Thermal membrane potential through charged membranes in electrolyte solutions

Measurements of the thermal membrane potential across cation and anion exchange membranes were carried out by using the same solution of various 1-1 electrolytes on both sides of the membrane. In all cases a good linear relationship was observed between the thermal membrane potential increment psi and the temperature difference increment T. The slope of the linear plot varied with the concentration of the electrolyte. The value of increment psi/increment T versus logarithmic activity of the electrolyte plot was linear with a slope of +/- R/F if the transport number of counterion was unity. The magnitude of increment psi/increment T was independent of coion species but dependent on counterions. These experimental results are in agreement with a theory presented previously. The thermal membrane potential caused by the direct effect of temperature differences and that by the indirect effect arising from the changes in ionic and water chemical potentials due to the temperature difference are separately discussed.