Russian Journal of Physical Chemistry A最新文献

Every year, the interest in obtaining new forms of phase change materials (PCM) and studying their physicochemical properties is growing. A topical task is to develop new experimental methods for studying the phase behavior of PCM. The paper presents the results of a study of the phase behavior of a nanosized aqueous dispersion of n-eicosane (C₂₀H₄₂) using an optical method. Samples of an aqueous dispersion of the studied paraffin were obtained using ultrasonic dispersion without adding surfactants. For the studied sample, the temperatures of phase transitions (melting, crystallization, rotator phases) were determined during heating and cooling. Phase transitions not observed in a bulk sample of the studied paraffin were discovered.

The study of the reactivity of heterocyclic thioamides exhibiting antithyroid activity is of scientific and practical interest. For objective evaluation of the reactivity of thioamides with biologically active and biogenic metal ions, reliable thermodynamic parameters of complexation are of great importance. The thermodynamic parameters of complexation can be determined by various complementary methods, which increases the reliability of results. The thermodynamic parameters of the reaction of formation of a silver(I) monocomplex with 1-methyl-2-mercaptoimidazole (logK°, ∆_rG°, ∆_rH°, ∆_rS°) were determined by isothermal titration calorimetry in water at T = 298.15 K. The results were compared with the thermodynamic parameters obtained previously by potentiometric titration using the temperature coefficient method to determine the enthalpy of complexation.

Vapor–liquid surface tension is calculated on the evaporation curve of n-nonane in the SAFT-γ Mie model. The calculations are made via molecular dynamics for temperatures in the range of 410 to 505 K. The effect the cutoff radius of the interparticle interaction potential in the model has on the coefficient of surface tension and the difference between densities of the liquid and vapor phases is studied. An extrapolation algorithm is proposed for estimating surface tension with an uncut potential of interaction. The results are in good agreement with tabular values of surface tension. Extrapolation allows the systematic error of calculations to be estimated, while reducing the computational complexity relative to the direct modeling of a system with a large potential cutoff radius.

Criteria for selecting the best antisolvent among aliphatic amines: dipropylamine, diisopropylamine, and triethylamine were developed. The phase behavior of 14 salt–water–amine ternary systems was analyzed, including salts with different solubilities and salting-out abilities (sodium and potassium formats; sodium, potassium, and cesium nitrates; lithium and sodium chlorides; potassium bromide and iodide). The temperature dependences of the composition of the critical solution were determined for the majority of systems, and isothermal phase diagrams were constructed for all of them. The compositions of the equilibrium phases of the monotectic state were used to calculate the yield of salt crystals depending on the antisolvent concentration and temperature. The optimum conditions for the process can be determined based on the analysis of the phase diagrams of systems in a certain temperature range. The revealed tendencies in extractive crystallization made it possible to significantly reduce the amount of experimental work to find the best conditions for extracting the salts from aqueous solutions and to propose a research algorithm. The algorithm makes it possible to reduce the experiment by 6–8 times and to carry out an express assessment of the effectiveness of an antisolvent for a particular salt without phase selection and their chemical analysis.

The authors investigate the solubility curves of nematic phenyl benzoates (p-hexyloxyphenyl esters of p-alkyloxybenzoic acids, n-alkyl = n-butyl and n-heptyl) in organic solvents of various kinds (n-hexane, n‑heptane, methanol, ethanol, 1-propanol, 2-propanol, 1,4-dioxane, diethyl ether, tert-butyl methyl ether, and ethyl acetate). The solubility of phenylbenzoates were estimated using the parameters of solubility. A scheme was proposed for estimating the enthalpy of vaporization, molar volume, and Hildebrand solubility parameter of aromatic esters of benzoic acid at 298.15 K.

The enthalpies of sublimation reactions of non-stoichiometric phases WO_2.985(s) and ZnWO_2.975(s) with the formation of gaseous oxides W₂O₆, W₃O₈, W₃O₉, W₄O₁₂ were obtained. It is shown that the difference with the enthalpies ​​obtained without taking into account deviations from stoichiometry is significantly less than the uncertainties of the enthalpies caused by high-temperature mass spectrometry method.

This work presents the results of the study of glycerol and water sorption using two complimentary approaches, simultaneous thermal analysis and isothermal sorption calorimetry, on zeolites differing in the framework topology and post modifications (natural clinoptilolite, protonated zeolite ZSM-5 with Si/Al ratio of 50, commercial Na-mordenite with Si/Al ratio of 6.5 then modified by ion exchange for copper ions, or by alkaline etching to develop mesoporosity, and pillared mordenite). For the studied mordenites a correlation between texture and composition and sorption capacity towards glycerol and water was shown. Analysis of glycerol and water desorption suggests the optimal temperature range for catalytic conversion of glycerol via dehydration and carboxylation.

The authors study the phase transitions, densities, and dynamic viscosities of choline chloride and urea mixtures. Temperature dependences of viscosity and density are described by empirical equations. It is shown that raising the concentration of urea in the eutectic system lowers the viscosity and increases the density of the mixture. A phase transition to the glassy state at a temperature of 211 K is detected for relin and does not shift upon changing the composition of the mixture.

The dew point approach is used for the first time to determine the activity of water in the H₂O–NaCl–KCl–AlCl₃ system at 298.15 K and in the constituent ternary subsystems at 298.15 and 323.15 K. A set of parameters for the Pitzer–Simonson–Clegg liquid phase model is proposed that adequately describes vapor–liquid equilibria, along with heat capacities of solutions and solubility in the H₂O–AlCl₃ system from 222.45 to 373.15 K; vapor–liquid equilibria and solubility in the H₂O–NaCl–AlCl₃ and H₂O–KCl–AlCl₃ systems in the range of 273.15 to 363.15 K, along with vapor-liquid equilibria in H₂O–NaCl–KCl–AlCl₃ at 298.15 K. The densities of solutions in the H₂O–NaCl–KCl–AlCl₃ system are measured at 298.15 K, and the resulting values are then compared to those calculated using the Laliberte model.

Results are presented from a thermodynamic study of compounds with a layered FeGa₂S₄ and Fe₂Ga₂S₅ structure. The EMF is measured for concentration chains of the type (−) FeS(solid)|glycerol + KCl + FeCl₂|(Fe in alloy) (+) in the 300–390 K range of temperatures. Results from X-ray diffraction analysis and data in the literature are used to establish the nature of solid-phase equilibria in the system Fe–Ga–S in the area of compositions FeS–Ga₂S₃–S. The formation of the above ternary compounds and a wide range of solid solutions based on Ga₂S₃ is confirmed. Partial molar functions of iron in ternary alloys are determined by combining thermodynamic data calculated from measurements of the EMF and the thermodynamic functions in the literature for compounds FeS₂ and FeS. These partial molar values and thermodynamic data for Ga₂S₃ are used to calculate the standard entropies and thermodynamic functions of the formation of compounds FeGa₂S₄ and Fe₂Ga₂S₅, and of solid solutions based on Ga₂S₃, according to the diagram of solid phase equilibria for subsystem FeS–Ga₂S₃–S.