- platina
- Platinum Plat"i*num, n. [NL., fr. Sp. platina, from plata
silver, LL. plata a thin plate of metal. See {Plate}, and cf.
{Platina}.] (Chem.)
A metallic element of atomic number 78, one of the noble
metals, classed with silver and gold as a precious metal,
occurring native or alloyed with other metals and also as the
platinum arsenide (sperrylite). It is a heavy tin-white metal
which is ductile and malleable, but very infusible (melting
point 1772[deg] C), and characterized by its resistance to
strong chemical reagents. It is used for crucibles in
laboratory operations, as a catalyst, in jewelry, for stills
for sulphuric acid, rarely for coin, and in the form of foil
and wire for many purposes. Specific gravity 21.5. Atomic
weight 195.1. Symbol Pt. Formerly called {platina}.
[1913 Webster +PJC]
{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. [1913 Webster]
The Collaborative International Dictionary of English. 2000.
