The movement of titration curves in the presence of specific adsorption

Abstract

The crossover point of potentiometric titration curves is usually identified with the point of zero charge. It is shown both theoretically and experimentally that in the presence of specific adsorption the crossover point and the point of zero charge do not necessarily coincide. When a specifically adsorbing anion is present in small and constant amounts in varying concentrations of indifferent electrolyte, the crossover point decreases relative to the pristine point of zero charge. When the specifically adsorbing anion is the only anion of the electrolyte, the crossover point increases relative to the pristine point of zero charge.