BARYTES, or Baryta, an oxide (BaO) of the metal barium, usually prepared from the two most common ores of the substance, the sulphate and the carbonate of baryta. It is a highly caustic alkaline poisonous body, which with water forms a hydrate of baryta. On a commercial scale baryta is prepared from the native carbonate (Witherite) by exposing the mineral, mixed with one-tenth of its weight of lamp black, to a very high heat. It is now largely employed in the beet sugar manufacture for separating crystallized sugar from the molasses. A solution of the hydrated oxide, under the name of baryta-water, is of very great use in the chemical laboratory for precipitating metallic oxides, and on account of its sensitiveness to carbonic acid. Sulphate of baryta, or heavy spar, the cawk of miners, is a mineral of very high specific gravity (4'59), found abundantly in veins in the mountain limestone of England and frequently associated with metallic ores. When reduced to powder the white varieties are sometimes used as a pigment, but the powder is more frequently applied as an adulterant to white lead. Heavy spar is also used in the manufacture of pottery. The powdered carbonate of baryta is used to some extent in the manufacture of glass, taking the place of a part of the alkali in plate glass, and of some portion of red-lead in flint glass. Cassel green, or liosenstiehl’s green, is a pigment manufactured from the calcined manganate of baryta. ’ Both the nitrate and the chloride are of great value as chemical reagents. The nitrate and chlorate are also used to produce a green light in pyrotechny.