Salts like LiCl, NaCI, KCl and NaI were dissolved in fused borax glass and the mole-refraction of the solidified glasses were determined. The mole-refraction of the dissolved salts calculated from the additivity formula shows considerable departure from values in the crystalline state and at infinite dilution. The concentration—mole. refraction curves for all these salts show a positive slope unlike the case in aqueous solutions. But the values are considerably smaller than those of the crystal and for infinite dilution, showing the existence of a very considerable deformation in the glass system. The positive character of the slope is explained as due to decreased dissociation of the salt in the glass medium. On the whole Fajans deformation rule is qualitatively established for solid solutions of these salts in glass systems.