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platinum |
4 definitions found From Webster's Revised Unabridged Dictionary (1913) [web1913]: 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, intermediate in value between silver and gold, occurring native or alloyed with other metals, also as the platinum arsenide (sperrylite). It is heavy tin-white metal which is ductile and malleable, but very infusible, and characterized by its resistance to strong chemical reagents. It is used for crucibles, 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 194.3. Symbol Pt Formerly called {platina}. {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. From WordNet r 1.6 [wn]: platinum n : a heavy precious metallic element; gray-white and resistant to corroding; occurs in some nickel and copper ores and is also found native in some deposits [syn: {Pt}, {atomic number 78}] From U.S. Gazetteer (1990) [gazetteer]: Platinum, AK (city, FIPS 61080) Location: 58.97394 N, 161.72523 W Population (1990): 64 (45 housing units) Area: 115.4 sq km (land), 0.0 sq km (water) Zip code(s): 99651 From Elements database 20001107 [elements]: 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, cyandies 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.
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