The liquid–liquid coexistence curves of {x 1-octyl-3-methylimidazolium hexafluorophosphate + (1 − x) 1-butanol} and {x 1-octyl-3-methylimidazolium hexafluorophosphate + (1 − x) 2-butanol} in the critical region

Coexistences curves were reported for the liquid–liquid phase transition of binary solutions of the room temperature ionic liquid (RTIL) 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim][PF6]) in 1-butanol and 2-butanol. The critical amplitude B and the critical exponent β corresponding to the coexistence curve were deduced and the values of β were found to be consistent with the 3D-Ising value. The experimental results are also analyzed to examine the asymmetry of the diameters for the coexistence curves. These asymmetries were discussed by the complete scaling theory.