THERMAL MEMBRANE-POTENTIAL ACROSS ANION-EXCHANGE MEMBRANES IN VARIOUS ELECTROLYTE-SOLUTIONS AND THE TRANSPORTED ENTROPY OF IONS

The thermal membrane potential cell with solution inlet channels was constructed from two blocks of poly(methyl methacrylate). Using the cell the thermal membrane potentials across anion-exchange membranes Aciplex A-201, A-211, and A-221, and Neosepta AM-1 were observed in inorganic electrolytes: KF, KCl, KI, KNO3, KClO3, and KIO3, and in organic electrolytes: HCOONa, CH3COONa, CH3COOK, and C6H5COONa. The thermal membrane potential DELTApsi across the anion-exchange membrane was always positive at the cold solution side. The temperature coefficient of the thermal membrane potential per unit temperature difference DELTApsi/DELTAT is proportional to the logarithmic activities of the ions and the slope of this plot was R/F in the range of ideal permselectivity for the counterions except Aciplex A-221. The transported entropies of the counterions in the membrane were estimated by combining data for the thermal membrane potential, thermoosmosis, and electroosmosis. For all types of membranes, both terms of water and ions in the thermal membrane potential increased with the increasing of the friction coefficient of ions.