Extended Hildebrand solubility approach applied to some sulphonamides in propylene glycol+water mixtures

Extended Hildebrand solubility approach (EHSA) was applied to evaluate the solubility of sulphanilamide, sulphapyridine and sulphamethizole in some propylene glycol + water mixtures at 298.15K. Reported experimental solubility and some properties of fusion of this drug were used for the calculations. In particular, a good predictive character of EHSA has been found by using a regular polynomial in order five of the interaction parameter W as a function of the solubility parameter of solvent mixtures free of drug. Nevertheless, the predictive character of EHSA is the same as the one obtained by direct correlation between drug solubilities and the same descriptor of polarity of the co-solvent mixtures.