Barium hydroxide

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

Preparation
Barium hydroxide can be prepared by dissolving barium oxide (BaO) in water.
 * BaO + 9H2O &rarr; 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 of weakly basic carbonate ions.

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


 * [[Image:2-carboxy-1,3-dihydroxynaphthalene prepn.png|400px]]


 * [[Image:Methylsuccinic acid prepn.png|500px]]

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

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


 * [[Image:Diacetone alcohol prepn.png|500px]]

Barium hydroxide is used in a demonstration of endothermic reactions since, when mixed with an ammonium salt, the reaction becomes cold as heat is absorbed from the surroundings.

Miscellaneous applications

 * Under the name baryta it is used in homeopathic remedies.
 * It is also used to clean up acid spills.
 * Also under the name of baryta it is used in the production of photographic paper for printing.

Safety
Barium hydroxide presents the same hazards as other strong bases and as other water-soluble barium compounds: it is corrosive and toxic.