Effect of the composition of a water-alcohol solvent on the thermodynamics of dissolution of DL-α-alanyl-β-alanine at 298.15 K

Enthalpies of solution for DL-α-alanyl-β-alanine in H₂O-ethanol, H₂O-1-propanol, and H₂O-2-propanol mixed solvents with the alcohol mole fraction x ₂ = 0–0.3 are measured at 298.15 K. Standard enthalpies of solution (Δ_sol H ^°), standard enthalpies of transfer of DL-α-alanyl-β-alanine from water to binary solvent (Δ_tr H ^°), and coefficients of enthalpies of pair interactions with alcohol molecules (h _xy ) are calculated. The effect the structure and properties of alcohols and the composition of a water-alcohol mixture have on the enthalpy of dissolution for DL-α-alanyl-β-alanine are discussed. The h _xy values for dipeptides of the alanine series in water-alcohol binary solvents are compared.     

Viscometric studies of divalent transition metal sulphates in mixtures of water–diethylene glycol at 298.15–318.15 K

Relative viscosities of divalent transition metal sulphates solutions, viz. manganese, cobalt, nickel, copper, zinc and magnesium sulphate has been determined in water–diethylene glycol mixtures. Effect of temperature on the viscosities at 298.15–318.15 K has been studied and B coefficients of Jones–Dole equation are determined for these solutions. The obtained parameters have been interpreted in terms of ion–ion and ion–solvent interactions. Magnesium sulphate is taken as the reference electrolyte to see the change in the behavior of divalent ions when we shift from divalent transition metal ions to some other divalent ions in these solutions. Here these transition metal and magnesium sulphates behave in the same manner i.e structure makers in both water and in DEG + water mixtures.     

Enthalpies of the dissolution and dilution of aqueous solutions of rubidium and cesium diclofenac at 293.15–318.15 K

Enthalpies of the dissolution and dilution of aqueous solutions of rubidium and cesium diclofenac (RbDC and CsDC) are measured at 293.15, 298.15, 308.15, and 318.15 K at concentrations of water of less than 0.1 mol/kg. The heat capacity of RbDC and CsDC crystal salts is determined. Changes in the thermodynamic properties of both a solution and its components vs. concentration and temperature is considered. An increase in the endothermicity of the dissolution of RbDC and CsDC with a rise in temperature is noted. It is shown that the dissolution of both RbDC and CsDC electrolytes in water is determined by the contribution from entropy. It is shown that in aqueous solutions of RbDC and CsDC, the degree of binding of water molecules is higher than in pure water at temperatures below 303.15 K.     

Solute–solvent interactions in 2,4-dihydroxyacetophenone isonicotinoylhydrazone solutions in N,N-dimethylformamide and dimethyl sulfoxide at 298–313 K on ultrasonic and viscometric data

The speed of sound (u), density (ρ), and viscosity (η) of 2,4-dihydroxyacetophenone isonicotinoylhydrazone (DHAIH) have been measured in N,N-dimethyl formamide and dimethyl sulfoxide at equidistance temperatures 298.15, 303.15, 308.15, and 313.15 K. These data were used to calculate some important ultrasonic and thermodynamic parameters such as apparent molar volume (V _{? s} ^st ), apparent molar compressibility (K _?), partial molar volume (V _? ⁰ ) and partial molar compressibility (K _? ⁰ ), were estimated by using the values of (V _? ⁰ ) and (K _?), at infinite dilution. Partial molar expansion at infinite dilution, (? _E ⁰ ) has also been calculated from temperature dependence of partial molar volume V _? ⁰ . The viscosity data have been analyzed using the Jones–Dole equation, and the viscosity, B coefficients are calculated. The activation free energy has been calculated from B coefficients and partial molar volume data. The results have been discussed in the term of solute–solvent interaction occurring in solutions and it was found that DHAIH acts as a structure maker in present systems.     

Investigation of molecular interactions in binary mixture of dimethyl carbonate + N-methylformamide at T = (303.15, 308.15, 313.15 and 318.15) K

Journal of Thermal Analysis and Calorimetry - Density (ρ) and speed of sound (u) of binary liquid mixtures of dimethyl carbonate and N-methylformamide have been determined at...     

