Journal of Chemical Thermodynamics最新文献

Manganese (II) sulfate (MnSO₄), also known as manganous sulfate, has gained attention due to its low temperature magnetic properties. Following a study of its magnetic structure, manganese sulfate was proposed as being the first orthorhombic compound to have a spiral magnetic structure. It was predicted to have a three-step magnetic transition at low temperatures, which neutron diffraction studies have since confirmed. This work represents the first time that heat capacity data has been collected on MnSO₄ and MnSO₄ 0.984(H₂O) at low temperatures, which we report from 1.8 K to 300 K and comment on the presentation of the magnetic transition in the low temperature heat capacity region. Previous studies report the heat capacity of the anhydrous form above 50 K, and the data collected herein is compared with those previously published results. Theoretical fits of the heat capacity data are used to calculate the smoothed thermodynamic data, including C_p,m°, ${\Delta }_0^T$ S_m°, ${\Delta }_0^T$ H_m°, and Φ_m°.

In this work, a Peltier-element-based adiabatic scanning calorimeter was used to investigate, with high-resolution and accuracy, the temperature dependence of the specific heat capacity and specific enthalpy difference of a series of linear alkanes. More specifically, results are reported for the even n-alkanes; namely n-eicosane, n-octadecane, n-hexadecane and for the odd n-alkanes, namely n-nonadecane, n-heptadecane and n-pentadecane. The measurements cover a temperature range from well in the crystalline solid phase across the solid–solid transitions (when present) in to the liquid phase across the melting transition. Accurate transition temperatures and heat of transitions were derived from the direct experimental data in view of the potential use of n-alkanes as phase change materials.

In this paper, the 65 isobaric specific heat capacity (c_p) and 9 viscosity (η) data of 3,3,3-trifluoroprop-1-ene (R1243zf) were measured at temperatures from (230 to 293) K and pressure up to 8 MPa using a flow calorimeter and a vibrating-wire viscometer. The uncertainty of temperature, pressure, isobaric specific heat capacity and viscosity were evaluated to be less than 11 mK, 0.02 MPa, 1.0 % and 2.7 %, respectively. Three saturated liquid viscosity (η_s) data were obtained based on the extrapolation of the viscosity data. Empirical correlations were established based on the c_p and η_s data, the average absolute relative deviation for c_p and η_s are 0.5 % and 1.3 %, respectively.

Thermodynamic inhibitors may be used to inhibit hydrate formation in industry. Alcohol substances, due to their hydrophilic hydroxyl groups in their molecular structure, are prone to form hydrogen bond with water molecules to inhibit hydrate formation. In this work, sec-butyl alcohol is chosen to study the effects on CO₂ hydrate dissociation equilibrium conditions, where the step-heating method is utilized to obtain hydrate equilibrium conditions. The equilibrium curve of carbon dioxide hydrate dissociation moves to the region of lower temperatures or higher pressures. The higher mass fraction of sec-butyl alcohol, the better effect of inhibiting hydrate formation. Sec-butyl alcohol can be used as a thermodynamic hydrate inhibitor.

The solubility of isophthalic acid (IPA) in four different binary solvent systems (water + methanol, water + ethanol, water + 1-propanol, and water + isopropanol) was measured by the gravimetric method at atmospheric pressure from 283.15 K to 323.15 K. Under certain solvent compositions, the solubility of IPA increased with increasing temperature. The trend of solubility under isothermal conditions setting differs as the mole fraction of organic solvent increases. The solubility of IPA in water + methanol and water + ethanol systems increased with the mole fraction of methanol or ethanol. In the system of water + 1-propanol and water + isopropanol, as the mole fraction of organic solvent increased, the solubility of IPA increased firstly and then decreased gradually. The Hansen solubility parameters of IPA and selected solvents were analyzed, the analysis showed that the miscibility of IPA with the selected solvent was the result of many factors. Molecular electrostatic potential surface (MEPS) and Hirshfeld surface (HS) analysis were used to investigate the intermolecular interactions. The solubility data were correlated using the Apelblat equation, van't Hoff equation, λh equation, and Jouyban–Acree model. Besides, the vant Hoff equation was employed to analyze the apparent thermodynamic properties of dissolving process including the Gibbs energy, enthalpy and entropy. All positive values indicated that the dissolving process of IPA was non-spontaneous, endothermic, and entropy-driven.

The present study describes the thermodynamic assessment of three pseudo-binary systems relevant to CsI solubility in molten iodide salts: KI-CsI, NaI-CsI, and NaF-CsI. The motivation for this study was to corroborate a single previously reported data set of the NaI-CsI system, resolve inconsistencies reported by two different data-sets of the KI-CsI system, and generate new experimental data on the NaF-CsI system. Equilibrium data for all systems were obtained using Differential Scanning Calorimetry. Thermodynamic treatments of the three pseudo-binary systems were revised using the CALPHAD method with the thermodynamic software FactSage and Thermochimica. Both experimental and computational investigations provide increased confidence in the thermochemical behaviour of CsI in Molten Salt Reactor nuclear systems.

