In order to improve the solubility of thioacetazone, binary (1:1) and ternary (1:1:1) deep eutectic solvents formed by choline chloride as HBA and malonic acid, oxalic acid and polyethylene glycol 400 as HBD were used in this work. All the obtained mixtures are good solubilisers of the drug, increasing its molar solubility at standard temperature from a minimum in the choline chloride/malonic acid mixture to a maximum in choline chloride/oxalic acid/PEG mixture, which is 52 and 684 times higher than its aqueous solubility, respectively. The obtained data indicate a synergistic effect of increasing the solubility of thioacetazone in ternary DES compared to binary ones. An evaluation of the drug dissolution kinetic profiles in eutectic solvents of varying compositions was conducted. Based on temperature-dependent solubility data, the drug dissolution process was characterized as endothermic and entropy-driven. The density and viscosity of deep eutectic solvents were measured in the temperature range of 293.15–313.15 K. It was also discussed how the introduction of a third component into binary systems influences the volumetric and rheological properties of eutectic mixtures.
Density (ρ) and speed of sound (c) measurements were carried out for tetracaine hydrochloride TC∙HCl (a local anesthetical drug) in aqueous and aqueous (0.0493, 0.1008 and 0.1494 Mol·kg−1) glycine (amino acid) solutions at 288.15, 293.15, 298.15, 303.15, 308.15, 313.15 and 318.15 K and at pressure of 1.013·105 Pa. The ρ and c data were used to calculate various volumetric parameters: apparent molar volume of solute (Vϕ), apparent molar volume of solute at infinite dilution (Vϕ0), coefficient of thermal expansion of solution (α), apparent molar expansibility of solute (Eϕ), apparent molar expansibility ϕVof solute at infinite dilution (Eϕ0) and compressibility parameters: Isentropic compressibility of solution (κs), apparent molar isentropic compressibility of solute (Kϕ,S), apparent molar isentropic compressibility of solute at infinite dilution (Kϕ,S0). The transfer partial molar volume (ΔtrVϕ0) of TC∙HCl from water to aqueous glycine solutions is also calculated. The results elucidate the nature of solute–solute and solute–solvent interactions as well as TC∙HCl modifies the surrounding water network within the studied systems and act as a water–structure breaker.
In this study, a volumetric Pitzer model was developed for unsaturated solutions in the Li2B4O7 – Li2SO4 – H2O, Li2B4O7 – LiCl – H2O, and Li2SO4 – LiCl – H2O ternary systems at 298.15, 308.15, and 318.15 K and 101.3 kPa. The model was parameterized using new density measurements obtained in this work together with literature data for the binary subsystems. Literature volumetric coefficients were adopted for Li2B4O7 – H2O and LiCl – H2O, whereas new coefficients were optimized for Li2SO4 – H2O. The resulting model reproduced the ternary density data satisfactorily, with overall RMSD values of 0.00143, 0.00073, and 0.00082 g·cm–3 for the Li2B4O7 – Li2SO4 – H2O, Li2B4O7 – LiCl – H2O, and Li2SO4 – LiCl – H2O systems, respectively. The optimized ternary volumetric interaction parameters, θijV and ψijkV, were numerically small, but their inclusion was necessary to achieve this level of agreement. When these parameters were set to zero, the overall RMSD increased markedly in all three systems, demonstrating the need for ternary volumetric interaction terms. A normalized local sensitivity analysis indicated that algebraic increases in the evaluated volumetric parameters decreased the calculated density, with the Li2B4O7 – Li2SO4 – H2O system showing the largest response. The calculated ∆Vm values were treated as model-derived quantities constrained indirectly by the density data, and their interpretation was therefore limited to a qualitative, model consistent discussion. Overall, the proposed model provides a useful basis for representing density in chloride, sulfate, and borate-bearing lithium brines under unsaturated conditions.
