The values of the mole refraction (R) of solutions of highly purified samples of Li2SO4, Na2SO4 and K2SO4, in fused glass in different concentrations have been compared to those of the pure crystal and of the aqueous solution st infinite dilution. The values exhibit considerable departure, attributable to the strong deformation which these salts suffer in solid solution in glass medium. The store of the R-c curve is positive in every ease (cf. the works of Fajans' school) implying meagre dissociation of the salt in the glass medium. The densities of the samples exhibit some peculiarities which can be explained by the recent views about the structure of glasses as proposed by Warren and Zachariasen.