battery

Indium(I) oxide black powder is received at 850 °C during reaction between indium andcarbon dioxide or during decomposition of indium(III) oxide at 1200 °C. Cyclopentadienylindium(I), which was the first organoindium(I) compound reported,[8] is polymer consisting of zigzag chains of alternating indium atoms and cyclopentadienyl complexes.Sony VAIO VGN-NS12S/S Battery

Less frequently, indium shows intermediate oxidation state +2, which lies between the common ones, most notably in halides, In2X4and [In2X6]2-. Several other compounds are known to combine indium(I) and indium(III), such as InI6(InIIICl6)Cl3,InI5(InIIIBr4)2(InIIIBr6), InIInIIIBr4.Sony VAIO VGN-NS21M/P Battery

Indium occurs naturally on Earth only in two primordial nuclides, indium-113 and indium-115. Out of this two, indium-115 makes up 95.7% of all indium but it is radioactive, decaying to tin-115 via beta decay with half-life of 4.41×1014 years, four orders of magnitude larger than the age of the universe and nearly 50,000 times longer than that of natural thorium.Sony VAIO VGN-NS21M/W Battery

This effect is uncommon among stable chemical elements; only indium, tellurium, and rhenium have been shown that their most abundant isotopes are radioactive. However, the less common natural isotope of indium, indium-113, is stable.

Indium has 39 known isotopes, ranging in mass between 97 and 135.Sony VAIO VGN-NS21S/S Battery

Only one of them is stable and one has half-life exceeding 1014 years; the most stable other indium isotope is indium-111, which has half-life of approximately 2.8 days. All other isotopes have half-lives shorter than 5 hours. Indium also has 47 meta states, out of which indium-114m1 is the most stable, being more stable than ground state of any indium isotope, except for the primordial ones.Sony VAIO VGN-NS21S/W Battery

Creation and occurrence

Indium is created via the long-lasting, (up to thousands of years), s-process in low-medium mass stars (which range in mass between 0.6 and 10 masses of Sun). When a silver-109 atom, which comprises approximately half of all silver in existence, catches a neutron, it undergoes a beta decay to become cadmium-110.Sony VAIO VGN-NS21Z/S Battery

Capturing further neutrons, it becomes cadmium-115, which decays to indium-115 via anotherbeta decay. This explains why the radioactive isotope predominates in abundance compared to the stable one.

Indium is 61st most abundant element in the Earth's crust at approximately 49 ppb, making indium approximately as abundant as mercury.Sony VAIO VGN-NS31M/P Battery

Fewer than 10 indium minerals are known, such as dzhalindite(In(OH)3) and indite (FeIn2S4), but none of these occurs in significant deposits.

Based on content of indium in zinc ore stocks, there is a worldwide reserve base of approximately 6,000 tonnes of economically viable indium.Sony VAIO VGN-NS31M/W Battery

This figure has led to estimates suggesting that, at current consumption rates, there is only 13 years' supply of indium left. However, the Indium Corporation, the largest processor of indium, claims that, on the basis of increasing recovery yields during extraction, recovery from a wider range of base metals (including tin, copper and other polymetallic deposits)Sony VAIO VGN-NS31S/S Battery

and new mining investments, the long-term supply of indium is sustainable, reliable and sufficient to meet increasing future demands.

This conclusion may be reasonable considering that silver, which is one-third as abundant as indium in the Earth's crust,Sony VAIO VGN-NS31Z/P Battery

is currently mined at approximately 18,300 tonnes per year, which is 40 times greater than current indium mining rates.

In 1863, the German chemists Ferdinand Reich and Hieronymous Theodor Richter were testing ores from the mines around Freiberg, Saxony.Sony VAIO VGN-NS31Z/S Battery

They dissolved the mineralspyrite, arsenopyrite, galena and sphalerite in hydrochloric acid and distilled the raw zinc chloride. As it was known that ores from that region sometimes containthallium they searched for the green emission lines with spectroscopic methods. The green lines were absent but a blue line was present in the spectrum.Sony VAIO VGN-NS31Z/W Battery

As no element was known with a bright blue emission they concluded that a new element was present in the minerals. They named the element with the blue spectral line indium, from the indigo color seen in its spectrum. Richter went on to isolate the metal in 1864.At the World Fair 1867 an ingot of 0.5 kg (1.1 lb) was presented.Sony VAIO VGN-NS38M/P Battery

In 1924, indium was found to have a valuable ability to stabilize non-ferrous metals, which was its first significant use for the element.It took until 1936 that the U.S. Bureau of Mines list indium as a commodity, and even in early 1950s only very limited applications for indium were known, the most of which was makinglight-emitting diodes and engines for aircrafts during the World War II.Sony VAIO VGN-NS38M/W Battery

The start of production of indium containing semiconductors started in 1952. The development and widespread use of indium containing nuclear control rods increased the demand during the 1970s, the use of indium tin oxide in liquid crystal displays increased and became the major application by 1992.Sony VAIO VGN-NS130E/L Battery

Production

The lack of indium mineral deposits and the fact that indium is enriched in sulfidic lead, tin, copper, iron and predominately in zinc deposits, makes zinc production the main source for indium. The indium is leached from slag and dust of zinc production. Further purification is done by electrolysis.Sony VAIO VGN-NS130E/S Battery

Indium is produced mainly from residues generated during zinc ore processing but is also found in iron, lead, and copper ores.[2]China is a leading producer of indium. The Teck Cominco refinery in Trail, British Columbia, is a large single source indium producer, with production of 32,500 kg in 2005, 41,800 kg in 2004 and 36,100 kg in 2003.Sony VAIO VGN-NS130E/W Battery

South American Silver Corporation's Malku Khota property in Bolivia is a large resource of indium with an indicated resource of 1,481 tonnes and inferred resource of 935 tonnes. Adex Mining Inc.’s Mount Pleasant Mine in New Brunswick, Canada, holds some of the world’s total known indium resources.Sony VAIO VGN-NS140E/L Battery

The amount of indium consumed is largely a function of worldwide LCD production. Worldwide production is currently 476 tonnes per year from mining and a further 650 tonnes per year from recycling. Demand has risen rapidly in recent years with the popularity of LCD computer monitors and television sets, which now account for 50% of indium consumption.Sony VAIO VGN-NS140E/S Battery

Increased manufacturing efficiency and recycling (especially in Japan) maintain a balance between demand and supply. According to theUNEP, indium's end-of-life recycling rate is less than 1%. Demand increased as the metal is used in LCDs and televisions, and supply decreased when a number ofChinese mining concerns stopped extracting indium from their zinc tailings.Sony VAIO VGN-NS140E/W Battery

In 2002, the price was US$94 per kilogram. The recent changes in demand and supply have resulted in high and fluctuating prices of indium, which from 2006 to 2009 ranged from US$382/kg to US$918/kg.

