Lithium And Platinum

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Lithium (from lithos, Greek for stone) is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammableSony VAIO VPCF135Z1E/B battery. For this reason, it is typically stored in mineral oil. When cut open, lithium exhibits a metallic luster, but contact with moist air corrodes the surface quickly to a dull silvery gray, then black tarnish. Because of its high reactivity, lithium never occurs freely in nature, and instead, only appears in compounds, which are usually ionic. Lithium occurs in a number of pegmatitic mineralsSony VAIO VPCF137HG/BI battery, but due to its solubility as an ion is present in ocean water and is commonly obtained from brines and clays. On a commercial scale, lithium is isolated electrolytically from a mixture of lithium chloride and potassium chloride.

The nuclei of lithium verge on instability, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative nuclear instabilitySony VAIO VPCF136FG/BI battery, lithium is less common in the solar system than 25 of the first 32 chemical elements even though the nuclei are very light in atomic weight.[1] For related reasons, lithium has important links to nuclear physics. The transmutation of lithium atoms to helium in 1932 was the first fully man-made nuclear reaction, and lithium deuteride serves as a fusion fuel in staged thermonuclear weaponsSony VAIO VPCF135FG/B battery.

Lithium and its compounds have several industrial applications, including heat-resistant glass and ceramics, high strength-to-weight alloys used in aircraft, lithium batteries and lithium-ion batteries. These uses consume more than half of lithium production.

Trace amounts of lithium are present in all organisms. The element serves no apparent vital biological function, since animals and plants survive in good health without itSony VAIO VPCF127HG/BI battery. Nonvital functions have not been ruled out. The lithium ion Li+ administered as any of several lithium salts has proved to be useful as a mood-stabilizing drug due to neurological effects of the ion in the human body.

Properties

Main article: Alkali metal

[edit]Atomic and physical

Lithium pellets covered in white lithium hydroxide (left) and ingots with a thin layer of black oxide tarnish (right)

Like the other alkali metals, lithium has a single valence electron that is easily given up to form a cationSony VAIO VPCF11Z1E battery.[2] Because of this, it is a good conductor of heat and electricity as well as a highly reactive element, though the least reactive of the even-more highly reactive alkali metals. Lithium's low reactivity compared to other alkali metals is due to the proximity of its valence electron to its nucleus (the remaining two electrons in lithium's 1s orbital and are much lower in energy, and therefore they do not participate in chemical bonds) Sony VAIO VPCF11S1E battery.[2]

Lithium metal is soft enough to be cut with a knife. When cut, it possesses a silvery-white color that quickly changes to gray due to oxidation.[2] While it has one of the lowest melting points among all metals (180 °C), it has the highest melting and boiling points of the alkali metals.[3]

It is the lightest metal in the periodic table, so light that it can float on water and even on oil, and it is one of three metals that can (the other two are sodium and potassium) Sony VAIO VPCF11M1E/H battery. It has a very low density, of approximately 0.534 g/cm3, which gives sticks of the metal a similar heft to dowels of a medium density wood, such as pine. It floats on water but also reacts with it.[2]

Lithium floating in oil

It is the least dense of all elements that are not gases at room temperature. The next lightest element is over 60% more dense (potassium, at 0.862 g/cm3). Furthermore, aside from helium and hydrogen, it is the least dense element in a solid or liquid state, being only 2/3 as dense as liquid nitrogen (0.808 g/cm3). Sony VAIO VPCF11M1E battery

Lithium's coefficient of thermal expansion is twice that of aluminium and almost four times that of iron.[5] It has the highest specific heat capacity of any solid element. Lithium is superconductive below 400 μK at standard pressure[6] and at higher temperatures (more than 9 K) at very high pressures (>20 GPa)[7] At temperatures below 70 K, lithiumSony VAIO VPCF11JFX/B battery, like sodium, undergoes diffusionless phase change transformations. At 4.2 K it has a rhombohedral crystal system (with a nine-layer repeat spacing); at higher temperatures it transforms to face-centered cubic and then body-centered cubic. At liquid-helium temperatures (4 K) the rhombohedral structure is the most prevalent.[8] Multiple allotropic forms have been reported for lithium at high pressures. Sony VAIO VPCF119FJ battery

[edit]Chemistry and compounds

Lithium reacts with water easily, but with noticeably less energy than other alkali metals do. The reaction forms hydrogen gas and lithium hydroxide in aqueous solution.[2] Because of its reactivity with water, lithium is usually stored under cover of a viscous hydrocarbon, often petroleum jelly. Though the heavier alkali metals can be stored in less dense substancesSony VAIO VPCF119FC/BI battery, such as mineral oil, lithium is not dense enough to be fully submerged in these liquids.[10] In moist air, lithium rapidly tarnishes to form a black coating of lithium hydroxide (LiOH and LiOH·H2O), lithium nitride (Li3N) and lithium carbonate (Li2CO3, the result of a secondary reaction between LiOH and CO2).[11]