In order to explore a new process for efficiently separating high-salt wastewater containing ammonium sulfate and sodium sulfate, this study conducted phase equilibrium research on the Na2SO4-(NH4)2SO4-CH3OH-H2O system at temperatures of 298.15 K and 323.15 K. Phase equilibrium data were determined using the isothermal method, and the corresponding phase diagrams were constructed. The study found that this system forms a new double-salt structure, 4Na2SO4·(NH4)2SO4·H2O, which differs from the double salt Na2SO4·(NH4)2SO4·4H2O in the Na2SO4-(NH4)2SO4-H2O system. The system comprises two single-salt crystallization regions corresponding to Na2SO4 and (NH4)2SO4, one double-salt crystallization region for 4Na2SO4·(NH4)2SO4·H2O, and two co-crystallization regions for Na2SO4 + 4Na2SO4·(NH4)2SO4·H2O and (NH4)2SO4 + 4Na2SO4·(NH4)2SO4·H2O. As the temperature increased from 298.15 K to 323.15 K, the crystallization regions of the single salts (NH4)2SO4 and Na2SO4 significantly expanded, while the crystallization region of the double salt 4Na2SO4·(NH4)2SO4·H2O decreased. Based on the extended Pitzer model, the interaction parameters among different particles in the Na2SO4-(NH4)2SO4-CH3OH-H2O system were correlated and calculated, and the solubility was predicted. The obtained values agree with the experimental results. Based on the phase diagrams of the Na2SO4-(NH4)2SO4-CH3OH-H2O system at 298.15 K and 323.15 K, a novel separation process for high-salinity wastewater containing ammonium sulfate and sodium sulfate was designed.
The surface adsorptions of GaZn, GaAl, CuAg, PbSb and CuSn binary liquid alloys are investigated with our surface adsorption theory. A new differential equation as well as its integration form of the surface tension are derived and used to interpret the negative and positive temperature coefficients of CuSn alloys with the molar fraction xCu = 0.3 and 0.5. The calculated partial derivatives ∂γ/∂T of CuSn alloys with xCu = 0.3 and 0.5 are negative and positive respectively, and are in agreement with the experimental results. The heats of phase transition from the bulk phase to the surface phase are determined for GaZn, GaAl, CuAg and PbSb alloys. The variation trends of the surface tension with concentration of solute in these alloys at constant temperatures are interpreted in term of the convex or concave shape of the corresponding solute surface concentration versus solute bulk concentration plot.
Gas-solid phase equilibrium under the influence of an electric field is a key area of technological innovation research in fields such as chemical engineering, catalysis and electric field-controlled refrigeration. However, research on this phenomenon remains hampered by the ambiguous multi-physics coupling mechanisms, the scarcity of experimental data, and the excessive complexity of theoretical models. Based on phase equilibrium theory and the chemical potential in an electrostatic field, this study elucidates the interplay between pressure, temperature, and permittivity during gas-solid phase transitions. A gas-solid phase equilibrium equation under the influence of an electrostatic field was established, in the absence of an electric field, this equation reduces to the classical Clapeyron equation. Based on the derived gas-solid phase equilibrium equation, the pressure and temperature control parameter of an electrostatic field on the sublimation of water vapor, naphthalene, and croconic acid were calculated. The results show that the electrostatic field induces a negative pressure control parameter or a positive temperature control parameter for water vapor, whilst it yields a negative temperature control parameter for croconic acid; the effect on naphthalene is weak. These theoretical predictions are consistent with experimental findings in the literature. Physically, a negative temperature control parameter (or positive pressure control parameter) occurs when the field-induced chemical potential change in the vapor phase surpasses that in the solid phase; conversely, the opposite trend is observed when the solid-phase response dominates.
The aim of this article is to define the key physicochemical characteristics of four azole derivatives containing the 5-phenyl-2H-tetrazole fragment. Two of the examined compounds, 3-[5-(4-methylphenyl)-2H-tetrazol-2-yl]butan-2-one (T1) and 4-(5-phenyl-2H-tetrazol-2-yl)butan-2-one (T2), display antifungal activity against the yeast Candida albicans, making investigation of their physicochemical behaviour particularly important. Thermal properties, including melting temperature and enthalpy, were measured by differential scanning calorimetry (DSC) to check for possible polymorphic transitions. Solid–liquid (binary) phase diagrams were established for each active compound in combination with three solvents: 1-octanol, water and ethanol, information that is valuable for designing optimal drug delivery forms. Experimental phase-equilibrium data were correlated with local-composition models (Wilson, UNIQUAC and NRTL). Additionally, the Bates–Schwarzenbach method was applied to determine the tetrazoles' acidity constants at 298.2 K (room temperature) and 310.2 K (human body temperature), data that can assist in defining appropriate pharmaceutical dosing.
