Electromotive force of transfer systems containing membranes

¹ Biology Department, Brookhaven National Laboratory, Upton, New York

Reversible Ag-AgCl electrodes have been inserted in the phases of a unit transfer system, phase , membrane, phase ß, and the electromotive force of the chemical source of electromotive force so produced has been determined in the presence of varying material flows through the membrane. The measured electromotive force was found to be a linear function of the ion-pair chemical potential difference between the phases when the concentration of the salt in the more concentrated phase was less than 0.5 M. This relation implies that an electric transport number, a mutual property of the ion and the membrane, is constant over a wide concentration range when a single salt is present in the system. When the system is in a stationary state, the emf is a linear function of the flow rate of water over the concentration range studied. Two membranes whose electric transport numbers are different, a millipore filter and a cellophane membrane, were used to construct a closed circuit containing two aqueous homogeneous phases of different concentrations. Evidence is presented which demonstrates that a spontaneous electric current flows in such a closed circuit.

Submitted on June 6, 1963