Barium hydroxide

Chembox new
Name = Barium hydroxide
Section1 = Chembox Identifiers
CASNo = 17194-00-2
RTECS = CQ9200000
Section2 = Chembox Properties
Formula = Ba(OH)₂
MolarMass = 171.342 g/mol (anhydrous)
189.36 g/mol (monohydrate)
315.46 g/mol (octahydrate)
Appearance = white solid
Solubility = 5.6 g/100 g (octahydrate & anhydrous)
Solvent = other solvents
SolubleOther = low
MeltingPt = 78 °C (octahydrate)
>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
Barium peroxide
OtherCations = Calcium hydroxide
Strontium 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 → Ba(OH)₂·8H₂OIt crystallises as the octahydrate, which converts to the monohydrate upon heating in air. At 100 °C in a vacuum, the monohydrate gives BaO. [(1960). "Gmelins Handbuch der anorganischen Chemie (8. Aufl.)", Weinheim: Verlag Chemie, p. 289.]

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. [VogelQuantitative]

Barium hydroxide is used in organic synthesis as a strong base, for example for the hydrolysis of esters [Meyer, K.; Bloch, H. S. (1945). " [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0637 Naphthoresorcinol] ". "Org. Synth." 25: 73; "Coll. Vol." 3: 637.] and nitriles. [Brown, G. B. (1946). " [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0615 Methylsuccinic acid] ". "Org. Synth." 26: 54; "Coll. Vol." 3: 615.] [Ford, Jared H. (1947). " [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0034 β-Alanine] ". "Org. Synth." 27: 1; "Coll. Vol." 3: 34.] [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.]

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

It is also used in the preparation of cyclopentanone, [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.] diacetone alcohol [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.] and D-Gulonic γ-lactone. [Karabinos, J. V. (1956). " [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0506D-Gulonic γ-lactone] ". "Org. Synth." 36: 38; "Coll. Vol." 4: 506.]

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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.

afety

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

References

External links

* [http://www.jtbaker.com/msds/englishhtml/b0422.htm Material Safety Data Sheet (MSDS)]