Hexameric structure of the n-butyllithium fragment in a crystal

When placed over a flame, lithium compounds give off a striking crimson color, but when it burns strongly the flame becomes a brilliant silver. Lithium will ignite and burn in oxygen when exposed to water or water vaporsSony VAIO VPCF119FC battery.[12] Lithium is inflammable, and it is potentially explosive when exposed to air and especially to water, though less so than the other alkali metals. The lithium-water reaction at normal temperatures is brisk but not violent, the hydrogen produced will not ignite on its own. As with all alkali metals, lithium fires are difficult to extinguish, requiring dry powder fire extinguishers, specifically Class D type Sony VAIO VPCF117HG/BI battery (see Types of extinguishing agents). Lithium is the only metal which reacts with nitrogen under normal conditions.[13][14]

Lithium has a diagonal relationship with magnesium, an element of similar atomic and ionic radius. Chemical resemblances between the two metals include the formation of a nitride by reaction with N2, the formation of an oxide (Li2O) and peroxide (Li2O2) when burnt in O2, salts with similar solubilities, and thermal instability of the carbonates and nitridesSony VAIO VPCF116FG/BI battery.[11][15] The metal reacts with hydrogen gas at high temperatures to produce lithium hydride (LiH).[16]

Other known binary compounds include the halides (LiF, LiCl, LiBr, LiI), and the sulfide (Li2S), the superoxide (LiO2), carbide (Li2C2). Many other inorganic compounds are known, where lithium combines with anions to form various salts: borates, amides, carbonate, nitrate, or borohydride (LiBH4) Sony VAIO VPCF115FG/B battery. Multiple organolithium reagents are known where there is a direct bond between carbon and lithium atoms effectively creating a carbanion that are extremely powerful bases and nucleophiles. In many of these organolithium compounds, the lithium ions tend to aggregate into high-symmetry clusters by themselves, which is relatively common for alkali cationsSony VAIO VPCF21ZHJ battery.[17]

[edit]Isotopes

Main article: Isotopes of lithium

Naturally occurring lithium is composed of two stable isotopes, 6Li and 7Li, the latter being the more abundant (92.5% natural abundance).[2][10][18] Both natural isotopes have anomalously low nuclear binding energy per nucleon compared to the next lighter and heavier elements, helium and beryllium, which means that alone among stable light elementsSony VAIO VPCF21Z1E/BI battery, lithium can produce net energy through nuclear fission. The two lithium nuclei have lower binding energies per nucleon than any other stable compound nuclides other than deuterium, and helium-3.[19] As a result of this, though very light in atomic weight, lithium is less common in the solar system than 25 of the first 32 chemical elements.[1] Seven radioisotopes have been characterized, the most stable being 8Li with a half-life of 838 ms and 9Li with a half-life of 178 msSony VAIO VPCF21AHJ battery. All of the remaining radioactive isotopes have half-lives that are shorter than 8.6 ms. The shortest-lived isotope of lithium is 4Li, which decays through proton emission and has a half-life of 7.6 × 10−23 s.[20]

7Li is one of the primordial elements (or, more properly, primordial nuclides) produced in Big Bang nucleosynthesis. A small amount of both 6Li and 7Li are produced in stars, but are thought to be burned as fast as producedSony VAIO VPCF21AGJ battery.[21] Additional small amounts of lithium of both 6Li and 7Li may be generated from solar wind, cosmic rays hitting heavier atoms, and from early solar system 7Be and 10Be radioactive decay.[22] While lithium is created in stars during the Stellar nucleosynthesis, it is further burnt. 7Li can also be generated in carbon starsSony VAIO VPCF21AFJ battery.[23]

Lithium isotopes fractionate substantially during a wide variety of natural processes,[24] including mineral formation (chemical precipitation), metabolism, and ion exchange. Lithium ions substitute for magnesium and iron in octahedral sites in clay minerals, where 6Li is preferred to 7Li, resulting in enrichment of the light isotope in processes of hyperfiltration and rock alteration. The exotic 11Li is known to exhibit a nuclear haloSony VAIO VPCF219FJ/BI battery. The process known as laser isotope separation can be used to separate lithium isotopes.[25]

[edit]Occurrence

Astronomical

Main article: Nucleosynthesis

According to modern cosmological theory, lithium—as both of its stable isotopes lithium-6 and lithium-7—was among the 3 elements synthesized in the Big Bang. Though the amount of lithium generated in Big Bang nucleosynthesis is dependent upon the number of photons per baryon, for accepted values the lithium abundance can be calculatedSony VAIO VPCF217HG/BI battery, and there is a "cosmological lithium discrepancy" in the Universe: older stars seem to have less lithium than they should, and some younger stars have far more. The lack of lithium in older stars is apparently caused by the "mixing" of lithium into the interior of stars, where it is destroyed.[26] Furthermore, lithium is produced in younger stars. Though it transmutes into two atoms of helium due to collision with a proton at temperatures above 2.4 million degrees Celsius Sony VAIO VPCF217HG battery (most stars easily attain this temperature in their interiors), lithium is more abundant than predicted in later-generation stars, for causes not yet completely understood.[10]

Though it was one of the three first elements (together with helium and hydrogen) to be synthesized in the Big Bang, lithium, together with beryllium and boron are markedly less abundant than other nearby elements. This is a result of the low temperature necessary to destroy lithium, and a lack of common processes to produce itSony VAIO VPCF14ZHJ battery.[27]

