Silicic acids are rarely observed in isolation, but are thought to exist in aqueous solutions, including seawater, and play a role in biomineralization.
Depending on the number of silicon atoms present, there are mono- and polysilicic (di-, tri-, tetrasilicic, etc.)
Indeed, in concentrated solutions, silicic acids generally polymerize and condense, and ultimately degrade to silicon dioxide and water.
Silica dissolves very sparingly in water[citation needed] and is present in seawater at concentrations below 100 parts per million.
Theoretical computations indicate that the dissolution of silica in water proceeds through the formation of a SiO2·2H2O complex and then orthosilicic acid.
[7] The silicon–oxygen double bond of metasilicic acid, implied by the formula H2SiO3, is hypothetical or highly unstable.