Diffusion across the oil/water interface

Abstract

Resistances to the diffusion of a third component across an interface separating two liquids may possibly arise from a slow process of re-solvation of the solute, or from a mechanical barrier associated with a film of surface-active additive. With an unstirred diffusion cell of accuracy great enough to detect an interfacial resistance of 1000 s cm -1 we have shown that neither the clean interface nor various monolayers offer any resistance to the passage of acetic acid or diethylamine between water and oils; polymolecular films, however, may give rise to considerable resistances. All the systems we have studied show spontaneous emulsification near the interface; the effect of this has been analyzed quantitatively, and appropriate corrections made to the experimental transfer results. The rate of transfer of solute across a stationary interface is unaffected by the spontaneous emulsion.