Electrokinetic Studies in Dispersed Systems. V. The Zeta Potential of Agl Precipitates in Mixed Solvents

The influence of acetone-water, dioxane-water and methanolwater solvent mixtures upon the electrokinetic potential of Ag! precipitates has .been studied. The same dielectric constant of the medium yields approximately the same zeta-potential only if the activity of the reversible electrode potential determining ions (constituent ions) is sufficiently large to determine a stable zetapotential in aqueous solution of the same composition. In the isoelectric region, in the case of the theoretically balanced positive and negative potential determining ions adsorption, the influence of solvent dipoles is predominant and specific, and the dielectric constant is not a measure of the electrokinetic potential. The mecha nism of the zeta-potential determining processes is manifold and any extrapolation of a single parameter of the system is insufficient to give answers of general importance