Also used in the preparation of cyclopentanone,  diacetone alcohol  and D-gulonic acid γ-lactone.
Barium hydroxide decomposes to barium oxide when heated to 800 °C. Reacts with carbon dioxide to form barium carbonate. Its aqueous solution is strongly alkaline, and because it is a strong base, neutralization reaction occurs with acid. It is especially useful for reactions requiring the titration of weak organic acids. Thus, it forms barium sulfate and barium phosphate with sulfuric acid and phosphoric acid, respectively. Reacts with hydrogen sulfide to form barium sulfide. When barium hydroxide aqueous solution is mixed with many other metal salt solutions, many insoluble or poorly soluble barium salts may precipitate. Barium hydroxide has the same hazards, such as skin irritation and burns, and eye damage, as other strong bases and other water-soluble barium compounds: it is corrosive and toxic.
The reaction of barium hydroxide with ammonium salts is strongly endothermic. The reaction of barium hydroxide octahydrate with ammonium chloride  or ammonium thiocyanate is often used as a classroom chemistry demonstration, producing temperatures sufficient for water to freeze and have Sufficient water was used to dissolve the resulting product mixture.
The barium hydroxide-initiated liquid-gas polycondensation of PPD and HQ in the temperature range of 15–95°C showed that [η] increased with increasing reaction temperature, with the unfractionated yield reaching a maximum at about 45°C. The results are compared with the temperature dependence of the base-catalyzed liquid-liquid polycondensation of HQ with PPD.
The molecular formula of barium hydroxide is Ba(OH)2, and its molecular weight is 121.6324 g/mol. It occurs as anhydrous, prismatic colorless crystals which are very deliquescent. Barium hydroxide can be prepared by dissolving barium oxide (BaO) in water:
Barium sulfate (BaSO4), made by reacting barium hydroxide and other barium sources with sulfuric acid, has a long history as a translucent white pigment. According to the preparation conditions, especially the supersaturation of its barium source, barium sulfate can form various shapes and structures such as plane, star or sphere, and the internal pore size also changes accordingly.