For some solute-solvent combinations a supersaturated solution can be prepared by raising the solubility ( for example by increasing the temperature ) to dissolve more solute, and then lowering it ( for example by cooling ).
32.
The large crystal can be grown by dipping the seed into a supersaturated solution, into molten material that is then cooled, or by growth on the seed face by passing vapor of the material to be grown over it.
33.
In order to prevent the formation of amorphous silica gels precipitating from supersaturated solutions without reacting with the aluminium or magnesium cations to form crystalline silicates, the silicic acid must be present in concentrations below the maximum solubility of amorphous silica.
