Volumetric Properties of Aqueous Solutions of L-Glutamic Acid and Magnesium-L-Glutamate

Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes, V _2,φ (m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂ C _p /∂ p) _T,m . They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate are present.     

Properties of DNA + Dipropylsulfoxide or Dibutylsulfoxide + Water Ternary Solutions

Aqueous solutions of DNA in the presence of dipropylsulfoxide (DPSO) and of dibutylsulfoxide (DBSO) have been studied using UV-vis spectroscopy and density measurements. It has been shown that significant thermal denaturation of DNA occurs when DPSO or DBSO are present. The results obtained were compared with those obtained previously with dimethylsulfoxide (DMSO) and diethylsulfoxide (DESO). It is suggested that the lowering of the transition enthalpy with increasing length of the carbon chain of the dialkylsulfoxides is due to significance contribution from hydrophobic interactions.     

Excess Volumes of Water + Acetonitrile and Water + Dimethylsulfoxide at 30°C and the Effect of the Excess Thermal Expansivity Coefficients on Derived Thermodynamic Properties

Excess molar volumes of water + acetonitrile, and water + dimethylsulfoxide mixtures were measured at 30°C. Excess thermal expansivity coefficients ^E were calculated from values of at 30° and 25°C previously reported.^(1,2) The ^E of polar mixtures are relatively large, several times 10^-5 K^-1 and as much 10^-4 K^-1, while those of nonpolar mixtures are at most several times 10^-6 K^-1. These values are several percent of the total expansivity coefficient of the mixture and significantly affect thermodynamic calculation of the estimation of isothermal compressibilities and isochoric heat capacities from isentropic compressibilities and isobaric heat capacities.     

Composition of Vapor and Liquid Phases in the Potassium Hydroxide + Methanol Reaction System at 25 °C

The composition of the vapor and liquid phases of the KOH + CH₃OH system has been studied by the gas chromatography (GC) method at 25 °C. It has been found that the methanol vapor concentration, and the quantity of potassium methoxide formed as a result of the acid–base reaction of potassium hydroxide with methanol, both depend on the KOH/CH₃OH mole ratio. The maximum mass fraction of potassium methoxide that forms is 2.6% at the mole ratio 0.018.     

Lamellar Liquid Crystals of Brij 97 Aqueous Solutions Containing Different Additives

Lamellar liquid crystals of Brij 97 aqueous solutions were investigated by means of rheological techniques and SAXS at 25 °C, in the presence of various additives including isopropyl myristate, oleic acid, ionic liquid bmim-PF₆ and bmim-BF₄. The lamellar phases show high elasticity as indicated by their mechanical and discrete relaxation spectra, which is expected to be an advantage when they are used as drug delivery vehicles. It is noted that in comparison with other systems, the lamellar phase formed in the Brij 97/water/IPM system has the lowest storage and loss moduli, implying that it has a weak network strength and less stable internal structure. The Brij 97/water/oleic acid system is the most shear resistance, whereas the Brij 97/water/bmim-PF₆ system exhibits fluid-like viscoelastic properties to some extent. These differences are analyzed through SAXS data for the different location of the additive in the lamellar phase.     

Volumetric Properties of Dilute Solutions of Water in Acetone between 288.15 and 318.15 K

Densities of dilute solutions of water in acetone, with solute mole fractions ranging up to 0.03, have been measured with an error of 8 ×10⁻⁶ g⋅cm⁻³, at 288.15, 298.15, 308.15 and 318.15 K, using a precision vibrating-tube densimeter. The partial molar volumes of the solute water (down to infinite dilution) and solvent acetone, as well as the excess molar volumes of the specified mixtures, have been calculated. The effects of the solute concentration and temperature on the volume packing changes, caused by solvation of water in acetone, have been considered.     

Investigation of the Thermodynamic Properties of the Cationic Surfactant CTAC in EG + Water Binary Mixtures

To understand the thermodynamic characteristics of cationic surfactants in binary mixtures, the aggregation behavior of hexadecyltrimethylammonium chloride (CTAC) has been investigated in ethylene glycol (EG) + water solvent mixtures at different temperatures and EG to water ratios. The critical micelle concentration (CMC) and degree of counter ion bonding (β) were calculated from electrical conductivity measurements. An equilibrium model for micelle formation was applied to obtain the thermodynamic parameters for micellization, including the standard Gibbs energies of micellization (DG_mic^o)\Delta G_{\mathrm{mic}}^{\mathrm{o}}), standard enthalpies of micelle formation (DH_mic^o)\Delta H_{\mathrm{mic}}^{\mathrm{o}}) and standard entropies of micellization (DS_mic^o)\Delta S_{\mathrm{mic}}^{\mathrm{o}}). Our results show that DG_mic^o\Delta G_{\mathrm{mic}}^{\mathrm{o}} is always negative and slightly dependent on temperature. The process of micellization is entropy driven in pure water, whereas in EG + water mixtures the micellization is enthalpy driven.     

Partial Molar Volumes of Uracil,Thymine, Adenine in Water and of Adenine in Aqueous Solutions of Uracil and Thymine

The partial molar volumes of uracil, thymine and adenine in water and adenine in aqueous solutions of uracil and thymine, at fixed composition, were determined over a range of temperatures. The partial molar volumes of adenine in aqueous uracil and thymine are less than in pure water.     

