Liquid-liquid equilibrium and heat capacity measurements of the binary solution {ethanol + 1-butyl-3-methylimidazolium hexafluorophosphate}

The liquid-liquid coexistence curves in a temperature range of about 10 K from the upper consolute point and the specific isobaric heat capacities in a wide temperature range for the critical binary solution of {ethanol + 1-butyl-3-methylimidazolium hexafluorophosphate} have been reported. The critical exponents corresponding to the heat capacity and the coexistence curve were deduced and found to be consistent with theoretical predictions. The complete scaling theory was used to analyze the asymmetric behavior of the diameter of the coexistence curve, which confirmed that the heat capacity related term was of importance. The crossover behavior from the 3D-Ising to the mean field was examined and shown to be monotonic and more pronounced than that of simple fluids. It was also found that the system-dependent critical amplitude A+ for the heat capacity had a comparative large value, and the reduced critical parameters calculated from the restricted primitive model (RPM) were significantly larger than the characteristic RPM values, indicating the nature of solvophobic criticality.