Lithium is also found in brown dwarf stars and certain anomalous orange stars. Because lithium is present in cooler, less-massive brown dwarf stars, but is destroyed in hotter red dwarf stars, its presence in the stars' spectra can be used in the "lithium test" to differentiate the two, as both are smaller than the Sun. Certain orange stars can also contain a high concentration of lithiumSony VAIO VPCF14AHJ battery. Those orange stars found to have a higher than usual concentration of lithium (such as Centaurus X-4) orbit massive objects—neutron stars or black holes—whose gravity evidently pulls heavier lithium to the surface of a hydrogen-helium star, causing more lithium to be observed.[10]

[edit]Terrestrial

Although lithium is widely distributed on Earth, it does not naturally occur in elemental form due to its high reactivitySony VAIO VPCF14AGJ battery.[2] The total lithium content of seawater is very large and is estimated as 230 billion tonnes, where the element exists at a relatively constant concentration of 0.14 to 0.25 parts per million (ppm),[31][32] or 25 micromolar;[33] higher concentrations approaching 7 ppm are found near hydrothermal vents.[32]

Estimates for crustal content range from 20 to 70 ppm by weight.[11] In keeping with its name, lithium forms a minor part of igneous rocksSony VAIO VPCF14AFJ battery, with the largest concentrations in granites. Granitic pegmatites also provide the greatest abundance of lithium-containing minerals, with spodumene and petalite being the most commercially viable sources.[11] Another significant mineral of lithium is lepidolite. [34] A newer source for lithium is hectorite clay, the only active development of which is through the Western Lithium Corporation in the United States.[35] At 20 mg lithium per kg of Earth's crustSony VAIO VPCF149FJ/BI battery,[36] lithium is the 25th most abundant element. Nickel and lead have about the same abundance.

According to the Handbook of Lithium and Natural Calcium, "Lithium is a comparatively rare element, although it is found in many rocks and some brines, but always in very low concentrations. There are a fairly large number of both lithium mineral and brine deposits but only comparatively a few of them are of actual or potential commercial value. Many are very small, others are too low in gradeSony VAIO VPCF148FJ/B battery."[37]

One of the largest reserve base[note 2] of lithium is in the Salar de Uyuni area of Bolivia, which has 5.4 million tonnes. US Geological Survey, estimates that in 2010 Chile had the largest reserves by far (7.5 million tonnes) and the highest annual production (8,800 tonnes). Other major suppliers include Australia, Argentina and China.[30][38] Other estimates put Chile's reserve base (7,520 million tonnes) above that of Argentina (6 million). Sony VAIO VPCF13ZHJ battery

In June 2010, the New York Times reported that American geologists were conducting ground surveys on dry salt lakes in western Afghanistan believing that large deposits of lithium are located there. "Pentagon officials said that their initial analysis at one location in Ghazni Province showed the potential for lithium deposits as large of those of Bolivia, which now has the world's largest known lithium reserves." Sony VAIO VPCF13Z0E/B batteryThese estimates are "based principally on old data, which was gathered mainly by the Soviets during their occupation of Afghanistan from 1979–1989" and "Stephen Peters, the head of the USGS's Afghanistan Minerals Project, said that he was unaware of USGS involvement in any new surveying for minerals in Afghanistan in the past two years. 'We are not aware of any discoveries of lithium,' he said." Sony VAIO VPCF13M8E/B battery

[edit]Biological

Lithium is found in trace amount in numerous plants, plankton, and invertebrates, at concentrations of 69 to 5,760 parts per billion (ppb). In vertebrates the concentration is slightly lower, and nearly all vertebrate tissue and body fluids have been found to contain lithium ranging from 21 to 763 ppb.[32] Marine organisms tend to bioaccumulate lithium more than terrestrial onesSony VAIO VPCF13AHJ battery.[42] It is not known whether lithium has a physiological role in any of these organisms,[32] but nutritional studies in mammals have indicated its importance to health, leading to a suggestion that it be classed as an essential trace element with an RDA of 1 mg/day.[citation needed] Observational studies in Japan, reported in 2011, suggested that naturally occurring lithium in drinking water may increase human lifespanSony VAIO VPCF13AGJ battery.[43]

[edit]History

Johan August Arfwedson is credited with the discovery of lithium in 1817

Petalite (LiAlSi4O10) was discovered in 1800 by the Brazilian chemist and statesman José Bonifácio de Andrada e Silva in a mine on the island of Utö, Sweden.[44][45][46] However, it was not until 1817 that Johan August Arfwedson, then working in the laboratory of the chemist Jöns Jakob Berzelius, detected the presence of a new element while analyzing petalite ore. Sony VAIO VPCF13AFJ battery This element formed compounds similar to those of sodium and potassium, though its carbonate and hydroxide were less soluble in water and more alkaline.[50] Berzelius gave the alkaline material the name "lithion/lithina", from the Greek word λιθoς (transliterated as lithos, meaning "stone"), to reflect its discovery in a solid mineral, as opposed to potassiumSony VAIO VPCF138FJ/BI battery, which had been discovered in plant ashes, and sodium which was known partly for its high abundance in animal blood. He named the metal inside the material as "lithium".[2][45][49]