Cymoxanil (CYM) as a novel fungicide combining high efficacy with safety, lacks systematic research on its solubility data. This study employed the static equilibrium method combining with ultraviolet spectroscopy to determine the solubility of CYM in twelve mono-solvents and a binary mixed solvent (butyl acetate + isopropanol) at 0.1 MPa and 283.15-328.15 K. The results indicate that solubility is positively correlated with temperature in all solvents. Within mono-solvents, solubility follows the order: esters > alcohols > water. In binary mixed solvents, solubility shows a broadly positive correlation with the molar fraction of butyl acetate. The drug's crystalline form was characterised using thermogravimetric-differential scanning calorimetry(TG-DSC) and X-ray diffraction (XRD). Further correlation of solubility data was performed using the Apelblat equation, van't Hoff equation, NRTL equation, Jouyban equation, GCM equation, and Apelblat-Jouyban-Acree equation, with all models demonstrating good correlation. Furthermore, a thermodynamic analysis of the dissolution process was conducted, and the influence of solute-solvent interactions on the solubility of CYM in pure solvents was investigated based on the KAT-LSER model.
In the production and use of methyl isobutyl ketone (MIBK), large volumes of industrial wastewater containing this substance are generated, and MIBK readily forms azeotropic mixtures with water. To achieve efficient and energy-saving separation of MIBK from wastewater, this study employed alkyl alcohols as extractants for experimental exploration and mechanism analysis. Liquid-liquid equilibrium (LLE) data for water + MIBK + alkyl alcohols (1-hexanol, 1-heptanol, 1-octanol, and 1-nonanol) were determined at 303.2 K under 101.3 kPa. The distribution coefficient (D) and separation factor (S) served as key metrics to evaluate the extraction performance of each system. Moreover, the LLE data were fitted using the non-random two-liquid (NRTL) and universal quasi-chemical (UNIQUAC) models, yielding satisfactory predictive results. The GMcal_TieLinesLL tool confirmed model parameters were in accordance with the Gibbs stability criterion. A comprehensive mechanistic investigation combining sigma-profile, deformation charge density, interaction energy, and reduced density gradient (RDG) revealed the separation mechanism.
The intermolecular interactions in the binary liquid mixtures of N-methylformamide (NMF) with alkyl acetates have been investigated using thermophysical properties and FTIR. The density, speed of sound and viscosity of NMF + methyl acetate (MAc)/ethyl acetate (EAc)/n-propyl acetate (PAc)/n-butyl acetate (BAc) binary mixtures were measured across the entire composition range at the temperatures (293.15, 298.15, 308.15, 318.15, 323.15, and 328.15) K and pressure (100 kPa). From the measured properties, the excess molar volumes, excess isentropic compressibilities, excess intermolecular free lengths, excess molar isentropic compressibilities, excess speeds of sound, excess specific acoustic impedances and deviations in viscosity were calculated. The partial molar volumes/compressibilities, excess partial molar volumes/compressibilities over the whole composition range, and at infinite dilution have also been calculated. The variations of these parameters with composition/ temperature have been interpreted in terms of interactions in these mixtures and it has been observed that NMFalkyl acetate interactions follow the order: MAc > EAc > PAc > BAc, i.e., the interaction decrease with increase in alkyl chain length of alkyl acetates. The speeds of sound were theoretically calculated by means of various theories/relations and the viscosities of these mixtures were correlated by means of several empirical and semi-empirical equations and compared with the experimental findings. FT-IR spectra of pure NMF, alkyl acetate and equimolar mixtures of NMF + alkyl acetates were recorded and analysed to gain a better understanding of the prevailing intermolecular interactions. Furthermore, natural bond orbital (NBO) analysis and theoretical IR spectra were also assessed using the density functional theory (DFT) to understand the intermolecular interactions between the binary system of NMF and alkyl acetates.
