Colloidal silica is a stable aqueous dispersion or sol of discrete amorphous silica particles having diameters of 1-100 nm. It is derived from sodium silicate [CAS: 1344-0908].
Silica sols do not gel or settle out of solution for at least several years of storage. Aqueous sols that contain up to 50% silica have been developed.
Particle sizes of ~130 nm in diameter are possible, but slowly settle out of solution.