Sulfate salts, generally contained in the feed materials for soda ash production, may have an important influence on the NaHCO3 precipitation in the carbonation tower of the Solvay process and the Trona process. The solubilities of NaHCO3 and NH4HCO3 solids were determined in Na2SO4, (NH4)(2)SO4, and NaCl solutions as well as their mixtures via a dynamic method from 283.15 to 323.15 K. It was found that NaHCO3 become less soluble with the addition of Na2SO4, whereas more NH4HCO3 is dissolved. The solubility of NaHCO3 increases with the increasing concentration of (NH4)(2)SO4, while that of NH4FICO3 decreases. The mixed -solvent electrolyte (MSE) model was modified by experimental data regression through the adjustment of the middle -range interaction parameters. The average relative deviation between the calculated results and experimental data is less than 5%. This work provides a basis for improving both the efficiency of the carbonation tower and the quality of end products.