Barium hydroxide is a basic chemical compound, with the chemical formula Ba(OH)₂. This compound is also called barium dihydroxide and has a molar mass of 171.34 g, a melting point of 78^o C, and a white granular or powdery appearance. The monohydrate is the common form, but it also is used in an octahydrate form.

Barium hydroxide may be prepared by dissolving barium oxide (BaO) in water.

This compound in used in the production of plastics, resins, soap, and petroleum additives. It is toxic and corrosive. Protective gear and ventilation is required for safe use.

Under the name Baryta it is used in homeopathic remedies.

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