SynopsisSelf-diffusion coefficient measurements have been applied to the study of Na+, Ca++, and Sr++ in the presence of a linear acidic polysaccharide extracted from cartilage, i.e., chondroitin sulfate. A series of experimental determinations was made with and wit.hout supporting electrolytes, and an analysis of experiments involving the separat,ion of the electrostatic interaction terms by an extension of Manning's theory produced results showing the preponderant nature of these electrostatic terms. The specificity of each type of ion or the influence of the pH can be considered merely as higher order corrections with respect to the preceding interact,ions. Counterion concent,rat.iori ranges and pH ranges were determined, where either the alkaline-eart,h counterions become free and hence move with their normal diffusion rate, or these cations are associated with the polyelectrolyte molecule, thus giving a diffusion coefficient. similar to that of the macromolecule, or the apparent diffusion coefficient,s vary between these two ext.reme diffusion rates as a function of the association equilibria. This variation can be expressed as a function of the linear charge density parameter related to the structure of the polyelectrolyte, the value of which was determined and found in good agreement, with published values.