Excess molar enthalpies of binary mixtures of n-octane, isooctane and cyclooctane with morpholine, 1,4-dioxane, piperidine, oxane, N-methyl piperidine and cyclohexane. Experimental results and DISQUAC modelling

Excess molar enthalpies, HE, for octane isomers (n-octane, isooctane and cyclooctane) + heterocycles (morpholine, 1,4-dioxane, piperidine, oxane and N-methyl piperidine) or + cyclohexane binary mixtures, were determined at 308.15 K and atmospheric pressure, using a flow calorimeter. All the mixtures are endothermic, over the whole range of compositions, except cyclooctane + cyclohexane which presents very small, positive and negative, excess molar enthalpies. HE values fall as follows: morpholine > 1,4-dioxane > piperidine > oxane > N-methyl piperidine > cyclohexane and n-octane > isooctane > cyclooctane. The purely physical model, DISQUAC, based on the rigid lattice theory developed by Guggenheim, was relatively well tested.