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iridiumplatinumgold
Pd

Pt

Ds
Appearance
grayish white
General properties
Name, symbol, number platinum, Pt, 78
Element category transition metal
Group, period, block 106, d
Standard atomic weight 195.084g·mol−1
Electron configuration [Xe] 4f14 5d9 6s1
Electrons per shell 2, 8, 18, 32, 17, 1 (Image)
Physical properties
Phase solid
Density (near r.t.) 21.45 g·cm−3
Liquid density at m.p. 19.77 g·cm−3
Melting point 2041.4 K, 1768.3 °C, 3214.9 °F
Boiling point 4098 K, 3825 °C, 6917 °F
Heat of fusion 22.17 kJ·mol−1
Heat of vaporization 469 kJ·mol−1
Specific heat capacity (25 °C) 25.86 J·mol−1·K−1
Vapor pressure
P/Pa 1 10 100 1 k 10 k 100 k
at T/K 2330 (2550) 2815 3143 3556 4094
Atomic properties
Oxidation states 6, 5, 4, 3 , 2, 1, -1, -2
(mildly basic oxide)
Electronegativity 2.28 (Pauling scale)
Ionization energies 1st: 870 kJ·mol−1
2nd: 1791 kJ·mol−1
Atomic radius 139 pm
Covalent radius 136±5 pm
Van der Waals radius 175 pm
Miscellanea
Crystal structure face-centered cubic
Magnetic ordering paramagnetic
Electrical resistivity (20 °C) 105 nΩ·m
Thermal conductivity (300 K) 71.6 W·m−1·K−1
Thermal expansion (25 °C) 8.8 µm·m−1·K−1
Tensile strength 125-240 MPa
Young's modulus 168 GPa
Shear modulus 61 GPa
Bulk modulus 230 GPa
Poisson ratio 0.38
Mohs hardness 4–4.5
Vickers hardness 549 MPa
Brinell hardness 392 MPa
CAS registry number 7440-06-4
Most stable isotopes
Main article: Isotopes of platinum
iso NA half-life DM DE (MeV) DP
190Pt 0.014% 6.5×1011 y α 3.18 186Os
191Pt syn 2.76 d ε  ? 191Ir
192Pt 0.782% 192Pt is stable with 114 neutrons
193Pt syn 50 y ε  ? 193Ir
193mPt syn 4.33 d IT 0.1355e 193Pt
194Pt 32.967% 194Pt is stable with 116 neutrons
195Pt 33.832% 195Pt is stable with 117 neutrons
195mPt syn 4.02 d IT 0.1297e 195Pt
196Pt 25.242% 196Pt is stable with 118 neutrons
197Pt syn 19.8913 h β 0.719 197Au
197mPt syn 1.59 h IT 0.3465 197Pt
198Pt 7.163% 198Pt is stable with 120 neutrons

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 in Group 10 of the periodic table of elements. A dense, malleable, ductile, precious, gray-white transition metal, platinum is resistant to corrosion and occurs in some nickel and copper ores along with some native deposits. Platinum is used in jewelry, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and catalytic converters. Platinum bullion has the ISO currency code of XPT. Platinum is a commodity with a value that fluctuates according to market forces. As of 8 March 2010 (2010 -03-08), platinum was worth US$51.89 per gram (US$1,614.00 per troy ounce).[2]

Contents

Characteristics

As a pure metal, platinum is silvery-white in appearance, lustrous, ductile, and malleable.[3] 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 aqua regia to form chloroplatinic acid, H2PtCl6.[4]

Platinum's wear- and tarnish-resistance characteristics are well suited for making fine jewelry. Platinum is more precious than gold or silver. Platinum possesses high resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties. All of these properties have been exploited for industrial applications.

Isotopes

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. 190Pt is the least abundant at only .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 as being greater than 3.2 × 1014 years, 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 years. Most of platinum's 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.[5]

Chemistry and compounds

Platinum's most common oxidation states are +2, and +4. 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 a square planar geometry. While elemental platinum is generally unreactive, it dissolves in aqua regia to give soluble hexachloroplatinic acid ("H2PtCl6", formally (H3O)2PtCl6·nH2O ):[6]

Pt + 4 HNO3 + 6 HCl → H2PtCl6 + 4 NO2 + 4 H2O

This compound has various applications in photography, zinc etchings, indelible ink, plating, mirrors, porcelain coloring, and as a catalyst.[7]

Treatment of hexachloroplatinic acid with an ammonium salt, such as ammonium chloride, gives ammonium hexachloroplatinate,[6] which is very insoluble in ammonium solutions. Heating the ammonium salt in the presence of hydrogen reduces it to elemental platinum. Platinum is often isolated from ores and recycled thus.[8] Potassium hexachloroplatinate is similarly insoluble, such that the acid has been used in the determination of potassium ions by gravimetry.[9]

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, cleanly:[10]

(H3O)2PtCl6·n H2O is in equilibrium with PtCl4 + 2 HCl + (n + 2) H2O
PtCl4 is in equilibrium with PtCl2 + Cl2
PtCl2 is in equilibrium with 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 oxidising oxygen.

Platinum(IV) oxide, PtO2, also known as Adams' Catalyst, is a black powder which is soluble in KOH solutions and concentrated acids.[11] PtO2 and the less common PtO both decompose upon heating.[3] Platinum(II,IV) oxide, Pt3O4, is formed in the following reaction:

2 Pt2+ + Pt4+ + 4 O2− → Pt3O4

Platinum also forms a trioxide, which is actually in the +4 oxidation state.

