Abstract: The silver rotating disc electrode was used to study the redox reaction: Fe(Ⅲ)-complex + Ag° + X^-→ Fe(Ⅱ)-complex + AgXThe redox reaction could be followed by galvanostatic reduction of AgX. The galvanostatic reduction time (τ) can easily be determined because of the jump at the end of the reduction of the silver halide. The kinetics of the reaction between Fe(Ⅲ)-complex and silver electrode in the presence of halide would be studied varing oxidation time, the concentration of the reactants and the rotation frequency of silver disc electrode.The redox reaction is a diffusion controlled reaction and is first order with respect to the Fe(Ⅲ)-complex and halide respectively. The initial rate of formation of silver bromide decreases with increasing pH.The diffusion coefficient of Fe(Ⅲ)EDTA was determined from the dependence of the limiting current on both the concentration of Fe(Ⅲ)-complex and square root of the rotation frequency of silver disc electrode.

Key words: Fe(Ⅲ)EDTA, silver halide, photographic bleaching, Galvanostat