Solubility as well as solution density in aqueous systems (Lid + MgCl2 + H2O) and (Li2SO4 + MgSO4 + H2O) at 288.15 K have been studied using the isothermal dissolution method. In the ternary system (LiCI + MgCl2 + H2O) at 288.15 K, two invariant points, three isothermal dissolution curves and three crystallization regions including MgCl2-6H(2)O, LiCl center dot 2H(2)O, and double salt LiCl-MgCl2.71420 were detected. Experimental results compared with values of this system at (273.15, 348.15, and 323.15) K shows that the LiCI.MgCl2.7H(2)O crystallization region is increased slightly with the increasing of temperature, while that of MgC1(2)center dot 6H(2)O and LiCl-2H(2)O are decreased obviously. In the ternary system (Li2SO4 + MgSO4 + H2O) at 288.15 K, there are one invariant point, two isothermal dissolution curves, and two crystallization regions corresponding to Li2SO4 center dot H2O and MgSO4-7H(2)0. When this experimental phase diagram at 288.15 K was compared with that at (298.15, 303.15, and 348.15) K, it shows that the L1(2)SO(4)center dot H2O crystallization region is increased with the increasing of temperature, while that of MgSO4 center dot 7H(2)O is decrease obviously. A Pitzer and Harvie Weare thermodynamic model were applied to calculate the solubility for this ternary system, and the calculated solubilities agree- reasonably with the experimental results.