Solid–Liquid Ternary Phase Equilibrium of 3,5-Dibromo-4-hydroxybenzaldehyde + 3-Bromo-4-hydroxybenzaldehyde + N,N-Dimethylformamide/1,4-dioxane/dimethylsulfoxide: Determination and Model Correlation

The solid–liquid ternary phase equilibrium for 3,5-dibromo-4-hydroxybenzaldehyde + 3-bromo-4-hydroxybenzaldehyde + N,N-dimethylformamide/1,4-dioxane/dimethylsulfoxide systems was experimentally obtained through the shake-flask method at three temperatures of 298.15, 308.15, and 318.15 K under a normal pressure of 101.2 kPa. Nine isothermal phase diagrams of the three systems were constructed by means of the mutual solubility data acquired. The equilibrated solids with different solvent systems were identified by Schreinemakers' wet residue method. Two neat solids corresponding to pure 3-bromo-4-hydroxybenzaldehyde and pure 3,5-dibromo-4-hydroxybenzaldehyde appeared in each equilibrium system at a specific temperature. The saturated regions of pure 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde positively increased as the temperature decreased. The saturated region of 3,5-dibromo-4-hydroxybenzaldehyde was bigger than that of 3-bromo-4-hydroxybenzaldehyde at the same conditions. Two activity coefficient models, NRTL and Wilson models, were utilized to mathematically describe the solid–liquid phase equilibrium. The back-calculated solubility data through the NRTL model were in good agreement with the experiment ones. The ternary phase diagrams and mutual solubility data for these systems are crucial in the purification of 3-bromo-4-hydroxybenzaldehyde and 3,5-dibromo-4-hydroxybenzaldehyde mixtures.