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.[12] The use of platinum(II) acetylacetonate has also been reported.[13]

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. As a soft acid, platinum has a great affinity for sulfur, such as on DMSO; numerous DMSO complexes have been reported and care should be taken in the choice of reaction solvent.[12]

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 agents.[14]

Several barium platinides have been synthesized, in which platinum exhibits negative oxidation states ranging from −1 to −2. These include BaPt, Ba3Pt2, and Ba2Pt.[15] Caesium platinide, Cs2Pt, has been shown to contain Pt2− anions.[16] Platinum is also shown to exhibit negative oxidation states at surfaces reduced electrochemically.[17] The negative oxidation states exhibited by platinum, which are unusual for metallic elements, are believed to be due to the relativistic stabilization of the 6s orbitals.[16]

Occurrence

Platinum nugget, native. Konder mine, Yakutia, Russia
Platinum output in 2005

Platinum is an extremely rare metal,[18] occurring as only 0.003 ppb in the Earth's crust. It is sometimes mistaken for silver (Ag).

Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium. 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 was found in the Ural Mountains, Russia, which is still mined.

In nickel and copper deposits platinum group metals occur as sulfides (i.e., (Pt,Pd)S)), tellurides (i.e., PtBiTe), antimonides (PdSb), and arsenides (i.e., 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. 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.[19]

The largest known primary reserves are in the Bushveld complex in South Africa.[20] 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 makes up for the fact that platinum is present as only 0.5 ppm in the ore. Smaller reserves can be found in the United States,[20] for example in the Absaroka Range in Montana.[21] This is also shown in the production of 2005. In 2005, South Africa was the top producer of platinum with an almost 80% share followed by Russia and Canada.[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 economically; the Sudbury Basin is one such example.

Production

1,000 cubic centimeters of 99.9% pure platinum, worth approx. US$910,000 at 30 October 2009 prices.

Platinum together 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.[23][24]

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 water bath. Platinum is also non-magnetic, while nickel and iron are both magnetic. 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 platinum.[25]

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 of the gold, the platinum is precipitated by the addition of ammonium chloride as ammonium chloroplatinate. Ammonium chloroplatinate can be converted to the metal by heating.[26]

Applications

Cross section of a metal-core converter

Of the 239 tonnes of platinum sold in 2006, 130 tonnes were used for automobile emissions control devices, 49 tonnes were used for jewelry, 13.3 tonnes were used in electronics, and 11.2 tonnes were used by the chemical industry as a catalyst. The remaining 35.5 tonnes produced were used in various other minor applications, such as electrodes, anticancer drugs, oxygen sensors, spark plugs and turbine engines.[27]

Catalysis

The most common use of platinum is as a catalyst in chemical reactions. It has been employed in this application since the early 1800s, when platinum powder was used to catalyze the ignition of hydrogen. The most important application of platinum is in automobiles as a catalytic converter, which allows the complete combustion of low concentrations of unburned hydrocarbon 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, 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.[7] Platinum metal also strongly catalyzes the decomposition of hydrogen peroxide into water and oxygen gas.[28]

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 1879.[29]

The standard hydrogen electrode also utilizes a platinized platinum electrode due to its corrosion resistance, and other attributes.

Precious metal

Platinum Eagle

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. In watchmaking, Vacheron Constantin, Patek Philippe, Rolex, Breitling and other companies use platinum for producing their limited edition watch series. Watchmakers highly appreciate the unique properties of platinum as it neither tarnishes nor wears out.[30]

Price

Average price of platinum from 1991 to 2007 in US$ per troy ounce (~$40/g).[31]

The price of platinum, like other industrial commodities, is more volatile than that of gold. In 2008 the price of platinum ranged from $774 to $2,252 per oz.[32]

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[33], 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.[34]

Other uses

In the laboratory, platinum wire is used for electrodes; platinum pans are used in thermogravimetric analysis. 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.[7] Platinum-based anodes are used in ships, pipelines, and steel piers.[4]

Symbol of prestige

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. "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”. 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.

History

Platinum occurs naturally in the alluvial sands of various rivers, though there is little evidence of its use by ancient peoples. 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 Mexico, "which no fire nor any Spanish artifice has yet been able to liquefy."[35]

A left-pointing crescent, tangent on its right to a circle containing at its centre a solid circular dot
The alchemical symbol for platinum (shown above) was made by joining the symbols of silver and gold.

In 1741, Charles Wood, 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 years. 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 Huancavelica.[35]

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. Brownrigg also made note of platinum's extremely high melting point and refractoriness toward borax. 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. Scheffer described platinum as being less pliable than gold, but with similar resistance to corrosion.[35]

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.[35]

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 that he was working with a single metal, but in truth the ore still contained the yet-undiscovered platinum group metals. 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. Chabeneau realized that 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.[35]

From 1875 to 1960 the SI unit of length (the standard meter) was defined as the distance between two lines on a standard bar of an alloy of ninety percent platinum and ten percent iridium, measured at 0 degrees Celsius.[29]

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]

Precautions

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 0.002 milligram per cubic meter of air averaged over an 8-hour work shift.[37]

Certain platinum complexes are used in chemotherapy and show good anti-tumor activity for some tumors. Cisplatin is particularly effective against testicular cancer; cure rate was improved from 10% to 85%.[38] However, the side effects are severe. Cisplatin causes cumulative, irreversible kidney damage and deafness.[39] As with other ototoxic agents, deafness may be secondary to interactions with melanin in the stria vascularis.

