Caesium perchlorate

CsClO₄ is the second least soluble of the alkali metal perchlorates (after Fr, followed by Rb, K, Li, and Na), a property which may be used for separatory purposes and even for gravimetric analysis. This low solubility played an important role in the characterization of francium as an alkali metal, as francium perchlorate coprecipitates with caesium perchlorate.

When heated, CsClO₄ decomposes to caesium chloride above 250 °C. Like all perchlorates, it is a strong oxidant and may react violently with reducing agents and organic materials, especially at elevated temperatures.