Vapour–liquid equilibria. Ternary non-electrolyte mixtures with two involatile components–squalane and dinonyl phthalate

Abstract

The vapour pressures of benzene, cyclohexane, pentane, hexane, and heptane mixed with squalane and/or dinonyl phthalate at 303 K have been measured by a static method and the compositions of the mixtures found by means of a microbalance, enabling the activity coefficient of the volatile component to be calculated. A curve fitting technique allowing for errors in the measurements has been used to test the ability of the Flory–Huggins expression and the Wilson equation to fit the results.

The Flory–Huggins expression, employing interaction parameters that are allowed to vary linearly with composition, has been found to give a fairly good description of the systems yielding a consistent interaction parameter for the involatile components, squalane and dinonyl phthalate. Thus the ternary systems studied can be expressed in terms of measured binary interaction parameters. Although the Wilson equation gives the best fit to all the systems it does not produce consistent interaction parameters for the pair of involatile components.