Applications

The first large-scale application for indium was as a coating for bearings in high-performance aircraft engines during World War II.Sony VAIO VGN-NS190J/L Battery

Afterward, production gradually increased as new uses were found in fusible alloys, solders, and electronics. In the 1950s, tiny beads of it were used for the emitters and collectors of PNP alloy junction transistors. In the middle and late 1980s, the development of indium phosphide semiconductors and indium tin oxide thin films for liquid crystal displays (LCD) aroused much interest.Sony VAIO VGN-NS190J/S Battery

By 1992, the thin-film application had become the largest end use.

Electronics

• Indium oxide (In2O3) and indium tin oxide (ITO) are used as a transparent conductive coating applied to glass substrates in the making of electroluminescent panels.Sony VAIO VGN-NS190J/W Battery

• Some indium compounds such as indium antimonide, indium phosphide,[38] and indium nitride[39] are semiconductors with useful properties.
• Indium is used in the synthesis of the semiconductor copper indium gallium selenide (CIGS), which is used for the manufacture of thin film solar cells.Sony VAIO VGN-NS235J/L Battery

• Used in light-emitting diodes (LEDs) and laser diodes based on compound semiconductors such as InGaN, InGaP that are fabricated by Metalorganic Vapor Phase Epitaxy (MOVPE) technology.
• Ultrapure metalorganics of indium include high purity trimethylindium (TMI), which is used as a precursor in III-V compound semiconductors, while it is also used as the semiconductor dopant in II-VI compound semiconductors.Sony VAIO VGN-NS235J/P Battery

• One of many substitutes for mercury in alkaline batteries to prevent the zinc from corroding and releasing hydrogen gas.[43]
• Very small amounts used in aluminium alloy sacrificial anodes (for salt water applications) to prevent passivation of the aluminium.Sony VAIO VGN-NS235J/S Battery

• To bond gold electrical test leads to superconductors, indium is used as a conducting adhesive and applied under a microscope with precision tweezers.
• In the form of a wire it is used as a vacuum seal and a thermal conductor in cryogenics and ultra-high vacuum applications. For example, in manufacturing gaskets which deform to fill gaps.Sony VAIO VGN-NS235J/W Battery

• Used as a calibration material for Differential scanning calorimetry.
• It is an ingredient in the gallium-indium-tin alloy Galinstan, which is liquid at room temperature while not being toxic like mercury.Sony VAIO VGN-NS240E/L Battery

• Indium tin oxide is used as a light filter in low pressure sodium vapor lamps. The infrared radiation is reflected back into the lamp, which increases the temperature within the tube and therefore improves the performance of the lamp.
• Indium's melting point of 429.7485 K (156.5985 °C) is a defining fixed point on the international temperature scale ITS-90.Sony VAIO VGN-NS290J/L Battery

• Indium's high neutron capture cross section for thermal neutrons makes it suitable for use in control rods for nuclear reactors, typically in an alloy containing 80% silver, 15% indium, and 5% cadmium.
• In nuclear engineering, the (n,n') reactions of 113In and 115In are used to determine magnitudes of neutron fluxes.Sony VAIO VGN-NS290J/S Battery

• Indium is also used as a thermal interface material by personal computer enthusiasts in the form of pre-shaped foil sheets fitted between the heat-transfer surface of a microprocessor and its heat sink. The application of heat partially melts the foil and allows the indium metal to fill in any microscopic gaps and pits between the two surfaces, removing any insulating air pockets that would otherwise compromise heat transfer efficiency.Sony VAIO VGN-NS50B/L Battery

• 111In emits gamma radiation and is used in indium leukocyte imaging, or indium scintigraphy, a technique of medical imaging that is particularly helpful in differentiating conditions such as osteomyelitis from decubitus ulcers for assessment of route and duration of antibiotic therapy.Sony VAIO VGN-NS50B/W Battery
• Indium leukocyte scintigraphy has many applications, including early phase drug development, and the monitoring of activity of white blood cells. For the test, blood is taken from the patient, white cells removed, labeled with the radioactive111In, then re-injected back into the patient.Sony VAIO VGN-NS51B/L Battery

• Gamma imaging will then reveal any areas of on-going white cell localization such as new and developing areas of infection.

Precautions and health issues

Pure indium in metal form is considered non-toxic by most sources. In the welding and semiconductor industries, where indium exposure is relatively high, there have been no reports of any toxic side-effects.Sony VAIO VGN-NS51B/P Battery

Indium compounds, like aluminum compounds, complex with hydroxyls to form insoluble salts in basic conditions, and are thus not well-absorbed from food, giving them fairly low oral toxicty. Soluble indium(III) is toxic when delivered parenterally, however, causing damage primarily to the kidney (both inner and outer parts), but additionally to heart and liver, and may be teratogenic.Sony VAIO VGN-NS51B/W Battery

Other indium compounds are toxic when administered outside the gastrointestinal tract: for example, anhydrous indium trichloride (InCl3) and indium phosphide (InP) are quite toxic when delivered into the lungs (the latter is a suspected carcinogen).

Tin is a chemical element with the symbol Sn (for Latin: stannum) and atomic number 50.Sony VAIO VGN-NS52JB/L Battery

It is a main group metal ingroup 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table.Sony VAIO VGN-NS52JB/P Battery

Tin is obtained chiefly from the mineralcassiterite, where it occurs as tin dioxide, SnO2.

This silvery, malleable poor metal is not easily oxidized in air and is used to coat other metals to prevent corrosion. The first alloy, used in large scale since 3000 BC, was bronze, an alloy of tin and copper.Sony VAIO VGN-NS52JB/W Battery

After 600 BC pure metallic tin was produced. Pewter, which is an alloy of 85–90% tin with the remainder commonly consisting of copper, antimony and lead, was used for flatware from the Bronze Age until the 20th century. In modern times tin is used in many alloys, most notably tin/lead soft solders, typically containing 60% or more of tin.Sony VAIO VGN-NS70B/W Battery

Another large application for tin is corrosion-resistant tin plating of steel. Because of its low toxicity, tin-plated metal is also used for food packaging, giving the name to tin cans, which are made mostly of steel.

Physical properties

Tin is a malleable, ductile and highly crystalline silvery-white metal. When a bar of tin is bent, a crackling sound known as the tin cry can be heard due to the twinning of the crystals.Sony VAIO VGN-NS71B/W Battery

Tin melts at a low temperature of about 232 °C, which is further reduced to 177.3 °C for 11-nm particles.