Arfwedson later showed that this same element was present in the minerals spodumene and lepidolite.[45] In 1818, Christian Gmelin was the first to observe that lithium salts give a bright red color to flame.[45] However, both Arfwedson and Gmelin tried and failed to isolate the pure element from its salts. Sony VAIO VPCF138FJ/B battery It was not isolated until 1821, when William Thomas Brande obtained it by electrolysis of lithium oxide, a process that had previously been employed by the chemist Sir Humphry Davy to isolate the alkali metals potassium and sodium.[10][51][52][53] Brande also described some pure salts of lithium, such as the chloride, and, estimating that lithia (lithium oxide) contained about 55% metalSony VAIO VPCF138FC/BI battery, estimated the atomic weight of lithium to be around 9.8 g/mol (modern value ~6.94 g/mol).[54] In 1855, larger quantities of lithium were produced through the electrolysis of lithium chloride by Robert Bunsen and Augustus Matthiessen.[45] The discovery of this procedure henceforth led to commercial production of lithium, beginning in 1923, by the German company Metallgesellschaft AG, which performed an electrolysis of a liquid mixture of lithium chloride and potassium chloride.Sony VAIO VPCF135FG battery

The production and use of lithium underwent several drastic changes in history. The first major application of lithium became high temperature grease for aircraft engines or similar applications in World War II and shortly after. This small market was supported by several small mining operations mostly in the United States. The demand for lithium increased dramatically during the Cold War with the production of nuclear fusion weaponsSony VAIO VPCF12AHJ battery. Both lithium-6 and lithium-7 produce tritium when irradiated by neutrons, and are thus useful for the production of tritium by itself, as well as a form of solid fusion fuel used inside hydrogen bombs in the form of lithium deuteride. The United States became the prime producer of lithium in the period between the late 1950s and the mid 1980s. At the end the stockpile of lithium was roughly 42,000 tonnes of lithium hydroxideSony VAIO VPCF12AGJ battery. The stockpiled lithium was depleted in lithium-6 by 75%.[56]

Lithium was used to decrease the melting temperature of glass and to improve the melting behavior of aluminium oxide when using the Hall-Héroult process.[57][57] These two uses dominated the market until the middle of the 1990s. After the end of the nuclear arms race the demand for lithium decreased and the sale of Department of Energy stockpiles on the open market further reduced pricesSony VAIO VPCF12AFJ battery.[56] But in the mid-1990s, several companies started to extract lithium from brine which proved to be a less expensive method than underground or even open pit mining. Most of the mines closed or shifted their focus to other materials as only the ore from zoned pegmatites could be mined for a competitive price. For example, the US mines near Kings MountainSony VAIO VPCF129FJ/BI battery, North Carolina closed before the turn of the century. The use in lithium ion batteries increased the demand for lithium and became the dominant use in 2007.[58] With the surge of lithium demand in batteries in to 2000s, new companies have expanded brine extraction efforts to meet the rising demand. Sony VAIO VPCF128FJ/B battery

[edit]Production

Satellite images of the Salar del Hombre Muerto, Argentina (left), and Uyuni, Bolivia (right), salt flats are rich in lithium. The lithium-rich brine is concentrated by pumping it into solar evaporation ponds (visible in the left image).

Since the end of World War II lithium production has greatly increased. The metal is separated from other elements in igneous minerals such as those above. Lithium salts are extracted from the water of mineral springs, brine pools and brine depositsSony VAIO VPCF127FJ/W battery. The metal is produced electrolytically from a mixture of fused lithium chloride and potassium chloride. In 1998 it was about 95 US$ / kg (or 43 US$/pound).[61]

There are widespread hopes of using lithium ion batteries in electric vehicles, but one study concluded that "realistically achievable lithium carbonate production will be sufficient for only a small fraction of future PHEV and EV global market requirements", that "demand from the portable electronics sector will absorb much of the planned production increases in the next decade"Sony VAIO VPCF11ZHJ battery, and that "mass production of lithium carbonate is not environmentally sound, it will cause irreparable ecological damage to ecosystems that should be protected and that LiIon propulsion is incompatible with the notion of the 'Green Car'".[62]

Deposits of lithium are found in South America throughout the Andes mountain chain. Chile is the leading lithium producer, followed by Argentina. Both countries recover the lithium from brine poolsSony VAIO VPCF11AHJ battery. In the United States lithium is recovered from brine pools in Nevada.[63] However, half the world's known reserves are located in Bolivia, a nation sitting along the central eastern slope of the Andes. In 2009 Bolivia is negotiating with Japanese, French, and Korean firms to begin extraction.[64] According to the US Geological Survey, Bolivia's Uyuni Desert has 5.4 million tonnes of lithium. Sony VAIO VPCF11AGJ battery China may emerge as a significant producer of brine-source lithium carbonate around 2010. There is potential production of up to 55,000 tonnes per year if projects in Qinghai province and Tibet proceed.[62]

Worldwide reserves of lithium are estimated as 13 million tonnes.[30] Using the battery efficiency figure of 400 g of lithium per kWh,[66] this gives a total maximum lithium battery capacity of 32.5 billion kWh which, assuming it is used exclusively for car batteries, is enough for approximately 1.4 billion cars with a 24 kWh battery (like a Nissan Leaf [67]) Sony VAIO VPCF11AFJ battery.

