Experimental liquid–liquid phase equilibria for binary systems: ethanenitrile with several hydrocarbon isomers

Liquid–liquid miscibility temperatures, as a function of composition, for the nine binary systems formed by ethanenitrile (acetonitrile), as common component, with 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane and cyclooctane, have been determined by the sealed-tube technique. All the studied systems show an upper critical solution temperature (UCST). We have used the Weimer–Prausnitz modification for polar components of Hildebrandʹs regular solution theory (RST) to calculate UCSTs and the results compare very well with those obtained experimentally for the systems studied. We have established that the value for the induction energy density parameter included in the modified RST, which arises from induction forces between the polar component and the nonpolar component, originally proposed only for linear and cyclic saturated hydrocarbons in polar solvents, is also valid for binary systems of the type polar component+branched paraffin. The RST with the Flory–Huggins entropy gives values of the critical composition which are systematically higher than the experimental values.