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TUNGSTEN, a rare metallic element, found in wolfram, which is a tungstate of iron and manganese, and likewise found in scheelite, which is a tungstate of lime. The metal (Swedish, tung-sten, "heavy stone”) is obtained either as a dark-gray powder or in heavy iron-gray bars, which are very hard and difficult of fusion, and have a sp. gr. of 19.1. Aqua regia and nitric acid convert it into tungstic acid. When 10 parts of this metal are alloyed with 90 of steel a mass of extraordinary hardness is obtained. Tungsten forms two compounds with oxygen—viz., a binoxide, WO2, which is obtained in the form of a brown powder by heating tungstic acid to low redness in a current of hydrogen, and which does not form salts with acids; and an acid oxide, known as tungstic anhydride, WO3. Various tungstates have been formed and examined. Of these the most important is the tungstate of soda, which answers admirably as a means of preventing muslin, etc., from bursting out in a flame when brought in contact with fire.