|
platinum 音标拼音: [pl'ætnəm] [pl'ætənəm] n. 白金,铂 白金,铂 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 [ synonym: { 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] platinumSymbol: PtAtomic number: 78Atomic weight: 195. 078Attractive 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 sixstable isotopes and three radioisotopes, the most stable being Pt- 193with a half- life of 60 years. Platinum is used in jewelry, laboratoryequipment, electrical contacts, dentistry, and anti- pollution devices incars. PtCl2( NH3) 2 is used to treat some forms of cancer. Platinum-{ cobalt} alloys have magnetic properties. It is also used in the definition ofthe Standard Hydrogen Electrode. Discovered by Antonio de Ulloa in SouthAmerica in 1735. The name comes from the Spanish word platina whichmeanssilver. Platinum metal is generally not a health concern due to itsunreactivity, however platinum compounds should be considered highlytoxic.
|
安装中文字典英文字典查询工具!
中文字典英文字典工具:
英文字典中文字典相关资料:
|