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Abstract

Thin membranes (50-800 A. thick) formed by spreading a solution of Parlodion in isoamyl acetate on the air-water interface have been characterized. The electrical resistance and capacitance of these membranes prepared from each of the three Parlodion concentrations viz., 5, 10, and 20 mg./ml. solution, have been measured as functions of both membrane thickness and external electrolyte (KCI) concentration. Capacitance values corroborate the thickness inferred from the weight of material transferred to cover a fixed area. Membrane resistance drops with increase in thickness. Resistivity of a membrane 100 A. thick rises with decrease in external electrolyte concentration. Acid and alkaline solutions of KCI lower membrane resistance due to increased porosity of the membrane brought about possibly by the hydrolysis of the membrane material. Membrane potentials arising across these membranes also have been measured as functions of both membrane thickness and external electrolyte concentration. The bi-ionic potentials confirmed the usual order of penetrability of alkali metal ions observed in artificial membranes. A study of the effect of pH on membrane potentials indicates that the electrochemical activity of the membrane may be attributed to the presence of odd and terminal carboxyl groups in the nitrocellulose matrix of the membrane.