The thermodynamic stability of palladium chloride (PdCl2) remains uncertain due to significant discrepancies in the standard enthalpy of formation (Delta fH degrees) values presented in various data compilations. This study aimed to obtain reliable thermodynamic quantities for PdCl2 by accurately measuring the equilibrium chlorine partial pressure (pCl2) over PdCl2/Pd. We employed the transpiration method, utilizing chlorine gas detector tubes for precise pCl2 determination in the temperature range of 661-741 K. Phase analysis and oxygen partial pressure dependence ofpCl2 confirmed that the equilibrium was governed by the dissociation of alpha-PdCl2 (s) into Pd(s) and Cl2 (g) in an Ar atmosphere. The temperature dependence of the equilibrium chlorine partial pressure was determined as follows: log(pCl2 /bar) = (6.176 +/- 0.985)-(7930.4 +/- 691.4) (T/K)-1. From this relationship, the Delta fH degrees value for alpha-PdCl2 (s) was calculated via second-law analysis as (-151.8 +/- 13.2) kJ mol-1 at 661-741 K. These results are consistent with early experimental reports and support earlier thermodynamic compilations (Barin(1977) and Knacke(1991)). The Delta fH degrees values in more recent compilations (Barin (1995), SGPS (2019), MALT (2024), FactPS (2025)) are inconsistent with the present experimental results. For a more definitive establishment of the thermodynamic properties, future research should focus on heat capacity measurements of PdCl2 (s) to facilitate the third-law analysis.
The thermodynamic properties of liquids are essential for design, selection and operation of instruments used in the engineering and science. Herein, the density of binary (1-hexyl-3-methylimidazolium bromide (1) + gammavalerolactone (2)) and ternary (1-hexyl-3-methylimidazolium bromide (1) + gamma-valerolactone (2) + 2methoxyethanol or 2-ethoxyethanol or 2-propoxyethanol or 2-butoxyethanol (3)) mixtures was measured at four different temperatures (298.15 - 313.15 K) under atmospheric pressure of 0.1 MPa. Further, excess molar volume was derived for working solutions. The calculated data of binary mixture was fitted to Redlich-Kister equation, and ternary data was correlated with Singh and Nagata-Tamura equation. Additionally, excess molar volume of binary system was analysed using Graph theory to comprehend the type and extent of interactions and Prigogine-Flory-Patterson theory to determine the interactional, free volume and pressure contribution within the system. Moreover, Graph theory was also used to obtain an expression for excess molar volume of ternary mixtures. The negative sign of excess molar volume of binary system was obtained, which may be due to tight packing of molecules in mixture. Further, the analysis of excess molar volume of ternary mixtures reveals that both positive and negative values occur depending on the composition ratio of the components involved.
The thermodynamic mechanisms governing water-solid interactions in complex biological matrices are critical for understanding their physical stability and hygroscopic behavior. This study investigates the comparative sorption thermodynamics of two arid-zone medicinal plants, Rhus tripartita (RT) and Periploca laevigata (PL), across a temperature range of 303 to 323 K utilizing the static gravimetric technique. Experimental equilibrium data were evaluated against eleven mathematical models, with the Guggenheim-Anderson-de Boer (GAB) model providing the optimal fit for RT adsorption (R-adj(2) > 0.98), while the White-Eyring and Halsey models best described the sorption hysteresis in PL. To elucidate the physical drivers of these behaviors, quantitative phytochemical profiling (total phenols, flavonoids, and condensed tannins) was performed. A comprehensive thermodynamic evaluation, corroborated by this chemical data, revealed a fundamental dichotomy in their hydration mechanisms. RT behaved as a classical, rigid adsorbent governed by an enthalpy-driven process (T beta > Thm). Its hydration was characterized by exothermic surface physisorption onto hydroxyl-rich active sites, demonstrated by a monotonic qst decay from approximate to 36 kJ/mol. Conversely, PL exhibited anomalous, endothermic sorption profiles. Enthalpy-entropy compensation analysis verified that PL sorption is a strictly entropy-driven process (T beta < Thm). This atypical thermodynamic signature is attributed to the solvent-dominated dissolution of crystalline cardiac glycosides and the subsequent plasticization of the amorphous biopolymer matrix. These findings quantitatively define the energetic thresholds and phase-transition boundaries required for the physicochemical stabilization of complex biomaterials.