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), the possibility that platinum could enter the body and cause adverse effects has merited study. The FDA and other countries have reviewed the issue and found no evidence to suggest toxicity in vivo.[40][41]

See also

Notes

  1. ^ Woods, Ian (2004) (in English). The Elements: Platinum. The Elements. Benchmark Books. ISBN 978-0761415503. 
  2. ^ "Live Market Quotes". Kitco. http://www.kitco.com/market/. Retrieved 2009-10-30. 
  3. ^ a b Lagowski, J. J., ed (2004). Chemistry Foundations and Applications. 3. Thomson Gale. pp. 267–268. ISBN 0-02-865724-1. 
  4. ^ a b CRC contributors (2007–2008). "Platinum". in Lide, David R.. CRC Handbook of Chemistry and Physics. 4. New York: CRC Press. pp. 26. ISBN 978-0-8493-0488-0. 
  5. ^ Audi, G. (2003). "The NUBASE Evaluation of Nuclear and Decay Properties". Nuclear Physics A (Atomic Mass Data Center) 729: 3–128. doi:10.1016/j.nuclphysa.2003.11.001. 
  6. ^ a b Kauffman, George B.; Thurner, Joseph J.; Zatko, David A. (1967). "Ammonium Hexachloroplatinate(IV)". Inorganic Syntheses 9: 182–185. doi:10.1002/9780470132401.ch51. 
  7. ^ a b c Krebs, Robert E. (1998). "Platinum". The History and Use of our Earth's Chemical Elements. Greenwood Press. pp. 124–127. ISBN 0-313-30123-9. 
  8. ^ Cotton, S. A. Chemistry of Precious Metals, Chapman and Hall (London): 1997. ISBN 0-7514-0413-6.
  9. ^ Smith, G. F.; Gring, J. L. (1933). "The Separation and Determination of the Alkali Metals Using Perchloric Acid. V. Perchloric Acid and Chloroplatinic Acid in the Determination of Small Amounts of Potassium in the Presence of Large Amounts of Sodium". Journal of the American Chemical Society 55 (10): 3957–3961. doi:10.1021/ja01337a007. 
  10. ^ Schweizer, A. E.; Kerr, G. T. (1978). "Thermal Decomposition of Hexachloroplatinic Acid". Inorganic Chemistry 17 (8): 2326–2327. doi:10.1021/ic50186a067. 
  11. ^ Perry, D. L. (1995). Handbook of Inorganic Compounds. CRC Press. pp. 296–298. ISBN 0-8492-8671-3. 
  12. ^ a b Han, Y.; Huynh, H. V.; Tan, G. K. (2007). "Mono- vs Bis(carbene) Complexes: A Detailed Study on Platinum(II)−Benzimidazolin-2-ylidenes". Organometallics 26: 4612. doi:10.1021/om700543p. 
  13. ^ Ahrens, Sebastian; Strassner, Thomas (2006). "Detour-free synthesis of platinum-bis-NHC chloride complexes, their structure and catalytic activity in the CH activation of methane". Inorganica Chimica Acta 359: 4789. doi:10.1016/j.ica.2006.05.042. 
  14. ^ Richards, A.D.; Rodger, A. (2007). "Synthetic metallomolecules as agents for the control of DNA structure". Chemical Society Reviews 36 (3): 471–483. doi:10.1039/b609495c. PMID 17325786. http://www.rsc.org/publishing/journals/CS/article.asp?doi=b609495c. 
  15. ^ Karpov,, Andrey; Konuma, Mitsuharu; Jansen, Martin (2006). "An experimental proof for negative oxidation states of platinum: ESCA-measurements on barium platinides". Chemical Communications: 838–840. doi:10.1039/b514631c. 
  16. ^ a b Jansen, M. (June 2005). "Effects of relativistic motion of electrons on the chemistry of gold and platinum". Solid State Sciences 7 (12): 1464–1474. doi:10.1016/j.solidstatesciences.2005.06.015.  edit
  17. ^ "Spectroscopic Evidence of Platinum Negative Oxidation States at Electrochemically Reduced Surfaces". The Journal of Physical Chemistry C 111 (15): 5701–5707. March 2007. doi:10.1021/jp068879d.  edit
  18. ^ Earth's natural wealth: an audit. New Scientist. May 23, 2007.
  19. ^ Xiao, Z.; Laplante, A. R. (2004). "Characterizing and recovering the platinum group minerals—a review". Minerals Engineering 17: 961–979. doi:10.1016/j.mineng.2004.04.001. 
  20. ^ a b Seymour, R. J.; O'Farrelly, J. I. (2001). "Platinum-group metals". Kirk Othmer Encyclopedia of Chemical Technology. Wiley. doi:10.1002/0471238961.1612012019052513.a01.pub2. 
  21. ^ "Mining Platinum in Montana". New York Times. 1998-08-13. http://query.nytimes.com/gst/fullpage.html?res=9802E3D6153AF930A2575BC0A96E958260. Retrieved 2008-09-09. 
  22. ^ "Platinum–Group Metals" (PDF). U.S. Geological Survey, Mineral Commodity Summaries. January 2007. http://minerals.usgs.gov/minerals/pubs/commodity/platinum/platimcs07.pdf. Retrieved 2008-09-09. 
  23. ^ George, M. W. (2008). "Platinum-group metals" (pdf). U.S. Geological Survey Mineral Commodity Summaries (USGS Mineral Resources Program). http://minerals.usgs.gov/minerals/pubs/commodity/platinum/mcs-2008-plati.pdf. 
  24. ^ George, M. W.. 2006 Minerals Yearbook: Platinum-Group Metals. United States Geological Survey USGS. http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf. 
  25. ^ Heiserman, David L. (1992). Exploring Chemical Elements and their Compounds. TAB Books. pp. 272–274. ISBN 0-8306-3018-X. 
  26. ^ Hunt, L. B.; Lever, F. M. (1969). "Platinum Metals: A Survey of Productive Resources to industrial Uses". Platinum Metals Review 13 (4): 126–138. http://www.platinummetalsreview.com/pdf/pmr-v13-i4-126-138.pdf. Retrieved 2009-10-02. 
  27. ^ George, Micheal W.. "Mineral Yearbook 2006: Platinum-Group Metals". United States Geological Survey. http://minerals.usgs.gov/minerals/pubs/commodity/platinum/myb1-2006-plati.pdf. Retrieved 2008-09-25. 
  28. ^ Petrucci, Ralph H. (2007). General Chemistry: Principles & Modern Applications (9th ed.). Prentice Hall. pp. 606. ISBN 0131493302. 
  29. ^ a b Gupta, S. V. (2009). Metre Convention and Evolution of Base Units. pp. 47. doi:10.1007/978-3-642-00738-5_4. 
  30. ^ "Unknown Facts about Platinum". watches.infoniac.com. http://watches.infoniac.com/index.php?page=post&id=44. Retrieved 2008-09-09. 
  31. ^ "London Platinum and Palladium Market". The London Platinum and Palladium Market. http://www.lppm.org.uk/statistics_cover.html. Retrieved 2008-08-08. 
  32. ^ "One Year Platinum". Kitco. http://www.kitco.com/charts/popup/pt0365nyb.html. Retrieved 2009-01-12. 
  33. ^ "Platinum versus Gold". The Speculative Invertor. http://www.speculative-investor.com/new/article150402.html. 
  34. ^ "Platinum". Minerals Zone. http://www.mineralszone.com/minerals/platinum.html. Retrieved 2008-09-09. 
  35. ^ a b c d e Weeks, M. E. (1968). Discovery of the Elements (7 ed.). Journal of Chemical Education. pp. 385–407. ISBN 0848685792. OCLC 23991202. 
  36. ^ Ertl, Gerhard (2008). "Reactions at Surfaces: From Atoms to Complexity (Nobel Lecture)". Angewandte Chemie International Edition 47: 385–407. doi:10.1002/anie.200800480. 
  37. ^ "Occupational Health Guideline for Soluble Platinum Salts (as Platinum)" (PDF). Centers for Disease Control and Prevention. http://www.cdc.gov/niosh/pdfs/0520.pdf. Retrieved 2008-09-09. 
  38. ^ Einhorn LH. (1 November 1990). "Treatment of testicular cancer: a new and improved model". J. Clin. Oncol. 8 (11): 1777–81. PMID 1700077. http://jco.ascopubs.org/cgi/content/abstract/8/11/1777. 
  39. ^ Von Hoff DD, et al. (1979). "Toxic effects of cis-dichlorodiammineplatinum(II) in man". Cancer Treat. Rep. 63 (9–10): 1527–31. PMID 387223. 
  40. ^ "FDA Backgrounder on Platinum in Silicone Breast Implants". U.S. Food and Drug Administration. http://www.fda.gov/cdrh/breastimplants/platinum.html. Retrieved 2008-09-09. 
  41. ^ Brook, Michael (2006). "Platinum in silicone breast implants". Biomaterials 27. doi:10.1016/j.biomaterials.2006.01.027. 

