Silicic Acids

Silicic Acids

 

derivatives of silica, SiO2; they are very weak acids, only slightly soluble in water. Metasilicic acid, H2SiO3 (more precisely, its polymeric form H8Si4O12), and H2Si2O5 have been obtained in pure form. Amorphous silicon dioxide (amorphous silica) primarily yields orthosilicic acid, H4SiO4, in an aqueous solution with an approximate solubility of 100 mg per liter. In supersaturated solutions prepared by various methods, silicic acids undergo changes and form colloidal particles (molecular weight up to 1,500) characterized by OH groups on the particle surfaces. The resulting product, known as sol, may be stable (pH ≈ 2) or it may aggregate to form a jelly (pH 5–6), depending on the hydrogen pH indicator. Stable, highly concentrated sols of silicic acids containing special substances known as stabilizers are used in the manufacture of paper and in the textile industry; they are also used for water purification.

REFERENCE

Iler, R. Kolloidnaia khimiia kremnezema i silikatov. Moscow, 1959. (Translated from English.)
References in periodicals archive ?
Suitable carriers are precipitated silicic acids and calcium silicates with an oil absorption number (OAN) of 350-400 ml/100 g.