?-tin (the metallic form, or white tin), which is stable at and above room temperature, is malleable. In contrast, ?-tin (nonmetallic form, or gray tin), which is stable below 13.2 °C, isbrittle. ?-tin has a diamond cubic crystal structure, similar to diamond, silicon or germanium.Sony VAIO VGN-NS72JB/W Battery

?-tin has no metallic properties at all because its atoms form a covalent structure where electrons cannot move freely. It is a dull-gray powdery material with no common uses, other than a few specialized semiconductor applications.  These two allotropes, ?-tin and ?-tin, are more commonly known as gray tin and white tin, respectively.Sony VAIO VGN-NS90HS Battery

Two more allotropes, ? and ?, exist at temperatures above 161 °C and pressures above several GPa. Although the ?-? transformation temperature is nominally 13.2 °C, impurities (e.g. Al, Zn, etc.) lower the transition temperature well below 0 °C, and upon addition of Sb or Bi the transformation may not occur at all, increasing the durability of the tin.Sony VAIO VGN-NS92JS Battery

Commercial grades of tin (99.8%) resist transformation because of the inhibiting effect of the small amounts of bismuth, antimony, lead and silver present as impurities. Alloying elements such as copper, antimony, bismuth, cadmium and silver increase its hardness. Sony VAIO VGN-NS92XS Battery

Tin tends rather easily to form hard, brittle intermetallic phases, which are often undesirable. It does not form wide solid solution ranges in other metals in general, and there are few elements that have appreciable solid solubility in tin. Simple eutectic systems, however, occur with bismuth, gallium, lead, thallium and zinc.Sony VAIO VGN-NW11S/S Battery

Tin becomes a superconductor below 3.72 K.[7] In fact, tin was one of the first superconductors to be studied; the Meissner effect, one of the characteristic features of superconductors, was first discovered in superconducting tin crystals.

Chemical properties

Tin resists corrosion from water but can be attacked by acids and alkalis. Tin can be highly polished and is used as a protective coat for other metals.Sony VAIO VGN-NW11S/T Battery

In this case the formation of a protective oxide layer is used to prevent further oxidation. This oxide layer forms on pewter and other tin alloys.[9] Tin acts as a catalyst when oxygen is in solution and helps accelerate chemical attack.

Tin is the element with the greatest number of stable isotopes, ten;Sony VAIO VGN-NW11Z/S Battery

these include all those with atomic masses between 112 and 124, with the exception of 113, 121 and 123. Of these, the most abundant ones are 120Sn (at almost a third of all tin),118Sn, and 116Sn, while the least abundant one is 115Sn. The isotopes possessing even atomic numbers have no nuclear spinwhile the odd ones have a spin of +1/2.Sony VAIO VGN-NW11Z/T Battery

Tin, with its three common isotopes 115Sn, 117Sn and 119Sn, is among the easiest elements to detect and analyze by NMR spectroscopy, and its chemical shifts are referenced against SnMe4 .

This large number of stable isotopes is thought to be a direct result of tin possessing an atomic number of 50, which is a "magic number" in nuclear physics.Sony VAIO VGN-NW21EF/S Battery

There are 28 additional unstable isotopes that are known, encompassing all the remaining ones with atomic masses between 99 and 137. Aside from 126Sn, which has a half-life of 230,000 years, all the radioactive isotopes have a half-life of less than a year.Sony VAIO VGN-NW21JF Battery

The radioactive 100Sn is one of the few nuclides possessing a "doubly magic" nucleus and was discovered relatively recently, in 1994. Another 30 metastable isomers have been characterized for isotopes between 111 and 131, the most stable of which being 121mSn, with a half-life of 43.9 years.Sony VAIO VGN-NW21MF Battery

Etymology

The English word 'tin' is Germanic; related words are found in the other Germanic languages—German zinn, Swedishtenn, Dutchtin, etc.—but not in other branches of Indo-European except by borrowing (e.g. Irish tinne). Its origin is unknown.Sony VAIO VGN-NW21MF/W Battery

The Latin name stannum originally meant an alloy of silver and lead, and came to mean 'tin' in the 4th century BCE[13]—the earlier Latin word for it was plumbum candidum 'white lead'. Stannum apparently came from an earlier st?gnum (meaning the same thing),[12] the origin of the Romance and Celtic terms for 'tin'.Sony VAIO VGN-NW21ZF Battery

The origin of stannum/st?gnum is unknown; it may be pre-Indo-European. The Meyers Konversationslexikon speculates on the contrary that stannum is derived from Cornishstean, and is proof that Cornwall in the first centuries AD was the main source of tin.Sony VAIO VGN-NW31EF/W Battery

Antiquity

Tin extraction and use can be dated to the beginnings of the Bronze Age around 3000 BC, when it was observed that copper objects formed of polymetallic ores with different metal contents had different physical properties.Sony VAIO VGN-NW31JF Battery

The earliest bronze objects had tin or arsenic content of less than 2% and are therefore believed to be the result of unintentional alloying due to trace metal content in the copper ore It was soon discovered that the addition of tin or arsenic to copper increased its hardness and made casting much easier,Sony VAIO VGN-NW320F/B Battery

which revolutionized metal working techniques and brought humanity from the Copper Age or Chalcolithic to the Bronze Age around 3000 BC. Early tin exploitation appears to have been centered on placer deposits of cassiterite.

The first evidence of tin use for making bronze appears in the Near East and the Balkans around 3000 BC.Sony VAIO VGN-NW320F/TC Battery

It is still unclear where the earliest tin was mined, as tin deposits are very rare and evidence of early mining is scarce. Europe's earliest mining district appears to be located in Erzgebirge, on the border between Germany and Czech Republic and is dated to 2500 BC. From there tin was traded north to the Baltic Sea and south to the Mediterranean following the Amber Road trading route.Sony VAIO VGN-NW35E Battery

Tin mining knowledge spread to other European tin mining districts from Erzgebirge and evidence of tin mining begins to appear in Brittany, Devon and Cornwall, and in the Iberian Peninsula around 2000 BC. These deposits saw greater exploitation when they fell under Roman control between the third century BC and the first century AD.Sony VAIO VGN-NW380F/S Battery

Demand for tin created a large and thriving network amongst Mediterranean cultures of Classical times.[20][21] By the Medieval period, Iberia's and Germany's deposits lost importance and were largely forgotten while Devon and Cornwall began dominating the European tin market.Sony VAIO VGN-NW380F/T Battery

In the Far East, the tin belt stretching from Yunnan province in China to the Malaysian Peninsulabegan being exploited sometime between the third and second millennium BC. The deposits in Yunnan province were not mined until around 700 BC, but by the Han Dynasty had become the main source of tin in China according to historical texts of the Han, Jin, Tang, and Song dynasties.Sony VAIO VGN-NW50JB Battery

Other regions of the world developed tin mining industries at a much later date. In Africa, theBantu culture extracted, smelted and exported tin between the 11th and 15th centuries AD,  in the Americas tin exploitation began around 1000 AD, and in Australia it began with the arrival of Europeans in the 17th century.Sony VAIO VGN-NW51FB/N Battery

Modern times

During the Middle Ages, and again in the early 19th century, Cornwall was the major tin producer. This changed after large amounts of tin were found in the Bolivian tin belt and the east Asian tin belt, stretching from China through Thailand and Laos to Malaya and Indonesia.Sony VAIO VGN-NW51FB/W Battery

Tasmania also hosts deposits of historical importance, most notably Mount Bischoff and Renison Bell.

