In the absence of a suitable solid phase for deposition and in supersaturated solutions of pH values from 7 to 10, monosilicic acid polymerizes to form discrete particles. Electrostatic repulsion of the particles prevents aggregation if the concentration of electrolyte is below ~0.2 N. The particle size that can be attained is dependent on the temperature. Particle size increases significantly with increasing temperature. For example, particles 4-8 nm in diameter are obtained at 50-100 C (122-212°F), whereas particles of up to 150 nm in diameter are formed at 350°C (662°F) in an autoclave However, the size of the particles obtained in an autoclave is limited by the conversion of amorphous silica to quartz at high temperatures. Particle size influences the stability of the sol because particles < 7 nm in diameter tend to grow spontaneously in storage, which may affect the sol properties. However, sols can be stabilized by the addition of sufficient alkali