Extended Hildebrand solubility approach applied to some sulphapyrimidines in some {methanol (1) + water (2)} mixtures

Extended Hildebrand solubility approach (EHSA) was applied to analyse the equilibrium solubility of sulphadiazine, sulphamerazine and sulphamethazine in some {methanol (1) + water (2)} mixtures at 298.15K. Reported experimental solubilities and some fusion properties of these drugs were used for EHSA calculations. A good predictive character of EHSA (with mean deviations lower than 4.0%) was found by using regular polynomials in order 4 when correlating the interaction parameter (W) and the Hildebrand solubility parameter of solvent mixtures free of drug (δ₁₊₂). Nevertheless, the predictive character of EHSA was almost the same as obtained when logarithmic drug solubilities (log x₃) were correlated with δ₁₊₂.