MECHANICAL AND SURFACE COAGULATION .6. DIFFERENTIAL SURFACE COAGULATION IN 2-COMPONENT COLLOIDAL SOLUTIONS

Surface coagulation is brought about by increasing the liquid-air interface of colloidal systems by shaking or stirring or by bubbling gases through them. The degree of surface coagulation that can be achieved is larger the lower the natural stability of a colloidal system; the Zeta potential is often a useful yardstick. On mixing two colloidal solutions differing in natural stability, different degrees of surface coagulation were expected for the two components. This was tested with positive results on mixtures of TiO2 sols, CuO sols, and α-FeOOH sols. The fractionation, by this new principle, of colloidal solutions containing two or more inorganic components was found, in the preliminary study reported here, to be strongly dependent on pH. © 1979.