Studies with inorganic precipitate membranes: Part XIV. Evaluation of effective fixed charge densities

Abstract

Effective fixed charge densities of cobalt and nickel sulphide (parchment supported) membranes in contact with various 1:1 electrolyte solutions have been evaluated from membrane potential measurements. The methods used for the estimation of charge densities were: (a) the Teorell–Meyer–Sievers method (TMS) and (b) the methods developed recently by Kobatake and co-workers. The two limiting forms of Kobatake's equation for dilute and concentrated solutions gave identical values of charge densities. The theoretical predictions for membrane potential were borne out quite satisfactorily by experimental results obtained with both the membranes. Apparent transference numbers of coions and permselectivities of the membranes for electrolytes have also been calculated. A method based on permselectivity values for the determination of charge density was also used. It was interesting to note that the charge densities evaluated from different methods of Kobatake and co-workers gave identical values and that the results were comparable to those derived from the TMS method.