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Abstract  

The influence of H2O–EtOH and H2O–Acetone mixed solvents at various compositions on the thermodynamics of complex formation reaction between crown ether 18-crown-6 (18C6) and glycine (Gly) was studied. The standard thermodynamic parameters of the complex [Gly18C6] (log K°, Δr H°, Δr S°) were calculated from thermochemical data at 298.15 K obtained by titration calorimetry. The complex stability and its formation enthalpy increase with increasing the non aqueous component concentration in both mixed solvents. The thermodynamic data were discussed on the basis of the solvation thermodynamic approach and the solvation contributions of the reagents and of the complex to the complex stability were analyzed.

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Journal of Thermal Analysis and Calorimetry
Authors: B. Marongiu, Silvia Porcedda, D. Falconieri, Alessandra Piras, E. Matteoli, and L. Lepori

Abstract

In this article are reported the excess enthalpies, H E, at 298.15 K, of liquid mixtures containing a linear mono-carboxylic acid (1) + di-n-butylether (2), determined by means of a titration calorimetric method. The experimental results, together with the literature data on thermodynamic properties of the above mentioned class of mixtures, have been interpreted in terms of the DISQUAC group contribution model. A set of structure-dependent interaction parameters, for the carboxylic group/oxygen contact, has been obtained. The model provides a fairly consistent description of the excess Gibbs energy, G E and excess enthalpy, H E, curves of the investigated mixtures.

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Abstract  

Literature data on molar excess enthalpies and molar excess Gibbs energies, liquid-liquid equilibria, activity coefficients at infinite dilution and partial molar enthalpies at infinite dilution of binary mixtures of n-perfluoroalkanes (C5−C8)+n-alkanes (C5−C8) and of n-perfluorohexane-linear monoethers of general formula, CH3(CH2)m-O-(CH2)n-CH3 (m,n=1–4), are treated in the framework of DISQUAC, an extended quasichemical group contribution theory. The systems are characterized by two or three types of contact surfaces: aliphatic (CH3, CH2, CH and C groups), fluorine (F group) and oxygen (O group). Using a limited number of adjusted contact interchange energies parameters, structure dependent, the model provides a fairly consistent description of the thermodynamic properties as a function of concentration. The model may serve to predict missing data.

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Journal of Thermal Analysis and Calorimetry
Authors: M. Angiuli, C. Ferrari, L. Lepori, E. Matteoli, G. Salvetti, E. Tombari, A. Banti, and N. Minnaja

Abstract  

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)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.

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