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Data on the solubility of neutral compounds in perfluoro-hexane, -heptane, and –octane have been obtained from the literature. It is shown that water-solvent and gas-solvent partition coefficients, P and K respectively, are effectively the same for all three perfluoroalkanes. Linear free energy relationships, LFERs, have been set up for these partition coefficients, as log P and log K. Comparison of the LFER coefficients in the log K equation for perfluoroheptane with those for a large number of other solvents shows that perfluoroheptane is an unusual solvent, in that small nonpolar solutes are more soluble than in other solvents. The comparative solubility of small nonpolar gaseous compounds in perfluoroheptane is due to a combination of cavity and interaction terms. Calculations using Pierotti's version of Scaled Particle Theory indicates that the solute-perfluoroheptane unfavourable cavity term is always smaller than that for solution in other solvents, which by itself would lead to enhanced solubilities in perfluoroheptane, as shown by small nonpolar solutes. As the solute becomes larger and more polar, the favourable interaction terms in other organic solvents become much larger than the corresponding interaction terms in perfluoroheptane. This results in the larger and/or more polar gaseous solutes being much more soluble in other organic solvents than in perfluoroheptane.

Partial molar enthalpies and excess enthalpies HE of binary mixtures of heptane + secondary and tertiary n-alkyl, primary cycloalkyl, and secondary (hetero)cyclic amines have been determined at 298.15 K by isothermal titration calorimetry in the whole composition range. All mixtures showed positive HE values which decrease with increasing amine size in each category, and decrease in the order cyclic primary > cyclic secondary > linear primary [1] > secondary > tertiary when comparing amines of similar size in different categories. From partial molar enthalpies at infinite dilution and known enthalpies of vaporization, the solvation enthalpies have been calculated either for heptane in amines and for amines in heptane. These quantities, together with their cavitational and interactional terms obtained applying the scaled particle theory, are discussed to get insight into the types and relative strength of solute–solvent interactions and into their effects on molecular structure features such as branching and cyclization.

Vapour–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and excess enthalpies (HE) of binary mixtures of perfluoro-n-hexane plus an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether), have been determined using a head-space gas-chromatographic technique, a turbidimetric apparatus, and a heat-flow calorimeter, respectively. A recently designed titration technique and calculation procedure have been used to obtain HE from heats of solution. The observed liquid–liquid coexistence curves have been compared with those predicted by the activity coefficients γi and their temperature dependence. All mixtures are strongly endothermic (HE > 0) and show large positive deviations from ideality (GE > 0), which increase with the size of the ether. Molecular interactions have been examined by calculating and discussing solvation functions and Kirkwood–Buff (KB) integrals. Perfluorohexane proved to be an inert molecule that interacts with ethers more weakly than hexane.

Excess molar volumes VE at 298.15 K have been determined by means of a vibrating-tube densimeter for binary mixtures of n-hexane with a perfluoroalkane, C5–C8, and of perfluorohexane with a n-alkane, C5–C8, or an ether (diethyl, dipropyl, dibutyl, butyl methyl, and butyl ethyl ether). The systems perfluoropentane+hexane, perfluorohexane+pentane or hexane or diethyl ether have been investigated in the entire mole fraction range, while the other mixtures only in the miscibility regions. The observed VE values are positive (up to 5.5 cm3 mol−1) and among the largest known for non-electrolyte systems. Limiting partial molar volumes, V ° , have been evaluated for each component of the examined mixtures. The behaviour of V ° has been discussed in terms of the scaled particle theory (SPT) and of a simple group additivity scheme based on surface interactions. An estimate has been made of the average separation distance of solvent from solute molecules.

Vapour–liquid equilibria (VLE) of binary mixtures of n -perfluorohexane plus a n -alkane (C 5 –C 8 ) and of n -hexane plus a n -perfluoroalkane (C 5 –C 8 ) were determined using a head-space gas-chromatographic technique. Excess molar Gibbs energies, G E , for the systems investigated have been obtained by a least-square treatment of equilibrium data. Liquid–liquid equilibria (LLE) were determined by turbidimetry for n -perfluorohexane+ n -C n H 2 n +2 ( n =6–8) mixtures and the observed T – x curves compared with those predicted by the temperature dependence of activity coefficients. All mixtures show strong positive deviations from ideality, which increase with the size of the second component. Solute–solvent and solute–solute interactions have been examined by calculating and discussing solvation Gibbs energies and Kirkwood–Buff integrals. Perfluoroalkanes proved to be inert molecules that interact weakly with themselves as well as with alkanes.

A calorimetric technique and a calculation procedure to obtain excess enthalpies HE of liquid mixtures is described and tested. It is based on a heat-flow calorimeter used as a titration calorimeter to measure the heat effects associated to small additions of one of the components, or a mixture of them, to the ampoule containing a known amount of the other component or of a mixture of them. The procedure takes into account the presence of a small vapour space and calculates the heat involved in the vapour–liquid equilibration after each addition. The experimental values are fitted with a parametric equation such as Redlich–Kister to determine the HE parameters by least-squares adjustment. The technique has been tested with respect to the systems ethanol+cyclohexane, dioxane+water and tetrachloromethane+benzene. The results show a good agreement with literature data for these mixtures, and confirm the capability of this technique to reliably replace the mix-flow technique when the components mix slowly, or show a mixture gap, or are available in small quantities. HE results are reported for the system perfluorohexane+hexane for which the mixing process is slow.

