A solution of the diffusion equation for a reversible redox electrochemical reaction in the presence of only one species (the reactant) and in the absence of products at the initiation of the reaction for a square wave perturbing potential is presented. The solution furnishes the concentration profiles for reactant and product and their dependence on the time elapsed from the initiation of the halfcycle t′, on the frequency of the periodic potential, on the number of cycles, N, and on the symmetry of the signal. In addition, the dependences of the current on t′ and N, and that of the charge density on N, were obtained. Conclusions from the theory are experimentally verified by using the reversible [Fe(CN)₆]⁴−/[Fe(CN)₆]³− redox couple on platinum as a test reaction.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas