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Abstract  

Evaluation has been carried out of the component of the second virial coefficient of steam related to the formation of dimers. The necessary equilibrium constants of dimerization have been evaluated within the MCY-B water pair interaction potential. The calculated isotopic difference in the second virial coefficient reflects the qualitative features found by observation but, nevertheless, the calculation quite distinctly overestimates the value of this isotopic difference as compared with the observation. The nature of these differences and the relation to the state behaviour of water are discussed.

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Molar excess enthalpies for aqueous solutions of 3-methoxy-1-butanol (3-MB) and 1-methoxy-2-butanol (M-2B) have been measured at 298.15 K over the whole concentration range with a flow microcalorimeter. From the experimental data, we evaluated the enthalpic interaction parameter hxx and obtained the following order:h xx(3 MB) hxx(M-2B)

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_DC) presented in Fig. 1 . The aim of this study was: to derive the experimental values of the solution enthalpies for K_DC in water at wide concentration and temperature intervals; to calculate the virial coefficients within Pitzer's model and determine the

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exact relations obtained so far. These approximations are indispensable when practical application of the thermodynamic relations is the goal. In particular, some current estimation techniques for auxiliary quantities, such as virial coefficients and

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Alternative biofuels

PVTx measurements for DME + propane

Journal of Thermal Analysis and Calorimetry
Authors: A. Arteconi, G. Di Nicola, M. Moglie, G. Santori, and R. Stryjek

Abstract  

This study presents the experimental results for the dimethyl ether (DME) + propane system obtained using the Burnett method. The apparatus was calibrated using helium. PVTx measurements were taken for four isotherms (344, 354, 364, and 375 K), performing 16 Burnett expansions in pressures ranging from about 3,000 to 70 kPa. The second and third virial coefficients were derived from experimental results. The experimental uncertainty in the second and third virial coefficients was estimated to be within ±5 cm3/mol and ±1,000 cm6/mol2, respectively.

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Abstract  

Enthalpies of solution and dilution of aqueous solutions of sodium diclofenac salt were measured by isoperibolic calorimeter at 293.15, 298.15, 303.15, 308.15 and 318.15 K. The concentration of the electrolyte was restricted to solubility salt at various temperatures and did not exceed 0.035–0.057 mol kg−1 values depending on the studied temperature. The virial coefficients were derived from Pitzer’s model and the excess thermodynamic functions of both the solution and the components of the solution were calculated. The analysis of thermodynamic characteristics of the solution from concentration and temperatures was carried out and discussed.

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Journal of Thermal Analysis and Calorimetry
Authors: G. Di Nicola, G. Giuliani, F. Polonara, and R. Stryjek

Summary In this work, the PVT properties have been object of study. In particular, the experimental work was performed both in the two-phase region and in the superheated vapor region phase by means of two different methods: the isochoric and the Burnett methods. The isochoric measurements were carried out at temperatures from 219 to 354 K and at pressures from 550 up to 5400 kPa. A total of 95 points, both in the two phases and in the superheated vapor region were obtained. For the Burnett measurements, in total, 14 runs along 7 isotherms in a pressure range from 170 to 5200 kPa were performed. The second and third virial coefficients were derived and a good consistency was found after comparison with other literature sources in the reduced temperature range of interest (0.9<Tr<1.2).

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Journal of Thermal Analysis and Calorimetry
Authors: W. Zielenkiewicz, I. Terekhova, A. Marcinowicz, M. Koźbial, and J. Poznanski

Abstract  

Interactions of native and modified α- and β-cyclodextrins with nicotinic acid, pyridoxine and pyridoxal were studied by isothermal titration calorimetry, solution calorimetry, and 1H NMR spectroscopy at 298.15 K and pH 6.8. Weak 1:1 complex formation was found only between α-cyclodextrin and nicotinic acid. The stability constant and corresponding thermodynamic parameters of complex formation (Δc G, Δc H and Δc S) were calculated using the calorimetric data. The 1H NMR data indicate the shallow insertion of the carboxylic group of the nicotinic acid molecule into α-CD cavity. For all other compounds the weak interactions, not accompanied by complex formation, were characterized by the enthalpic virial coefficients calculated on the basis of McMillan-Mayer approach. The obtained thermodynamic parameters were analyzed in the terms of influence of the solutes’ structure on the selectivity of intermolecular host-guest interactions.

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The Ostwald coefficients L2,1 of He, Ne, Ar, Kr, Xe, N2, O2, CH4 CF4 and SF6 dissolved in several homologousn-alkanes,n-C1H21+2, 6≤l≤16, andn-alkan-1-ols,n-C1H21+1OH, 1≤l≤11, were recently measured at 298.15 K and atmospheric pressure with a modified Ben-Naim/Baer apparatus. Altogether, 201 gas/liquid systems were investigated. For about half of these systems, both pressure control and measurement of the volume of gas dissolved in a given volume of solvent were achieved with a microprocessor. This improved medium-precision instrument (σ≤0.5% in most cases) combines easy handling with fully automated data retrieval, and is totallymercury-free. In this communication, the salient points of data reduction are presented, with the focus on the estimation of several important auxiliary quantities such as second virial coefficients and partial molar volumes at infinite dilution. The effect of the chain lengthl of then-alkane or then-alkan-1-ol upon solubility is demonstrated, and some correlations betweenL 2,1, or the derived Henry fugacitiesH 2,1, and appropriate molecular and/or bulk properties of the gases and the solvents are discussed.

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