Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

A differential scanning calorimetric (DSC) technique has been used to obtain solid-liquid equilibrium temperatures for n-C20, or n-C24, or biphenyl + 1-octadecanol, or + 1-eicosanol mixtures. All the systems show a simple eutectic point. The final composition of these points is determined on the basis of the Tamman plots using the values of the eutectic heat and of the heat of melting, which are also reported. Deviations from the Raoult s law for the mentioned mixtures and for the systems n-C24 or n-C28 + cyclododecane, or + cyclododecanol and for dodecane + cyclohexanol are discussed in terms of the alcohol self-association and size effects. Mixtures with alkanols show positive deviations from the Raoult's law. Larger deviations are observed for the cyclohexanol system, as this is the most self-associated alcohol considered. Size effects lead to slightly negative deviations from the Raoult's law for the cyclododecane solutions. DISQUAC provides a good description of the phase diagrams for the mixtures under consideration. The influence of size effects on the interaction parameters is discussed.