By means of a vibrating tube densimeter, the excess molar volumes V E at 298.15 K have been determined in the whole composition domain for the ternary system ethanol+tetrahydrofuran+cyclohexane and for the relevant binary mixtures. While ethanol+tetrahydrofuran shows slight V E values and a S-shaped V E curve, the other two binaries have similar largely positive V E s. The ternary V E surface is almost always positive with a small maximum. The binary V E data have been described with different correlation equations. The capabilities of different models of either predicting or reproducing the ternary data have been compared. The behaviour of V E and of the partial molar excess volumes of the components in the ternary system is discussed and it is found that hydrogen-bonding decreases with alcohol dilution and increases with the tetrahydrofuran solution content.

Vapour-liquid equilibria for the ternary system ethanol + tetrahydrofuran + cyclohexane and for the relevant binary mixtures have been determined at 298.15 K by head-space gas-chromatographic analysis of the vapour phase directly withdrawn from an equilibration apparatus. Experimental data have been described with different equations (Redlich-Kister, Wilson, NRTL and UNIQUAC) and excess Gibbs energies GE as well as activity coefficients γi of components have been obtained. All systems exhibit positive deviations. The binaries containing cyclohexane form azeotropic mixtures at 298.15 K, while ethanol + tetrahydrofuran and the ternary systems do not. The excess entropy and the temperature dependence of GE and γi have been calculated in the whole ternary domain from the known excess enthalpy and heat capacity.

Excess enthalpies and excess heat capacities at 298.15 K for the ternary system ethanol + dimethylformamide + tetrahydrofuran were determined by means of a flow calorimetric apparatus built in our laboratory. Experimental data were described with a Redlich-Kister type equation and compared with those of other ternary systems previously studied (ethanol + tetrahydrofuran + cyclohexane, ethanol + dimethylformamide + cyclohexane, dimethylformamide + tetrahydrofuran + cyclohexane). A peculiar behaviour was observed for mixtures containing dimethylformamide, namely the negative values of both H E and C p E ternary contributions. A satisfactory prediction of experimental H E data is provided by the UNIQUAC model, while UNIFAC (Dortmund, Germany) clearly fails probably owing to an unsufficient definition of interaction parameters involving dimethylformamide.

Excess enthalpies and excess heat capacities at 298.15 K for the ternary system ethanol + dimethylformamide + cyclohexane, and for the related binary mixtures dimethylformamide + ethanol or cyclohexane were determined by means of a flow calorimetric apparatus built in our laboratory. Experimental data were described with a Redlich-Kister type equation. H E and C P E data are positive in the whole region of miscibility; however, their ternary contributions to the excess quantities, referred to the combination of the Redlich-Kister representation of the parent binary mixtures, present opposite features. UNIQUAC and UNIFAC models were used for the description or prediction of experimental results.

Spanedda, A., Lepori, L. and Matteoli, E., 1991. Volumes of mixing of ethers with tetrachloromethane at 298.15 K. Fluid Phase Equilibria , 69: 209-222. The excess molar volumes V E , at 298.15 K, have been determined by means of a vibrating-tube densimeter in the whole mole fraction range for binary mixtures of tetra-chloromethane with an ether (diethyl ether, dimethoxymethane, diethoxymethane, 1,2-di-methoxyethane, 1,2-diethoxyethane, diethyleneglycol dimethyl ether, oxepane or 1,3-dioxolane). The V E values are negative for all systems and become less negative with increasing number of oxygen atoms in the ether molecule. The V E values of some of the present mixtures have been analyzed in terms of the Flory theory of non-polar solutions. Limiting partial molar volumes − V o have been evaluated for each component of the examined systems. The behaviour of − V o of ethers is discussed and a simple group additivity scheme is presented.

A head-space gas chromatographic technique has been used to determine vapour—liquid equilibria for binary mixtures of: cyclohexane+an aldehyde (ethanal, butanal, pentanal); tetrachloromethane+ethanal, +pentanal and +cyclobutanone; and heptane+cyclobutanone or+a diketone (2,3-butanedione, 2,5-hexanedione). Excess molar Gibbs energies, GE, for the mixtures investigated were obtained by a least-squares treatment of the equilibrium results. All systems exhibit positive deviations. For mixtures involving aldehydes, the GE values are larger when the other component is cyclohexane than when it is tetrachloromethane and decrease with increasing aldehyde chain length. Activity coefficients at infinite dilution, f∞, as well as free energies of solvation, δG°, were evaluated for each component of the systems examined. A tentative approach, based on an additivity scheme of surface interactions combined with the Scaled Particle Theory, is presented to estimate and to analyse group contributions to δG°.

Marongiu, B., Pittau, B., Porcedda, S., and Tine, M.R., 1994. Thermodynamics of binary mixtures containing linear or cyclic alkenes + n -alkanes or cyclohexane. Fluid Phase Equilibria 93; 249-276. A head-space technique has been used to determine vapor-phase equilibria for binary mixtures of linear or cyclic mono- and polyalkenes + n-alkanes or + cyclohexane. Excess molar Gibbs energies GE for the mixtures investigated were obtained by a least-squares treatment of the equilibrium results. These data the previously measured excess enthalpies HE and the data available in the literature on GE HE activity coefficients at infinite dilution γi∞ and molar excess enthalpies at infinite dilution hiE,∞ are examined on the basis of the DISQUAC group contribution model. The model provides a fairly consistent description of the phase equilibria and the related excess functions using a unique set of structure-dependent dispersive parameters.