Anharmonic Oscillations in Electrical Potential at Probe Electrodes in Membrane Transport Cells

Abstract

FORGACS¹ has described experiments which led to the conclusion that steady-state flow may not occur during ion transport through ion-selective membranes. His observations may be summarized as follows. Constant direct current (from rectified power supply or accumulators) was passed through the cell: where M is a homogeneous cation or anion exchange membrane. The solutions were stirred at 1,100 r.p.m. Saturated calomel probe electrodes connected through 0.01 M potassium chloride/0.01 M potassium nitrate salt bridges to an oscilloscope were used to measure potential differences across the membrane. It was found that: (1) the observed potential underwent anharmonic oscillation (frequency not stated) about a constant average value; (2) the peak-to-peak amplitude of the oscillations increased with increasing current density; (3) similar oscillations of smaller amplitude were observed when the membrane was removed; (4) similar oscillations of much greater amplitude were observed when the solutions were replaced with 0.01 M silver nitrate in an agar gel.