Abstract: The system investigated are the solutions of monosilicic acid and poly silicic acids with different polymerization degrees. The 'reaction of (he spontaneous polymerisation of soluble silicic acid to form colloidal silicic acid was determined to be a second order reaction. When F~ion present has a concentration ratio F-/SiO2≤0.5, the rate of polymerization increases due to the fact that fluoride ions take part in the polymerization. The rate of polymerization is proportional to the square of the concentration of silicic acid, as well as to the concentration of fluoride ions. When F-/SiO2 is larger than 0.5, the rate of polymerization gradully decreases. The effects of fluoride ions on the polymerization were discussed.Three methods were used to prepare colloidal silicic acid and their properties and influence on the emulsification were investigated. The comparison between the colloidal silicic acid solutions and the leach liquor was made. The mechanism of the emulsification caused by silicon was also discussed in the present paper.