Electric potentials of bi-zonal clay film membranes

Summary

By filling and draining a smallU glass tube of 4 cm length and 2 mm in internal diameter with 1 and/or 5 percent montmorillonite suspensions, thin clay films were formed on the internal surface of the tube. These films could be prepared as a single homogeneous zone or as two zones that differ in their clay particle concentration. The films were stable over few minutes and were interposed between two KCl solutions of equal or different concentrations in a concentration cell. Emf measurements across calomel electrodes were carried out as a function of the KCl concentration in and outside the films. Membrane potentials of films having one zone followed classical membrane theory with constant ion transport numbers in the films. The sign and magnitude of the potentials obtained with bizonal clay films were found to depend on the ratio of the KCl concentrations inside and outside the film as well as on the difference in the transport number of the ions in each zone of the film.

Zusammenfassung

In der vorliegenden Arbeit wird über EMK-Messungen an Filmen aus Montmorillonit berichtet, die als Membranen zwischen Konzentrationszellen eingesetzt sind. Die Filme bestanden aus einer oder aus zwei homogenen Zonen. Im ersten Falle wurden

Membranpotentiale gemessen, die der klassischen Membrantheorie mit konstanten Überführungszahlen im Film entsprachen. Im letzteren Falle waren Richtung und Größe der Potentiale abhängig vom Verhältnis der KCl-Konzentrationen außerhalb und innerhalb des Films und von der Differenz der Überführungszahlen der Ionen in den beiden Zonen des Films.