platinum
    n 1: a heavy precious metallic element; grey-white and resistant
         to corroding; occurs in some nickel and copper ores and is
         also found native in some deposits [syn: platinum, Pt,
         atomic number 78]

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