References

External links


1911 encyclopedia

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PLATINUM [[[symbol]] Pt, atomic weight 195.0 (0= '6)1, a metallic chemical element. The name, derived from platina, the diminutive of Span. plata (silver), was first given to a mineral, platinum ore or native platinum, originally discovered in South America, from the resemblance to silver. Russia furnishes about 95% of the world's annual supply of platinum. Native platinum occurs usually in small metallic scales or flat grains, sometimes in the form of irregular nuggets, and occasionally, though rarely, in small crystals belonging to the cubic system. Grains of platinum have been found embedded, with chromite, in serpentine derived from an olivine-rock, the metal having probably separated out from an original basic magma. It is said to occur also in veins in syenitic and other rocks. Usually, however, platinum is found in detrital deposits, especially in auriferous sands, where it is associated with osmiridium (known also as iridosmine), chromite, magnetite, corundum, zircon, &c. The platinum has a steel grey or silver-white colour and a metallic lustre; is often magnetic, sometimes with polarity; has a hardness of about 4.5 and a specific gravity varying with its composition from 14 to 19. Native platinum usually contains more or less iron and copper, often gold, and invariably a small proportion of some of the allied metals - iridium, osmium, ruthenium, rhodium and palladium. From the associated metals it was named by J. F. L. Hausmann polyxene (Gr. wroXvs, many, and Ebios, a guest), whilst from its occurrence as a white metal in auriferous alluvia it is sometimes known to miners as "white gold." Platina del Pinto was the name by which native platinum was first introduced into Europe from South America about the middle of the 18th century. Although it appears to have been known locally much earlier, the attention of scientific men in Europe was first directed to it by Antonio de Ulloa y Garcia de La Torre, a Spaniard who joined a French scientific expedition to Peru in 1735, and published in 1 74 8 an account of his journey, in which he refers to platinum, though not under that name, as occurring with gold in New Granada (now Colombia). Sir William Watson, an English physicist, had, however, in 1741 received some grains of the mineral, probably from the 1 Reproduced by J. F. Riano, in Studies of Early Spanish Music (London, 1887).

2 See facsimile edited by Dr George Warner, pl. xxviii. fol. 51. See F. J. Furnivall, Captain Cox, his ballads and Books, or Robert Laneham's Letter A.D. 1 575 (London, 1871), clx. 86.

same locality, though brought by way of Jamaica; and it was he who first described it in 1750 as a new metal.

Native platinum was discovered in 1819 in the gold washings of Verkhniy-Isetsk, in the Urals, but it was not until 1822 that its true nature was recognized. The chief Russian localities are in the districts of Nizhne Tagilsk and Goroblagodatsk, where it is found in shallow drift deposits, containing pebbles of serpentine, which represent the original matrix. The Iset district has acquired importance in recent years. Although the platinum-bearing gravels usually contain a very small proportion of the metal, the average in 1895 being only 12 dwt. to the ton, rich discoveries have occasionally been made in the history of the workings, and nuggets of exceptional size have been unearthed. The largest recorded specimens are one of 310 oz. from Nizhne Tagilsk, and another of 722 oz. from the Goroblagodatsk district.

