NONISOTHERMAL MEMBRANE PHENOMENA ACROSS PERFLUOROSULFONIC ACID-TYPE MEMBRANES, FLEMION-S .2. THERMAL MEMBRANE-POTENTIAL AND TRANSPORTED ENTROPY OF IONS

Thermal membrane potentials across the perfluorosulfonic acid-type membrane. Flemion S. were measured for HCI. alkali metal chlorides, and ammonium and methyl ammonium chlorides. The difference between the mean molar transported entropy of the counterions in the membrane and the partial molar entropy of the counterions in the external solution (s+ - s+) was determined from the experimental data on thermal membrane potential, thermoosmosis and electroosmosis. The sign of the thermal membrane potential in HCl solution varies from positive to negative with the concentration. In HCl and alkali metal chloride solutions, the order of their thermal membrane potentials (-DELTApsi/DELTAT) is H+ > Li+ = Na+ > K+ which is roughly the inverse of that of the crystallographic radii of the ions. However, the order of their entropy differences (s+ - s+) is H+ > Na+ > K+ > Li+ which is just the inverse of that of their thermoosmotic coefficients (D) or the entropy difference of water (s0 - s0) in thermoosmosis. For the ammonium and methyl ammonium ion forms, the orders of both -DELTApsi/DELTAT and (s+ - s+) increase with an increasing number of methyl groups: (CH3)4N+ >(CH3)3NH+ >(CH3)2NH2+ > CH3NH3+ > NH4+, which is also the inverse of that of D or (s0 - s0).