In 1931 the tin producers founded the International Tin Committee, followed in 1956 by the International Tin Council, an institution to control the tin market. After the collapse of the market in October 1985 the price for tin nearly halved.Sony VAIO VGN-NW70JB Battery

Tin foil was once a common wrapping material for foods and drugs; replaced in the early 20th century by the use of aluminium foil, which is now commonly referred to as tin foil. Hence one use of the slang term "tinnie" or "tinny" for a small pipe for use of a drug such as cannabis or for a can of beer.Sony VAIO VGN-NW71FB/N Battery

Today, the word "tin" is often improperly used as a generic term for any silvery metal that comes in sheets. Most everyday materials that are commonly called "tin", such as aluminium foil,beverage cans, corrugated building sheathing and tin cans, are actually made of steel or aluminium, although tin cans (tinned cans) do contain a thin coating of tin to inhibit rust.Sony VAIO VGN-NW71FB/W Battery

Likewise, so-called "tin toys" are usually made of steel, and may have a coating of tin to inhibit rust. The original Ford Model T was known colloquially as the "Tin Lizzy".

Compounds and chemistry

In the great majority of its compounds, tin has the oxidation state II or IV.Sony VAIO VGN-NW91FS Battery

Inorganic compounds

Halide compounds are known for both oxidation states. For Sn(IV), all four halides are well known: SnF4, SnCl4, SnBr4, and SnI4. The three heavier members are volatile molecular compounds, whereas the tetrafluoride is polymeric. All four halides are known for Sn(II) also: SnF2, SnCl2, SnBr2, and SnI2. All are polymeric solids. Of these eight compounds, only the iodides are coloured.Sony VAIO VGN-NW91GS Battery

Tin(II) chloride (also known as stannous chloride) is the most important tin halide in a commercial sense. Illustrating the routes to such compounds, chlorine reacts with tin metal to give SnCl4 whereas the reaction of hydrochloric acid and tin gives SnCl2 and hydrogen gas. Alternatively SnCl4 and Sn combine to stannous chloride via a process called comproportionationSony VAIO VGN-NW91VS Battery

SnCl4 + Sn ? 2 SnCl2

Tin can form many oxides, sulfides, and other chalcogenide derivatives. The dioxide SnO2 (cassiterite) forms when tin is heated in the presence of air. SnO2 isamphoteric, which means that it dissolves in both acidic and basic solutions. There are also stannates with the structure [Sn(OH)6]2?, like K2[Sn(OH)6], although the free stannic acid H2[Sn(OH)6] is unknown.Sony VAIO VGN-SR11M Battery

The sulfides of tin exist in both the +2 and +4 oxidation states: tin(II) sulfide and tin(IV) sulfide (Mosaic gold).

Hydrides

Stannane (SnH4), where tin is in the +4 oxidation state, is unstable. Organotin hydrides are however well known, e.g. tributyltin hydride (Sn(C4H9)3H). These compound release transient tributyl tin radicals, rare examples of compounds of tin(III).Sony VAIO VGN-SR11MR Battery

Organotin compounds

Organotin compounds, sometimes called stannanes, are chemical compounds with tin-carbon bonds. Of the compounds of tin, the organic derivatives are the most useful commercially. Some organotin compounds are highly toxic and have been used as biocides.Sony VAIO VGN-SR140D Battery

The first organotin compound to be reported was diethyltin diiodide ((C2H5)2SnI2), reported byEdward Frankland in 1849.

Most organotin compounds are colorless liquids or solids that are stable to air and water. They adopt tetrahedral geometry. Tetraalkyl- and tetraaryltin compounds can be prepared usingGrignard reagents:Sony VAIO VGN-SR140D/B Battery

SnCl4 + 4 RMgBr ? R4Sn + 4 MgBrCl

The mixed halide-alkyls, which are more common and more important commercially than the tetraorgano derivatives, are prepared by redistribution reactions:

SnCl4 + R4Sn ? 2 SnCl2R2

Divalent organotin compounds are uncommon, although more common than related divalent organogermanium and organosilicon compounds.Sony VAIO VGN-SR140D/P Battery

The greater stabilization enjoyed by Sn(II) is attributed to the "inert pair effect". Organotin(II) compounds include both stannylenes (formula: R2Sn, as seen for singlet carbenes) and distannylenes (R4Sn2), which are roughly equivalent to alkenes. Both classes exhibit unusual reactions.Sony VAIO VGN-SR140D/S Battery

Occurrence

Tin is generated via the long S-process in low-medium mass stars (with masses of 0.6 to 10 of that of Sun). It arises via beta decay of heavy isotopes of indium.

Tin is the 49th most abundant element in the Earth's crust, representing 2 ppm compared with 75 ppm for zinc, 50 ppm for copper, and 14 ppm for lead.Sony VAIO VGN-SR140E Battery

Tin does not occur as the native element but must be extracted from various ores. Cassiterite (SnO2) is the only commercially important source of tin, although small quantities of tin are recovered from complex sulfides such as stannite, cylindrite, franckeite, canfieldite, andteallite. Minerals with tin are almost always associated with granite rock, usually at a level of 1% tin oxide content.Sony VAIO VGN-SR140E/B Battery

Because of the higher specific gravity of tin dioxide, about 80% of mined tin is from secondary deposits found downstream from the primary lodes. Tin is often recovered from granules washed downstream in the past and deposited in valleys or under sea. The most economical ways of mining tin are through dredging, hydraulic methods or open cast mining.Sony VAIO VGN-SR140E/P Battery

Most of the world's tin is produced from placer deposits, which may contain as little as 0.015% tin.

It was estimated in January 2008 that there were 6.1 million tons of economically recoverable primary reserves, from a known base reserve of 11 million tons. Below are listed the nations with the largest known reserves.Sony VAIO VGN-SR140E/S Battery

Estimates of tin production have historically varied with the dynamics of economic feasibility and the development of mining technologies, but it is estimated that, at current consumption rates and technologies, the Earth will run out of tin that can be mined in 40 years.Sony VAIO VGN-SR140N/S Battery

However Lester Brown has suggested tin could run out within 20 years based on an extremely conservative extrapolation of 2% growth per year.

Secondary, or scrap, tin is also an important source of the metal. The recovery of tin through secondary production, or recycling of scrap tin, is increasing rapidly.Sony VAIO VGN-SR165E/B Battery

Whereas the United States has neither mined since 1993 nor smelted tin since 1989, it was the largest secondary producer, recycling nearly 14,000 tons in 2006.

New deposits are reported to be in southern Mongolia, and in 2009, new deposits of tin were discovered in Colombia, South America, by the Seminole Group Colombia CI, SAS.Sony VAIO VGN-SR165E/P Battery

Production

Tin is produced by reducing the ore with carbon in a reverberatory furnace.

