TITANIUM (sym. Ti, eq. 25—new system, 50—sp. gr. undetermined) is a compara tively rare metal, which, according to the method by which it is procured, occurs as a gray, heavy, iron-like powder, which burns with brilliant scintillations in the air, and is converted into titanic acid, or in prismatic crystals. At 212° it decomposes water, and it is soluble in hydrochloric acid. It is obtained in the crystalline form by heating sodium in the vapor of bichloride of titanium. It never occurs native, but is found in association with other elements in various minerals, of which the most important are anastase, rutile, and brookite, containing titanic acid; titanite, containing silicate of lime and titanic acid; perowskite, containing titanite of lime; aschynite, containing titanic and niobic acids, and the oxides of cerium and lanthanum; and lastly, titanic iron, com posed of titanate of pi otoxide of iron. A remarkable artificial compound of the metal is often found in the form of copper-colored cubic crystals, adhering to the slags of iron furnaces. They are hard enough to scratch agate; and no acid except a mixture of
nitric and hydrofluoric acids has any action on them; but they are volatile at an extremely high temperature. They consist of a combination of cyanide with nitride of titanium, and are represented by the remarkable formula, TiCy,3TiN. The most important compound of this metal is titanic acid which occurs in the minerals menaccanite and iserine, as titanate of iron, but is more common in the uncombined state, as titanic anhydride, in the form of rutile, brookite, and anastase, each of which possesses a distinct crystalline form, and has a different specific gravity. Hence titanic acid in the anhydrous state is trimorphous. It is usually obtained by a somewhat com plicated process from rutile. Titanium was discovered by Gregor, as a constituent of menaccanite, in 1791.