Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The solubility of 3-methyl-4-nitrobenzoic acid (MNBA) in binary (1,4-dioxane + methanol), (N-methyl-2- pyrrolidone (NMP) + methanol) and (N,N-dimethylformamide (DMF) + methanol) solvent mixtures were investigated by the isothermal dissolution equilibrium method under atmospheric pressure. The studies were performed at different mass fractions of 1,4-dioxane, DMF or NMP ranging from 0.1 to 0.9 at temperature T = (283.15 to 318.15) K. The solubility of MNBA in mixed solutions increased with increasing temperature and mass fraction of 1,4-dioxane, DMF or NMP for the three systems including (1,4- dioxane + methanol), (NMP + methanol) and (DMF + methanol). At the same mass fraction of 1,4- dioxane, DMF or NMP and temperature, the solubility of MNBA was greater in (DMF + methanol) than in the other mixed solvents. The obtained solubility data were correlated with Jouyban-Acree model, van t Hoff-Jouyban-Acree model, modified Apelblat-Jouyban-Acree model, Ma model, Sun model and CNIBS/R-K model. The largest values of relative average deviations (RAD) and the root-mean-square deviations (RMSD) between the experimental and calculated solubility were 4.62*10-2 and 2.41*10-3, respectively. The calculated solubility with the six models agreed well with the experimental results. On the basis of the solubility obtained, the standard dissolution enthalpy of the dissolution process was calculated. Dissolution of MNBA in these mixed solvents was an endothermic process. The experimental solubility and the models in this study could be helpful in purifying the crude MNBA.