Volumetric Properties of Amino Acids in Aqueous N-methylacetamide Solutions at 298.15 K

The apparent molar volumes (V _φ ) of glycine, L-alanine and L-serine in aqueous 0 to 4 mol⋅kg⁻¹ N-methylacetamide (NMA) solutions have been obtained by density measurement at 298.15 K. The standard partial molar volumes (V_f⁰)V_{\phi}^{0}) and standard partial molar volumes of transfer (D_trV_f⁰)\Delta_{\mathrm{tr}}V_{\phi}^{0}) have been determined for these amino acids. It has been show that hydrophilic-hydrophilic interactions between the charged groups of the amino acids and the –CONH– group of NMA predominate for glycine and L-serine, but for L-alanine the interactions between its side group (–CH₃) and NMA predominate. The –CH₃ group of L-alanine has much more influence on the value of D_trV_f⁰\Delta_{\mathrm{tr}}V_{\phi}^{0} than that of the –OH group of L-serine. The results have been interpreted in terms of a co-sphere overlap model.     

Volumetric Properties of l-Alanine and l-Serine in Aqueous N,N-Dimethylformamide Solutions at 298.15 K

The densities of l-alanine and l-serine in aqueous solutions of N,N-dimethylformamide (DMF) have been measured at 298.15 K with an Anton Paar Model 55 densimeter. Apparent molar volumes $ (V_{\phi } ) $ ( V ? ) , standard partial molar volumes $ (V_{\phi }^{0} ) $ ( V ? 0 ) , standard partial molar volumes of transfer $ (\Updelta_{\text{tr}} V_{\phi }^{0} ) $ ( Δ tr V ? 0 ) and hydration numbers have been determined for the amino acids. The $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 values of l-serine are positive which suggest that hydrophilic–hydrophilic interactions between l-serine and DMF are predominant. The –CH₃ group of l-alanine has much more influence on the volumetric properties and the $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 have smaller negative values. The results have been interpreted in terms of the cosphere overlap model.     

Enthalpies of Dilution of N,N′-hexamethylenebisacetamide in Pure Water and Aqueous Solutions of Alkali Halide at 298.15 K

Enthalpies of dilution of N,N′-hexamethylenebisacetamide in water and aqueous alkali halide solutions at the concentration of 0.150 mol⋅kg⁻¹ (approximately the concentration of physiological saline) have been determined by isothermal titration microcalorimetry at 298.15 K. The enthalpic interaction coefficients in the solutions have been calculated according to the excess enthalpy concept based on the calorimetric data. The values of enthalpic pair-wise interaction coefficients (h ₂) of the solute in aqueous solutions of different salts were discussed in terms of the different alkali salt ions and weak interactions of the diluted component with coexistent species as well as the change in solvent structure caused by ions.     

Composition and Properties of Aqueous Fluoroplastic Dispersion for Deposition of Metal–Polymer Coatings

Russian Journal of Applied Chemistry - Formulation of an aqueous dispersion of F-40 tetrafluoroethylene–ethylene copolymer for applying metal–polymer coatings by cathodic...     

The Volumetric and Thermochemical Properties of Dipropylsulfoxide in Water

Volumetric and thermal properties of aqueous solutions of dipropylsulfoxide (DPSO) have been studied. Densities of binary mixtures of DPSO with water were measured over the full range of compositions at temperatures from 298.15 K to 338.15 K by means of a vibrating-tube densimeter. We also investigated the thermal properties of the [DPSO + water] system using differential scanning calorimetry at a low heating/cooling rate (2 K⋅min⁻¹). The results obtained are compared with those of dimethylsulfoxide (DMSO) and diethylsulfoxide (DESO) aqueous solutions.     

Transfer Volumes of Small Peptides from Water to Aqueous Xylitol Solutions at 298.15 K

Densities have been measured by an oscillating-tube densimeter for aqueous solutions of glycylglycine and glycylglycylglycine in aqueous xylitol solutions with xylitol mass fractions ranging from 0 to 0.15 at 298.15 K. Apparent molar volumes and limiting partial molar volumes have been used to calculate the corresponding transfer volumes from water to different concentrations of xylitol + water mixtures. The results are interpreted in terms of the cosphere overlap model.     

Thermodynamic Properties of the Ternary System Potassium Bromide + Lithium Bromide + Water at 25°C

Activity coefficients of potassium bromide in aqueous mixtures of potassium bromide and lithium bromide were determined by emf measurement at 25°C and at six ionic strengths from 0.1 to 2.5 mol·kg^-1. The experimental data were fitted using the Scatchard–Rush–Johnson and Pitzer models. The osmotic coefficients, excess Gibbs energies of mixing, and activity coefficients of lithium bromide in aqueous mixtures were calculated using Pitzer mixing parameters obtained in this work.     

Calorimetric and Volumetric Studies of the Interactions of Propionamide in Aqueous Alkan-1-ol Solutions at 298.15 K

Enthalpies of solution and apparent molar volumes have been determined for propionamide in aqueous methanol, ethanol and propanol solutions at 298.15 K using a C-80 microcalorimeter and a DMA60/602 vibrating-tube digital densimeter. The enthalpic and volumetric interaction coefficients have been calculated. Using the present results along with results from previous studies for formamide, the pair-interaction coefficients are discussed from the perspective of dipole-dipole and structural interactions. In addition, the triplet interaction coefficients are interpreted by using the solvent-separated association mechanism.     

Osmotic and Activity Coefficients of Trimethyloctylammonium Bromide and Decyltrimethylammonium Bromide in Aqueous Solutions as a Function of Temperature

Osmotic coefficients of aqueous solutions of trimethyloctylammonium bromide and decyltrimethylammonium bromide were measured by the isopiestic method at the following temperatures: 298.15, 293.15, 288.15 and 283.15 K. Activity coefficients of the solutes were calculated from the osmotic coefficients. The results were compared with the Debye-Hückel limiting law and analyzed according to their variation with the alkyl chain length of the cation and with the change in temperature.