Rhodium

Rhodium, chemical element, symbol Rh; for physical constants see Periodic Table. Rhodium was discovered by William H. Wollaston in 1803. It occurs in the minerals sperrylite, iridosmine, and in some copper-nickel sulfide ores. Rhodium is a silver-white, high-melting, unreactive metal, a member of the platinum family of elements. It is one of the few substances that is not attacked by fluorine. The metal is used to harden platinum and palladium. Plated or evaporated coatings of the element have high reflectance and are used in optical instruments. Rhodium and its compounds are used in thermocouples, crucibles, electrodes, and electrical contacts and as catalysts.