[edit]Applications

Ceramics and glass

Lithium oxide is a widely used flux for processing silica, reducing the melting point and viscosity of the material and leading to glazes of improved physical properties including low coefficients for thermal expansion. Lithium oxides are a component of ovenware. Worldwide, this is the single largest use for lithium compounds (see chart) Sony VAIO VPCF118FJ battery.

[edit]Electrical and electronics

In the later years of the 20th century lithium became important as an anode material. Used in lithium-ion batteries because of its high electrochemical potential, a typical cell can generate approximately 3 volts, compared with 2.1 volts for lead/acid or 1.5 volts for zinc-carbon cells. Because of its low atomic mass, it also has a high charge- and power-to-weight ratio. Lithium batteries are disposable (primary) batteries with lithium or its compounds as an anodeSony VAIO VPCF117FJ battery. Lithium batteries are not to be confused with lithium-ion batteries, which are high energy-density rechargeable batteries. Other rechargeable batteries include the lithium-ion polymer battery, lithium iron phosphate battery, and the nanowire battery. New technologies are constantly being announcedSony VAIO VGN-CS33H battery.

[edit]Lubricating greases

The third most common use of lithium is in greases. Lithium hydroxide is a strong base, and when heated with a fat it produces a soap made of lithium stearate. Lithium soap has the ability to thicken oils, and it is used to manufacture all-purpose, high-temperature lubricating greasesSony VAIO VGN-CS33H/Z battery.

[edit]Other chemical and industrial uses

Lithium use in flares and pyrotechnics is due to its rose-red flame

[edit]Inorganic lithium salts

Lithium chloride and lithium bromide are extremely hygroscopic and are used as desiccants.[63] Lithium hydroxide (LiOH) is an important compound of lithium obtained from lithium carbonate (Li2CO3).

Metallic lithium and its complex hydrides, such as Li[AlH4], are used as high energy additives to rocket propellants. Sony VAIO VGN-CS33H/B battery

[edit]Air purification

Lithium peroxide, lithium nitrate, lithium chlorate and lithium perchlorate are used as oxidizers in rocket propellants, and also in oxygen candles that supply submarines with oxygen.[71]

Lithium hydroxide and lithium peroxide are the salts most used in confined areas, such as aboard spacecraft and submarines, for carbon dioxide removal and air purification. Lithium hydroxide absorbs carbon dioxide from the air by reacting with it to form lithium carbonateSony VAIO VGN-CS31Z/Q battery, and is preferred over other alkaline hydroxides for its low weight. Lithium peroxide (Li2O2) in presence of moisture not only absorbs carbon dioxide to form lithium carbonate, but also releases oxygen.[72][73] For example:

2 Li2O2 + 2 CO2 → 2 Li2CO3 + O2.

[edit]Optics

Lithium fluoride, artificially grown as crystal, is clear and transparent and often used in specialist optics for IR, UV and VUV (vacuum UV) applications. It has one of the lowest refractive indexes and the farthest transmission range in the deep UV of most common materialsSony VAIO VGN-CS31S/W battery.[74] Finely divided lithium fluoride powder has been used for thermoluminescent radiation dosimetry (TLD): when a sample of such is exposed to radiation, it accumulates crystal defects which, when heated, resolve via a release of bluish light whose intensity is proportional to the absorbed dose, thus allowing this to be quantified.[75] Lithium fluoride is sometimes used in focal lenses of telescopes. Sony VAIO VGN-CS31S/V battery

The high non-linearity of lithium niobate also makes it useful in non-linear optics applications. It is used extensively in telecommunication products such as mobile phones and optical modulators, for such components as resonant crystals. Lithium applications are used in more than 60% of mobile phones. Sony VAIO VGN-CS31S/T battery

[edit]Elemental lithium and reagents prepared from it

Because of its specific heat capacity, the highest of all solids, lithium metal is often used in coolants for heat transfer applications.[63]

The launch of a torpedo using lithium as fuel

The Mark 50 Torpedo stored chemical energy propulsion system (SCEPS) uses a small tank of sulfur hexafluoride gas which is sprayed over a block of solid lithium. The reaction generates enormous heat which is used to generate steam from seawater. The steam propels the torpedo in a closed Rankine cycle. Sony VAIO VGN-CS31S/R battery

When used as a flux for welding or soldering, metallic lithium promotes the fusing of metals during the process and eliminates the forming of oxides by absorbing impurities. Its fusing quality is also important as a flux for producing ceramics, enamels and glass. Alloys of the metal with aluminium, cadmium, copper and manganese are used to make high-performance aircraft parts (see also Lithium-aluminium alloys) Sony VAIO VGN-CS31S/P battery.[79] Lithium compounds are also used as pyrotechnic colorants and oxidizers in red fireworks and flares.

Lithium metal is also used in the pharmaceutical and fine-chemical industry in the manufacture of organolithium reagents, which are used both as strong bases and as reagents for the formation of carbon-carbon bonds. Organolithium compounds are also used in polymer synthesis as catalysts/initiators[81] in anionic polymerization of unfunctionalized olefins. Sony VAIO VGN-CS28 battery Lithium is used in the preparation of organolithium compounds, which are in turn very reactive and are the basis of many synthetic applications.[85]

[edit]Nuclear

Lithium-6 is valued as a source material for tritium production and as a neutron absorber in nuclear fusion. Natural lithium contains about 7.5% lithium-6 from which large amounts of lithium-6 have been produced by isotope separation for use in nuclear weapons.[86] Lithium-7 gained interest for use in nuclear reactor coolants. Sony VAIO VGN-CS28/Q battery

Lithium deuteride was used as fuel in the Castle Bravo nuclear device.

