Dependence of ζ-Potential upon Particle Size and Capillary Radius at Streaming Potential Study in Nonaqueous Media

The effect of particle size and capillary radius on electrokinetic potential (ζ-potential) was studied in order to check the influence of overlapping of the electrical double layer and radius effect on the measured ζ-potential by the streaming potential method. The streaming potential was measured with varying particle size and capillary radius of glass in the benzene solution of (C4H9)4NI. The measurement was carried out over the range where the laminar flow and the Quincke’s law hold. The surface conductance was corrected experimentally. ζ-Potential increased with increase of the particle size in the glass column. It was unsuccessful to obtain the ζ-potential independent of the reduced radius of the capillary pore with the Oldham’s treatment. ζ-Potential increased with increase of the capillary radius. The increase was elucidated by the Wood’s method using the appropriate constants, and the constant ζ-potential which was not affected by the capillary radius was obtained. The value was still different from that obtained by the electrophoretic method, but the difference was considerably small as compared with the previous data.