Caesium acetate

Caesium acetate or cesium acetate is an ionic caesium compound with the molecular formula CH₃CO₂Cs often used in organic synthesis especially in Perkin synthesis; formation of unsaturated cinnamic-type acids by the condensation of aromatic aldehydes with fatty acids.

It may be formed by the reaction of caesium hydroxide or caesium carbonate with acetic acid. Caesium acetate holds the record for the highest density of an aqueous solution (1010 g CsOAc per 100 mL H₂O. i.e. 91% w/w). This is not so much due its molar solubility (only 5.26 M) but more due to its high molar weight. Caesium acetate is occasionally used instead of caesium formate in petroleum drilling fluids.