The solubility of Sn(IV) oxide was determined in a dilute NaClO4 solution with pH 2 through 12 at ambient temperature. Both oversaturation and undersaturation experiments were carried out in an inert gas glovebox where the concentration of the oxygen and carbon dioxide were less than 1 ppm. The solubility of Sn(IV) oxide was 3×10-8 mol/1 at neutral pH, and increased at pH >7.5. Equilibrium constants of soluble reactions were calculated from the experimental data, using curve fitting method.
The study suggests that the solubility of Sn(IV) oxide would be higher than that provisionally used in current safety assessments of HLW disposal sites.