Thermodynamic properties of polyelectrolyte solutions determined from studies of Donnan equilibria

Abstract

A new rapid potentiometric method for the determination of Donnan equilibria in polyelectrolyte solutions is described. The method has good accuracy down to the lowest concentrations of the permeable electrolyte. It has been used to study solutions of sodium polyacrylate and sodium carboxymethylcellulose in the presence of sodium chloride. The measurements are in accord with the additivity rule down to concentrations of ≈ 10^–4 mol dm^–3 of the permeable salt. At still lower concentrations deviations from this rule occur, the activity of the salt apparently increasing in this region.