Lithium deuteride was the fusion fuel of choice in early versions of the hydrogen bomb. When bombarded by neutrons, both 6Li and 7Li produce tritium — this reaction, which was not fully understood when hydrogen bombs were first tested, was responsible for the runaway yield of the Castle Bravo nuclear test. Tritium fuses with deuterium in a fusion reaction that is relatively easy to achieveSony VAIO VGN-CS27 battery. Although details remain secret, lithium-6 deuteride still apparently plays a role in modern nuclear weapons, as a fusion material.[88]

Lithium fluoride, when highly enriched in the lithium-7 isotope, forms the basic constituent of the fluoride salt mixture LiF-BeF2 used in liquid fluoride nuclear reactors. Lithium fluoride is exceptionally chemically stable and LiF-BeF2 mixtures have low melting pointsSony VAIO VGN-CS27/W battery. In addition, 7Li, Be, and F are among the few nuclides with low enough thermal neutron capture cross-sections not to poison the fission reactions inside a nuclear fission reactor.

In conceptualized nuclear fusion power plants, lithium will be used to produce tritium in magnetically confined reactors using deuterium and tritium as the fuel. Tritium does not occur naturally and will be produced by surrounding the reacting plasma with a 'blanket' containing lithium where neutrons from the deuterium-tritium reaction in the plasma will react with the lithium to produce more tritiumSony VAIO VGN-CS27/R battery:

6Li + n → 4He + 3T.

Lithium is also used as a source for alpha particles, or helium nuclei. When 7Li is bombarded by accelerated protons 8Be is formed, which undergoes fission to form two alpha particles. This feat, called "splitting the atom" at the time, was the first fully man-made nuclear reaction. It was produced by Cockroft and Walton in 1932. (Nuclear reactions and human-directed nuclear transmutation had been accomplished as early as 1917Sony VAIO VGN-CS27/P battery, but by using natural radioactive bombardment with alpha particles).

[edit]Medicine

Main article: Lithium pharmacology

In the treatment of bipolar disorder, lithium compounds continue to be the standard against which newer medications are measured. Lithium salts may also be helpful for related diagnoses, such as schizoaffective disorder and cyclic major depression. The active principle in these salts is the lithium ion Li+, although detailed mechanisms are debatedSony VAIO VGN-CS27/C battery.

[edit]Precautions

Lithium is corrosive and requires special handling to avoid skin contact. Breathing lithium dust or lithium compounds (which are often alkaline) initially irritate the nose and throat, while higher exposure can cause a buildup of fluid in the lungs, leading to pulmonary edema. The metal itself is a handling hazard because of the caustic hydroxide produced when it is in contact with moistureSony VAIO VGN-CS26T/W battery. Lithium is safely stored in non-reactive compounds such as naphtha.[92]

There have been suggestions of increased risk of developing Ebstein's cardiac anomaly in infants born to women taking lithium during the first trimester of pregnancy.[93]

[edit]Regulation

Some jurisdictions limit the sale of lithium batteries, which are the most readily available source of lithium for ordinary consumers. Lithium can be used to reduce pseudoephedrine and ephedrine to methamphetamine in the Birch reduction method, which employs solutions of alkali metals dissolved in anhydrous ammoniaSony VAIO VGN-CS26T/V battery. Carriage and shipment of some kinds of lithium batteries may be prohibited aboard certain types of transportation (particularly aircraft) because of the ability of most types of lithium batteries to fully discharge very rapidly when short-circuited, leading to overheating and possible explosion in a process called thermal runaway. Most consumer lithium batteries have thermal overload protection built-in to prevent this type of incidentSony VAIO VGN-CS26T/T battery, or their design inherently limits short-circuit currents. Internal shorts have been known to develop due to manufacturing defects or damage to batteries that can lead to spontaneous thermal runaway.

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, which is literally translated into "little silver". It is a dense, malleable, ductile, precious, gray-white transition metalSony VAIO VGN-CS26T/R 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 5 μg/kg. It is the least reactive metal. It occurs in some nickel and copper ores along with some native deposits, mostly in South Africa, which accounts for 80% of the world productionSony VAIO VGN-CS26T/Q 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 platinumSony VAIO VGN-CS26T/P 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 scientistsSony VAIO VGN-CS26T/C 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. 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 metalsSony VAIO VGN-CS25H battery. Its compounds, most notably cisplatin, are applied in chemotherapy against certain types of cancer.[3]

Characteristics

Physical

As a pure metal, platinum is silvery-white, lustrous, ductile, and malleable.[4] 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 [5][6] It does not oxidize at any temperature, although it is corroded by halogens, cyanides, sulfur, and caustic alkalis. Platinum is insoluble in hydrochloric and nitric acid, but dissolves in hot aqua regia to form chloroplatinic acid, H2PtCl6. Sony VAIO VGN-CS25H/W 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.[8]

