platinum

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A silver-white metallic element occurring worldwide, usually mixed with other metals such as iridium, osmium, or nickel. It is ductile and malleable, does not oxidize in air, and is used as a catalyst and in electrical components, jewelry, dentistry, and electroplating. Atomic number 78; atomic weight 195.08; melting point 1,772°C; boiling point 3,827°C; specific gravity 21.45; valence 2, 3, 4. See Table at element.
2. n. A medium to light gray.

Century Dictionary and Cyclopedia

1. n. Chemical symbol, Pt; atomic weight, 194.9. An important metal, introduced into Europe about the middle of the eighteenth century from South America. It does not occur as an ore, but alloyed with other metals, especially with rhodium, osmium, iridium, and palladium, all of which, together with iron, copper, and gold, are almost always present in it in small quantity in what is called its native state. Platinum is surpassed in ductility only by gold and silver, and in malleability only by those metals and copper. It is easily rolled into sheets or drawn into wire. Its specific gravity is 21.5, which is higher than that of any other known substance except osmium and iridium. It. is not oxidized in the air at any temperature, and is not attacked by any of the simple acids. It is infusible in the strongest heat of a blast-furnace, but can be melted in the flame of the oxyhydrogen blowpipe or by means of the electric current. It is a rare metal, and the regions which supply it are few. Most of the platinum of commerce conies from the Urals, South America, and Borneo. It is used chiefly in chemical manufacture and analysis, where its resistance to heat and acids is of special value, and in electrical work. It was used for coinage in Russia from 1823 to 1845.

Wiktionary

1. adj. Of a whitish grey colour, like that of the metal.
2. adj. Of a musical recording that has sold over one million copies (for singles), or two million (for albums).
3. n. The metallic chemical element with atomic number 78 and symbol Pt.
4. n. A whitish grey colour, like that of the metal.
5. n. music A single or album that has achieved platinum sales, i.e. over 1 million or 2 million.

GNU Webster's 1913

1. n. (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° 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.

WordNet 3.0

1. n. 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