the present paper, liquid-liquid equilibrium in binary system 1-butyl-3-methylimidazolium hexafluorophosphate + 1-butanol has been studied. Experimental liquid phase behavior was investigated using a volumetric method and a cloud-point method, the former enabling us to obtain tie lines (compositions of equilibrium phases), the latter yielding points of the binodal curve. The results have been compared with previous works and correlated by the NRTL and the Flory-Huggins equations. In addition, as data were obtained in the critical region of the binary system, they were described using the extended scaling-law equation.