THERMAL MEMBRANE-POTENTIAL ACROSS ANION-EXCHANGE MEMBRANES IN KCL AND KIO3 SOLUTIONS AND THE TRANSPORTED ENTROPY OF IONS

New simple thermal membrane potential cells with a solution inlet channel were constructed from two blocks of poly(methyl methacrylate) resin. Using these cells the thermal membrane potentials across anion-exchange membranes Aciplex (R) A-201 and A-211, and Neosepta (R) AM-1 were observed in KCl and KIO3 solution systems. It is easier to handle the new cells because of the simple cell construction compared with the cells with a solution inlet nozzle used up till now. The thermal potentials measured with the new cells were similar to those obtained with the old ones. The thermal membrane potential Delta psi across the anion-exchange membranes was always positive at the cold solution side. The temperature coefficient of the thermal membrane potential per unit temperature difference Delta psi/Delta T is proportional to the logarithm of the activities of the ions and the slope of this plot was R/F in the range of ideal permselectivity for counterions as expected from the previously presented theory. The transported entropies of the counterions in the membrane were estimated by combining data for the thermal membrane potential, thermoosmosis and electroosmosis. It is shown that the contribution of the water term to the thermal membrane potential as well as to the concentration membrane potential plays an important role.