Mining and smelting

In 2006, total worldwide tin mine production was 321,000 tons, and smelter production was 340,000 tons. From its production level of 186,300 tons in 1991, around where it had hovered for the previous decades, production of tin increased 89% to 351,800 tons in 2005.Sony VAIO VGN-SR165E/S Battery

Most of the increase came from China and Indonesia, with the largest spike in 2004–2005, when it increased 23%. While in the 1970s Malaysia was the largest producer, with around a third of world production, it has steadily fallen, and now remains a major smelter and market center.Sony VAIO VGN-SR190EBJ Battery

In 2007, the People's Republic of China was the largest producer of tin, where the tin deposits are concentrated in the southeast Yunnan tin belt, with 43% of the world's share, followed byIndonesia, with an almost equal share, and Peru at a distant third, reports the USGS.Sony VAIO VGN-SR190EBQ Battery

The table below shows the countries with the largest mine production and the largest smelter output.

After the discovery of tin in what is now Bisie, North Kivu in the Democratic Republic of the Congo in 2002, illegal production has increased there to around 15,000 tons. This is largely fueling the ongoing and recent conflicts there, as well as affecting international markets.Sony VAIO VGN-SR190EEJ/C Battery

Industry

The ten largest companies produced most of world's tin in 2007. It is not clear which of these companies include tin smelted from the mine at Bisie, Democratic Republic of the Congo, which is controlled by a renegade militia and produces 15,000 tons. Most of the world's tin is traded on the London Metal Exchange (LME), from 8 countries, under 17 brands.Sony VAIO VGN-SR190NAB Battery

Prices of tin were at US$11,900 per ton as of Nov 24, 2008. Prices reached an all-time high of nearly $25,000 per ton in May 2008, largely because of the effect of the decrease of tin production from Indonesia.

Exchanges

• London Metal Exchange (LME), contract marketSony VAIO VGN-SR190NBB Battery

• Kuala Lumpur Tin Market (KLTM), contract market
• Indonesia Tin Exchange (INATIN), the solely physical market for tin will formally launchs at January 12, 2012

In 2006, about half of tin produced was used in solder. The rest was divided between tin plating, tin chemicals, brass and bronze, and niche uses.Sony VAIO VGN-SR190NDB Battery

Solder

Tin has long been used as a solder in the form of an alloy with lead, tin accounting for 5 to 70% w/w. Tin forms a eutectic mixture with lead containing 63% tin and 37% lead. Such solders are primarily used for solders for joining pipes or electric circuits.Sony VAIO VGN-SR190NEB Battery

Since the European Union Waste Electrical and Electronic Equipment Directive (WEEED) and Restriction of Hazardous Substances Directive (RoHS) came into effect on 1 July 2006, the use of lead in such alloys has decreased. Replacing lead has many problems, including a higher melting point, and the formation of tin whiskers causing electrical problems. Replacement alloys are rapidly being found, however.Sony VAIO VGN-SR190NGB Battery

Tin plating

Tin bonds readily to iron and is used for coating lead or zinc and steel to prevent corrosion. Tin-plated steel containers are widely used for food preservation, and this forms a large part of the market for metallic tin. A tinplate canister for preserving food was first manufactured in London in 1812.Sony VAIO VGN-SR190PAB Battery

Speakers of British English call them "tins", while speakers of American English call them "cans" or "tin cans". One thus-derived use of the slang term "tinnie" or "tinny" means "can of beer". The tin whistle is so called because it was first mass-produced in tin-plated steel.Sony VAIO VGN-SR190PCB Battery

Specialized alloys

Tin in combination with other elements forms a wide variety of useful alloys. Tin is most commonly alloyed with copper. Pewter is 85–99% tin; Babbitt metal has a high percentage of tin as well. Bronze is mostly copper (12% tin), while addition of phosphorus givesphosphor bronze. Bell metal is also a copper-tin alloy, containing 22% tin.Sony VAIO VGN-SR190PFB Battery

Tin has also sometimes been used in coinage; for example, it once formed a single figure percentage of the American and Canadian pennies. Because copper is often the major metal in such coins, and zinc is sometimes present as well, these could technically be called bronze and/or brass alloys.Sony VAIO VGN-SR19VN Battery

The niobium-tin compound Nb3Sn is commercially used as wires for superconducting magnets, due to the material's high critical temperature (18 K) and critical magnetic field (25 T). A superconducting magnet weighing only a couple of kilograms is capable of producing magnetic fields comparable to a conventional electromagnet weighing tons.Sony VAIO VGN-SR19VN Battery

A addition of a few percent tin is commonly used in zirconium alloys for the cladding of nuclear fuel.

Most metal pipes in a pipe organ are made of varying amounts of a tin/lead alloy, with 50%/50% being the most common. The amount of tin in the pipe defines the pipe's tone, since tin is the most tonally resonant of all metals.Sony VAIO VGN-SR19VRN Battery

When a tin/lead alloy cools, the lead cools slightly faster and produces a mottled or spotted effect. This metal alloy is referred to as spotted metal.

Other applications

Punched tin, also called pierced tin, is an artisan technique originating in central Europe for creating housewares that are both functional and decorative.Sony VAIO VGN-SR19XN Battery

Decorative piercing designs exist in a wide variety, based on geography or the artisan's personal creations. Punched tin lanterns are the most common application of this artisan technique. The light of a candle shining through the pierced design creates a decorative light pattern in the room where it sits.Sony VAIO VGN-SR19XN Battery

Punched tin lanterns and other punched tin articles were created in the New World from the earliest European settlement. A well-known example is the Revere type lantern, named after Paul Revere.

Before the modern era, in some areas of the Alps, a goat or sheep's horn would be sharpened and a tin panel would be punched out using the alphabet and numbers from one to nine.Sony VAIO VGN-SR210J/S Battery

This learning tool was known appropriately as "the horn". Modern reproductions are decorated with such motifs as hearts and tulips.

In America, pie safes and food safes came into use in the days before refrigeration. These were wooden cupboards of various styles and sizes - either floor standing or hanging cupboards meant to discourage vermin and insects and to keep dust from perishable foodstuffs.Sony VAIO VGN-SR21M/S Battery

These cabinets had tinplate inserts in the doors and sometimes in the sides, punched out by the homeowner, cabinetmaker or a tinsmith in varying designs to allow for air circulation. Modern reproductions of these articles remain popular in North America.

Window glass is most often made by floating molten glass on top of molten tin (creating float glass) in order to produce a flat surface. This is called the "Pilkington process".Sony VAIO VGN-SR21RM/H Battery

Tin(II) fluoride is added to some dental care products as stannous fluoride (SnF2). Tin(II) fluoride can be mixed with calcium abrasives while the more common sodium fluoride gradually becomes biologically inactive combined with calcium compounds. It has also been shown to be more effective than sodium fluoride in controlling gingivitis.Sony VAIO VGN-SR21RM/S Battery

Organotin compounds

Of all the chemical compounds of tin, the organotin compounds are most heavily used. Worldwide industrial production probably exceeds 50,000 tonnes.

