Abstract
A modification is proposed to the lower boundary condition used by Noyes in deriving the rate of a diffusion-controlled reaction by the “sink” model. By assuming that the probability of reaction occurring on a collision is simply related to the critical energy requirements, Arrhenius parameters have been calculated as a function of the latter, or of the steric factor, for a number of values of the other parameters. Measured activation energies of some fast reactions are consistent with these predictions.