Baryta

Collier's New Encyclopedia (1921)

or BARYTES, or OXIDE OF BARIUM, symbol BaO-the earth present in the minerals witherite (carbonate of barium) and heavy spar (sulphate of barium). Baryta belongs to the group of alkaline earths, and has the property of acting like an alkali on coloring matters. It has a very harsh taste, is highly caustic, and is very poisonous. The presence of carbonic acid gas may be detected by exposing a solution of baryta to the air, when carbonic acid combines with the baryta and forms a film of white carbonate of barium, BaCO3. Baryta exposed to air or oxygen absorbs oxygen, forming peroxide of barium. On this being heated oxygen is liberated and baryta again produced. The sulphate of baryta, BaSO4, otherwise called ponderous or heavy spar, is found in fissures or cracks in other rocks. It is crystalline, and is sometimes found pure and white, but generally presents a flesh-red color, from the red oxide of iron (rust) incorporated in it. The rust can be got quit of by reducing the sulphate of baryta to a fine powder under rollers or traveling wheels, and subjecting the pulverized material to the action of dilute sulphuric acid, which dissolves the oxide of iron, and leaves the sulphate of baryta as a white, dense powder. The principal use of heavy spar is as a pigment under the name of permanent white; but having little opacity, it be cannot employed by itself, but only when mixed with ordinary white lead. Several mixtures of sulphate of baryta and white lead are manufactured, and are known in com- Venice white contains one part merce. sulphate of baryta and one part white lead. Hamburg white contains two parts sulphate of baryta and one part of white lead. Dutch white contains three parts sulphate of baryta and one part white lead. The native sulphate of baryta has been employed by the celebrated potter Wedgewood in the manuformation of white figures, etc.