The bis(malonato)diaquochromate(III) ion, $Cr(C_3H_2O_4)_2^-$ in acidic solution hydrolyzes to give $Cr(C_3H_2O_4)^{+}.$ This reaction is catalyzed by ferric ion and the rate law for this cation catalyzed-aquation in a $HClO_4/NaClO_4$ medium, $I = 1.00 M, is-d[Cr(C_3H_2O_4)_2^-]/dt = ({kappa}_1[Fe^{3+}] + {kappa}_2[H^+])[Cr(C_3H_2O_4)_2^-]$ where ${kappa}_1(25^{circ}C) = 4.72×10^{-5} M^{-1}sec^{-1} ({Delta}H^{ eq} = 22.5 Kcal/mol, {Delta}S^{ eq} = - 2.58 eu) and {kappa}_2(25^{circ}C) = 4.75{ imes}10^{-5} M^{-1}sec^{-1} ({Delta}H^{ eq} = 21.2 Kcal/mol, {Delta}S^{ eq} = - 7.13 eu).$ Rapid preequilibrium association of basic Cr-bound oxygen with $Fe^{3+},$ followed by rate-determining ring opening, is proposed to account for the ${kappa}_1,$ hydrolysis pathway.