Abstract The kinetics of oxidation of S2O32- by K3[Fe(C2O4)3].3H2O has been investigated in aqueous acid medium at λmax = 420nm, T = 27.0 ± 1.0 °C, I = 0.4 moldm-3 (NaCl) and [H+] = 0.02 moldm-3 (HCl). The reaction is first order with respect to oxidant and reductant concentrations and obeyed the general rate law:
where a = 0.0402 s-1 and b = 1.26 dm6 mol2 s-1. Added ions affected the rate of the reaction. The reaction was acid dependent and was unaffected by changes in ionic strength of the reaction medium. A plausible mechanism is proposed for the reaction.