PVC stabilizers

The major commercial application of organotin compounds is in the stabilization of PVC plastics.Sony VAIO VGN-SR220J/B Battery

In the absence of such stabilizers, PVC would otherwise rapidly degrade under heat, light, and atmospheric oxygen, to give discolored, brittle products. Tin scavenges labile chloride ions (Cl-), which would otherwise initiate loss of HCl from the plastic material.Sony VAIO VGN-SR220J/H Battery

Typical tin compounds are carboxylic acid derivatives of dibutyltin dichloride, such as the dilaurate.

Biocides

Organotin compounds can have a relatively high toxicity, which is both advantageous and problematic. They have been used for their biocidal effects in/as fungicides,pesticides, algaecides, wood preservatives, and antifouling agents.Sony VAIO VGN-SR240J/B Battery

Tributyltin oxide is used as a wood preservative.Tributyltin was used as additive for ship paint to prevent growth of marine organisms on ships, with use declining after organotin compounds were recognized as persistent organic pollutants with an extremely high toxicity for some marine organisms, for example the dog whelk.Sony VAIO VGN-SR240N/B Battery

The EU banned the use of organotin compounds in 2003, while concerns over the toxicity of these compounds to marine life and their effects on the reproduction and growth of some marine species, some reports describe biological effects to marine life at a concentration of 1 nanogram per liter) have led to a worldwide ban by the International Maritime Organization.Sony VAIO VGN-SR290JTH Battery

Many nations now restrict the use of organotin compounds to vessels over 25 meters long.

Organic chemistry

Some tin reagents are useful in organic chemistry. In the largest application, stannous chloride is a common reducing agent for the conversion of nitro and oximegroups to amines. The Stille reaction couples organotin compounds with organic halides or pseudohalides.Sony VAIO VGN-SR290JTJ Battery

Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Although the use of antimony is limited by its toxicity, its compounds have been of fundamental value in chemistry – a prominent example being the development of superacids derived from antimony pentafluoride.Sony VAIO VGN-SR290JTQ Battery

Antimony compounds are prominent fire retardantsfound in many commercial and domestic products. Certain alloys are valuable for use in solders and ball bearings. An emerging application is the use of antimony in microelectronics.

Antimony's sulfide compound, antimony(III) sulfide, Sb2S3 was recognized in antiquity, at least as early as3000 BC.Sony VAIO VGN-SR290JVB/C Battery

An artifact, said to be part of a vase, made of antimony dating to about 3000 BC was found at Tello,Chaldea (part of present-day Iraq), and a copper object plated with antimony dating between 2500 BC and 2200 BC has been found in Egypt.Sony VAIO VGN-SR290JVH/C Battery

One contemporary (Austen, at a lecture by Herbert Gladstone, published in 1892) was reported  to comment that "we only know of antimony at the present day as a highly brittle and crystalline metal, which could hardly be fashioned into a useful vase, and therefore this remarkable 'find' must represent the lost art of rendering antimony malleable."Sony VAIO VGN-SR290NTB Battery

However, Moorey was unconvinced that the artefact was indeed a vase, mentioning that Selimkhanov, after his analysis of the Telloh object (published in 1975), "attempted to relate the metal to Transcaucasian natural antimony" (i.e. native metal) and that "the antimony objects from Transcaucasia are all small personal ornaments."Sony VAIO VGN-SR29VN/S Battery

This weakens the evidence for a lost art "of rendering antimony malleable."

The first European description of a procedure for isolating antimony is in the book De la pirotechnia of 1540 by Vannoccio Biringuccio. This book predates the more famous 1556 book by Agricola, De re metallica, even though Agricola has been often incorrectly credited with the discovery of metallic antimony.Sony VAIO VGN-SR29XN/S Battery

A text describing the preparation of metallic antimony that was published in Germany in 1604 purported to date from the early fifteenth century, and if authentic it would predate Biringuccio. The book, written in Latin, was called "Currus Triumphalis Antimonii" (The Triumphal Chariot of Antimony), and its putative author was a certain Benedictine monk, writing under the name Basilius Valentinus.Sony VAIO VGN-SR2RVN/S Battery

An English translation of the "Currus Triumphalis" appeared in English in 1660, under the title The Triumphant Chariot of Antimony. The work remains of great interest, chiefly because it documents how followers of the renegade German physician, Philippus TheophrastusParacelsus von Hohenheim (of whom Thölde was one), came to associate the practice of alchemy with the preparation of chemical medicines.Sony VAIO VGN-SR390NAB Battery

Pure antimony was well known to J?bir ibn Hayy?n, sometimes called "the Father of Chemistry", in the 8th century. Here there is still an open controversy: Marcellin Berthelot, who translated a number of J?bir's books, stated that antimony is never mentioned in them,Sony VAIO VGN-SR390NAH Battery

but other authors  claim that Berthelot translated only some of the less important books, while the more interesting ones (some of which might describe antimony) are not yet translated, and their content is completely unknown.

The first natural occurrence of pure antimony ('native antimony') in the Earth's crust was described by the Swedish scientist and local mine district engineer Anton von Swab in 1783.Sony VAIO VGN-SR41M/P Battery

The type-sample was collected from the Sala Silver Mine in the Bergslagen mining district of Sala, Västmanland, Sweden.

Etymology

The ancient words for antimony mostly have, as their chief meaning, kohl, the sulfide of antimony. Pliny the Elder, however, distinguishes between male and female forms of antimony;Sony VAIO VGN-SR41M/S Battery

his male form is probably the sulfide, while the female form, which is superior, heavier, and less friable, is probably native metallic antimony.

The Egyptians called antimony m?dmt; in hieroglyphs, the vowels are uncertain, but there is an Arabic tradition that the word is ???????? mesdemet.Sony VAIO VGN-SR49VN/H Battery

The Greek word, ?????? stimmi, is probably a loan word from Arabic or Egyptian sdm

, and is used by the Attic tragic poets of the 5th century BC; later Greeks also used ????? stibi, as did Celsus andPliny, writing in Latin, in the first century AD. Pliny also gives the names stimi [sic], larbaris, alabaster, and the "very common" platyophthalmos, "wide-eye" (from the effect of the cosmetic).Sony VAIO VGN-SR51B/P Battery

Later Latin authors adapted the word to Latin asstibium. The Arabic word for the substance, as opposed to the cosmetic, can appear as ?????? ????? ?????? ????? ithmid, athmoud, othmod, or uthmod. Littré suggests the first form, which is the earliest, derives from stimmida, (one) accusative for stimmi.Sony VAIO VGN-SR51B/S Battery

The use of Sb as the standard chemical symbol for antimony is due to the 18th century chemical pioneer, Jöns Jakob Berzelius, who used this abbreviation of the name stibium.The medieval Latin form, from which the modern languages and lateByzantine Greek, take their names, is antimonium. Sony VAIO VGN-SR51MF Battery

The origin of this is uncertain; all suggestions have some difficulty either of form or interpretation. The popular etymology, from ??????????? anti-monachos or French antimoine, still has adherents; this would mean "monk-killer", and is explained by many early alchemists being monks, and antimony being poisonous.Sony VAIO VGN-SR51MF/P Battery

So does the hypothetical Greek word ????????? antimonos, "against one", explained as "not found as metal", or "not found unalloyed". Lippmann conjectured a Greek word, ?????????? anthemonion, which would mean "floret", and he cites several examples of related Greek words (but not that one) which describe chemical or biologicalefflorescence.Sony VAIO VGN-SR51MF/S Battery

The early uses of antimonium include the translations, in 1050–1100, by Constantine the African of Arabic medical treatises. Several authorities believe that antimonium is a scribal corruption of some Arabic form; Meyerhof derives it from ithmid;Sony VAIO VGN-SR51MF/W Battery

other possibilities include Athimar, the Arabic name of the metal, and a hypothetical as-stimmi, derived from or parallel to the Greek.