In 1831 platinum ore was recognized in the gold-bearing deposits of Borneo, where it had previously been regarded as worthless, being known to the natives as mas kodok (frog gold). Although recorded from various parts of the island, its occurrence seems to be definitely known only in Tanah-Laut, in the south-east of Borneo. In Australia platinum ore has been found near Fifield (near Condobolin), New South Wales; whilst in New Zealand it occurs in sands and gravels in the Thames gold-field, the Takaka River and the Gorge River flowing into Awarua Bay. Many localities in North America have yielded platinum, generally in beach sands or in auriferous alluvia, and in some cases the deposits are of commercial importance. The metal is found in Alaska, British Columbia, Oregon (Douglas county) and California (Butte county, Trinity county, Del Norte county). It has been recorded also from the states of New York and North Carolina. In a nickeliferous sulphide ore worked at Sudbury, in Ontario, platinum has been discovered in the form of an arsenide (Pt As2), which has been called sperrylite by H. L. Wells, who analysed it in 1889, and named it after F. L. Sperry, of Sudbury. It belongs to the pyrites group, and is interesting as being the only known mineral in which platinum occurs in combination except as alloy.

Native platinum seems to be a mineral of rather wide distribution, but in very sparse quantity. The sands of the Rhine, derived from Alpine rocks, have been found to contain platinum in the proportion of 0.0004%. It has also been found in the sands of the Ivalo River in Lapland; it is recorded from Rbros in Norway; and it was detected by W. Mallet in some of the gold-sands of the streams in Co. Wicklow, Ireland.

Year.

Amount.

Year.

Amount.

1890

116,640

1904

161,950

1895

141,757

1905

167,950

1900

163,060

1906

185,492

1901

203,257

'907

172,758

1902

197,024

1908

157,005

1903

192,976

The table shows the official amount (in ounces Troy) of platinum produced in Russia for certain years, the actual amounts are much larger: (Rothwell's Mineral Industry, 1908.) Platinum is largely used for the manufacture of chemical apparatus, incandescent lamps, thermo-couples; in the manufacture of sulphuric acid by the contact process, in photography, and in jewelry. The price of the metal has risen considerably, not so much on account of the restricted supply, but chiefly because the sources of supply have passed into the hands of a few individuals. The following data show the fluctuations in the average price of platinum ingot per once Troy: £ s. d. s. d.

1814-1898: I 5 2 to 2201899-1905: 3136 „ 4 to 1906: 4 15 2 „ 7 19 8 1907: 7 0 0„ 6 18 8 :908: 5 2 6 (average) price.

Platinum may be extracted from its ore by both wet and dry processes. In the latter method, due to H. Sainte-Claire-Deville and H. J. Debray, the ore is smelted in a furnace constructed of two blocks of lime, and the metallic button so obtained is re-melted in a reverberatory furnace with galena or litharge, the lead platinum alloy being then cupeled, and the platinum fused into an ingot by re-smelting in a lime furnace (see Dingler's Polytech. Journ. 18 59, 1 53, p. 38; 18 59, 1 54, p. 383, 1862, 165, p. 205). The platinum so obtained is not pure. In Wollaston's wet method the ore is dissolved in aqua regia, the osmiridium, ruthenium and rhodium being left unattacked, and the platinum precipitated as ammonium platinochloride by adding ammonium chloride in the presence of an excess of acid. The double chloride is then washed, dried and ignited, leaving a residue of metal. G. Matthey (Chem. News, 18 79, 39, p. 1 75) obtains pure platinum from the commercial metal by fusing the latter with a large excess of lead. The lead alloy is then treated with a dilute nitric acid and the insoluble portion taken up in dilute aqua regia. From the solution so obtained lead is precipitated as sulphate, and platinum and rhodium as double ammonium chlorides. The rhodium ammonium chloride is converted by fusing with potassium and ammonium bisulphates into rhodium sulphate, which is then removed by extraction with water, when a residue of finely divided platinum remains. The German firm of Hera,us (in Hanover) heat the raw ore with aqua ,regia and water under pressure, evaporate the solution to dryness, and heat the residue to 125° C. A clear aqueous extract of the residue is then acidified with hydrochloric acid and precipitated with ammonium chloride. The double chloride is ignited and the finely divided platinum so obtained is fused in the oxyhydrogen blowpipe.

Platinum is a greyish-white metal which is exceedingly malleable and ductile; the addition of a small quantity of iridium hardens it and diminishes its ductility very considerably. Its specific gravity is 20.85 to 21 71, and its mean specific heat from o to 100° C. is 0.0323 (J. Violle, Comptes rendus, 18 77, 85, p. 543); W. P. White (Amer. Journ. Sci., 1909, iv. 28, p. 334) gives the general formula S t =o-03198+3.4X to - 't. S t being the specific heat at 1°C. Its temperature of fusion is in the neighbourhood of 1700 to 1800°C., various intermediate values having been obtained by different investigators (see J. A. Harker, Chem. News, 1905, 91, p. 262; C. Fery and C. Cheneveau, Comptes rendus, 1909, 148, p. 401; also C. W. Waidner and G. H. Burgess, ibid., 1909, 148, p. 1177). Its latent heat of fusion is 27.18 calories (Violle, loc. cit). The metal has been obtained in the crystalline condition by distillation in the electric furnace, or by decomposing its fluoride at a red heat (H. Moissan). Platinum, like palladium, absorbs large quantities of hydrogen and other gases, the occluded gas then becoming more "active"; for this reason platinum is used largely as a catalytic agent. Several forms of platinum, other than the massive form, may be obtained. Spongy platinum is produced when ammonium platinochloride is ignited; platinum black on the reduction of acid solutions of platinum salts; and colloidal platinum by passing an electric arc between two platinum wires under the surface of pure water (G. Bredig, Zeit. phys. Chem., 1901, 37, pp. 1, 323). Platinum is practically unoxidizable; it combines directly with phosphorus, arsenic, antimony, silicon, boron, and fluorine, and with almost all other metals. It is practically unattacked by all acids, dissolving only in aqua regia or in mixtures which generate chlorine. When fused with alkaline hydroxides in the presence of air it forms platinates. It is readily attacked by fused nitrates, and by potassium cyanide and ferrocyanide. All the platinum compounds when heated strongly decompose, and leave a residue of the metal. Of platinum salts, in the true sense of the word, none exist; there is no carbonate, nitrate, sulphate, &c; halide salts, however, are known, but are obtained in an indirect manner.

