Asymmetric criticality of ionic solution containing 1-hexyl-3-methylimidazolium tetrafluoroborate and 2-propanol

• Liquid–liquid equilibrium of {2-propanol + RTIL} binary solution was measured.
• The critical exponents were deduced and showed well agreements with 3D-Ising universality.
• Asymmetry of the coexistence curve was analyzed by the complete scaling theory.
• RPM-rescaled critical parameters were calculated.

The liquid–liquid coexistence curve for binary solution {2-propanol + 1-hexyl-3-methylimidazolium tetrafluoroborate ([C6mim][BF4])} has been measured. The isobaric heat capacities per unit volume were obtained in both critical and non-critical regions. The critical exponents α and β were deduced and showed good agreement with those predicted for the 3D-Ising universality class. The asymmetric behaviour of the diameter of the coexistence curve was analysed based on the complete scaling theory, which indicated that the heat capacity related term plays an important role in describing the asymmetric behaviour of the coexistence curve. Furthermore, the RPM (restricted primitive model)-rescaled critical parameters were calculated and suggested the solvophobic criticality for this system.