Tungsten

Tungsten (sym. W, equiv. 183.5), a rare metal, chiefly derived from Wolfram (whence the symbol W), which is a tungstate of iron and manganese, and likewise found in Scheelite, which is a tungstate of lime. The metal (Swed. 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 specific gravity 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, &c. from bursting out in a flame when brought in contact with fire.