On the slip process in electrokinetics

The slip process in electrokinetics is reconsidered in terms of recent insights into the structure of water near surfaces. There is an apparent stagnant layer on the surface, but this observation is not in conflict with substantial tangential conduction in that layer. Zeta potentials, computed for a limited number of well-defined systems, after correction for surface conduction, level off at plateaux below that corresponding to about 2.5 μC cm−2 of electrokinetic charge. The plateaux are almost independent of the nature of the surface and may be explained in terms of the viscoelectric effect. The desirability of further systematic studies is stressed.