Temperature dependence of ternary phase diagrams for water + sodium chloride + ethylene glycol monopropyl ether at atmospheric pressure

• Ternary phase diagrams for water + sodium chloride + ethylene glycol monopropyl ether were measured at different temperature.
• Binodal data and tie-line data were correlated.
• Lower critical solution temperature (LCST) of the ternary system was determined.
• A non-linear equation which could predict the LCST only using triple-phase points data was put forward.
• Three-dimensional phase diagram to show the temperature dependence was given.

Phase equilibria have been measured throughout the temperature range from 283.15 to 333.15 K for the water + sodium chloride (NaCl) + ethylene glycol monopropyl ether (EGMPE) ternary system. From the experimental data, the binodal and tie-line data have been correlated with four and three empirical equations, respectively. The plait points at various temperatures were also determined. In addition, the lower critical solution temperature (LCST) of the investigated system was estimated by calculating the intersection of two fitting curves which correlated the mass fractions of EGMPE at the triple-phase points with the temperature. The predicted value of the LCST approached the experimental value by using a titration method. The area, in which two liquid phases coexist, increases with increasing temperature, which was shown clearly in the tridimensional phase diagram.