Characteristics

Antimony is in the nitrogen group (group 15) and has an electronegativity of 2.05. As expected by periodic trends, it is more electronegative than tin or bismuth, and less electronegative than tellurium or arsenic.Sony VAIO VGN-SR51MR Battery

Antimony is stable in air at room temperature but reacts with oxygen if heated to formantimony trioxide, Sb2O3.

Antimony is a silvery, lustrous gray metal that has a Mohs scale hardness of 3. Therefore, antimony by itself is not used to make hard objects: coins made of antimony were issued in China's Guizhou province in 1931, but because of their rapid wear their minting was discontinued.Antimony is resistant to attack by acids.Sony VAIO VGN-SR59VG Battery

Four allotropes of antimony are known: a stable metallic form, and three metastable forms: explosive, black and yellow. Metallic antimony is a brittle, silver-white shiny metal. When molten antimony is slowly cooled, metallic antimony crystallizes in an hexagonal cell,isomorphic with that of the grey allotrope of arsenic.Sony VAIO VGN-SR59VG/H Battery

A rare explosive form of antimony can be formed from the electrolysis of antimony(III) trichloride. When scratched with a sharp implement, an exothermic reaction occurs and white fumes given off as metallic antimony is formed; alternatively, when rubbed with a pestle in a mortar, a strong detonation occurs.Sony VAIO VGN-SR70B/S Battery

Black antimony is formed upon rapid cooling of gaseous metallic antimony. It has the same crystal structure as red phosphorus and black arsenic, it oxidizes in air and may ignite spontaneously. At 100 °C, it gradually transforms into the stable form. The yellow allotrope of antimony is the most unstable. It has only been generated by oxidation of stibine (SbH3) at ?90 °C.Sony VAIO VGN-SR72B/P Battery

Above this temperature and in ambient light, this meta stable allotrope transforms into the more stable black allotrope.

Metallic antimony adopts a double-layered structure (space group R3m No. 166) consisting of many interlocked ruffled six-membered rings.Sony VAIO VGN-SR72B/S Battery

Nearest and next-nearest neighbors form a distorted octahedral complex, with the three atoms in the same double-layer being slightly closer than the three atoms in the next. This relatively close packing leads to a high density of 6.697 g/cm3 whereas the low hardness and brittleness of antimony originate from the weak bonding among the layers.Sony VAIO VGN-SR73JB/S Battery

Antimony exists as two stable isotopes, 121Sb with a natural abundance of 57.36% and 123Sb with a natural abundance of 42.64%. It also has 35 radioisotopes, of which the longest-lived is 125Sb with a half-life of 2.75 years. In addition, 29 metastable states have been characterised.Sony VAIO VGN-SR74FB/S Battery

Occurrence

The abundance of antimony in the Earth's crust is estimated at 0.2 to 0.5 parts per million, comparable to thallium at 0.5 parts per million and silver at 0.07 ppm. Even though this element is not abundant, it is found in over 100 mineral species.Sony VAIO VGN-SR90FS Battery

Antimony is sometimes found native, but more frequently it is found in the sulfide stibnite (Sb2S3) which is the predominant ore mineral. Commercial forms of antimony are generally ingots, broken pieces, granules, and cast cake. Other forms are powder, shot, and single crystals.Sony VAIO VGN-SR90NS Battery

In 2005, the People's Republic of China was the top producer of antimony with about 84% world share followed at a distance by South Africa, Bolivia and Tajikistan, reports the British Geological Survey. The mine with the largest deposits in China is Xikuangshan Mine in Hunan province with a estimated deposit of 2.1 million metric tons.Sony VAIO VGN-SR90S Battery

In October 2011 a deposit of antimony was found in a shallow seabed about 50 km off Amami-Oshima Island in Kagoshima Prefecture. The discovery was the first time that antimony had been found at such shallow depths(480 meters), with this type of mineral deposit only ever having been found in depths in excess of 1000 meters.Sony VAIO VGN-SR90US Battery

Production

The extraction of antimony from ores depends on the quality of the ore, which is usually a sulfide. The sulfide is converted to an oxide and advantage is often taken of the volatility of antimony(III) oxide, which is recovered from roasting.Sony VAIO VGN-SR91NS Battery

This material is often used directly for the main applications, impurities being arsenic and sulfide. Antimony can be isolated from its ore by a reduction with scrap iron:

Sb2S3 + 3 Fe ? 2 Sb + 3 FeS

Isolating antimony from its oxide is performed by a carbothermal reduction:Sony VAIO VGN-SR91PS Battery

2 Sb2O3 + 3 C ? 4 Sb + 3 CO2

Compounds

Antimony compounds are often classified into those of Sb(III) and Sb(V).[26] Relative to its neighboring element As, the 5+ oxidaton state is more stable.

Oxides and hydroxides

Antimony trioxide (Sb4O6) is formed when antimony is burnt in air. In the gas phase, this compound exists as Sb4O6, but it polymerises upon condensing.Sony VAIO VGN-SR91S Battery

Antimony pentoxide, (Sb4O10) can only be formed by oxidation by concentrated nitric acid. Antimony also forms a mixed-valence oxide, antimony tetroxide (Sb2O4), which features both Sb(III) and Sb(V). Unlike phosphorus and arsenic, these various oxides are amphoteric and do not form well-defined oxoacids and react with acids to form antimony salts.Sony VAIO VGN-SR91US Battery

Antimonous acid Sb(OH)3 is unknown but the conjugate base sodium antimonite ([Na3SbO3]4) forms upon fusing sodium oxide and Sb4O6.[21]:763 Transition metal antimonites are also known.  Antimonic acid exists only as the hydrate HSb(OH)6, forming salts containing the antimonate anion Sb(OH)?6. Dehydrating metal salts containing this anion yields mixed oxides.Sony VAIO VGN-SR92NS Battery

Many antimony ores are sulfides, including stibnite (Sb2S3), pyrargyrite (Ag3SbS3), zinkenite, jamesonite, and boulangerite.[21]:757 Antimony pentasulfide is non-stoichiometric and features antimony in the +3 oxidation state and S-S bonds. Several thioantimonides are known such as [Sb6S10]2? and [Sb8S13]2?.Sony VAIO VGN-SR92PS Battery

