Solubility, density and refractive index of formamide/N-methylformamide/N, N-dimethylformamide + Rb2SO4 + H2O ternary systems at 283.2, 298.2 and 313.2 K

Abstract

In this work, the solid–liquid equilibrium (SLE) of the ternary systems formamide (FA)/N-methylformamide (NMF)/N, N-dimethylformamide (DMF) + Rb2SO4 + H2O was measured at temperatures of 283.2, 298.2, and 313.2 K. The isothermal solubility of Rb2SO4 in mixed solvents, the density and refractive index of the saturated solutions were determined. At a given temperature, with the increase of the amide content in the mixed solvent, the saturated solubility of Rb2SO4 decreased significantly. The density trend was consistent with the solubility. However, the refractive index increased with increasing the content of amide. The solubility increased with increasing the temperature, whereas, the density curves and refractive index curves at the three temperatures showed a point of intersection. In addition, the influence of the polarity and structure of amide on the solubility of the ternary system was also discussed. Finally, the experimental data were fitted with empirical equations.