Silica Existence, Solubility, and Synthesis

Silicon is never found in nascent form in nature however, in combination with oxygen it is abundant in the form of silica with the general formula Si02 H20 

The dissolution of silica in water is slow, and its depolymerization is gradual. It follows a reversible reaction  

The solubility of silica in aqueous solutions depends on the following factors  

As shown by equation 1, silica imdergoes hydrolysis to form monosilicic acid. This compound is unstable and thus it can be neither isolated nor observed. Thus, the term silicic acid is loosely used in the literature and typically indicates monosilicic acid as well as various oligomeric polysihcic acids. 

The formation of a silica sol (solution of colloidal particles of sizes 1-1000 nm, in a liquid solvent) from the monosilicic acid follows three steps  

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