Platinum

Platinum black (Chem.), a soft, dull black powder, consisting of finely divided metallic platinum obtained by reduction and precipitation from its solutions. It absorbs oxygen to a high degree, and is employed as an oxidizer. -- Platinum lamp (Elec.), a kind of incandescent lamp of which the luminous medium is platinum. See under Incandescent. -- Platinum metals (Chem.), the group of metallic elements which in their chemical and physical properties resemble platinum. These consist of the light platinum group, viz., rhodium, ruthenium, and palladium, whose specific gravities are about 12; and the heavy platinum group, viz., osmium, iridium, and platinum, whose specific gravities are over 21. -- Platinum sponge (Chem.), metallic platinum in a gray, porous, spongy form, obtained by reducing the double chloride of platinum and ammonium. It absorbs oxygen, hydrogen, and certain other gases, to a high degree, and is employed as an agent in oxidizing.