Tungsten (Swed. Tung Heavy And Sten, Stone), a metal existing in the form of an acid combined with lime in the mineral scheelite or tungstate of lime, and also combined with iron and manganese in the mineral wolfram.. Tungstic acid was discovered by Scheele in 1781, and metallic tungsten two years later by the brothers D'Elhujar. Its German name Wolframium gives its symbol, "W. It is obtained as a heavy iron-gray metal, very hard and difficult of fusion, and of the high specific gravity 17.6, by intensely heating tungstic acid made into a paste with oil, in a crucible lined with charcoal, for some hours. The tungstic acid is procured by decomposing the tungstate of lime with hydrochloric acid, which dissolves the lime and leaves the tungstic acid. The chemical equivalent of tungsten is 184. - Tungsten combines with several other metals, forming alloys of interest. Its combination with cast iron is remarkable for its extraordinary hardness; and it is said that cast steel containing 10 per cent, of tungsten is greatly improved in tenacity, hardness, and susceptibility of taking a fine temper. Notwithstanding its reputed qualities, tungsten steel has not been generally introduced, and comparatively little is made. - Of the two oxides of tungsten, WO2 and WO3, the latter oniy, or tungstic anhydride, is of particular interest.

This occurs native in bright yellow cubes, also as an earthy substance like ochre at Lane's mine, Monroe, Conn., Cabarrus co., N. C, and a few other places. But the usual form of the acid is in the combinations already named, and of these wolfram is the most common ore of the metal. This is a brownish black mineral, of metallic lustre, of hardness 5 to 5.5, and specific gravity 7'1 to 7'55. It is often found associated with tin ore in Cornwall, Saxony, Bohemia, and France. In the United States it has been found at Monroe, Conn., with native bismuth, galena, blende, etc.; also at Trumbull in the same state, and near Mine La Motte, Mo., and Blue Hill bay, Me. Tungstic acid is also found in combination with lead, forming the mineral scheeletine, and artificial tungstate of lead is prepared as a pigment resembling white lead. The following are some of the attempted applications of the compounds of tungsten to economical purposes: tungstic acid for coloring yellow; oxide of tungsten for coloring blue; tungstate of soda in dyeing and calico printing, and as a substitute for stannate of soda.

The compounds of tungsten have been thoroughly studied by Roscoe and Zettnow, but none of them possess particular interest beyond those already described.