Barium hydroxide is an inorganic substance with a chemical formula of Ba(OH)₂, a colorless transparent crystal or white powder. Hydrate can lose 7 molecules of crystal water in the sulfuric acid dryer, and lose all crystal water at about 78°C. It is soluble in water and methanol, slightly soluble in ethanol, and almost insoluble in acetone. If carbon dioxide is rapidly absorbed from the air and turned into carbonate, it cannot be completely dissolved in water. The relative density is 2.188, the melting point is 78°C (octahydrate, in the case of pure barium hydroxide is >408°C), the refractive index is 1.471, highly toxic, and highly corrosive. It is used for the determination of carbon dioxide in the air, the quantification of chlorophyll, the refining of sugar and animal and vegetable oils, boiler water cleaners, pesticides, and rubber industry.