On a theory for the passive transport of solute through semipermeable membranes.

It has been shown that thin-film dialysis can be performed in such a way that the limiting rate is the rate of entry of the solute into the membrane from the high-concentration side. The rate of diffusion, therefore, reflects the probability of a molecule entering the pores on the surface and does not depend on the resistance to diffusion offered by the internal structure of the membrane. The good correlation, so generally found, of the order of escape times of given solutes with the order of free diffusion rates is thus explained. The data from stretching experiments with wet cellophane, in which the pore structure is distorted, are also explained.