Investigation of the Solubility and Phase Diagrams of Sodium 4-Tolylsulfinate in Different Solvents and Ternary Sodium 4-Tolylsulfinate + Sodium Chloride/Sodium Sulfate + Water Systems

The method of isothermal saturation was utilized to experimentally obtain the sodium 4-tolylsulfinate (4-STS) solubility in nine neat solvents including ethanol, acetone, methanol, N , N -dimethylformamide (DMF), isopropanol, acetonitrile, water, n -butanol, and n -propanol, and solvent mixtures of water + isopropanol/acetonitrile. With a rise in temperature, the mole fractions of 4-STS in the equilibrium liquor increased. Among the solvents tested, methanol has the largest solubility values. To match the solubility data, the Apelblat, the Jouyban–Acree, and the modified van't Hoff–Jouyban–Acree models were utilized. The values of 9.23 × 10 –4 and 5.30 × 10 –2 were the highest root-mean-square and relative mean error values, respectively. The recommended anti-solvents for crystallization of the 4-STS from aqueous solution are isopropanol and acetonitrile. The mutual solubility of 4-STS and Na 2 SO 4 /NaCl in water was determined at the temperatures from T = 283.15 K to 313.15 K at intervals of 15 K. The phase diagrams of 4-STS + Na 2 SO 4 /NaCl + water ternary systems were also constructed. We found that, the addition of a certain amount of Na 2 SO 4 /NaCl can significantly decrease the aqueous solubility of 4-STS.