PLATINA, or PLATINUM (Spanish plata, silver), is a metal of a white colour, exceedingly ductile, malleable, and difficult of fusion. It is the heaviest substance with which we are acquainted, its specific gravity being about 21.5. It is subject to no change from air or moisture, is not attacked by any pure acid, is dissolved by the influence of chlorine and nitro-muriatic acid, and is subject to oxidation by pure potassa and lithia. It is found only in the Ural Mountains and in South America, where it is usually procured in small lustrous grains combined with palladium, rhodium, &c., and is for the most part commingled with sand. The portions of it which are found seldom exceed a small pea in size, but occasionally it has been found in lumps varying in size from a hazel nut to a pigeon's egg. (See CHEMISTRY; also MINES AND MINING.)
PLATING is the art of covering the baser metals with silver or gold, either for use or ornament. Of late, manufacturers have availed themselves of electro-chemical decomposition for the purpose.