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Four binary mixtures with potential for stabilizing energetic materials have been investigated. The phase diagrams of N-(2-methoxyethyl)-p-nitroaniline + diphenylamine, N-(2-methoxyethyl)-p-nitroaniline + N-(2-acetoxyethyl)-p-nitroaniline, N-(2-methoxyethyl)-p-nitroaniline + 2-nitrodiphenylamine, and N-(2-methoxyethyl)-p-nitroaniline + 1,3-diethyl-1,3-diphenylurea have been determined by differential scanning calorimetry. All systems display a simple eutectic behavior. Consistency tests have been applied to inspect the quality of the SLE data, showing very satisfactory quality factors. The SLE data have also been correlated by Wilson and NRTL models. The employed equations calculated the equilibrium temperatures with a root mean square deviations varying from 1.37 to 2.29 K. These models have been applied to compute the excess thermodynamic functions as well, giving highly comparable values for a further qualitative and quantitative analysis. The results show a positive deviation from ideality for all the investigated systems due to the dominant effect of the self-association molecules. The XRD studies revealed the existence of weak interactions between the components in the formed eutectics and suggested that they are mechanical systems. • The four investigated mixtures are simple eutectic. • The quality of the SLE data has been checked by consistency tests. • The Wilson and NRTL models correlate accurately the SLE data. • Excess thermodynamic functions allow highlighting the nature and the intensity of the existing interactions. • XRD results showed that the eutectics are mechanical systems. [ABSTRACT FROM AUTHOR]

The ability to extract thermodynamic properties of mixtures from molecular geometry and interactions is one of the major advantages of atomistic simulations, but, at the same time, can be a great challenge, especially for statistical properties such as the Gibbs energy of mixing (Δ mix G ). This challenge becomes even greater in the case of mixtures of complicated molecules or macromolecules. Kirkwood-Buff theory offers a promising avenue for estimating Δ mix G from atomistic simulation of binary mixtures. In this work we perform molecular dynamics simulations of both ideal and real binary Lennard-Jones mixtures at various mole fractions. We estimate the Kirkwood-Buff integrals by two different methods and identify the most efficient one. Then we validate our methodology by comparing several thermodynamic properties of the ideal mixtures against the theoretical expressions of thermodynamics. Finally, we calculate the mixing thermodynamic properties for the real mixtures, namely the enthalpy, Gibbs energy, volume, and entropy of mixing, as well as their excess parts relative to an ideal solution. We compare our results against the predictions of the well-known modified Benedict-Webb-Rubin equation of state for Lennard-Jones systems and find good agreement. [ABSTRACT FROM AUTHOR]

The properties of fluoride in wet phosphoric acid processes were of interest us to understand the processes and roles that fluorosilicic acid plays in phosphoric acid solutions. The literature data indicate that some deficiencies exist in the thermodynamic properties of hexafluorosilicic acid aqueous solutions. In this investigation, the water activity and osmotic coefficients of H 2 SiF 6(aq) were determined in the temperature range from T = 298.15 to 353.15 K. The measurements of the water activity were performed at molalities from 0.10 to 3.00 mol kg −1 of H 2 SiF 6(aq) using the hygrometric method. The modelling approach based on the Pitzer model was developed to determine the thermodynamic properties. From these measurements, the ion interaction parameters in binary solution were evaluated at different temperatures ranging from 298.15 K to 353.15 K and were used to predict the solute activity coefficients. The development of a model for solution behaviour was also employed to determine the excess molal Gibbs energy, enthalpy, entropy and heat capacity of the H 2 SiF 6 aqueous solution within the temperature range from 298.15 K to 353.15 K. [ABSTRACT FROM AUTHOR]

Abstract: The coefficient of compressibility, k =ΔV/V o , of {water (1)+ethylene glycol (2)} binary mixture was measured at pressures from 0.1 to 100MPa and temperatures from 278.15 to 323.15K over the whole concentration range. At all state parameters the following characteristics were calculated: excess molar volumes of the mixture, ; changes of excess molar Gibbs energy, ; changes of excess molar entropy, ; changes of excess molar enthalpy, ; mixing enthalpy, , of water with ethylene glycol at high pressure, and partial molar volumes of the components. It was shown that the coefficients of compressibility, k, sharply decreased over the concentration interval x 2 =0–0.2, where x 2 was ethylene glycol mole fraction, and further changed insignificantly. It was revealed that excess molar volumes were negative at all temperatures studied and went down with pressure increasing. The dependence of partial molar volumes of the mixture components on ethylene glycol mole fraction passes extreme at all isobars. Limiting partial molar volumes of water and ethylene glycol decrease with pressure growth. The mixture compression leads to its ordering due to new hydrogen bonds formation. [Copyright &y& Elsevier]

Abstract: The high-pressure phase diagram and excess thermodynamic properties of the binary mixture of carbon dioxide and water are examined using the statistical associating fluid theory for potentials of variable range (SAFT-VR). The carbon dioxide molecule is modelled with two tangentially bonded spherical segments, while the water molecule is modelled as spherical with four associating sites to represent the hydrogen bonding. Dispersion interactions are modelled using square-well potentials. The optimised intermolecular parameters are taken from the works of Galindo and Blas [F.J. Blas, A. Galindo, Fluid Phase Equilib. 194–197 (2002) 501–509; A. Galindo, F.J. Blas, J. Phys. Chem. B 106 (2002) 4503–4515] and Clark et al. [G.N.I. Clark, A.J. Haslam, A. Galindo, G. Jackson, Mol. Phys. 104 (2006) 3561–3581] for carbon dioxide and water, respectively. The mixture exhibits type III phase behaviour in the classification of Scott and van Konynenburg, with the gas–liquid critical line continuously changing into a liquid–liquid line at high pressures. In this work one unlike intermolecular interaction parameter is fitted to give the best possible representation of the minimum temperature of the gas–liquid critical line of the mixture, and is then used in a transferable manner to study other thermodynamic conditions and properties. The phase diagrams predicted by the SAFT-VR approach are found to be in very good agreement with the experimental data at low and high pressures and temperatures. In addition, a good qualitative description of the excess molar volume and excess enthalpy and different temperatures and pressures is obtained. [Copyright &y& Elsevier]