Development of Mathematical Model of H2O-HNO3-UO2(NO3)2-TBP-diluent System

The mathematical model of H₂O-HNO₃-UO₂(NO₃)₂-TBP-dodecane system has been elaborated. Mole fractions and volume ones and rational activity coefficients have been used in order to create the system of equations on the base of mass action law. Method for calculating activity coefficients was provided. The formation constants of uranyl nitrate di-solvate and mono-solvate and di-solvate of acid have been determined. Interaction between uranyl nitrate di-solvate and dodecane and between TBP and dodecane was taken into account. Activity coefficients of nitric acid and uranyl nitrate in mixed solutions were considered. Errors of adequacy have been determined for the systems containing 30% and 12% TBP concentrations.     

Solubility of Lead Nitrate in Aqueous Solutions of Nitric Acid and Zinc Nitrate

Solubility of lead nitrate in the system H₂O-Zn(NO₃)₂-HNO₃ was studied using the simplexlattice design method. The equations describing the effect of nitric acid and zinc nitrate concentrations on the content of lead nitrate in solution at 25 and 55°C were derived.     

Solubility of Lead Nitrate in Aqueous Solutions of Nitric Acid and Iron(III) Nitrate

Solubility of lead(II) nitrate in the system H₂O-Fe(NO₃)₃-HNO₃ was studied using the simplex-lattice method of experiment design.     

钨酸钠水溶液的活度系数和渗透系数

The activity coefficients and osmotic coefficients of Na_2WO_4 aqueous solution in the concentration range of 0.3--2.5 mol·kg~(-1) have been determined by the isopiestic method. The excess Gibbs free energies are evaluated with the correspording activity coefficientc and osmotic coefficients.     

Activity Coefficients in the Surface Phase of Liquid Mixtures

A novel equation for evaluating surface activity coefficients is obtained from a recent thermodynamic formalism describing the surface phase of liquid mixtures. The input quantities are the surface tension, bulk activity coefficients and pure constituent thermophysical properties. It is demonstrated thermodynamically that the order of magnitude of each component surface and bulk activity coefficients must be the same. This order is intrinsically associated with the sign of excess surface tension. Reliable activity coefficients of ethanol and water in the surface phase of their mixtures are computed and reported for the first time, by using literature data for the required input quantities. It is shown that the so‐called transferring method for estimating surface activity coefficients is severely flawed, because it leads to contradictory values of predicted excess surface tensions depending on which component this prediction is based.     

Aquafac: Aqueous Functional Group Activity Coefficients

Abstract

AQUAFAC, a new group contribution method for estimating aqueous activity coefficients, has been applied to a large set of organic compounds. The current work introduces 27 new group values for hydrocarbon, halogen, and non-hydrogen bond donating oxygen groups. Group values (q-values) have been derived from a data set of 621 compounds representing over 1700 individual solubility values. No correction factors were used in generating the current group values. AQUAFAC was found to give acceptable results when applied to some environmentally important compounds.     

Activity Coefficients of Potassium Chloride in Water–Ethanol Mixtures

Activity coefficients of KCl were determined in water–ethanol solvents in the range 5–20% (w/w) ethanol, from experimental electromotive force (emf) data. The molalities varied from 0.1 mol-kg^–1 to near saturation and measurements were taken in the temperature range 25 to 45°C. The Pitzer model was used to describe the nonideal behavior of the electrolyte and the corresponding coefficients were determined for each solvent. The Pitzer–Simonson equations were also applied and found superior in the study of KCl in those nonaqueous solutions.     

在盐的水溶液中非电解质活度系数的研究——正己酸和正庚酸在小离子盐水溶液中的溶解度

本文在25℃下分别测定了正己酸和正庚酸在纯水和小离子盐水溶液中的溶解度.标出了弱酸未解离部分的活度系数f_u,作出氯化锂等八种盐的lgf_u～Cs图,均呈直线关系.计算并比较了乙酸等五种脂肪酸在小离子盐水溶液中的盐效应和盐析常数的各种理论值.     

Temperature Dependences of HCl Activity Coefficients in Aqueous Solutions

Temperature coefficients of activity of the ionic fraction of HCl in water, calculated from tensimetric and calorimetric data, are compared. A correlation dependence is suggested for recalculating the activity coefficients of hydrochloric acid from 298 K to other temperatures.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 211–213.Original Russian Text Copyright © 2005 by Poltoratskii, Osovskaya, Chumanov.     

Reaction of Octyl Ether with Nitric Acid and its Mixtures

Russian Journal of Organic Chemistry -     

Binary Diffusion Coefficients for Aqueous Solutions of Lactic Acid

Taylor dispersion equipment installed at the University of Coimbra for the measurement of diffusion in liquids has been tested to ensure adequate accuracy and precision by measuring mutual diffusion coefficients for binary aqueous solutions of sucrose, glycine, lithium chloride, potassium chloride, and hydrochloric acid at 298.15 K. In addition, binary mutual diffusion coefficients for aqueous solutions of lactic acid (not previously reported in the literature) have been measured at 298.15 and 303.15 K and concentrations up to 0.20 mol-dm⁻³.     

