Abstract
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 SO32−. Although the solubility in pure water was the same as that in a NaCl solution, the solubility in a Na2SO3 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.
