THERMAL MEMBRANE-POTENTIAL ACROSS CATION-EXCHANGE MEMBRANES FOR VARIOUS HALIDE SOLUTIONS

Thermal membrane potential across cation-exchange membranes was measur ed for various halide solutions. Linear relationships between thermal membrane potential (Delta psi) and temperature difference (Delta T) we re observed, and the temperature coefficient of thermal membrane poten tial (Delta psi/Delta T) decreases with increase in the molality of th e external solution as predicted by a theory reported. When counterion s of membranes are hydrogen ions, the sign of the coefficients turns i nto minus near 0.01 mol/kg of the external solution for all membranes, although the coefficients are always positive for all the other forms . The dependence of the coefficients on the molality of the external s olutions sometimes deviated slightly from the theory. This deviation i s attributed to some change in water content of the membranes. A repro ducible method of measuring water content of membranes was applied to discuss the change in the state of the membranes.