Platinum (oz.)

(chemistry) A chemical element, symbol Pt, atomic number 78, atomic weight 195.08.
(metallurgy) A soft, ductile, malleable, grayish white noble metal with relatively high electric resistance; used in alloys, in electrical and electronic devices, and in jewelry.

A chemical element, Pt, atomic number 78, and atomic weight 195.09. Platinum is a soft, ductile, white noble metal. The platinum-group metals—platinum, palladium, iridium, rhodium, osmium, and ruthenium—are found widely distributed over the Earth. Their extreme dilution, however, precludes their recovery, except in special circumstances. For example, small amounts of the platinum metals, palladium in particular, are recovered during the electrolytic refining of copper. See also Iridium; Osmium; Palladium; Periodic table; Rhodium; Ruthenium.

The platinum-group metals have wide chemical use because of their catalytic activity and chemical inertness. As a catalyst, platinum is used in hydrogenation, dehydrogenation, isomerization, cyclization, dehydration, dehalogenation, and oxidation reactions. See also Catalysis; Electrochemical process.

Platinum is not affected by atmospheric exposure, even in sulfur-bearing industrial atmospheres. Platinum remains bright and does not visually exhibit an oxide film when heated, although a thin, adherent film forms below 450°C (840°F). Platinum may be worked to fine wire and thin sheet, and by special processes, to extremely fine wire. Important physical properties are given in the table.

Platinum can be made into a spongy form by thermally decomposing ammonium chloroplatinate or by reducing it from an aqueous solution. In this form it exhibits a high absorptive power for gases, especially oxygen, hydrogen, and carbon monoxide. The high catalytic activity of platinum is related directly to this property. See also Cracking; Hydrogenation.

Platinum strongly tends to form coordination compounds. Platinum dioxide, PtO₂, is a dark-brown insoluble compound, commonly known as Adams catalyst. Platinum(II) chloride, PtCl₂, is an olive-green water-insoluble solid. Chloroplatinic acid, H₂PtCl₆, is the most important platinum compound. See also Coordination chemistry.

In the glass industry, platinum is used at high temperatures to contain, stir, and convey molten glass. In the electrical industry, platinum is used in contacts and resistance wires because of its low contact resistance and high reliability in contaminated atmospheres. Platinum is clad over tungsten for use in electron tube grid wires. In the medical field, the simple coordination compounds cisplatin and carboplatin are two of the most active clinical anticancer agents. In combination with other agents, cisplatin is potentially curative for all stages of testicular cancer. Both agents are used for advanced gynecologic malignancies, especially ovarian tumors, and for head and neck and lung cancers. Carboplatin was developed in attempts to alleviate the severe toxic side effects of the parent cisplatin, with which is shares a very similar spectrum of anticancer efficacy. See also Chemotherapy.

(Platinum Technology, Inc., Oakbrook Terrace, IL, www.platinum.com) A major software vendor acquired by Computer Associates in 1999, with more than 160 data, systems and application software products to its credit. Founded in 1987, Platinum's key business areas were database and systems management, application life cycle, data warehousing, the Internet and Y2K compliance. Key alliances with HP, IBM, Intel, Microsoft and SAP helped the company expand to more than 40 countries.

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