Barium Hydroxide Monohydrate (CAS: 22326-55-2)

Barium hydroxide is the chemical compound with the formula Ba(OH)2. Also known as baryta, or baryta-water, it is one of the principal compounds ofbarium. The white granular monohydrate is the usual commercial form.

Preparation

Barium hydroxide can be prepared by dissolving barium oxide (BaO) in water:

BaO + 9 H2O → Ba(OH)2•8H2O

It crystallises as the octahydrate, which converts to the monohydrate upon heating in air. At 100 °C in a vacuum, the monohydrate gives BaO.

Uses

Barium hydroxide is used in analytical chemistry for the titration of weak acids, particularly organic acids. Its clear aqueous solution is guaranteed to be free of carbonate, unlike those of sodium hydroxide and potassium hydroxide, as barium carbonate is insoluble in water. This allows the use of indicators such as phenolphthalein or thymolphthalein (with alkaline colour changes) without the risk of titration errors due to the presence ofcarbonate ions, which are much less basic.

Barium hydroxide is used in organic synthesis as a strong base, for example for the hydrolysis of esters and nitriles.

It has been used to hydrolyse one of the two equivalent ester groups in dimethyl hendecanedioate.

Barium hydroxide is used, as well, in the decarboxylation of amino acids liberating barium carbonate in the process. 

It is also used in the preparation of cyclopentanone,[9] diacetone alcohol and D-Gulonic γ-lactone.

Miscellaneous applications

•     It is also used to clean up acid spills.

•     It is also used to neutralize sulfuric acid solutions. Use of Ba(OH)2 is particularly beneficial in complete removal sulphate ions because the BaSO4form .

Barium hydroxide decomposes to barium oxide when heated to 800 °C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkaline, undergoes neutralization reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double replacement reaction when a barium hydroxide aqueous solution is mixed with many solutions of other metal salts.

Reactions of barium hydroxide with ammonium salts are strongly endothermic. The reaction of barium hydroxide octahydrate with ammonium chloride or ammonium thiocyanate is often used as a classroom chemistry demonstration, producing temperatures cold enough to freeze water and enough water to dissolve the resulting mixture.