A violet or ruby-red crystalline solid, K2SO4.Cr2(SO4)3.24H2O, that is soluble in water and insoluble in ethanol; cubic or octahedral; r.d. 1.826; m.p. 89°C; loses 10H2O at 100°C, 12H2O at 400°C. Six water molecules surround each of the chromium(III) ions and the remaining ones are hydrogen bonded to the sulphate ions. Like all alums, the compound may be prepared by mixing equimolar quantities of the constituent sulphates. See alums.