Halides

Antimony forms two series of halides, SbX3 and SbX5. The trihalides SbF3, SbCl3, SbBr3, and SbI3 are all molecular compounds having trigonal pyramidal molecular geometry. The trifluoride SbF3 is prepared by the reaction of Sb2O3 with HF:Sony VAIO VGN-SR92S Battery

Sb2O3 + 6 HF ? 2 SbF3 + 3 H2O

It is Lewis acidic and readily accepts fluoride ions to form the complex anions SbF?
4 and SbF2?
5. Molten SbF3 is a weak electrical conductor. The trichloride SbCl3 is prepared by dissolving Sb2S3 in hydrochloric acid:Sony VAIO VGN-SR92US Battery

Sb2S3 + 6 HCl ? 2 SbCl3 + 3 H2S

The pentahalides SbF5 and SbCl5 have trigonal bipyramidal molecular geometry in the gas phase, but in the liquid phase, SbF5is polymeric, whereas SbCl5 is monomeric.[21]:761 SbF5 is a powerful Lewis acid used to make the superacid fluoroantimonic acid ("HSbF6").Sony VAIO VGN-SR93DS Battery

Oxyhalides are more common for antimony than arsenic and phosphorus. Antimony trioxide dissolves in concentrated acid to form antimony oxo- (antimonyl) compounds such as SbOCl and (SbO)2SO4.

Antimonides, hydrides, and organoantimony compounds

Compounds in this class generally are described as derivatives of Sb3-. Antimony forms antimonides with metals, such as indium antimonide(InSb), and silver antimonide (Ag3Sb).Sony VAIO VGN-SR93JS Batery

The alkali metal and zinc antimonides, e.g. Na3Sb and Zn3Sb2, are more reactive. Treating these antimonides with acid produces the unstable gas stibine, SbH3:

Sb3? + 3 H+ ? SbH3

Stibine can also be produced by treating Sb3+ salts with hydride reagents such as sodium borohydride. Stibine decomposes spontaneously at room temperature.Sony VAIO VGN-SR93PS Batttery

Because stibine is thermodynamically unstable (positive heat of formation), antimony does not react with hydrogen directly.

Organoantimony compounds are typically prepared by alkylation of antimony halides with Grignard reagents.A large variety of compounds are known with both Sb(III) and Sb(V) centers including mixed chloro-organic derivatives, anions, and cations.Sony VAIO VGN-SR93YS Battery

Examples include Sb(C6H5)3 (triphenylstibine), Sb2(C6H5)4 (with an Sb-Sb bond), and cyclic [Sb(C6H5)]n. Pentacoordinated organoantimony compounds are common, examples being Sb(C6H5)5 and several related halides.

Flame retardants

The main use of antimony is in the form of antimony trioxide is used in the making of flame-proofing compounds.Sony VAIO VGN-SR94FS Battery

Markets for these flame-retardant applications include children's clothing, toys, aircraft and automobile seat covers. It is also used in the fiberglass composites industry as an additive to polyester resins for such items as light aircraft engine covers. The resin will burn while a flame is held to it but will extinguish itself as soon as the flame is removed. Fireproofing consumes about half of the annual production of antimony.Sony VAIO VGN-SR94GS Battery

Alloys

Antimony forms a highly useful alloy with lead, increasing its hardness and mechanical strength. The Sb–Pb alloy is used in lead–acid batteries. It is used in antifriction alloys, such as Babbitt metal. It is used as an alloy in bullets and lead shot, cable sheathing, type metal (e.g. for linotype printing machines ), solder – some "lead-free" solders contain 5% Sb, in pewter, and in hardening alloys with low tin content in the manufacturing of organ pipes.Sony VAIO VGN-SR94HS Battery

Other applications

The second main application is as a catalyst for the production of the polymer polyethyleneterephthalate. It is an additive in some glasses. In the latter application, antimony oxides serve as fining agents, aiding in the removal of microscopic bubbles. This application is mainly used for TV screens.Sony VAIO VGN-SR94VS Battery

Microelectronics

In tiny amounts, antimony is increasingly being used in the semiconductor industry as a dopant for ultra-high conductivity n-type silicon wafers in the production of diodes, infrared detectors, and Hall-effect devices.

In the 1950s, tiny beads of a lead-antimony alloy were used to dope the emitters and collectors of NPN alloy junction transistors with antimony.Sony VAIO VGN-SZ35B/B Battery

Medical

Few biological or medical applications exist for antimony. Treatments principally containing antimony are known as antimonials and are used as emetics.

Antimony compounds are used as antiprotozoan drugs. Antimony potassium tartrate, or tartar emetic, was once used as an anti-schistosomal drug, subsequently replaced by praziquantel.Sony VAIO VGN-SZ54B/B Battery

Antimony and its compounds are used in several veterinary preparations like anthiomaline or lithium antimony thiomalate, which is used as a skin conditioner inruminants.

Antimony has a nourishing or conditioning effect on keratinized tissues, at least in animals.Sony VAIO VGN-SZ55B/B Battery

Antimony-based drugs, such as meglumine antimoniate, are also considered the drugs of choice for treatment of leishmaniasis in domestic animals. Unfortunately, as well as having low therapeutic indices, the drugs are poor at penetrating the bone marrow, where some of the Leishmania amastigotes reside, and so cure of the disease – especially the visceral form – is very difficult.Sony VAIO VGN-SZ55GN/B Battery

Elemental antimony as an antimony pill was once used as a medicine. It could be reused by others after ingestion.

Other uses

In the heads of some safety matches  and in nuclear reactors together with beryllium as startup neutron sources.

Antimony sulfides have been shown to help stabilize the friction coefficient in automotive brake pad materials.Sony VAIO VGN-SZ56 Battery

Antimony also is used in the making of bullets and bullet tracers. This element is also used in cosmetics and event paint and glass art crafts.

Precautions

Antimony and many of its compounds are toxic, and the effects of antimony poisoning are similar to arsenic poisoning. Inhalation of antimony dust is harmful and in certain cases may be fatal;Sony VAIO VGN-SZ561N Battery

in small doses, antimony causes headaches, dizziness, and depression. Larger doses such as prolonged skin contact may cause dermatitis; otherwise it can damage the kidneys and the liver, causing violent and frequent vomiting, and will lead to death in a few days.Sony VAIO VGN-SZ562N Battery

Antimony is incompatible with strong oxidizing agents, strong acids, halogen acids, chlorine, or fluorine. It should be kept away from heat.

Antimony leaches from polyethylene terephthalate (PET) bottles into liquids.  Sony VAIO VGN-SZ57N Battery

While levels observed for bottled water are below drinking water guidelines, fruit juice concentrates (for which no guidelines are established) produced in the UK were found to contain up to 44.7 µg/L of antimony, well above the EU limits fortap water of 5 µg/L.Sony VAIO VGN-SZ58GN Battery,Sony VAIO VGN-SZ58GN/C Battery,Sony VAIO VGN-SZ58N Battery,Sony VAIO VGN-SZ61MN/B Battery,Sony VAIO VGN-SZ61VN/X Battery