Abstract
Useful information on the polymerization of silicic acid is obtained from a combined use of (1) spectrophotometry based on the formation of yellow molybdosilicic acid, (2) trimethylsilylation of silicic acid and determination of trimethylsilyl derivatives by gas-liquid chromatography and (3) gel permeation chromatography of silicic acid. The polymerization of silicic acid is divided into three processes: (1) the formation of polysilicic acid by the reaction between molybdate reactive silicic acids (MRS acid), (2) the particle growth of polysilicic acid by the reaction between MRS acid and polysilicic acid, and (3) the particle growth of polysilicic acid by the reaction between polysilicic acids. The pH value giving maximum rate of polymerization of silicic acid is different among these three processes. Fluoride promotes processes (1) and (2); the effect of fluoride on the process (3) is relatively small.