Platinum monoxide, PtO, obtained by heating the corresponding hydrate, is a dark-coloured powder which is easily reduced to the metal (L. Wohler, Ber., 1903, 3 6, p. 3475). The hydrated form, PtO-2H20, is obtained impure by precipitating the dichloride with caustic soda, or by adding caustic soda to a boiling solution of potassium platinous chloride, K 2 PtC1 4, the precipitate being rapidly washed and dried in vacuo (L. Wohler, Zeit. anorg. Chem., 1904, 40, p. 423). It is a black powder; when freshly prepared it is soluble in concentrated acids, but when dried it is insoluble. It is an acidic oxide, the dioxide being both acidic and basic. It behaves as a strong oxidizing and reducing agent. C. Engler and L. Wohler (Zeit. anorg. Chem., 1901, 29, p. I) have shown that platinum black, containing occluded oxygen, is soluble in dilute hydrochloric acid and also liberates iodine from potassium iodide, and that the ratio between the amount of platinum dissolved and the amount of oxygen occluded agrees with the formation of a compound corresponding to the formula PtO. Platinum dioxide (platinic 4 oxide), Pt0 2.4H 2 0, is obtained by adding an excess of caustic soda solution to a boiling solution of chlorplatinic acid, the hot solution being diluted and neutralized with acetic acid. It loses its water of hydration when heated, finally decomposing into platinum and oxygen. When freshly prepared it is soluble in dilute acids. Other hydrated forms of composition, Pt02.3H20 and PtO 2.2H 2 O, have been described (E. Prost, Bull. soc. chim., 1886, 46, p. 156; H. Topsoe, Ber., 1870, 3,. 462). The tetrahydrate may be considered as an acid, H 2 Pt(OH)s, for salts are known (namely the platinates) corresponding to it, those of the alkali metals being soluble in water, and possessing an alkaline reaction (M. Blondel, Ann. chim. phys., 1905 [viii.], 6, p. 81). A similar set of chlorine-holding compounds is also known, the chlorine replacing one or more hydroxyl groups and giving rise to complexes of composition, H2[PtC15(OH)], H 2 [PtC1 4 (OH) 2 ], H 2 [PtC1 2 (OH) 4 ] and H 2 [PtC1(OH) 5 ]. The platinic salts (derived from Pt02) are yellow or brown solids, which are readily reduced to the metallic condition. They give with sulphuretted hydrogen a dark brown precipitate, soluble in excess of ammonium sulphide. Potassium iodide gives a brown solution with gradual formation of a precipitate. They form characteristic precipitates with potassium and ammonium chlorides. The platinous salts are brown or colourless solids which, with sulphuretted hydrogen, give a dark brown precipitate of platinum sulphide, and with potassium iodide a gradual precipitation of platinic iodide, PtI 2. Platinum trioxide, Pt03, is obtained as K 2 0.3Pt0 3, by electrolysing a solution of platinic hydroxide in potash, this compound with acetic acid giving the oxide as a brown, easily decomposable powder (L. Miller and F. Martin, Ber., 1909, 42, P 3326).

Platinum bichloride, PtC1 2, is obtained by heating chlorplatinic acid to 30o-350° C. (J. J. Berzelius), or, mixed with more or less platinic chlorite, by passing chlorine over spongy platinum at a temperature of 250 C. (P. Schutzenberger, Comptes rendus, 1870, 70, pp. 1134, 1287). It may also be obtained by the decomposition of the compound HCl PtCl 2.2H 2 O (see below) at 100° C., this method giving a very pure product (L. F. Nilson, Journ. prak. Chem., 1877 (2), 15, p. 260). It is a brown or greyish green coloured solid, which is soluble in hydrochloric acid. It decomposes into its constituent elements when heated. It combines with many chlorides to form characteristic double salts. Platinum bichloride combines with carbon monoxide, yielding compounds of composition, PtC12.CO, PtC1 2.2CO, 2PtC1 2.3CO (P. Schutzenberger, Ann. chim. Whys., 1870 (4), 21, p. 350). Hydrogen platinochloride or chlorplatinous acid, H 2 PtC1 4, is only known in solution, and as such is obtained when platinum bichloride is dissolved in hydrochloric acid, or by decomposing the barium salt with sulphuric acid, or the silver salt with hydrochloric acid. Its salts, the platinochlorides or chlorplatinites, are obtained by reducing the chlorplatinates or directly from the acid itself. They are mostly soluble in water giving red solutions. They are readily oxidized, and nascent hydrogen reduces them to metallic platinum. Potassium platinochloride or chlorplatinite, K 2 PtC1 41 is prepared by reducing hydrogen platinichloride with sulphur dioxide, or potassium platinichloride with potassium oxalate in the presence of iridium (Klason, Ber., 1904, 37, p. 1360); or by adding potassium chloride to a solution of platinum bichloride in hydrochloric acid. It crystallizes in dark red prisms, is readily soluble in water, but insoluble in alcohol. The solution of the free acid when concentrated in vacuo leaves a residue of HCI.PtC1 2.2H 2 0. When the free acid is reduced by alcohol, or when ethylene is passed into a solution of platinum bichloride in hydrochloric acid, PtC1 2 C 2 H 4 is obtained as a brown amorphous mass which decomposes when heated. When the bichloride is heated in a current of carbon monoxide, a sublimate of platinomonocarbonyl dichloride, PtC1 2 CO, dicarbonyl dichloride,PtC12(CO)2, and tricarbonyl tetrachloride, Pt 2 C1 4 (CO) 3, is obtained. The first forms bright yellow needles and the second white acicular crystals. The bichloride also combines with phosgene to form PtC12.2COC12.

