The carbonation Mg-rich natural minerals or industrial wastes is an attractive route to store CO2. Recently, an approach involving the indirect mineral carbonation of serpentine with recyclable (NH4)(2)SO4 or NH4HSO4 is receiving widespread attention. In this study, the solubilities associated with the mineral process (ternary system of (NH4)(2)SO4-MgSO4-H2O) were measured and calculated using the isothermal method and Pitzer model, respectively. The effects of adding small amounts of H2SO4 and iron sulfate on the solubilities were evaluated. The results showed that the crystalline region of MgSO4 center dot(NH4)(2)SO4 center dot 6H(2)O (boussingaultite) is larger than those of the other species, which indicates that boussingaultite is crystallized out easily. The presence of H2SO4 at a concentration of up to 10 wt % and iron sulfate of 2.5 wt % almost had no effect of the solubilities. The minimal ratios of liquid to solid during the leaching unit were calculated as 3.45, 2.19, and 1.36 mL/g at 25, 55, and 80 degrees C, respectively. Compared with the case of 25 degrees C, the energy consumption for the evaporation could be reduced by 36.5% at 55 degrees C and 60.6% at 80 degrees C. During the crystallization of ammonium sulfate, high purity (NH4)(2)SO4 is hardly obtained due to the small crystalline field.