Studies with thin membranes. II. Measurement of membrane potentials and evaluation of membrane fixed charge density

Membranes prepared from 5% Parlodion solution have been characterized. These and other membranes prepared from 0.38, 0.5, 1.0, 2.0, and 3.0% Parlodion solutions and already characterized, have been used severally to estimate the number of anionic sites present in them by two different methods. The potentiometric method, which is indirect, gave values of X̄ P which were higher than X̄ T , the values obtained by a direct isotopic method. The order was reversed for well‐characterized ion‐exchange membranes. These discrepancies were attributed to the shortcomings of the Teorell, Meyer, and Sievers theory of membrane potentials from which the potentiometric method was derived.