Effect of CaO additive on sintering and crystallization behavior of cordierite glass–ceramic prepared by sol–gel method

In the present work, cordierite glass–ceramic was prepared via sol–gel method using TEOS, AlCl₃·6H₂O, MgCl₂·6H₂O as starting materials. Different steps of phase transformations to cordierite have been studied by DSC and XRD. Various phases have been formed at different heat-treatment temperatures. Addition of CaO led to an increase in both the formation rate and the intensity of α-cordierite. Sinterability of the samples was determined too. The results showed that high content of CaO improved sintering. Morphology of hexagonal prism for α-cordierite was displayed by SEM.     

Effect of solvent on phase composition and particle morphology of lanthanum niobates prepared by polymeric complex sol–gel method

Lanthanum niobates were prepared by a new polymeric complex sol–gel method using Nb-citrate or -tartrate complexes in different solvent (ethanol or methanol) and calcination at 750–1,050 °C. The perovskite La_1/3NbO₃ and pyrochlore LaNb₅O₁₄ phases were formed after calcination at 900 and 1,050 °C from gels synthesized from ethanol and methanol solvents respectively. The very similar xerogel thermal decomposition processes were observed independently on applied solvents, where the pyrochlore monoclinic LaNbO₄ and Nb₂O₅ phases were intermediate products at lower calcination temperatures during transformation. The particle morphologies changed from spherical 20–50 nm particles at 750 °C to granular LN particles (ethanol) or rectangular (methanol) at 1,050 °C. HRTEM images and SAED verified the coexistence of minority monoclinic LaNbO₄ phase with majority phases in individual LN particles after annealing. The strong effect of alcohol solvent on phase formation was shown, while the effect of chelating agent was insignificant.     

Solubility behavior,dissolution thermodynamics and solute–solvent intermolecular interactions of a solid antioxidant product in water + isopropanol liquid mixtures from 298.15 to 320.15 K

The solid–liquid equilibria of a poorly water-soluble antioxidant agent namely naringoside were assayed to determine solubility in binary liquid mixtures of water?+?isopropanol (iso-PrOH) between 298.15 K and 320.15 K under atmospheric pressure. The mole fraction solubilities of naringoside in the saturated solution were determined using a combination of static shake-flask and ultraviolet spectrophotometry techniques. The dissolution behavior of naringoside was correlated with three solution models consisting of the van’t Hoff equation, the modified Apelblat equation and the Buchowski-Ksiazczak λH equation. The modified Apelblat equation was more consistent than the two other correlation models. Apparent thermodynamic analysis of naringoside dissolution was also performed at the mean harmonic temperature using the model parameters of the modified Apelblat equation. Furthermore, the Kamlet, Abboud and Taft Linear Solvation Energy Relationship (KAT-LSER) model was applied to analyze the effect of the solute–solvent intermolecular interactions on the solubility of this natural bioactive product.     

Influence of pressure in the 0.1–100 MPa interval on the first dissociation constant of arsenous acid in water solutions at 298.15 K

The influence of pressure on the dissociation of arsenous acid H₃AsO₃ was studied at 298.15 K by the potentiometric method. In the pressure interval from 0.1 to 100 MPa the values of logK ₁^o = −9.32 + 0.00246P. The change in the molar volume of the reaction of the dissociation of H₃AsO₃ from the first step (ΔV ₁^o = −15.4 ± 1 cm³/mol) and the partial molar volume of its dissociation product, H₂AsO₃⁻ (V ^o = 32.1 ± 1 cm³/mol) were determined.     

Thermochemistry of CuCl2 dissolution in a water—2-propanol—NaCl mixture at 298.15 K

The enthalpies of solution of CuCl₂ (m < 0.07 mol per kg of the solvent) in a water—2-propanol—NaCl mixture at a NaCl content from 0 to 5 mol % and a 2-propanol content from 0 to 40 mol % were determined by calorimetry at 298.15 K. The effect of the electrolyte and organic component on the solvation of CuCl₂ is discussed.     

Investigation of double-diffusive mixed convection effect on the particles dissolution in the shear flow using coupled SPM–LBM

Journal of Thermal Analysis and Calorimetry - In the present study, double-diffusive mixed convection related to the heat and mass transfer of the solid particles dissolution in a shear flow was...     

