Thermodynamic interpretation of polyionic membrane cell emfs in terms of mixed electrolyte activities

Many applications of ion-exchange membranes involve polyionic transfers between multicomponent electrolyte solns. Polyionic membrane cell potentials are usually interpreted in terms of individual ionic activities, i.e. nonthermodynamic, conventionally established quantities. A new, complete scheme is here described for evaluating emfs. of polyionic membrane cells in terms of thermodn. mean ionic activities in mixed electrolytes together with the relevant ion and solvent transference nos. Applications of the proposed scheme are described for (1) the detn. of transference nos. of ions and solvent across membrane, and (2) the detn. of selectivities of membranes to be used in ion-selective electrodes.