Temperature Quenching of Uranyl Ion Photoluminescence in Frozen Deuterated Aqueous Solutions of Sulfuric Acid

The effect of solvent deuteration revealed as a difference in the shape of temperature dependence curves for the lifetime of uranyl ion in the electronically excited state () upon warming H₂SO₄ solutions in ₂ and D₂SO₄ solutions in D₂O frozen at 77 K was detected. The value of in the case of D₂SO₄ was shown to be shorter in the glassy solution than in the polycrystalline sample, whereas the reverse was observed in frozen H₂SO₄ solutions. This effect was explained by dissimilar occurrence of phase transitions in H₂SO₄ and D₂SO₄ solutions, as well as by a decrease in the probability of nonradiative deactivation of *(UO²⁺ ₂) adsorbed on the surface of the crystal hydrate D₂SO₄·4D₂O as compared with that on the surface of the crystal hydrates H₂SO₄·4H₂O and H₂SO₄·6.5H₂O.     

Estimation of the Activity Coefficients in Liquid Mixtures by Using Volumetric Data

We present an equation that relates the partial molar volume of binary liquid mixtures with the natural logarithms of the activity coefficients of solute and solvent. This equation, in combination with one of the activity coefficient models such as those of Margules, Wilson, Van Laar or NRTL, can be used to estimate the activity coefficients of binary liquid mixtures, knowing only the densities of the mixtures over the full range of concentration. In addition, we show a comparison of the estimated activities and activity coefficients at infinite dilution with experimental values for aqueous solutions of 1,2-butanediol, 2,3-butanediol, 1,3-butanediol, and 1,4-butanediol at 298.15?K. This method for the estimation of activity coefficients can be applied to aqueous binary mixtures, because the equation presented is deduced from physicochemical principles.     

Nitrogen Trioxide in Irradiated Aqueous Nitric Acid Solutions of Hydrazine

The rate constants of reactions of the NO₃ radical with hydrazoic acid (7.6 × 10⁶l mol^–1s^–1) and the hydrazonium ion (2.3 × 10⁶l mol^–1s^–1) in 6 M nitric acid at 290 ± 2 K were measured by a pulse radiolysis technique. The reaction scheme was refined by the computer simulation of the -radiolysis of aqueous nitric acid solutions of hydrazine with the use of the measured rate constants and published data on the reactivity of intermediates. The results of computations were compared with experimental data on the continuous radiolytic degradation of hydrazine in aqueous 2 M nitric acid solutions at 313 K.     

Activity Coefficients of Aqueous Mixed Ionic Surfactant Solutions from Osmometry

Osmotic techniques for measuring thermodynamic activities, such as isopiestic equilibration, are well established for multicomponent solutions, especially mixed salt solutions. Surprisingly, these techniques have not yet been applied to mixed ionic surfactants, despite the numerous practical applications of these systems and the importance of the Gibbs free energy for micelle stability. In this study, mass-action equations are developed for the osmotic coefficients of solutions of ionic surfactant CA + ionic surfactant CB, with common counterion C. Extended Debye–Hückel equations are used for the ionic activity coefficients. The equilibrium constants for mixed micelle formation are evaluated by Gibbs–Duhem integration of critical micelle concentrations. Fitting the derived equations to the osmotic coefficients of aqueous sodium decanoate + sodium dodecylsulfate solutions measured by freezing-point osmometry is used to evaluate the activities of the total surfactant components. Very large departures from ideal solution behavior are indicated, including stoichiometric surfactant activity coefficients and micelle activity coefficients that drop below 0.05 and 10^?8, respectively, relative to unity for ideal solutions. Osmometry offers many interesting and unexplored possibilities for studies of mixed surfactant thermodynamics.     

Photolysis of ortho-Azidobenzoic Acid in Aqueous Solutions and Water–Organic Solvent Mixtures

The photolysis of o-azidobenzoic acid and its potassium salt in water, ethanol, tetrahydrofuran (THF), and ethanol–water and THF–water mixtures was studied by IR and UV spectroscopy and thin-layer chromatography. It was found that the photolysis of o-azidobenzoic acid and potassium o-azidobenzoate in aqueous solutions mainly resulted in 2,1-benzisoxazolone, the intramolecular cyclization product. The process of azepine formation in ethanol or an ethanol–water mixture depends on the nucleophilic nature of ethanol; in this case, water is practically of no importance. The presence of THF in an aqueous solution shifted the singlet nitrene–dehydroazepine equilibrium toward dehydroazepine, which reacts with water to give azepines.