CONDITIONS OF THERMODYNAMIC STABILITY WITH CONSIDERATION OF SHORT- AND LONG-RANGE FORCES: COAGULATING ACTION OF A CATIONIC SURFACTANT AND AN ELECTROLYTE IN AQUEOUS DISPERSIONS OF HYDROPHILIC SILICA.

The stability of colloidal dispersions of hydrophilic (unmodified) silica in aqueous solutions of cationic cetylpyridinium bromide (CPB) and inorganic salts has been studied and compared to direct measurements of the adhesive forces between hydrophilic silicate surfaces in model experiments and the adsorption of CPB on silica. It has been shown that the coagulating action of CPB is related to an increase in the binding energy of the particles in the potential minimum, which results in a loss of thermodynamic stability. In its absence and at low concentrations of CPB the depth of the potential minimum is small and the suppression of the forces of repulsion of the electric double layers by the addition of an inorganic electrolyte does not cause coagulation.