Barium hydroxide

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Barium hydroxide
Barium hydroxide octahydrate
Identifiers
CAS number17194-00-2 YesY
22326-55-2 (monohydrate)
12230-71-6 (octahydrate)
PubChem28387
ChemSpider26408 YesY
ChEBICHEBI:32592 YesY
RTECS numberCQ9200000
Jmol-3D imagesImage 1
Properties
Molecular formulaBa(OH)2
Molar mass171.34 g/mol (anhydrous)
189.39 g/mol (monohydrate)
315.46 g/mol (octahydrate)
Appearancewhite solid
Density3.743 g/cm3 (monohydrate)
2.18 g/cm3 (octahydrate, 16 °C)
Melting point78 °C (octahydrate)
300°C (monohydrate)
407 °C (anhydrous)
Boiling point780 °C
Solubility in wateroctahydrate:
1.67 g/100 mL (0 °C)
3.89 g/100 mL (20 °C)
11.7 g/100 mL (50 °C)
20.94 g/100 mL (60 °C)
101.4 g/100 mL (100 °C)
Solubility in other solventslow
Basicity (pKb)-2.02
Refractive index (nD)1.50 (octahydrate)
Structure
Crystal structureoctahedral
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−944.7 kJ/mol
Hazards
MSDSExternal MSDS
EU Index056-002-00-7
EU classificationHarmful (Xn)
R-phrasesR20/22
S-phrases(S2), S28
NFPA 704
Flash pointNon-flammable
Related compounds
Other anionsBarium oxide
Barium peroxide
Other cationsCalcium hydroxide
Strontium hydroxide
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral dataUV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references
 
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Barium hydroxide
Barium hydroxide octahydrate
Identifiers
CAS number17194-00-2 YesY
22326-55-2 (monohydrate)
12230-71-6 (octahydrate)
PubChem28387
ChemSpider26408 YesY
ChEBICHEBI:32592 YesY
RTECS numberCQ9200000
Jmol-3D imagesImage 1
Properties
Molecular formulaBa(OH)2
Molar mass171.34 g/mol (anhydrous)
189.39 g/mol (monohydrate)
315.46 g/mol (octahydrate)
Appearancewhite solid
Density3.743 g/cm3 (monohydrate)
2.18 g/cm3 (octahydrate, 16 °C)
Melting point78 °C (octahydrate)
300°C (monohydrate)
407 °C (anhydrous)
Boiling point780 °C
Solubility in wateroctahydrate:
1.67 g/100 mL (0 °C)
3.89 g/100 mL (20 °C)
11.7 g/100 mL (50 °C)
20.94 g/100 mL (60 °C)
101.4 g/100 mL (100 °C)
Solubility in other solventslow
Basicity (pKb)-2.02
Refractive index (nD)1.50 (octahydrate)
Structure
Crystal structureoctahedral
Thermochemistry
Std enthalpy of
formation
ΔfHo298
−944.7 kJ/mol
Hazards
MSDSExternal MSDS
EU Index056-002-00-7
EU classificationHarmful (Xn)
R-phrasesR20/22
S-phrases(S2), S28
NFPA 704
Flash pointNon-flammable
Related compounds
Other anionsBarium oxide
Barium peroxide
Other cationsCalcium hydroxide
Strontium hydroxide
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral dataUV, IR, NMR, MS
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

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

Preparation[edit]

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

BaO + 9 H2O → 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]

Uses[edit]

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 carbonate ions, which are much less basic.[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]

Barium hydroxide-catalyzed 2-carboxy-1,3-dihydroxynaphthalene preparation.svg
Barium hydroxide-catalyzed methylsuccinic acid preparation.svg

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

Barium hydroxide is used, as well, in the decarboxylation of amino acids liberating barium carbonate in the process. [8]

It is also used in the preparation of cyclopentanone,[9] diacetone alcohol[10] and D-Gulonic γ-lactone.[11]

Barium hydroxide-catalyzed diacetone alcohol preparation.svg

Miscellaneous applications[edit]

Reactions[edit]

Barium hydroxide decomposes to barium oxide when heated to 800 °C. Reaction with carbon dioxide gives barium carbonate. Its aqueous solution, being highly alkaline, undergoes neutralization reactions with acids. Thus, it forms barium sulfate and barium phosphate with sulfuric and phosphoric acids, respectively. Reaction with hydrogen sulfide produces barium sulfide. Precipitation of many insoluble, or less soluble barium salts, may result from double replacement reaction when a barium hydroxide aqueous solution is mixed with many solutions of other metal salts. [12]

Reactions of barium hydroxide with ammonium salts are strongly endothermic. The reaction of barium hydroxide octahydrate with ammonium chloride[13] [14] or[15] ammonium thiocyanate[15][16] is often used as a classroom chemistry demonstration, producing temperatures cold enough to freeze water and enough water to dissolve the resulting mixture.

Safety[edit]

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

See also[edit]

References[edit]

  1. ^ (1960). Gmelins Handbuch der anorganischen Chemie (8. Aufl.), Weinheim: Verlag Chemie, p. 289.
  2. ^ Mendham, J.; Denney, R. C.; Barnes, J. D.; Thomas, M. J. K. (2000), Vogel's Quantitative Chemical Analysis (6th ed.), 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. ^ [1]
  9. ^ Thorpe, J. F.; Kon, G. A. R. (1925). "Cyclopentanone". Org. Synth. 5: 37; Coll. Vol. 1: 192.
  10. ^ Conant, J. B.; Tuttle, Niel. (1921). "Diacetone alcohol". Org. Synth. 1: 45; Coll. Vol. 1: 199.
  11. ^ Karabinos, J. V. (1956). "D-Gulonic γ-lactone". Org. Synth. 36: 38; Coll. Vol. 4: 506.
  12. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  13. ^ "Endothermic Reactions of Hydrated Barium Hydroxide and Ammonium Chloride". UC San Diego. Retrieved 2 April 2014. 
  14. ^ Endothermic Solid-Solid Reactions
  15. ^ a b Camp, Eric. "Endothermic Reaction". Univertist of Washington. Retrieved 2 April 2014. 
  16. ^ "Endothermic solid-solid reactions". Classic Chemistry Demonstrations. The Royal Society of Chemistry. Retrieved 2 April 2014. 

External links[edit]