Tracer diffusion coefficients of sodium hyaluronate in 0.005 mol dm(-3) aqueous drug solutions were investigated by using Taylor dispersion technique at 298.15 K. The drugs studied were caffeine, isoniazid, sodium sulfamerazine, sodium salicylate, and paracetamol. The positive cross-diffusion coefficient between the supporting drug and tracer polyelectrolyte obtained for all systems, particularly for isoniazid, sodium sulfamerazine, and sodium salicylate, indicate the existence of NaHy-drugs interactions and significant coupled diffusion. These findings suggest that sodium hyaluronate may facilitate drug transport, acting as a carrier in aqueous media.
This study reports dynamic viscosities (η) for binary mixtures of tetrahydrofuran (THF) with n-butanol (NBA), sec-butanol (SBA), and tert-butanol (TBA) over the full composition range at T = 303.15–323.15 K and P = 0.10 MPa. Viscosity deviations (Δη) and Gibbs free energies of activation for viscous flow (ΔG≠), and excess Gibbs free energies of activation (ΔG≠E) were evaluated to elucidate composition- and temperature-dependent molecular interactions. All systems exhibit negative Δη across the studied range, with minima near x₂ ≈ 0.30–0.40, indicating that THF disrupts the hydrogen-bonded structure of the butanols and that THF–butanol hetero-association is weaker than butanol–butanol self-association. The ΔG≠E values are also negative and become more pronounced at lower temperatures, implying a reduced barrier to flow in the mixed state relative to ideal mixing. DFT-optimized 1:1 complexes suggest stabilization follows THF–TBA > THF–SBA > THF–NBA, aligning with the experimentally observed branching dependence. Experimental data were successfully correlated using the Jouyban–Acree model and the Redlich–Kister equation for excess functions, yielding smooth trends with small residuals. Group-contribution predictions show that UNIFAC-THERMO provides improved accuracy (overall mean absolute relative deviation, MARD = 3.93%) relative to UNIFAC-VISCO (6.08%), particularly for mixtures containing branched alcohols. These combined results provide reliable insights and predictive capabilities for viscosity behavior of cyclic-ether–alcohol mixtures.
A Peltier-element-based adiabatic scanning calorimeter was used to obtain with high resolution and high accuracy, the temperature dependence of the specific heat capacity and of the specific enthalpy of ten alkanes from heneicosane to triacontane. The measurements cover a temperature range from well in the crystalline solid phase across the order-disorder transition to the rotator phase(s) and the melting transition from a rotator phase to the liquid phase. Both heating and cooling runs have been executed for all compounds. Accurate transition temperatures and heats were derived from the direct experimental data and compared with existing literature data.
Carbon dioxide (CO2) capture using absorbents is widely recognized as the most mature technology for large-scale applications. Aqueous solutions of zwitterionic bases (ZBs) have recently been proposed as a promising alternative to conventional amine-based systems. As a first step toward understanding more complex phase equilibria involving these substances, the present study investigates the vapor–liquid equilibrium (VLE) of water and ZBs. Experimental data were obtained using the hygrometric method at 298.15 K and 313.15 K. The NRTL model parameters were fitted to the experimental VLE data, while the predictive performance of a COSMO-SAC variant was evaluated against experimental measurements. The studied mixtures showed negative deviations from ideality, reflecting favorable water–ZB interactions. Remarkably, the NRTL model fitted the equilibrium data with an overall deviation of 0.80% on equilibrium pressure, using a single set of parameters for both temperatures. A COSMO-SAC model was able to represent the negative deviation for one of the systems but missed the negative deviation for the more symmetric molecule. A possible explanation is the formation of anti-parallel dimers in this case, indicating the complexity of the interactions in these aqueous systems.
