Barium hydroxide
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| Barium hydroxide | |
|---|---|
| General | |
| 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 |
| CAS number | [17194-00-2] (anhydrous) [22326-55-2] (monohydrate) [12230-71-6] (octahydrate) |
| Properties | |
| Density (solid) | 2.2 g/cm3 (anhydrous) 3.74 g/cm3 (monohydrate) |
| Solubility in water | 5.6g/100g of water |
| Melting point | 78 °C (octahydrate) >408 °C (anhydrous) |
| Boiling point | 780 °C |
| Basicity (pKb) | 0 |
| Structure | |
| Coordination geometry |
? |
| Crystal structure | ? |
| Thermodynamic data | |
| Std enthalpy change of formation, ΔfH |
−944.7 kJ/mol |
| Standard molar entropy, S |
100±6 J.K−1.mol−1 |
| Heat of fusion | 93.3805 (anhydrous) |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Harmful (Xn) |
| NFPA 704 |
0
3
0
|
| R-phrases | R20/22 |
| S-phrases | S2, S28 |
| Flash point | non-flammable |
| RTECS number | CQ9200000 |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| Related compounds | |
| Other anions | Barium oxide Barium peroxide |
| Other cations | Calcium hydroxide Strontium hydroxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
|
Barium hydroxide (Ba(OH)2), also known as baryta, is a basic chemical compound with a white granular or powdery appearance. The monohydrate is the usual commercial form.
Contents |
[edit] Preparation
Barium hydroxide may be prepared by dissolving barium oxide (BaO) in water. It crystallises as the octahydrate, which may be converted to the monohydrate by heating in air or completely dehydrated at 100 °C in a vacuum.
[edit] 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.
Barium hydroxide is used in organic synthesis as a strong base, for example for the hydrolysis of esters and nitriles.
It is also used to clean up acid spills and make them significantly less harmful.
It has been used to hydrolyse one of the two equivalent ester groups in dimethyl hendecanedioate.
It is also used in the preparation of cyclopentanone, diacetone alcohol and D-Gulonic γ-lactone.
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.
Under the name baryta it is used in homeopathic remedies.
[edit] Safety
Barium hydroxide presents the same hazards as other strong bases and as other water-soluble barium compounds: it is corrosive and toxic.
[edit] References
- ↑ Gmelins Handbuch der anorganischen Chemie (8. Aufl.), Weinheim:Verlag Chemie, 1960, p. 289.
- ↑ 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.
- ↑ Meyer, Karl; Bloch, Henry S. (1945). "Naphthoresorcinol". Org. Synth. 25:73; Coll. Vol. 3:637.
- ↑ Brown, George Bosworth (1946). "Methylsuccinic acid". Org. Synth. 26:54; Coll. Vol. 3:615.
- ↑ Ford, Jared H. (1947). "β-Alanine". Org. Synth. 27:1; Coll. Vol. 3:34.
- ↑ Anslow, W. K.; King, Harold; Orten, James M.; Hill, Robert M. (1925). "Glycine". Org. Synth. 4:31; Coll. Vol. 1:298.
- ↑ Durham, Lois J.; McLeod, Donald J.; Cason, James (1958). "Methyl hydrogen hendecanedioate". Org. Synth. 38:55; Coll. Vol. 4:635.
- ↑ Thorpe, J. F.; Kon, G. A. R. (1925). "Cyclopentanone". Org. Synth. 5:37; Coll. Vol. 1:192.
- ↑ Conant, J. B.; Tuttle, Niel. (1921). "Diacetone alcohol". Org. Synth. 1:45; Coll. Vol. 1:199.
- ↑ Karabinos, J. V. (1956). "D-Gulonic γ-lactone". Org. Synth. 36:38; Coll. Vol. 4:506.
