Solubility of the quaternary system acetic acid – n-amyl alcohol – n-amyl acetate – water was investigated at 293.15 K, 303.15 K, 313.15 K, 323.15 K and atmospheric pressure. Binodal curves and binodal
surfaces were determined using isothermal titration (cloud-point technique) and presented in composition simplices including 3D phase diagrams in composition tetrahedron. Binary mixtures were carried
out by the gas chromatography method. Experimental data were predicted using UNIFAC model, and it
was found that the calculating results of liquid–liquid equilibria (LLE) are in inconsistent agreement with
the experimental data on solubility at all temperatures.