October 31 - November 3, 2004
Element of the Day
Tuesday, October 19
Palladium
is named after the asteroid "Pallas" which was discovered at about the
same time and from the Greek name "Pallas", goddess of wisdom. At room
temperatures the metal has the unusual property of absorbing up to 900 times its
own volume of hydrogen. Hydrogen readily diffuses through heated palladium and
this provides a means of purifying the gas.
Discovered by: William Hyde Wollaston discovered palladium in 1803-4 in crude platinum ore from South America. He dissolved the ore in aqua regia (a mixture of hydrochloric and nitric acids), neutralized the acid with sodium hydroxide (NaOH), and precipitated the platinum by treatment with ammonium chloride, NH4Cl, as ammonium chloroplatinate. Palladium was then removed as palladium cyanide by treatment with mercuric cyanide. The metal was produced from this cyanide by heating.
Uses: Automobile catalytic converters use palladium in the catalytic converters, and accounted for 60% of the demand for palladium in 1999. It is used in the auto industry for reducing exhaust emissions of hydrocarbons, carbon monoxide, and oxides of nitrogen. Palladium is also employed in the electronics sector and in the formulation of dental alloys. It is used in the production of multilayer ceramic capacitors, components of mobile phones, personal computers, and numerous auto and home electronics. Palladium has been long used in jewelry, either alone or mixed with gold to produce "white gold". It is used in fine instruments such as watches and some surgical instruments. Palladium when finely divided is a good catalyst for hydrogenation and dehydrogenation reactions. It is also used to purify hydrogen gas. When annealed, it is soft and ductile. Cold working increases its strength and hardness. It is used in some watch springs.