Solid/liquid phase equilibria in the mixtures methane + n-hexane and methane + n-pentane

Experimental phase diagrams have been obtained for the mixtures methane + n-hexane and methane + n-pentane from an analysis of their cooling curves. Both systems exhibit large positive deviations from ideality, and for methane + n-hexane a distinct flatness in the temperature against composition diagram at high methane concentrations is indicative of the close proximity of liquid/liquid immiscibility. A thermodynamic treatment of the data using an analytic equation of state confirms more quantitatively the position of this hypothetical upper critical solution point.