Barium hydroxide
601816
222676582
2008-06-30T15:48:49Z
Calvero JP
1361741
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{{Chembox new
| Name = Barium hydroxide
| Section1 = {{Chembox Identifiers
| CASNo = 17194-00-2
| RTECS = CQ9200000
}}
| Section2 = {{Chembox Properties
| Formula = Ba(OH)<sub>2</sub>
| MolarMass = 171.342 g/mol (anhydrous)<br />189.36 g/mol (monohydrate)<br />315.46 g/mol (octahydrate)
| Appearance = white solid
| Solubility = 5.6 g/100 g (octahydrate)
| Solvent = other solvents
| SolubleOther = low
| MeltingPt = 78 °C (octahydrate)<br />>408 °C (anhydrous)
| BoilingPt = 780 °C
| pKb = -2.02
}}
| Section3 = {{Chembox Structure
| Coordination =
| CrystalStruct = octahedral
}}
| Section4 = {{Chembox Thermochemistry
| DeltaHf = −944.7 kJ/mol
}}
| Section7 = {{Chembox Hazards
| EUClass = Harmful ('''Xn''')
| NFPA-H = 3
| NFPA-F =
| NFPA-R =
| RPhrases = {{R20/22}}
| SPhrases = {{S2}}, {{S28}}
| FlashPt = non-flammable
}}
| Section8 = {{Chembox Related
| OtherAnions = [[Barium oxide]]<br />[[Barium peroxide]]
| OtherCations = [[Calcium hydroxide]]<br />[[Strontium hydroxide]]
}}
}}
'''Barium hydroxide''' is the [[chemical compound]] with the [[chemical formula|formula]] Ba(OH)<sub>2</sub>. Also known as baryta, it is one of the principal compounds of [[barium]]. The white granular [[Hydrate|monohydrate]] is the usual commercial form.
==Preparation==
Barium hydroxide can be prepared by dissolving [[barium oxide]] (BaO) in water.
:BaO + 9H<sub>2</sub>O → Ba(OH)<sub>2</sub>·8H<sub>2</sub>O
It crystallises as the octahydrate, which converts to the monohydrate upon heating in air. At 100 °C in a vacuum, the monohydrate gives BaO.<ref>(1960). ''Gmelins Handbuch der anorganischen Chemie (8. Aufl.)'', Weinheim: Verlag Chemie, p. 289.</ref>
==Uses==
Barium hydroxide is used in [[analytical chemistry]] for the titration of [[weak acid]]s, particularly [[organic acid]]s. 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]] [[error]]s due to the presence of weakly basic [[carbonate]] ions.<ref>{{VogelQuantitative}}</ref>
Barium hydroxide is used in organic synthesis as a strong base, for example for the hydrolysis of esters<ref>Meyer, K.; Bloch, H. S. (1945). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0637 Naphthoresorcinol]". ''[[Org. Synth.]]'' '''25''': 73; ''Coll. Vol.'' '''3''': 637.</ref> and nitriles.<ref>Brown, G. B. (1946). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0615 Methylsuccinic acid]". ''[[Org. Synth.]]'' '''26''': 54; ''Coll. Vol.'' '''3''': 615.</ref><ref>Ford, Jared H. (1947). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0034 β-Alanine]". ''[[Org. Synth.]]'' '''27''': 1; ''Coll. Vol.'' '''3''': 34.</ref><ref>Anslow, W. K.; King, H.; Orten, J. M.; Hill, R. M. (1925). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0298 Glycine]". ''[[Org. Synth.]]'' '''4''': 31; ''Coll. Vol.'' '''1''': 298.</ref>
:[[Image:Barium hydroxide-catalyzed 2-carboxy-1,3-dihydroxynaphthalene preparation.svg|418px]]
:[[Image:Barium hydroxide-catalyzed methylsuccinic acid preparation.svg|346px]]
It has been used to hydrolyse one of the two equivalent ester groups in dimethyl hendecanedioate.<ref>Durham, L. J.; McLeod, D. J.; Cason, J. (1958). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0635 Methyl hydrogen hendecanedioate]". ''[[Org. Synth.]]'' '''38''':55; ''Coll. Vol.'' '''4''':635.</ref>
It is also used in the preparation of [[cyclopentanone]],<ref>Thorpe, J. F.; Kon, G. A. R. (1925). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0192 Cyclopentanone]". ''[[Org. Synth.]]'' '''5''': 37; ''Coll. Vol.'' '''1''': 192.</ref> [[diacetone alcohol]]<ref>Conant, J. B.; Tuttle, Niel. (1921). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0199 Diacetone alcohol]". ''[[Org. Synth.]]'' '''1''': 45; ''Coll. Vol.'' '''1''': 199.</ref> and [[Gulonic acid|<small>D</small>-Gulonic γ-lactone]].<ref>Karabinos, J. V. (1956). "[http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0506<small>D</small>-Gulonic γ-lactone]". ''[[Org. Synth.]]'' '''36''': 38; ''Coll. Vol.'' '''4''': 506.</ref>
<!-- :[[Image:Cyclopentanone prepn.png|500px]] -->
:[[Image:Barium hydroxide-catalyzed diacetone alcohol preparation.svg|275px]]
Barium hydroxide is used in a demonstration of [[endothermic reaction]]s 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.
==References==
<references />
==External links==
*[http://www.jtbaker.com/msds/englishhtml/b0422.htm Material Safety Data Sheet (MSDS)]
[[Category:Barium compounds]]
[[Category:Hydroxides]]
[[ar:هيدروكسيد باريوم]]
[[cs:Hydroxid barnatý]]
[[de:Bariumhydroxid]]
[[et:Baariumhüdroksiid]]
[[fr:Hydroxyde de baryum]]
[[it:Idrossido di bario]]
[[lv:Bārija hidroksīds]]
[[ja:水酸化バリウム]]
[[pl:Wodorotlenek baru]]
[[pt:Hidróxido de bário]]
[[ru:Гидроксид бария]]
[[zh:氢氧化钡]]