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Excess molar volumes VE at 298.15 K were determined by means of a vibrating tube densimeter for binary mixtures of heptane + primary n-alkyl (C3 to C10) and branched amines (iso-propyl-, iso-, sec-, and tert-butyl-, iso-, tert-pentyl-, and pentan-3-amine) in the whole composition range. The apparent molar volumes of solid dodecyl- and tetradecylamine in heptane dilute solution were also determined. The VE values were found positive for mixtures involving C3 to C8 linear amines, with VE decreasing with chain lengthening. Heptane + nonyl and decylamine showed s-shaped, markedly asymmetric, curves. Mixtures with branched C3 to C5 amines displayed positive VE’s larger than those observed in the mixtures of the corresponding linear isomers. Partial molar volumes V° at infinite dilution in heptane were evaluated for the examined amines and compared with those of alkanes and alkanols taken from the literature. An additivity scheme, based on the intrinsic volume approach, was applied to estimate group (CH3, CH2, CH, C, NH2, and OH) contributions to V°. The effect of branching on V° and the limiting slope of the apparent excess molar volumes were evaluated and discussed in terms of solute–solvent and solute–solute interactions.

There are little data in the literature on how to authenticate edible oils through calorimetry techniques. However, oil melting curves can be used to represent correlations between calorimetric results and oil quality. A calorimetric method has been developed for studying the solid-liquid phase transitions of olive oil and seed oils, in which melting peak behavior is correlated to the type, quality, and composition of the oil. Good reproducible thermograms were obtained by defining precise protocols for use in testing, which take into account the specific characteristics of a particular oil. This approach does not replace classical analytical methods; nevertheless, it is believed that calorimetric tests could be a useful preliminary stage for quality testing. The calorimetric technique allows the detection of the adulterant (seed oils or refined olive oil), oil origin, and possible photo-oxidation degradation processes, before more complex and expensive procedures and analyses are applied.

The aim of this paper is to promote calorimetry for olive oil authentication. It is our belief that the melting and freezing curves by DSC of olive oil and other edible oils could be correlated with quality, origin and storage history of the oil in a simple way, suitable for oil industry and market. Nucleation, crystallization kinetics and transition enthalpies of oil are indeed strongly dependent on molecular interactions, that is any change of oil acidic composition and minor components can be detected, as we have recently demonstrated. In particular, addition of low-cost oils to extra virgin olive oil (EVOO) and thermal and/or mechanical treatments (refinement, deodorization, filtration, etc.) of EVOO can be assessed by a first-sight analysis of the thermograms. Protocols to obtain reproducible DSC thermograms and experiments to understand the origin of the often-observed non-reproducibility, which prevented until now the use of calorimetry for oil authentication, are here described. An explanation of the melting curves even limited to the main features is a hard task owing to the polymorphism of the numerous triacylglycerols (TAG), the main component of the oil, the complexity of their mutual interactions and the effects of the minority components. To outline the level of this challenge we report: (i) the evidence that thermodynamic and kinetic processes overlap during heating of solid EVOOs and (ii) the melting curve of one pure TAG with its polymorphic transitions.

The excess enthalpies, H-E, at 298.15 K for binary mixtures of 1, 1,2,2-tetrachloroethane (TCE) + an hydrocarbon (n-heptane, cyclohexane, benzene, toluene, ethyl-, n-propyl-, iso-propyl-, n-butyl-, sec-butyl-, and tert-butylbenzene) have been measured by flow microcalorimetry. All mixtures containing an aromatic hydrocarbon as second constituent exhibit negative H-E while mixtures with n-heptane or cyclohexane are endothermic. The H-E data have been analysed in terms of the DISQUAC model. Using a limited number of adjusted interchange energy parameters, C, taken as structure dependent, the model provides a fairly consistent description of H-E as a function of concentration. The enthalpies of solvation, Delta H degrees, of hydrocarbons in TCE, as obtained from heats of solution at infinite dilution and known vaporization enthalpies, have been described using an additive scheme of surface interactions. The effects of aromatic ring, chain lengthening, branching, and cyclization on both H-E and Delta H degrees have been discussed.

Extra Virgin olive oils (7 samples) originating from different areas of Tuscany, defective olive oils (5 samples), commercial edible seed oils (4 samples) and two commercial samples of olive oil (one declared 'extra virgin olive oil' and one olive oil') were studied by different calorimetric techniques: high sensitivity isothermal, differential scanning, and modulated scanning calorimetry. The temperature interval (-60)-(+30)degrees C was explored for monitoring: i) the main features of the liquid solid phase transitions, ii) the nucleation and growth rate of the polymorphous crystalline phases of the triacylglicerols, and iii) the melting process. This investigation was planned for verifying the utility and effectiveness of calorimetry for screening quality and origin of olive oil. To this end, the main calorimetric operation modes have been applied, the experimental results reported and their utility for developing an effective and reliable screening protocol discussed.

A newly designed calorimetric technique and calculation procedure has been used to obtain partial molar enthalpies and excess enthalpies HE at 298.15 K for binary mixtures of heptane + primary n-alkyl (C3-C10) and + branched (iso-propyl, sec-, iso-, and tert-butyl) amines in the whole composition range. All mixtures examined showed positive HE's, which decrease with increasing amine size. From partial molar enthalpies at infinite dilution and from the known enthalpies of vaporization, the enthalpies of solvation DsolvH° have been evaluated either for amines in heptane and heptane in amines. An additive scheme of surface interactions combined with the scaled particle theory is presented to estimate and analyse different group (CH3, CH2, CH, C, NH2, O, OH, CO, CN, COO, CHO) contributions to DsolvH° as well as to its cavitational and interactional terms.

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 to C8, and of perfluorohexane with a n-alkane, C5 to 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 cm3mol-1) and among the largest known for non electrolyte systems. Limiting partial molar volumes have been evaluated for each component of the examined mixtures. The behaviour of has been discussed in terms of the Scaled Particle Theory 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 (C5-C8) and of n-hexane plus a n-perfluoroalkane (C5-C8) were determined using a head-space gas-chromatographic technique. Excess molar Gibbs energies, GE, 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 + alkane(C6-C8) 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.