THE MOBILITY AND CONDUCTIVITY OF DILUTE POLYSTYRENE LATEX DISPERSIONS

The electrokinetic equations which describe colloidal phenomena have yet to be properly tested. We report results from conductivity and mobility measurements made on dilute suspensions of polystyrene latices. The ζ potentials predicted by the theory from the measured conductance increments and mobilities in a range of electrolyte concentrations of both KCl and HCl are compared. The measured conductance increments depend on the method used to prepare the suspension. Using ultrafiltration, the suspension filtrate concentration is found to vary with the suspension volume fraction at volume fractions of particles less than φ = 0.05. The presence of the particles affects the "supporting" electrolyte concentration in a manner dependent on the volume fraction. The variation of the supporting electrolyte concentration obscures the true value of the conductance increment due to the particles. The measured conductance increment is then composed of the particle contribution and an electrolyte contribution which is also linear in the volume fraction. The volume fraction dependence of the supporting electrolyte concentration potentially explains the discrepancies between the mobility and conductance-predicted ζ potentials reported previously and herein. © 1992.