Chromium, Molybdenum, Tungsten, Uranium
Chromium (Cr), never found in nature except in combination, is produced by reduction of its ore by carbon in the electric furnace, or by the Thermit process mentioned on p. 318. It is a brilliant white metal, having a specific gravity of about 6–5, and melting at about 1,800°C. It possesses the property of imparting to iron and steel a high degree of hardness and tenacity, and for that reason has become in recent years of great industrial importance. For this purpose an alloy of iron and chromium (ferro-chrome, produced in the electric furnace) is commonly used; it is cheaper to make, melts at a lower temperature, and is consequently better under control than the pure metal. Stainless steel contains as much as 18 per cent of chromium. The compounds of chromium are also of considerable industrial importance. Chromite, an oxide of iron and chromium, is used very extensively as a refractory material for furnace linings. Other salts, artificially prepared, are used as pigments, and in various industries, such as chromium-plating, dyeing, tanning, photography, etc.
KeywordsUranium Mineral Molybdenum Oxide Tungstic Acid Tungsten Mineral Molybdic Acid
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