inside the shear plane (3,4). Unfortunately, this anomalous Mobility vs potassium chloride concentration data in the thin surface conduction rendered classical electrokinetic theory double layer region has been determined for three untreated com-(5) inapplicable and so modification of the latex surface mercial polystyrene latices. Using classical thin double layer electhrough heat treatment was attempted (6, 7). There has been trokinetic theory, it has been possible to fit these plots theoretically some success in removing the anomalous surface conduction if it is assumed that there is a constant electrokinetic charge and using this procedure. Recently Gittings and Saville (8) disno anomalous surface conduction. Calculating the z potential uscovered an untreated commercial latex, which showed near ing the same theory gave data that when plotted against log 10 ideal electrokinetic behavior (i.e., anomalous surface con-[electrolyte concentration] gave linear plots with slopes approxiduction was absent). Inspired by this, it was decided to try mately equal to the Nernst constant. The calculated electrokinetic charge was almost constant across the electrolyte concentration a number of commercial latices to discover more systems range, and for the lowest charged latex it was close to the titration where anomalous surface conduction was absent. Because charge. As a result, it was concluded that these latices, at least in simple expressions exist for the thin double layer regime, it the electrolyte concentration range studied, do not exhibit anomawas decided to work with relatively large polystyrene latices lous surface conduction inside the shear plane and that their besuch that ka ΓΊ 25. In this paper, mobility vs electrolyte havior may be described as almost ideal. The data therefore proconcentration plots are reported for three commercial latices, vide further evidence for the validity of classical electrokinetic and the data are interpreted using classical thin double electheory.