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Jai Ganesh

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Registered: 2005-06-28

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Platinum

Platinum

Gist

Platinum is known for its superior durability, resisting scratches and tarnish better than gold. It has a higher density and doesn't wear down as quickly as gold, making it ideal for rings and bracelets. Gold, particularly in higher purity forms like 24-carat, is softer and more prone to bending or scratching.

The auto industry uses platinum for catalytic converters, which can help reduce the toxicity of gases and pollutants in the exhaust that an internal combustion engine creates. Platinum and other platinum-grade metals in catalytic converters have led to a secondary market for scrap converters, which scrap businesses will buy in order to extract the metal for resale. The metal is also used in thermometers, laboratory equipment, electrodes, and dentistry equipment.

Summary

Platinum is a chemical element; it has symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish platina, a diminutive of plata "silver".

Platinum is a member of the platinum group of elements and group 10 of the periodic table of elements. It has six naturally occurring isotopes. It is one of the rarer elements in Earth's crust, with an average abundance of approximately 5 μg/kg. It occurs in some nickel and copper ores along with some native deposits, with 90% of current production from deposits across Russia's Ural Mountains, Colombia, the Sudbury basin of Canada, and a large reserve in South Africa. Because of its scarcity in Earth's crust, only a few hundred tonnes are produced annually, and given its important uses, it is highly valuable as well as a major precious metal commodity.

Platinum has remarkable resistance to corrosion, even at high temperatures, and is therefore considered a noble metal. Consequently, platinum is often found chemically uncombined as native platinum. 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 the 16th century, but it was not until Antonio de Ulloa published a report on a new metal of Colombian origin in 1748 that it began to be investigated by scientists.

Platinum is used in catalytic converters, laboratory equipment, electrical contacts and electrodes, platinum resistance thermometers, dentistry equipment, and jewelry. Platinum is used in the glass industry to manipulate molten glass, which does not "wet" platinum. Elemental platinum has not been linked to adverse health effects. Compounds containing platinum, such as cisplatin, oxaliplatin and carboplatin, are applied in chemotherapy against certain types of cancer.

Details

Platinum (Pt) is a chemical element, the best known and most widely used of the six platinum metals of Groups 8–10, Periods 5 and 6, of the periodic table. A very heavy, precious, silver-white metal, platinum is soft and ductile and has a high melting point and good resistance to corrosion and chemical attack. For example, its surface remains bright after being brought to white heat in air, and, though it readily dissolves in aqua regia, it is scarcely attacked by simple acids. (It does dissolve slowly in hydrochloric acid in the presence of air.) Small amounts of iridium are commonly added to give a harder, stronger alloy that retains the advantages of pure platinum.

Platinum, one of the most abundant platinum metals, and its alloys are indispensable in the chemical laboratory for electrodes and for crucibles and dishes in which materials can be heated to high temperatures. Platinum is used for electrical contacts and sparking points because it resists both the high temperatures and chemical attack of electric arcs. Jewelry and dental alloys account for much of its use; platinum-iridium is used for surgical pins. The prototype international standard kilogram of mass was made from an alloy of 90 percent platinum and 10 percent iridium. The electrical resistivity of platinum is relatively high and depends markedly upon the temperature; the International Temperature Scale from −259.35 to 961.78 °C (−434.83 to 1,763.2 °F)is defined in terms of a resistance thermometer made with platinum wire. As a catalyst, platinum has many applications, notably in automotive catalytic converters and in petroleum refining.

The Italian-French physician Julius Caesar Scaliger alluded (1557) to a refractory metal, probably platinum, found between Darién and Mexico. The first certain discovery was in the alluvial deposits of the Río Pinto, Colombia. The Spaniards called the new metal platina del Pinto for its resemblance to silver. The world’s most important deposits occur in the Transvaal of South Africa. Other deposits are found in Russia, Finland, Ireland, Borneo, New South Wales, New Zealand, Brazil, Peru, and Madagascar. In North America native platinum is found in Alaska, California, and Oregon, in British Columbia, and in Alberta. Placer deposits are the most productive sources of the native element. The ordinary variety of native platinum is called polyxene; it is 80 percent to 90 percent platinum, with 3 percent to 11 percent iron, plus the other platinum metals, and gold, copper, and nickel. For mineralogical properties, see native element (table). Platinum is also found in the very rare native alloy platiniridium. Platinum occurs combined with math as sperrylite (PtAs2) in the copper–nickel mining district near Sudbury, Ontario, and with sulfur as cooperite (PtS) in the Transvaal. (For information about the mining, recovery, and production of platinum, see platinum processing.)

Platinum is rapidly attacked by fused alkali oxides and peroxides and also by fluorine and chlorine at about 500 °C. It is capable of absorbing large volumes of hydrogen, and, with palladium, it is one of the most reactive platinum metals.

Platinum forms an important series of compounds with the oxidation states of +2 and +4. Many of these compounds contain coordination complexes in which chloride ion (Cl−), ammonia (NH3), or other groups are bonded to a central platinum atom. Among the transition metals, platinum has one of the greatest tendencies to form bonds directly with carbon. Platinum also combines with a number of nonmetallic elements on heating, such as phosphorus, math, antimony, silicon, sulfur, and selenium.

Natural platinum is a mixture of six isotopes: platinum-190 (0.012 percent), platinum-192 (0.782 percent), platinum-194 (32.86 percent), platinum-195 (33.78 percent), platinum-196 (25.21 percent), and platinum-198 (7.36 percent). All are stable except platinum-190, which has been reported as a long-lived alpha emitter.

Element Properties
atomic number  :  78
atomic weight  :  195.09
melting point  :  1,769 °C (3,216 °F)
boiling point  :  3,827 °C (6,920 °F)
specific gravity  :  21.45 (20 °C)
oxidation states  :  +2, +4.

Additional Information

Appearance:

A shiny, silvery-white metal as resistant to corrosion as gold.

Uses

Platinum is used extensively for jewellery. Its main use, however, is in catalytic converters for cars, trucks and buses. This accounts for about 50% of demand each year. Platinum is very effective at converting emissions from the vehicle’s engine into less harmful waste products.

Platinum is used in the chemicals industry as a catalyst for the production of nitric acid, silicone and benzene. It is also used as a catalyst to improve the efficiency of fuel cells.

The electronics industry uses platinum for computer hard disks and thermocouples.

Platinum is also used to make optical fibres and LCDs, turbine blades, spark plugs, pacemakers and dental fillings.

Platinum compounds are important chemotherapy drugs used to treat cancers.

Biological role

Platinum has no known biological role. It is non-toxic.

Natural abundance

Platinum is found uncombined in alluvial deposits. Most commercially produced platinum comes from South Africa, from the mineral cooperite (platinum sulfide). Some platinum is prepared as a by-product of copper and nickel refining.

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