Barium hydroxide

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Template:Chembox E numberTemplate:Chembox SolubilityInWater
Barium hydroxide
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RTECS number CQ9200000
Molar mass 171.342 g/mol (anhydrous)
189.36 g/mol (monohydrate)
315.46 g/mol (octahydrate)
Appearance white solid
Melting point
Boiling point
Solubility in other solvents low
Basicity (pKb) -2.02
Crystal structure octahedral
Std enthalpy of
−944.7 kJ/mol
EU classification {{{value}}}
R-phrases R20/22
S-phrases (S2), S28
Flash point {{{value}}}
Related compounds
Other anions {{{value}}}
Other cations {{{value}}}
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

Infobox disclaimer and references

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.


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

BaO + 9H2O → 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.[1]


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.[2]

Barium hydroxide is used in organic synthesis as a strong base, for example for the hydrolysis of esters[3] and nitriles.[4][5][6]


It has been used to hydrolyse one of the two equivalent ester groups in dimethyl hendecanedioate.[7]

It is also used in the preparation of cyclopentanone,[8] diacetone alcohol[9] and D-Gulonic γ-lactone.[10]


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.


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


  1. Gmelins Handbuch der anorganischen Chemie (8. Aufl.), Weinheim:Verlag Chemie, 1960, p. 289.
  2. Template:VogelQuantitative
  3. Meyer, K.; Bloch, H. S. (1945). "Naphthoresorcinol". Org. Synth. 25:73; Coll. Vol. 3:637.
  4. Brown, G. B. (1946). "Methylsuccinic acid". Org. Synth. 26:54; Coll. Vol. 3:615.
  5. Ford, Jared H. (1947). "β-Alanine". Org. Synth. 27:1; Coll. Vol. 3:34.
  6. Anslow, W. K.; King, H.; Orten, J. M.; Hill, R. M. (1925). "Glycine". Org. Synth. 4:31; Coll. Vol. 1:298.
  7. Durham, L. J.; McLeod, D. J.; Cason, J. (1958). "Methyl hydrogen hendecanedioate". Org. Synth. 38:55; Coll. Vol. 4:635.
  8. Thorpe, J. F.; Kon, G. A. R. (1925). "Cyclopentanone". Org. Synth. 5:37; Coll. Vol. 1:192.
  9. Conant, J. B.; Tuttle, Niel. (1921). "Diacetone alcohol". Org. Synth. 1:45; Coll. Vol. 1:199.
  10. Karabinos, J. V. (1956). "D-Gulonic γ-lactone". Org. Synth. 36:38; Coll. Vol. 4:506.

External links

ar:هيدروكسيد باريوم cs:Hydroxid barnatý de:Bariumhydroxid et:Baariumhüdroksiid it:Idrossido di bario lv:Bārija hidroksīds