[edit]Chemical

See also: Platinum group

Platinum dissolves in hot aqua regia

The most common oxidation states of platinum are +2 and +4. The +1 and +3 oxidation states are less common, and are often stabilized by metal bonding in bimetallic (or polymetallic) speciesSony VAIO VGN-CS25H/R battery. As is expected, tetracoordinate platinum(II) compounds tend to adopt 16-electron square planar geometries. While elemental platinum is generally unreactive, it dissolves in hot aqua regia to give soluble hexachloroplatinic acid ("H2PtCl6", formally (H3O)2PtCl6·nH2O ):[9]

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. Sony VAIO VGN-CS25H/Q battery

[edit]Isotopes

Main article: Isotopes of platinum

Platinum has six naturally occurring isotopes: 190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt. The most abundant of these is 195Pt, 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). 190Pt is the least abundant at only 0.01%Sony VAIO VGN-CS25H/P battery. Of the naturally occurring isotopes, only 190Pt is unstable, though it decays with a half-life of 6.5×1011 years. 198Pt can undergo alpha decay, but its decay had never been observed (the half-life is known to be longer than 3.2×1014 years), therefore it is considered stable. 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 yearsSony VAIO VGN-CS25H/C battery. 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.[11]

[edit]Occurrence

A native platinum nugget, Kondyor mine, Khabarovsk Krai

Platinum output in 2005

Platinum is an extremely rare metal,[12] occurring at a concentration of only 0.005 ppm in the Earth's crust.[13][14] It is sometimes mistaken for silver (Ag). Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridiumSony VAIO VGN-CS23T/W 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. Sony VAIO VGN-CS23T/Q 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. At Platinum, Alaska, about 545,000 troy ounces had been mined between 1927 and 1975Sony VAIO VGN-CS23H battery. The mine ceased operations in 1990.[15] The rare sulfide mineral cooperite, (Pt,Pd,Ni)S, contains platinum along with palladium and nickel. Cooperite occurs in the Merensky Reef within the Bushveld complex, Gauteng, South Africa.[16]

In 1865, chromites were identified in the Bushveld region of South Africa, followed by the discovery of platinum in 1906.[17] The largest known primary reserves are in the Bushveld complex in South AfricaSony VAIO VGN-CS23H/S battery.[18] The large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin, Canada, are the two other large deposits. 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,[18] for example in the Absaroka Range in Montana.[19] In 2009, South Africa was the top producer of platinum, with an almost 80% shareSony VAIO VGN-CS23H/B battery, followed by Russia at 11%; world production in 2009 was 178,000 kg.[20]

In 2010 July its been announced that Platinum is present in the state of Tamil Nadu, India[21] and a MOU has been signed between Geological Survey of India with TAMIN – Tamil Nadu Minerals Ltd.[22]

Platinum exists in higher abundances on the Moon and in meteorites. 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 economicallySony VAIO VGN-CS23G battery; the Sudbury Basin is one such example.[23]

Compounds

Halides

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 catalystSony VAIO VGN-CS23G/W battery.[24]

Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate,[9] which is relatively insoluble in ammonium solutions. Heating this ammonium salt in the presence of hydrogen reduces it to elemental platinum. Potassium hexachloroplatinate is similarly insoluble, and hexachloroplatinic acid has been used in the determination of potassium ions by gravimetrySony VAIO VGN-CS23G/Q battery.[25]

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:[26]

(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 oxygenSony VAIO VGN-CS23G/P battery.

[edit]Oxides

Platinum(IV) oxide, PtO2, also known as Adams' catalyst, is a black powder which is soluble in KOH solutions and concentrated acids.[27] PtO2 and the less common PtO both decompose upon heating.[4] Platinum(II,IV) oxide, Pt3O4, is formed in the following reaction:

2 Pt2+ + Pt4+ + 4 O2− → Pt3O4

Platinum also forms a trioxide, where it is present in the +4 oxidation state.

[edit]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.[10] The use of platinum(II) acetylacetonate has also been reportedSony VAIO VGN-CS21Z/Q battery.[28]

Several barium platinides have been synthesized in which platinum exhibits negative oxidation states ranging from −1 to −2. These include BaPt, Ba3Pt2, and Ba2Pt.[29] Caesium platinide, Cs2Pt, a dark-red transparent crystalline compound[30] has been shown to contain Pt2−

anions.[31] Platinum also exhibits negative oxidation states at surfaces reduced electrochemically.[32] The negative oxidation states exhibited by platinum are unusual for metallic elements, and they are attributed to the relativistic stabilization of the 6s orbitalsSony VAIO VGN-CS21S/W battery.[31]

Zeise's salt, containing an ethylene ligand, was one of the first organometallic compounds discovered. 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.Sony VAIO VGN-CS21S/V battery

Cisplatin, or cis-diamminedichloroplatinum(II) is the first of a series of square planar platinum(II)-containing chemotherapy drugs, including carboplatin and oxaliplatin. These compounds are capable of crosslinking DNA, and kill cells by similar pathways to alkylating chemotherapeutic agentsSony VAIO VGN-CS21S/T battery.[33]

History

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. 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 MexicoSony VAIO VGN-CS21S/R battery, "which no fire nor any Spanish artifice has yet been able to liquefy."[34]

This alchemical symbol for platinum was made by joining the symbols of silver and gold.

