Barium sulfate (BaSO4) is a white or yellow powder or crystalline salt with no taste or odor. Its density is 4.24-4.5 and it melts at 2,876°F (1,580°C), decomposing above that temperature. The compound is insoluble in water, but dissolves in hot concentrated sulfuric acid.
Barium sulfate occurs in nature as the mineral barite, or baryte, which is mined in Canada and Mexico and, in the United States in Arkansas, Missouri, Georgia, and Nevada. It is also prepared synthetically either by treating a solution of a barium salt with sodium sulfate or as a by-product in the manufacture of hydrogen peroxide.
Barium sulfate is used in diagnostic radiology of the digestive system. A suspension of barium sulfate in water is administered either orally or via an enema, which coats the lining of the upper or lower digestive tract. Because barium is a heavy metal, the compound is opaque to x rays, and the shapes of the coated organs can be clearly seen. Although barium in solutions is highly toxic, the sulfate is so insoluble that the suspension is harmless.
Barium sulfate is also used as a filler to products such as rubber, linoleum, oil cloth, plastics, paper, and lithographic inks. The compound is also used in paints and pigments, especially in the manufacture of colored papers and wall papers. Recently, barium sulfate has become popular as a substitute for natural ivory.