Effect of sodium sulfite on the dissolution of amorphous silica in aqueous solution

The dissolution rate and solubility of amorphous silica were determined in pure water, a sodium chloride solution and a sodium sulfite solution in the concentration range of 10 ^-3-10 ^-1 M. The initial dissolution rate (0-12 hours) was enhanced in the presence of Na ⁺, while it was not. affected by Cl ^- and SO ₃ ^2-. Although the solubility in pure water was the same as that in a NaCl solution, the solubility in a Na ₂SO ₃ solution increased depending on its concentration, suggesting the formation of complexes of silicic acid with sulfite ion. The conditional formation constants of the hypothetical 1:1 complex were estimated to be 105-1951 M ^-1 based on difference between the solubility of amorphous silica in the sodium sulfite solution and that in sodium chloride solution.