Appraisal of the determination of molecular size and mass by membrane diffusion

Abstract

The diffusion of dissolved substances through porous membranes, the pores of which approach molecular or macro-molecular dimensions, may provide a simple and sensitive means of determining molecular size or mass and of detecting changes in molecular, especially macro-molecular, size that have been brought about by changing the solvent composition or temperature. The value of the method depends largely on the ability of such membranes to hinder to varying degrees the diffusion of different solute species having similar molecular sizes or masses. An explicit mathematical formulation of the problem is undertaken with a view to assessing, in the light of experimental results published by other workers, the potential value of the method.