Phosphate glass dissolution in aqueous solutions

Rates of aqueous dissolution are reported for a series of phosphate glasses having the composition (50 − X)M2O·(X)CaO·50P2O5. Dissolution reactions involving the consumption of H+ and OH− were monitored using pH stat titration techniques, solution analyses using inductively coupled plasma emission, and depth profiling of corroded glass surfaces for H and other elements using elastic recoil detection analysis and Rutherford backscattering. These analytical results indicate that the phosphate glasses dissolve uniformly due to acid- or base-catalyzed hydration of the polymeric phosphate network. The rate and nature of this hydration appears to be controlled by the surface pH and/or charge which develops at the glass/ solution interface. The implication of these results on dissolution models for both the phosphate and silicate glasses is discussed.