ABSTRACT
Abstract: A complete procedure, starting from the experimental techniques to obtain accurate thermodynamic GE and VE data for mixing, is accurately described for the calculation of Kirkwood-Buff integrals (KBIs) and local compositions in the whole mole fraction domain of a ternary mixture of organic compounds. Proper equations to represent GE and VE are suggested, and these are used in a computer program, which calculates the values of all the intermediate quantities necessary to obtain the KBIs. The computer routines allow an easy and fast calculation of the KBIs, and of the local compositions, in correspondence with a lattice of mole fraction values that is then used to plot the KBIs as continuous surfaces. This treatment is applied to three ternary mixtures containing components of different polarity, purposely chosen to examine the roles played by different types of interactions (H-bond, dipole-dipole, dipole-induced dipole, dispersion) in the determination of the local composition around each solute species. The mixture of ethanol (Et) + tetrahydrofuran (THF) + cyclo hexane (cyH) (system I) is investigated and the capability of THF to perturb the strong Et self-association characteristics of the alcohol-hydrocarbon binary mixtures is examined. In system II, 2-methoxyethanol (MEt) + THF + cyH, the KBIs and local composition behaviors are compared with system I to examine the effects of the additional ether oxygen of MEt on the molecular interactions among the components. Finally, the mixture of trichloromethane (TCM) + THF + cyH (III) is studied to indicate the degree to which the strength of the TCM-THF interaction competes with the TCM and THF respective self-associative interactions shown in their binary mixtures with cyH.
