Liquid-liquid equilibrium in the-n-heptane-n-perfluorohexane system

The shape of the liquid-liquid coexistence curve in the C₇H₁₆-C₆F₁₄ system in the molar concentration-temperature coordinates close to the critical solution point was studied by narrow-beam gamma-raying of two-phase samples. The molar volumes of the coexisting liquid phases and critical point coordinates (critical temperature T _c = 316.266 ± 0.03 K and critical concentration x _c = 39.0 ± 0.4 mol % C₆F₁₄) were determined. The critical index β of the coexistence curve was found to be 0.322 ± 0.005. The diameter of the coexistence curve did not obey the classic “rectilinear diameter rule.”