Rhodium(III) perchlorate refers to the inorganic compound with the formula Rh(H2O)6(ClO4)3. It is a hygroscopic yellow solid. It is the perchlorate salt of the tricationic aquo complex [Rh(H<sub>2</sub>O)<sub>6</sub>]3+. The compound is prepared by treating hydrated rhodium(III) chloride and perchloric acid at elevated temperatures:[1]
[Rh(H<sub>2</sub>O)<sub>6</sub>]Cl3 + 3 HClO4 → [Rh(H<sub>2</sub>O)<sub>6</sub>](ClO4)3 + 3 HCl
The reaction of rhodium(III) hydroxide with concentrated perchloric acid also produce rhodium(III) perchlorate.[2]
Rh(OH)3 + 3 HClO4 → Rh(ClO4)3 + 3 H2O