Caesium hydroxide


Caesium hydroxide is a strong base (pKa= 15.76), much like the other alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. In fact, caesium hydroxide is corrosive enough to dissolve through glass quickly.[7]

Caesium hydroxide
Cesium hydroxide monohydrate.jpg
Other names
Cesium hydrate
  • 21351-79-1 checkY
3D model (JSmol)
  • Interactive image
  • CHEBI:33988 checkY
  • 56494 checkY
ECHA InfoCard 100.040.298 Edit this at Wikidata
EC Number
  • 244-344-1
  • 62750
RTECS number
  • FK9800000
  • 458ZFZ6235
UN number 2682
  • DTXSID7066699 Edit this at Wikidata
  • InChI=1S/Cs.H2O/h;1H2/q+1;/p-1 checkY
  • InChI=1/Cs.H2O/h;1H2/q+1;/p-1
  • [OH-].[Cs+]
Molar mass 149.912 g/mol
Appearance Whitish-yellow deliquescent crystals
Density 3.675 g/cm3
Melting point 272 °C (522 °F; 545 K)[3]
300 g/100 mL at 30 °C
Solubility Soluble in ethanol[1]
Acidity (pKa) 15.76 [2]
69.9 J·mol−1·K−1[4]
104.2 J·K−1·mol−1
−416.2 kJ·mol−1
GHS labelling:
GHS05: CorrosiveGHS08: Health hazard
H302, H314, H361, H373
P201, P202, P260, P264, P270, P280, P281, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P314, P321, P330, P363, P405, P501
NFPA 704 (fire diamond)
Flash point Not flammable
Lethal dose or concentration (LD, LC):
570 mg/kg (oral, rat)[6]
NIOSH (US health exposure limits):
PEL (Permissible)
REL (Recommended)
TWA 2 mg/m3[5]
IDLH (Immediate danger)
Safety data sheet (SDS) ICSC 1592
Related compounds
Other anions
Cæsium oxide
Cæsium fluoride
Other cations
Lithium hydroxide
Sodium hydroxide
Potassium hydroxide
Rubidium hydroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Due to its high reactivity, caesium hydroxide is extremely hygroscopic. Laboratory caesium hydroxide is typically a hydrate.

It is an anisotropic etchant of silicon, exposing octahedral planes. This technique can form pyramids and regularly shaped etch pits for uses such as Microelectromechanical systems. It is known to have a higher selectivity to etch highly p-doped silicon than the more commonly used potassium hydroxide.

This compound is not commonly used in experiments due to the high extraction cost of caesium and its reactive behaviour. It acts in similar fashion to the compounds rubidium hydroxide and potassium hydroxide, although more reactive.


  1. ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, pp. 4–51, ISBN 0-8493-0594-2
  2. ^ "Sortierte Liste: pKb-Werte, nach Ordnungszahl sortiert. – Das Periodensystem online".
  3. ^ "ICSC 1592 - Cesium Hydroxide".
  4. ^ Lide, David R. (1998), Handbook of Chemistry and Physics (87 ed.), Boca Raton, Florida: CRC Press, pp. 5–14, ISBN 0-8493-0594-2
  5. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0111". National Institute for Occupational Safety and Health (NIOSH).
  6. ^ Chambers, Michael. "ChemIDplus - 21351-79-1 - HUCVOHYBFXVBRW-UHFFFAOYSA-M - Cesium hydroxide - Similar structures search, synonyms, formulas, resource links, and other chemical information".
  7. ^ "Cesium | Cs (Element) - PubChem". Retrieved 2022-04-18.

External linksEdit

  • NIOSH Pocket Guide to Chemical Hazards
  • NIST Standard Reference Database