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]
|
platinum
Symbol: Pt
Atomic number: 78
Atomic weight: 195.078
Attractive greyish-white metal. When pure, it is malleable and ductile.
Does not oxidize in air, insoluble in hydrochloric and nitric acid.
Corroded by halogens, cyanides, sulphur and alkalis. Hydrogen and
oxygen react explosively in the presence of platinum. There are six
stable isotopes and three radioisotopes, the most stable being Pt-193
with a half-life of 60 years. Platinum is used in jewelry, laboratory
equipment, electrical contacts, dentistry, and anti-pollution devices in
cars. PtCl2(NH3)2 is used to treat some forms of cancer.
Platinum-cobalt
alloys have magnetic properties. It is also used in the definition of
the Standard Hydrogen Electrode. Discovered by Antonio de Ulloa in South
America in 1735. The name comes from the Spanish word platina which
means
silver. Platinum metal is generally not a health concern due to its
unreactivity, however platinum compounds should be considered highly
toxic.
|
Platinum, AK -- U.S. city in Alaska
Population (2000): 41
Housing Units (2000): 26
Land area (2000): 44.630629 sq. miles (115.592794 sq. km)
Water area (2000): 0.071778 sq. miles (0.185904 sq. km)
Total area (2000): 44.702407 sq. miles (115.778698 sq. km)
FIPS code: 61080
Located within: Alaska (AK), FIPS 02
Location: 59.006890 N, 161.815290 W
ZIP Codes (1990): 99651
Note: some ZIP codes may be omitted esp. for suburbs.
Headwords:
Platinum, AK
Platinum
|