RELATIONSHIP OF SELF-DIFFUSION COEFFICIENTS TO MEMBRANE-POTENTIAL AND SALT FLUX ACROSS AN ION-EXCHANGE MEMBRANE

The self-diffusion coefficients of Ba2+ and Cl- within a cation-exchange membrane were measured over a wide range of external solution concentrations (10-3-1 M) of BaCL2. Membrane potential and salt flux were calculated from them by use of the Nernst-Planck equation and the calculated values were compared with the experimental ones. The calculated membrane potential could reproduce the deviation of the observed one from the ideal Nernst potential at high salt concentration. The tendency for the variation of the salt flux with concentrations was explained well but the observed salt flux was less than the calculated one by 20-30%. This difference was attributed to osmotic water flow occurring across the membrane. © 1979 American Chemical Society.