Abstract: This patent disclose a method for making ultra pure colloidal silica having metal impurities except potassium of less than about 1 ppm, at a pH of greater than about 6, with an average particle size of less than about 200 nm. Hydrolyzable silanes that can be purified by distillation, or their oligomers, are used as raw materials which are first dissolved in water with organic or inorganic acids. This acidic solution is slowly mixed with a basic solution with or without silicate at a temperature range 50-105° C. to form colloidal silica. The colloidal silica can be further concentrated to higher concentrations, greater than about 20% by evaporation or by ultrafiltration, or a combination thereof.