H2SiO3

H2SiO3, frequently referred to in silicate chemistry as metasilicic acid, is an inorganic silicon-oxide hydroxide species with the same overall composition as a silicate unit. In aqueous systems it is not typically observed as a stable, discrete monomer; instead, silica chemistry is dominated by orthosilicic acid (H4SiO4) and by polymerized silicate species formed through condensation reactions among silanol groups. H2SiO3 is discussed mainly as a transient or intermediate species in solution rather than as a isolable compound.

Structure and chemistry: In solution, H2SiO3 is viewed as a silicate-related species arising from condensation processes among silanol groups. The exact molecular structure in water is not fixed, because silicate species readily polymerize to short and long-chain forms. In aqueous solution, H2SiO3 can act as a weak Brønsted acid, with deprotonation dependent on pH and ionic strength, contributing to the overall speciation of silica in geochemical and environmental contexts. The balance between orthosilicic and metasilicic (and higher) species shifts with concentration, pH, and temperature.

Preparation and occurrence: Metasilicic acid is typically obtained or discussed under controlled laboratory conditions as a transient species or in the context of silicate hydrolysis and polymerization. In nature and in most practical settings, dissolved silica exists as a mixture of orthosilicic acid and various polymeric silicates, with H2SiO3 serving mainly as a conceptual reference point for condensation pathways.

Applications and significance: H2SiO3 is of interest in fundamental silicon chemistry, geochemistry, and materials science for understanding silica dissolution, hydrolysis, and surface hydroxyl chemistry of silica-based materials. It helps describe how silicate species evolve from monomeric to polymeric forms in aqueous environments.

See also: orthosilicic acid, silicic acid, silicates, silica.