Antonio de Ulloa is credited with the discovery of platinum.

In 1741, Charles Wood,[35] a British metallurgist, found various samples of Colombian platinum in Jamaica, which he sent to William Brownrigg for further investigation. 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 yearsSony VAIO VGN-CS21S/P battery. His historical account of the expedition included a description of platinum as being neither separable nor calcinable. Ulloa also anticipated the discovery of platinum mines. 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 in HuancavelicaSony VAIO VGN-CS215J/R battery.[34]

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.[36] Brownrigg also made note of platinum's extremely high melting point and refractoriness toward borax. Other chemists across Europe soon began studying platinum, including Andreas Sigismund Marggraf[37] Torbern BergmanSony VAIO VGN-CS215J/Q battery, 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. Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosionSony VAIO VGN-CS19/W battery.[34]

Carl von Sickingen researched platinum extensively in 1772. He succeeded in making malleable platinum by alloying it with gold, dissolving the alloy in hot 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 arsenicSony VAIO VGN-CS19/R battery.[34]

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 its hardness – which is slightly more than for pure iron – platinum was a relatively non pliable material, even brittle at times, when in fact its ductility and malleability are close to that of goldSony VAIO VGN-CS19/Q 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. Alloying this impure platinum residue called "plyoxen" with gold was the only solution at the time to obtain a pliable compound, but nowadaysSony VAIO VGN-CS19/P battery, very pure platinum is available and extremely long wire can be drawn from pure platinum, very easily, due to its crystalline structure which is similar to that of many soft metals.[38]

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 metalsSony VAIO VGN-CS17H/W 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-hotSony VAIO VGN-CS17H/Q 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.[34]

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) Sony VAIO VGN-CS16T/W battery.[39]

[edit]Production

1,000 cubic centimeters of 99.9% pure platinum, worth about US

$910,000 at 30 October 2009 prices

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 selenium and 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-CS16T/T 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 magneticSony VAIO VGN-CS16T/R 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. Metal impurities can be removed by stirring the mixture in either of the two acids and recovering the remaining platinumSony VAIO VGN-CS16T/Q battery.[42]

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, 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 chlorideSony VAIO VGN-CS16T/P battery. Ammonium chloroplatinate can be converted to the metal by heating.[43]

[edit]Applications

Cross section of a metal-core catalytic converter

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 enginesSony VAIO VGN-CS13T/W battery.[44]

[edit]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. 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 vaporSony VAIO VGN-CS13H/W battery. Platinum is also used in the petroleum industry as a catalyst in a number of separate processes, 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.[24] Platinum metal also strongly catalyzes the decomposition of hydrogen peroxide into water and oxygen gasSony VAIO VGN-CS13H/R battery.[45]

[edit]Standard

International Prototype Meter bar

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 1879Sony VAIO VGN-CS13H/Q battery.[46]

The standard hydrogen electrode also uses a platinized platinum electrode due to its corrosion resistance, and other attributes.[47]

[edit]Precious metal

Platinum Eagle

Main articles: Platinum as an investment and Platinum coin

Platinum is a precious metal commodity; its bullion has the ISO currency code of XPT. Coins, bars, and ingots are traded or collected. 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. Sony VAIO VGN-CS13H/P battery

In watchmaking, Vacheron Constantin, Patek Philippe, Rolex, Breitling, and other companies use platinum for producing their limited edition watch series. Watchmakers appreciate the unique properties of platinum, as it neither tarnishes nor wears out (relative to gold).[50]

Average price of platinum from 1991 to 2007 in US$ per troy ounce (~$20/g)[51]

The price of platinum, like other industrial commodities, is more volatile than that of gold. In 2008, the price of platinum dropped from $2,252 to $774 per ozSony VAIO VGN-CS11Z/T battery,[52] a loss of nearly 2/3 of its value. By contrast, the price of gold dropped from ~$1,000 to ~$700/oz 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, whereas during periods of economic uncertainty,[53] the price of platinum tends to decrease due to reduced industrial demand, falling below the price of goldSony VAIO VGN-CS11Z/R battery. 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.[54]

[edit]Other uses

In the laboratory, platinum wire is used for electrodes; platinum pans and supports are used in thermogravimetric analysis because of the stringent requirements of chemical inertness upon heating to high temperatures (~1000 °C) Sony VAIO VGN-CS11S/W 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.[24] Platinum-based anodes are used in ships, pipelines, and steel piersSony VAIO VGN-CS11S/Q battery.[7]

[edit]Symbol of prestige

See also: Platinum album and Platinum (color)

An assortment of native platinum nuggets

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.[55] "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"Sony VAIO VGN-CS11S/P battery, whereas an album that sold more than 10 million copies will be certified as "diamond".[56] 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(Sony VAIO VGN-AW11M/H battery). It was the first British crown to be made of this particular metal.[57]

[edit]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(Sony VAIO VGN-AW11S/B battery).[58]

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%.[59] However, the side effects are severe. Cisplatin causes cumulative, irreversible kidney damage and deafness.[60] 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-AW11Z/B battery).[61]

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. The Food and Drug Administration and other institutions have reviewed the issue and found no evidence to suggest toxicity in vivo(Sony VAIO VGN-AW170C battery).

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