Viscosity and electroviscous effect of the AgI sol. II. influence of the concentration of AgI and of electrolyte on the viscosity

Abstract

Viscosity measurements were carried out on silver iodide sols with different sol concentrations and electrolyte concentrations. Independent of the electrolyte concentration the measurements extrapolated to a value of K = ηrel/ of 3.55 for a volume concentration = 0.

At higher sol concentration and with low electrolyte concentration, the interaction of the double layers gave rise to an increased viscosity (electroviscous effect). With electrolyte concentrations above 25 mmoles/l. the electroviscous effect has practically disappeared. The remaining excess viscosity can be explained by hydrodynamic interaction. So, an electroviscous effect is not measurable at = 0. This is in accord with Booth's theory but does not conflict either with the theory of Smoluchowski, within the range of application of the latter (thin double layer).

A theoretical explanation of the electroviscous effect at high concentrations is given, based upon the repulsive forces between particles passing each other in the laminar flow.