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Barium hydroxide

Barium hydroxide
CAS number 17194-00-2
RTECS number CQ9200000
Molecular formula Ba(OH)2
Molar mass 171.342 g/mol (anhydrous)
189.36 g/mol (monohydrate)
315.46 g/mol (octahydrate)
Appearance white solid
Melting point

78 °C (octahydrate)
>408 °C (anhydrous)

Boiling point

780 °C

Solubility in water 5.6 g/100 g (octahydrate)
Solubility in other solvents low
Basicity (pKb) -2.02
Crystal structure octahedral
Std enthalpy of
−944.7 kJ/mol
MSDS External MSDS
EU classification Harmful (Xn)
NFPA 704
R-phrases R20/22
S-phrases (S2), S28
Flash point non-flammable
Related Compounds
Other anions Barium oxide
Barium peroxide
Other cations Calcium hydroxide
Strontium hydroxide
Supplementary data page
Structure and
n, εr, etc.
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
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. ^ Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M.J.K.; Denney, R. C.; Thomas, M. J. K. Vogel's Quantitative Chemical Analysis (6th Edn.) New York:Prentice Hall. ISBN 0-582-22628-7.
  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.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Barium_hydroxide". A list of authors is available in Wikipedia.
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