PATTERN OF INFLUENCE OF MINERAL ACIDS ON THE KINETICS OF GEL FORMATION IN COLLOIDAL SILICA

The electrosurface properties and the kinetics of gel formation in col loidal silica after the introduction of mineral acids were investigate d A specific influence of sulfuric and boric acids was detected. The i ncrease in the electrical potential of colloidal silica when sulfuric acid is introduced is explained by adsorption of SO42-anions together with OH- ions. Boric acid induces an increase in the electronegative c haracter of silica close to neutral pH values and a decrease in it in alkaline medium. hypotheses on the structure of surface heteropolycomp ounds of boric and silicic acids and the nature of their influence on the kinetics of gel formation are proposed.