Solubility in the liquid-solid metastable system Li2SO4 + MgSO4 + Na2SO4 + H2O at T=263.15 K was studied using the isothermal evaporation method. Based on experimental data, dry-salt phase and water-phase diagrams of the system were plotted. The dry-salt phase diagram of the system includes one three-salt co-saturation point, three metastable solubility isotherm curves, and three crystallization regions corresponding to lithium sulphate monohydrate (Li2SO4 center dot H2O), epsomite (MgSO4 center dot 7H(2)O), and mirabilite (Na2SO4 center dot 10H(2)O). Neither a solid solution nor double salts were found. Based on the extended Harvie-Weare (HW) model and its temperature-dependent equation, the values of the Pitzer parameters beta((0)), beta((1)), beta((2)), and C-Phi for Li2SO4, MgSO4, and Na2SO4, the mixed ion-interaction parameters theta(Li,Na), theta(Li,Mg),. theta(Na,Mg), Psi(Li,Na,SO4), Psi(Li,Mg,SO4), and Psi(Na,Mg,SO4), and the Debye-Huckel parameter A(Phi) in the quaternary system at 263.15K were obtained. The solubility of the quaternary system Li2SO4 + MgSO4 + Na2SO4 + H2O at T=263.15 K was also calculated. A comparison between the calculated and experimental results shows that the predicted solubility agrees well with experimental data. (C) 2010 Elsevier B.V. All rights reserved.