A theoretical equation corresponding to square wave voltammetry for a pseudo-first-order catalytic mechanism at spherical electrodes of any radius is presented. The effects of the electrode sphericity are analysed. Methods for calculating equilibrium and rate constants of the chemical reaction are proposed and applied to the system Fe(III)-triethylamine / Fe(II)-trietylamine in the presence of hydroxylamine. The advantages of this equation for analytical purposes are laid out.