Abstract
A sodium silicate glass and ternary glasses derived from it by substituting AI2O3 and ZrO2 for SiO2 were exposed to water and aqueous solutions of pH 1.4 to 12.7; the kinetics of the reactions were studied. Diffusion of alkali ions and leaching of alkali and SiO2 from the glasses were influenced by the occupancy of surface sites by alkali ions above a critical pH; however, the activation energies of the processes varied linearly with the logarithm of mole fraction of surface sites occupied by Hplus;. Identical slopes were obtained for all glasses for a given process. The results are explained on the basis that transport of alkali ions is retarded as a result of increased boundary concentration and that suitable sites for reaction are lacking.

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