ELECTROPHORETIC PROPERTIES OF POLYSTYRENE SPHERES

The zeta-potential of monodisperse polystyrene latices as a function o f ionic strength is reported. Latices exhibit anomalous electrokinetic behavior: instead of the expected decrease in mobility with increasin g electrolyte concentration, a maximum occurs. In this paper it is sho wn that both in electrophoresis of dilute dispersions and in electroom osis of concentrated plugs, the zeta-potential as a function of ionic strength passes through approximately the same maximum at about the sa me electrolyte concentration. After the correction for the influence o f conductance by ions in the diffuse electrical double layer, using O' Briens model, still a slight maximum exists. The results provided an e stimate of the Stern layer thickness. An analysis using the hairy laye r model, when surface conductance was neglected, provided an estimate of the hairy layer thickness.