Multi-Ionic Potential and Membrane Permeability Matrix. II. Na+–Ca2+ Bi-Ionic System with a Cation-Exchange Membrane and Effects of Cl− on Cation Transport

Transport characteristics of Na+–Ca2+ bi-ionic system with a highly selective cation-exchange membrane were investigated on the basis of nonequilibrium thermodynamic theory. As a principal transport parameter, the membrane permeability matrix or membrane conductance matrix can be estimated from the membrane potential, conductance, and ion flux data. Significances of diffusional and electroconductive processes of ion transport across membrane were systematically discussed in terms of these matrix elements. Partial contributions of inter-cationic (Na+–Na+, Na+–Ca2+, and Ca2+–Ca2+) correlations to the membrane transport process of ions were examined by means of comparing the estimated values of corresponding matrix elements. It was suggested that Ca2+ ions, of which membrane concentrations are kept at high level independently of the Na+/Ca2+ concentration ratio of external aqueous solutions, play a critical role in the membrane transport phenomena. Participations of Cl− transport in the cation-exchange proce...