Data on the solubility of manganese sulphate monohydrate in water, and in aqueous alcohols is essential for salting-out crystallization studies. The solubilities for the quaternary system MnSO 4 ·H 2 O+MgSO 4 ·7H 2 O+H 2 O+MeOH solution were determined in the temperature ranges 293.2–308.2K over the mole fraction methanol ranges of 0.00–0.16. The solubility data were used for modelling with the modified extended electrolyte non-random two-liquid (NRTL) equation. The present extension uses ion-specific parameters instead of the electrolyte-specific NRTL binary interaction parameters. This approach has feasibility for many electrolytes and mixed aqueous solution systems principally. The model was found to correlate the solubility data satisfactory.