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| Caesium hydroxide | |
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| Identifiers | |
| CAS number | [21351-79-1] |
| RTECS number | FK9800000 |
| Properties | |
| Molecular formula | CsOH |
| Molar mass | 149.91 g/mol |
| Appearance | white solid, deliquescent |
| Density | 3.675 g/cm3, solid |
| Melting point |
272.3°C 342°C? |
| Solubility in water | 395.5 g/100 ml (15°C) |
| Solubility in ethanol | Soluble |
| Basicity (pKb) | -1.76 |
| Thermochemistry | |
| Std enthalpy of formation ΔfH |
−416.73 kJ/mol |
| Standard molar entropy S |
98.74 J.K−1.mol−1 |
| Hazards | |
| EU classification | not listed |
| Flash point | non flammable |
| Related compounds | |
| Other anions | Caesium oxide |
| Other cations | Potassium hydroxide Rubidium hydroxide |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Caesium hydroxide (CsOH) is a chemical compound consisting of an atom of caesium and a hydroxide group (also known as hydroxyl). It is a powerful base, much like other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. Caesium hydroxide can corrode glass.
Due to its high reactivity, caesium hydroxide is extremely hygroscopic. Laboratory caesium hydoxide is typically a hydrate.
It is an anisotropic etchant of silicon, exposing octahedral planes. This technique can create pyramids and regularly-shaped etch pits for uses such as MEMS. It is known to have a higher selectivity to etch highly p-doped silicon than the more commonly used potassium hydroxide.
However, this compound is not usually used in experiments as the extraction of caesium is very expensive and the fact that it behaves very much like rubidium hydroxide and potassium hydroxide but reacts chemically stronger than they do.
Caesium hydroxide can be obtained by the following chemical reaction:
- 2 Cs + 2 H2O → 2 CsOH + H2
The above reaction occurs explosively. Caesium metal will react with ice above -116 °C.
References
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