1 Introduction
Water is a very good solvent for certain types of compound and, in many respects, oxidic glasses have very similar properties when in the molten state. It is because the detailed chemistry and physics of aqueous media have received so much attention, that in order to gain an understanding of glasses and glass melts comparisons with aqueous solutions are frequently made. Such comparisons can work very well. For example, metal ions dissolved in glass are often coloured similarly to their aqueous solutions, e.