Stability of silica dispersions

Abstract

Recently reported anomalies in the resistance of precipitated silica to coagulation are also shown by pyrogenic silica, but only occur in grades containing particles below a certain size. Methylation of the silica surface with hexamethyldisilazane left electrophoretic mobility unchanged, but restored the theoretically expected dependence of stability on pH. This does not conflict with an earlier report that methylation of the surface of crushed quartz affected neither mobility nor stability, as the particles lay in a different size range.