Effect of dispersed particles on the response of indicator electrode in suspensions

Abstract

A novel interpretation of suspension effect is presented. It is based on recent experiments carried out in this laboratory, and on the established electrical double layer theory for suspensions containing solid charged particles. Experimental evidence shows that the suspension effect of the second kind, as defined by Overbeek, is a rough experimental error of usual potentiometric methods. New experimental results presented here confirm the existence of the suspension effect of the first kind. This effect is reflected in difference of the potential of the indicator electrode depending on whether it is immersed in the sediment of the suspension, or in its supernatant solution. The difference of the potential is assumed to be due to the interaction of the particle double layer with the double layer of the indicator electrode introduced in the suspension for measurement. A simple model relating to the dependence of the electrode potential on the particle characteristics (size and surface potential) and on the suspension properties is proposed. A qualitative agreement with experiments has been found. Some new terms had to be introduced in order to clarify the analysis and discussion.