Interaction of sodium with simple glasses

The interactions of binary and ternary silicates with sodium were found to be similar to that of vitreous silica in that the number of Si-O^– bonds was observed to increase at the expense of the Si-O bonds as the temperature of exposure to sodium is raised. From the model developed for vitreous silica 1], it was argued that Si-O^– bonds are more stable than Si-O bonds in the presence of sodium. Using this concept, the discoloration behaviour of these binary and ternary silicates could be explained. The more general problem of selecting materials compatible with sodium is also dealt with by collecting a set of criteria based on equilibrium thermodynamics, and the shortcomings of these criteria are discussed.