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Barium Sulfate

Author: Hans Lohninger

Barium sulfate, BaSO4, is a white crystalline solid that is insoluble in water (solubility product Ksp = 1.110-10). The main commercial source of barium sulfate is the mineral baryte. However baryte is normally highly impure. Thus baryte is reduced by heating with coke to barium sulfide, BaS:

BaSO4 + 4 C BaS + 4 CO

Barium sulfide is soluble in water can be easily converted to the oxide, carbonate, and the halides. In order to produce highly pure barium sulfate, barium sulfide or barium chloride is treated with sulfuric acid:

BaS + H2SO4 BaSO4 + H2S
BaCl2 + H2SO4 BaSO4 + 2 HCl

Barium sulfate belongs to the most insoluble sulfates. Its low solubility results in many important applications, such as contrast agent in x-ray imaging, detection of Ba2+ ions, or the detoxification of barium salt solutions.

Most of the synthetic barium sulfate is used as a white pigment (together with TiO2 or ZnS) for paints. One particular inorganic pigment called lithopone is a combination of barium sulfate and zinc sulfide.

Last Update: 2011-02-21