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 ?
Synthetic silicates are made up of simple or complex salts of silicic acids, and have been used extensively for various commercial and industrial applications, such as food additives, glass and ceramic filler materials, and anti-caking agents.
Suitable carriers are precipitated silicic acids and calcium silicates with an oil absorption number (OAN) of 350-400 ml/100 g.
They are synthesized using the sol-gel process which involves the hydrolysis of silicic acids esters modified with organic residues.