Water solubility and diffusion in alkali silicate melts

Water solubilities and diffusivities have been measured in melts of binary alkali silicate compositions. The results are compared to the classic work of Scholze and co-workers. Water solubilities obtained in the present study for sodium and lithium silicate melts are similar to those of the earlier work while there is some question regarding results for a potassium silicate melt. Water diffusivities found in the present study are consistently greater than those of the earlier work by a factor of 2 to 3. The activation energies for water diffusion into two sodium silicate melts obtained in the present study are lower than those of the earlier work for water diffusion out of melts. The difference in diffusivities may be due to the difference in diffusion direction but this cannot be established at this time. It is shown for the first time that water diffusivity is independent of the partial pressure of water vapour in the melting atmosphere. Finally the correlation between water diffusivity and melt viscosity proposed by Scholze & Mulfinger cannot be applied to the results of this study which raises doubts regarding the universality of this model.