SUSPENSION STABILITY OF SOLID PARTICLES IN PRESENCE OF VARIOUS TYPES OF ELECTROLYTES

Stabilities of titanium dioxide and ferric oxide suspensions in the presence of various types of electrolytes have been studied by measuring their sedimentation volume, rate of sedimentation and optical absorption as a measure of the degree of suspension. The stabilizing ability in suspensions with condensed phosphates is relatively high as compared with that with electrolytes other than the phosphates. This would indicate strong adsorption of phosphate ions onto the surface of the particle. A correlation is found between the extent of stability of a suspension and the electrophoretic mobility of the particle suspended in electrolyte solution, except with silicates. With polyphosphates (Nan+2PnO3n+1) the stabilizing effect is noticeable at n≥2, while with metaphosphates (NanPnO3n) it becomes noticeable and constant at n≥4. The stabilities of titanium dioxide and ferric oxide suspensions containing silicates are high in spite of low electrophoretic mobilities of their suspended particles, which are comparable with the stability operated by tripolyphosphate or a typical dispersing agent. The suspension stability data of acid and neutral condensed phosphates and of the electrolytes used commonly as builders in the presence of a surfactant have also been included. © 1969 AOCS Press.