Rhodium

Rhodium (sym. Rh, at. wt. 104, sp. gr. 12.1) is one of the metals of the platinum group. It is a white, very hard metal, resembling aluminium rather than silver. It fuses less easily than platinum. It is ductile and malleable when pure and after fusion, and insoluble in all acids; but when alloyed in small quantity with platinum, copper, bismuth, and lead it dissolves with them in aqua regia. It usually forms about one-half per cent. of the ore of platinum, from which it is extracted by a somewhat complicated process. Three oxides, two sulphides, and a chloride of rhodium have been obtained and examined by chemists. The chloride unites with several soluble chlorides to form crystallisable double salts, which are of a rose colour (whence the name rhodium, from the Gr. rhodon, 'a rose'). The metal was discovered in 1803 by Wollaston.