Excess properties and spectroscopic studies of binary system of 1-methoxy-2-propanol + dimethyl sulfoxide at T = (298.15–318.15) K

Thermophysical property data for the binary system of 1-methoxy-2-propanol (PGME) + dimethyl sulfoxide (DMSO), a potential candidate for use as the scrubbing liquid for the absorption of SO₂, are lacking in the literature. This paper presents experimental data at 0.1 MPa on the density and viscosity for this binary system measured over the whole composition range at T = (298.15, 303.15, 308.15, 313.15 and 318.15) K. The extended combined uncertainty U_c with a 0.95 level of confidence for the pycnometer method and Ubbelohde viscometer used in this study is 0.002 g·cm^?3 and 0.028 cm²·s^?1, respectively. The PGME + DMSO system shows negative values of the excess molar volume at all temperatures and compositions. Based on UV-Vis and FTIR, the intermolecular interaction of PGME with DMSO was confirmed as hydrogen bonding between the hydroxyl hydrogen atom in PGME and the oxygen atom in DMSO.     

The effect of heat treatment in the reducing atmosphere on the physical properties of TiO2 thin films prepared by sol–gel method

Multilayered nanostructured TiO₂ thin films were prepared by sol–gel and dipping deposition on quartz substrate followed by thermal treatment under reducing atmosphere (20 %H₂–80 %Ar). Heat treatment at progressively higher temperatures caused structural, morphological, and optical changes, which were investigated by X-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy, and UV–Vis spectroscopy. The conductivities of the thin films were also measured by 4-point probe method. The XRD results showed that the calcined TiO₂ thin films consist of single anatase phase which was completely transformed into rutile phase after heat treatment at 1,000 °C. The grains of films grew by intra-agglomerate densification after heat treatment at higher temperatures. The root mean square roughness of the samples was found to be in the range of 0.58–3.36 nm. The partially reduced TiO₂ samples have red-shifted transmittance bands due to new energy band formed by oxygen vacancies. The electrical conductivity of the films was also enhanced after heat treatment in reducing atmosphere.     

Investigation of the effect of cobalt on the Ni–Al2O3 catalyst prepared by the mechanochemical method for CO2 methanation

Research on Chemical Intermediates - Various Ni–Co catalysts supported on alumina were produced by the mechanochemical technique and applied to CO2 Methanation. X-ray diffraction,...     

Dissociation Constant of Acetic Acid in (N,N-Dimethylformamide + Water) Mixtures at the Temperature 298.15 K

In the present work the thermodynamic dissociation constants of acetic acid were determined in (N,N-dimethylformamide (DMF) + water) mixtures over the DMF mole fraction range from 0 to 0.65 at the temperature 298.15 K by the potentiometric titration method. The dissociation constant in pure DMF was obtained by extrapolation and comparative calculation methods. The dependence of the acetic acid dissociation constant on the mixed solvent composition was fitted with linear multiple regression of the solvatochromic parameters of (DMF + water) mixtures at every studied composition.     

The relative reduced Redlich–Kister equations for correlating excess properties of N,N-dimethylacetamide + 2-methoxyethanol binary mixtures at temperatures from 298.15 K to 318.15 K

Knowledge and prediction of physicochemical properties of binary mixtures is of great importance for understanding intermolecular interactions. The literature shows that most such systems exhibit non-linear behaviour. Excess molar volumes, viscosity deviations and isentropic compressibility changes in N,N-dimethylacetamide?+?2-methoxyethanol binary mixtures at 298.15, 308.15 and 318.15?K were calculated from experimental density, viscosity and sound velocity data presented in previous work. Here these experimental values were used to test the applicability of the correlative reduced Redlich–Kister equation and the recently proposed Herráez equation as well as their corresponding relative functions. Their correlation ability at different temperatures, and the use of different numbers of parameters, is discussed for the case of limited experimental data. These relative functions are important to reduce the effect of temperature and, consequently, to reveal the effects of different types of interactions. Limiting excess partial molar volume at infinite dilution were deduced from different methods, activation parameters and partial molar Gibbs energy of activation of viscous flow against compositions were investigated. The results of these observations have been interpreted in terms of structural effects of the solvents. In this frame, a correlating equation is recently proposed by Belda and in order to assess the validity of the proposed equation, it has also been applied to the present system for molar volume properties.