KINETICS OF HETEROCOAGULATION .2. THE EFFECT OF THE DISCRETENESS OF SURFACE-CHARGE

Coagulation rates in dispersions of uniform spherical particles of surfactant-free sulfate latices, silica and cerium (hydrous) oxide were measured as a function of the ionic strength by a low-angle scattering technique. The results were used to interpret the significant discrepancies between theoretical predictions and experimental results of slow coagulation kinetics. The variations in values of all usual parameters in the accepted theoretical models were tested in order to eliminate the disagreements, but the task proved unsuccessful. However, the assumption of the segregated surface charge on the smooth spherical particles has led to the concordance between the measured and calculated stability ratios. In the model employed, the heterocoagulation theory is required even though one deals with systems of identical particles.