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For dental crowns.
Palladium was named after the asteroid Pallas, which was discovered at about the same
time. Pallas was the Greek goddess of wisdom.
Discovered in 1803 by Wollaston, Palladium is found with platinum and other metals of
the platinum group in placer deposits of Russia, South America, North America, Ethiopia,
and Australia. It is also found associated with the nickel-copper deposits of South Africa
and Ontario. Palladium's separation from the platinum metals depends upon the type of ore
in which it is found.
The element is a steel-white metal, it does not tarnish in air, and it is the least
dense and lowest melting of the platinum group of metals. When annealed, it is soft and
ductile; cold-working greatly increases its strength and hardness. Palladium is attacked
by nitric and sulfuric acid.
At room temperatures, the metal has the unusual property of absorbing up to 900 times
its own volume of hydrogen, possibly forming Pd2H.
It is not yet clear if this is a true compound. Hydrogen readily diffuses through heated
palladium, providing a means of purifying the gas.
Finely divided palladium is a good catalyst and is used for hydrogenation and
dehydrogenation reactions. It is alloyed and used in jewelry trades.
White gold is an alloy of gold decolorized by the addition of palladium. Like gold,
palladium can be beaten into leaf as thin as 1/250,000 in. The metal is used in dentistry,
watchmaking, and in making surgical instruments and electrical contacts.
The metal sells for about $150/troy oz.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.