Platinic chloride, PtC1 41 is obtained when chlorplatinic acid is heated in a current of dry hydrochloric acid gas to 165° C. (W. Pullinger, Journ. Chem. Soc., 1892, 61, p. 422) or in a current of dry chlorine at 275° C. (A. Rosenheim and W. Lowenstamm, Zeit. anorg. Chem., 1903, 37, p. 394). It forms a reddish brown crystalline mass which is very hygroscopic. Numerous hydrates are known. The chloride is characterized by the readiness with which it forms double salts with the metallic chlorides and with the hydrochlorides of most organic bases. Chlorplatinic acid, H 2 PtC1 6.6H 2 0, is obtained by dissolving platinum in aqua regia containing an excess of h y drochloric acid, or by the action of chlorine (dissolved in hydrochloric acid) on platinum sponge. It crystallizes in needles, which are very deliquescent and dissolve easily in water. It melts in its own water of crystallization at 70° C., and when heated in vacuo to 100° C. it leaves a residue of composition HC1.PtC1 4.2H 2 0. The potassium and ammonium salts and the salts it forms with organic bases are characterized by their exceedingly small solubility in water. The aqueous solution of the acid reddens litmus and decomposes the metallic carbonates. Its salts may he prepared by the direct action of the acid on the metallic hydroxides or carbonates, and are usually of an orange or yellow colour and are mostly soluble in water. Potassium chlorplatinate, K 2 PtC1 61 is obtained, in the form of a yellow crystalline precipitate, when a concentrated solution of a potassium salt is added to a solution of chlorplatinic acid. It crystallizes in octahedra which are scarcely soluble in water, and practically insoluble in absolute alcohol. It decomposes at a red heat into platinum, chlorine and potassium chloride. The corresponding sodium salt, Na 2 PtC1 6.6H 2 O, is much more soluble in water and in alcohol. The ammonium salt, (NH 4) 2 PtC1 6, resembles the potassium salt in its solubility in water and in alcohol. Corresponding bromoand iodocompounds are known. Platinum bifluoride and tetrafluoride, PtF 2 and PtF 4, were obtained simultaneously by H. Moissan (Ann. chim. phys., 1894 (6), 24,, p. 82) by the action of fluorine on platinum at 500-600° C. They may be separated by taking advantage of their different solubilities in water.

Platinum monosulphide, PtS, is obtained by the direct union of platinum and sulphur; by heating ammonium chlorplatinate with sul phur; or by the action of sulphuretted hydrogen on the chlorplatinites. It is a dark coloured powder which is almost insoluble in aqua regia. It decomposes when heated strongly leaving a residue of metallic platinum, the same reduction taking place at comparatively low temperatures when it is heated in a current of hydrogen. Platinic sulphide, PtS 2, is formed when the chlorplatinates are heated with sulphuretted hydrogen to 60° C. The precipitate must be rapidly washed and dried in vacuo, since it oxidizes rapidly on exposure to air. It is a black powder, which when heated strongly in air decomposes and leaves a residue of platinum, but if heated in absence of air leaves a residue of the monosulphide. It is scarcely affected by acids and is little soluble in solutions of the alkaline sulphides. Sulphides of composition Pt 2 S 3 and Pt5S6 have been described (R. Schneider, Pogg. Ann., 1869, 138, p. 604; 18 73, 1 4 8, p. 6 33; 18 73, 1 49, p. 381). A salt of composition, Pt(OH) 4 .H 2 SO 4 .H 2 O, has been prepared by M. Blondel (Ann. chim. phys., 1905, (8), 6, p. 81) by the solution of the hydrate H 2 Pt(OH) 61 i.e. PtO 2.4H 2 O, in dilute sulphuric acid (1 :1) at o° C. On the addition of cold concentrated sulphuric acid to the solution so obtained, the above salt is precipitated in the form of minute needles, which readily decompose in the presence of water. A platinum sulphate, Pt(SO 4) 2.2H 2 O, has been obtained. by L. Stuchlik (Ber., 1904, 37, p. 2913) by the action of sulphuric acid (s.g. 1.84) on platinum under the influence of an alternating current. A crystalline precipitate is obtained, which is soluble in water and is very hygroscopic.

The platinonitrites of composition M 2 Pt (NO 2) 4 are mostly obtained by double decomposition from the potassium salt, which is formed by adding a warm aqueous solution of potassium nitrite to one of potassium chlorplatinate. They are mostly colourless or pale yellow solids which are more or less soluble in water (L. F. Nilson, Ber., 1876, 9, p. 1722). The corresponding platino-oxalates M2Pt(C204)2 were first obtained by J. W. Dobereiner (Pogg. Ann., 1833, 104, p. 180) and their constitution was determined by H. G. Soderbaum (Ber., 1888, 21, p. 567 R; Zeit. anorg. Chem., 1894, 6, P. 45). The sodium salt, from which the others are obtained by double decomposition, is formed by adding a warm solution of oxalic acid to sodium platinate. On recrystallization from alkaline solutions the salts are obtained in yellow or orange crystals (see M. Vezes, Bull. soc. chim., 18 9 8 (3), 19, p. 8 75). These salts are scarcely soluble in water and decompose explosively when suddenly heated. The free acid is obtained by decomposing the silver salt with hydrochloric acid, the indigo blue solution so obtained on concentration in vacuo yielding a red crystalline mass, which dissolves in water with an indigo blue colour, changing to yellow on dilution.

