Transport studies with model membrane

The most recent theory for salt concentration dependence of biionic potential, developed by Ikeda and his colleagues on the basis of thermodynamics of irreversible processes, has been compared with that of Nozaki et al. to get a relationship for the calculation of theoretical values of biionic potential. The latter are in good agreement with the experimental data gathered for the parchment‐supported manganese ferricyanide membrane in contact with various alkali chloride solutions. The conclusion of selectivity sequence of group Ia cations, reached on the basis of measurements of biionic potentials, is consistent not only with the findings of thermodynamic effective fixed charge density, evaluated by utilizing membrane potential equations provided by nonequilibrium thermodynamics, but also with the data on activation parameters calculated by making use of the theory of absolute reaction rates. The values of impedance Z, membrane resistance Rm, and membrane capacitance Cm have also been evaluated on the basis of a simple equivalent circuit model. Impedance values follow the theoretical predictions at high frequencies, but at lower frequencies there is a marked deviation from the ideal behavior probably due to roughness and nonhomogeneity of the membrane used in this investigation.