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 (MnSO4H2O)-H-.+MgSO(4)(.)7H(2)O+H2O+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. (c) 2005 Elsevier B.V. All rights reserved.