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Definition: palladium from Philip's Encyclopedia

(symbol Pd) Shiny silver-white metallic element of the transition elements. It was discovered (1803) by the English chemist William Wollaston (1766-1828). Malleable and ductile, palladium is found in nickel ores associated with platinum, to which it is chemically similar. It does not tarnish or corrode and is used for electroplating, surgical instruments, dentistry, jewellery and in catalytic converters for cars. Properties: 46; r.a.m. 106.4; r.d. 12.02; m.p. 1,552°C (2,826°F); b.p. 3,140°C (5,684°F); most common isotope Pd106 (27.3%).

Summary Article: palladium, chemical element
from The Columbia Encyclopedia

[Gr. Pallas, goddess of wisdom], metallic chemical element; symbol Pd; at. no. 46; at. wt. 106.42; m.p. 1,554 degrees Celsius; b.p. 2,970 degrees Celsius; sp. gr. 12.02 at 20 degrees Celsius; valence +2, +3, or +4. Palladium is a lustrous silver-white metal with a face-centered cubic crystalline structure. Directly above platinum, it is one of the platinum metals in Group 10 of the periodic table. It is strongly resistant to corrosion in air and to the action of acids (except nitric acid) at ordinary temperatures. However, it is attacked by hot acids, and it dissolves in aqua regia. It forms many compounds, including oxides, chlorides, fluorides, sulfides, phosphides, and several complex salts. Palladium has a great ability to absorb hydrogen; when finely divided, one volume of palladium absorbs as many as 900 volumes of the gas. When heated, it allows hydrogen to diffuse rapidly through it; it is thus used to purify hydrogen gas. Palladium is found in nature with platinum minerals and in association with the nickel ores mined near Sudbury, Ont., Canada.

Because of its corrosion resistance, a major use of palladium is in alloys used in low voltage electrical contacts. Palladium is used extensively in jewelry-making in certain alloys called “white gold.” It may be alloyed with platinum or substituted for it. It is used in watch bearings, springs, and balance wheels and also for mirrors in scientific instruments. For use in dentistry it is alloyed with silver, gold, and copper. In chemistry it is a catalyst in sulfuric acid manufacture and in hydrogenation processes; it used as a catalyst also in motor vehicle catalytic converters. Palladium salts are used in electroplating. Although palladium is not as abundant as platinum, it is less expensive. Palladium was discovered in 1803 by W. H. Wollaston.

The Columbia Encyclopedia, © Columbia University Press 2018

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