Caesium hydroxide

  • 21351-79-1 (anhydrous)
  • 35103-79-8 (monohydrate)

White to yellowish crystals


3.68 g · cm -3

272.3 ° C

Soluble in water


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Cesium hydroxide, CsOH, is the hydroxide of cesium. It is one of the strongest bases in aqueous solution.

Production and representation

Cesium hydroxide formed in addition to hydrogen at the extremely violent reaction ( explosion) of water with cesium:

Another synthesis possibility is given by the reaction of cesium oxide with water.

During the mixing violent reactions may occur.


Aqueous solutions of cesium are basic solutions. Cesium and its aqueous solutions etch glass.


The Caesiumlauge is a high quality base for the catalytic alkynylation of aldehydes and ketones.

Cesium hydroxide is used as an electrolyte in galvanic cells.

Pictures of Caesium hydroxide