Platinum cyanide, Pt(CN) 2, is formed by the addition of mercuric cyanide to a solution of a chlorplatinite, or by the decomposition of mercury or ammonium platinocyanide by heat. It is an amorphous powder which is insoluble in water, acids or alkalis, but is soluble in a solution of hydrocyanic acid. It burns when heated.. The platinocyanides are derived from the acid H2Pt(CN)6, which is formed by the decomposition of the mercury or copper salt with sulphuretted hydrogen, or of the barium salt with sulphuric acid. It crystallizes from water in cinnabar-red prisms which contain five molecules of water of crystallization; in the anhydrous condition it is of a yellowish green colour. It decomposes carbonates. Its salts, which are characterized by the property of polychroism, may be prepared by the usual methods, or by the solution of metallic platinum in the alkaline cyanides or alkaline earth cyanides under the influence of an alternating current (A. Brochet and J. Petit, Ann. chim. phys., 1904 (8), 3, p. 460; M. Berthelot, Comptes rendus, 1904, 138, p. 1130). Those of the alkali and alkaline earth metals are soluble in water. Many combine with the halogen elements to form complex salts of the type M 2 Pt(CN) 4 .C1 2. x H 2 O. By the decomposition of the barium salts of this type, addition products of the free acid, of composition H 2 Pt(CN) 4 .C1 2.4H 2 0 and H 2 Pt(CN) 4 .Br 2, have been obtained (C. Blomstrand, Ber., 1869, 2, p. 202). They are deliquescent solids which are exceedingly soluble in water. Potassium platinocyanide, K 2 Pt(CN) 4.3H 2 O, is obtained by dissolving platinum bichloride in potassium cyanide; by heating potassium ferrocyanide with spongy platinum; or by heating ammonium chlorplatinate with potassium cyanide. It crystallizes in needles which effloresce readily. The dry salt is exceedingly hygroscopic and is very soluble in water. When boiled with aqua regia it forms the chlorine addition product, K 2 Pt(CN) 4 .C1 2.2H 2 O. It combines directly with iodine. Barium platinocyanide, BaPt(CN) 4.4H 2 O, is prepared by the action of ,baryta water on the copper salt; by dissolving platinum in barium cyanide under the influence of an alternating current; by the addition of barium cyanide to platinum bichloride; or by the simultaneous action of hydrocyanic and sulphurous acids on a mixture of baryta and chlorplatinic acid (P. Bergsoe, Zeit. anorg. Chem., 1899, 19, p. 318). It crystallizes in yellow monoclinic prisms and is soluble in hot water. It is employed for the manufacture of fluorescent screens used for the detection of X-rays.

The platinum salts combine with ammonia to form numerous derivatives which can be considered as salts of characteristic bases. The first compound of this type was isolated in 1828 by Magnus, who obtained a green salt by the action of ammonia on platinum bichloride. Two series of these salts are known, one in which the metal corresponds to bivalent platinum, the other in which it corresponds to tetravalent platinum. The general formulae of the groups in each series are shown below, the method of classification being that due to Werner.

Divalent (platinous) Salts.

Tetravalent (platinic) Salts.

Hexammine salts[Pt(NH3)6]X4

Tetrammine salts[Pt(NH3)4]X2

Tetrammine „ [Pt(NH3)4X2]X2

Triammine „ [Pt(NH 3) 3 X]X

Triammine „ [Pt(NH3)3X3]X

Diammine „ [Pt(NH 3) 2 X 2 ]

Diammine „ [Pt(NH3)2X4]

Monammine „ [Pt(NH,)X,]R

Monammine „ [Pt(NH3)X5]R

In the above table X represents a monovalent acid radical and R a monovalent basic radical. For methods of preparation of salts of these series see P. T. Cleve, Bull. soc. chim. 1867 et seq.; S. M. Jorgensen, Journ. prak. Chem. 1877 et seq.; C.W. Blomstrand, Ber. 1871 et seq.; and A. Werner, Zeit. anorg. Chem. 1893 et seq. A very complete account of the method of classification and the general theory of the metal ammonia compounds is given by A. Werner, Ber. 1907, 40, p. 15.

Platinum also forms a series of complex phosphorus compounds. At 250° finely divided platinum and phosphorus pentachloride combine to form PtC1 2 .PC1 31 as dark claret-coloured crystals. With chlorine this substance gives PtC13.PC1 4 as a yellow powder, and with water it yields phosphoplatinic acid, PtC1 2 .P(OH) 3, which may be obtained as orange-red deliquescent prisms.

The atomic weight of platinum was determined by K. Seubert (Ann. 1888, 207, p. i; Ber. 1888, 21, p. 2179) by analyses of ammonium and potassium platinochlorides, the value 194.86 being obtained.


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Simple English

File:Platinum
Some platinum nuggets from nature.
Simple English Wiktionary has the word meaning for:

Platinum is a soft, heavy, white metal. It is a precious metal, not a common metal. It usually costs more than gold.

In chemistry, platinum is element number 78. It has an atomic weight of 195 a.m.u. The symbol for platinum is Pt, from Spanish platina meaning "little silver".

Platinum is very malleable and ductile, which means it can be hammered into thin sheets and it can be pulled into wire. Platinum is very stable. Acids do not affect platinum. In the nineties lots and lots of urban people began wearing platinum as opposed to gold. White gold never became popular amongst America's urban population, thus Platinum originated the whole bling bling revolution.

The most common use of Platinum is in a vehicle catalytic converter.








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