Curcumin (Cur), a naturally occurring bioactive compound belonging to the polyphenol class is loaded with a variety of medicinal properties. Its poor bioavailability and suboptimal absorption within the body limit its therapeutic effectiveness which raises the thrust of the development of effective curcumin analogs. In this context, we have synthesized boron-derivatized curcumin variants of Cur, curcumin-BF2 (Cur-BF₂), and iodinated-curcumin-BF2 (I-Cur-BF₂) and performed a detailed biophysical and thermodynamic analysis for the interactions of the Cur and its derivatives with the carrier plasma protein human serum albumin (HSA). A combination of fluorescence spectroscopy and isothermal titration calorimetry (ITC) was employed to study the binding of Cur and its derivatives with HSA. ITC results indicated that the Cur compounds bind sequentially with HSA in a three-step manner. The binding constant in all three events for all three compounds is in the range of 10⁴-10⁵ mol⁻¹·kg. ITC results also suggested that Cur and its derivatives bind to HSA with moderate affinity via a combination of electrostatic/ionic/H-bonding and hydrophobic interactions, however, the hydrophobic interactions dominate in the case of Cur derivatives. The conformational changes in HSA upon binding of Cur derivatives were studied by circular dichroism spectroscopy. Further, differential scanning calorimetry (DSC) confirms the increase in the thermal stability of HSA by Cur compounds as depicted by the increase in transition temperature (T_1/2) and transition enthalpy (Δ_calH). Such qualitative and quantitative studies are essential for gaining insights into drug-protein interactions and optimization of various binding parameters for enhanced therapeutic effects.

The phase equilibrium of ternary systems RbX/CsX + CuX₂ + H₂O (X = Cl, Br) at T = 298.15 K were investigated by the isothermal dissolution equilibrium method, in which the composition of equilibrium solid phases was determined by the Schreinemaker’s wet residue method. In the system RbCl + CuCl₂ + H₂O, there were three crystallization regions corresponding to RbCl, Rb₂CuCl₄·2H₂O and CuCl₂·2H₂O, respectively. Five crystallization fields corresponding to CsCl, CsCuCl₃, Cs₃Cu₂Cl₇·2H₂O, Cs₂CuCl₄ and CuCl₂·2H₂O were formed in the system CsCl + CuCl₂ + H₂O. The ternary system RbBr + CuBr₂ + H₂O had three crystalline regions corresponding to RbBr, Rb₂CuBr₄·2H₂O and CuBr₂. In the system CsBr + CuBr₂ + H₂O, the solid-phases of CsCuBr₃, Cs₂CuBr₄, besides CsBr and CuBr₂, were discovered. The results were compared with available literature data for cesium bromide/copper bromide salt-water system. The seven new solid phase were characterized using the X-ray diffraction method and thermogravimetric/differential analysis. The dissolution enthalpies of Rb₂CuCl₄·2H₂O, Rb₂CuBr₄·2H₂O, CsCuCl₃, Cs₃Cu₂Cl₇·2H₂O, Cs₂CuCl₄, CsCuBr₃ and Cs₂CuBr₄ at T = 298.15 K were measured. Their standard enthalpies of formation were obtained, and the results were in order with −(1714.4 ± 3.2) kJ·mol⁻¹, −(1533.6 ± 3.3) kJ·mol⁻¹, −(697.8 ± 3.1) kJ·mol⁻¹, −(2418.9 ± 6.1) kJ·mol⁻¹, −(1134.8 ± 3.2) kJ·mol⁻¹, −(563.5 ± 3.2) kJ·mol⁻¹ and −(966.2 ± 3.3) kJ·mol⁻¹, respectively.

In this work, we present experimental densities, viscosities, and speed of sound of a Deep Eutectic Solvent (Glyceline) with 1-alcohols (C₂-C₄) from (288.15 to 343.15) K at 0.1 MPa. Densities and speed of sound are from a vibrating tube densimeter while dynamic viscosities are from a rolling ball microviscosimeter. The binary mixture of Glyceline + 1-Butanol presents a liquid–liquid separation. Excess molar volumes, viscosity deviations, speed of sound deviations and isentropic compressibility deviations are calculated from experimental measurements. Excess molar volumes and viscosity deviations are negative at all temperatures. Speed of sound deviations are negative and positive. The Redlich-Kister equation is used to correlate the excess molar volume and the viscosity, speed of sound and isentropic compressibility deviations. We have used the Akaike Information Criterion corrected for small samples to obtain the optimal number of coefficients in the Redlich-Kister equation. Kinematic viscosities are correlated using the McAllister and the Nava-Rios equations. The average absolute percentage deviation of the McAllister equation is 3.09 % while for the Nava-Rios equation is 1.82 %.

Solid-liquid equilibrium solubility of 1,3,5-Tribromobenzene (m-TBB) in 16 pure solvents, including ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, amyl acetate, acetone, 2-butanone, cyclohexanone, 1,2-dichloroethane, chloroform, cyclohexane, toluene, tetrahydrofuran (THF), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA) were determined by gravimetric method at different temperatures. The solubility of m-TBB increases gradually with the increase of temperature. The order of solubility of m-TBB in alkanes solvents is: chloroform > 1,2-dichloroethane > cyclohexane. The order of solubility of m-TBB in esters solvents is: amyl acetate > butyl acetate > propyl acetate > ethyl acetate > methyl acetate > ethyl formate. The order of solubility of m-TBB in ketones solvents is: cyclohexanone > 2-butanone > acetone. The order of solubility of m-TBB in other solvents is: THF > toluene > DMA > DMF. The KAT-LSER model was selected to explore the solvent effect of m-TBB in the tested solvents. Four thermodynamic models, i.e., the modified Apelblat model, the λh model, the NRTL model and the Wilson model, were selected for correlate the solubility data of m-TBB in 16 mono-solvents. The RAD and the RMSD values of NRTL model were all less than 1.67 × 10^-2 and 3.82 × 10^-4, respectively. All the four theoretical models can correlate the solubility data of m-TBB well in the selected solvents. The dissolution process of m-TBB were calculated based on the Wilson model. The dissolution process of m-TBB is endothermic, entropy increase and spontaneous. The entropy contributes more to Gibbs free energy.