Complexation of Calcium Ions with Dicarboxylic Acids in Aqueous Solutions

Complexation of calcium ion with malonic, succinic, glutaric, adipic acids at 25°C, ionic strength I = 0.3 (KCl) was studied by pH-potentiometric titration.     

Dissolution of Calcium Carbonate in Aqueous Solutions of Acetic Acid

A kinetic equation for the calcium carbonate dissolution, fitting the experimental data to within 8.1%, was obtained. The additional diffusion hindrance caused by the CO₂ evolution in the course of the dissolution was considered.     

Radiolytic Gas Formation in Dilute Oxalic Acid Aqueous Solutions

The radiolytic gas formation in aqueous oxalic acid solutions was studied. The concentrations of ₂ and ₂, the gas phase constituents, were measured. It was found that gas evolution is mainly due to the degradation of both oxalic acid and its radiolysis products.     

Tetraalkylammonium Ions in Aqueous and Non-aqueous Solutions

Property data for tetraalkylammonium cations, [H(CH₂) _n ]₄N⁺, are reviewed. They pertain to the isolated cations and their transfer from the gas phase into aqueous solutions. Various properties of these cations in aqueous and non-aqueous solutions and data for their transfer between these are also reviewed. Emphasis is placed on the dependence of data on the length n of the alkyl chains rather than on the absolute values. Most of the data are available only for the first four members of the series. The properties of the isolated ions increase linearly with the chain length. Molar enthalpies of formation of the gaseous and aqueous cations, and absolute standard molar enthalpies of hydration, are derived. Standard molar entropies of dissolution of several salts in water are obtained from their solubilities and enthalpies of solution. The molar entropies of the crystalline iodides of the first four members of the series then give the standard partial molar entropies of the aqueous cations and their molar entropies of hydration. The standard partial molar volumes in aqueous and non-aqueous solutions are quite linear with n and in non-aqueous solutions the molar volume hardly depends on the nature of the solvent. On transfer from water to non-aqueous solvents the volume of Me₄N⁺ suffers some shrinkage, that of Et₄N⁺ appears to be unaffected, but from Pr₄N⁺ onwards an increasing expansion takes place. This unexpected result is tentatively explained by hydrophobic intra-molecular association of pairs of alkyl chains in aqueous solutions, resulting in a tightening of the structure. The transfer of the R₄N⁺ cations from water into non-aqueous solvents is governed by a large positive entropy change, outweighing the smaller positive enthalpy change. The transport properties of the aqueous R₄N⁺ cations are non-linear with n. A major impediment to movement is thus the sticking of the water molecules to the ice-like hydrophobic hydration sheaths of the larger cations. The number of water molecules affected by the hydrophobic cations is open to widely differing estimates resulting from various approaches, and constitute an open issue.     

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.     

Interaction of Polyacrylic Acid with Copper,Cobalt, and Nickel Ions in Aqueous Solutions

Russian Journal of General Chemistry - Potentiometric and spectrophotometric titration methods were applied to study the relationships in the interaction of polyacrylic acid with copper, cobalt,...     

A Diffusion-Kinetic Model for Radiation-Chemical Transformations of Oxalic Acid and Oxalate Ions in Aqueous Solutions

A diffusion-kinetic model for the radiation-chemical degradation of oxalic acid and oxalates in aqueous solutions was developed. The model adequately describes published data on the formation of H₂, H₂O₂, and CO₂ over wide ranges of acid concentrations and pH values.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 4, 2005, pp. 250–254.Original Russian Text Copyright © 2005 by Gordeev, Ershov, Kosareva.     

Complex Formation of Copper(II) Ions with Galactaric Acid

Complex formation of copper(II) ions with the galactarate ion [Gala]^{2 -} in aqueous solution was studied by means of potentiometric titration. Stability constants of the [CuGala] and [Cu(Gala)₂]^{2 -} complexes were determined. A complex compound was synthesized electrochemically and isolated from a DMSO solution containing a copper(II) salt and galactaric acid, and its composition was determined. The structure of the complex was determined by ESR.     

Degradation of Polyacrylamide and Its Derivatives in Aqueous Solutions

General features of degradation of polyacrylamide and its anionic and cationic derivatives under the action of radical degradative agents are considered. The molecular weight of these polymers can be controlled by varying the structure and concentration of the degradative agent and salt additions, the concentration, molecular weight, and composition of the initial (co)polymer, and the process temperature and time.     

Ternary Complex Formation between Vanadium(III), Dipicolinic Acid and Picolinic Acid in Aqueous Solution

Ternary complex species formed by the V³⁺ cation with the picolinic acid (Hpic, HL) and dipicolinic acid (H₂dipic, H₂L) ligands in aqueous solutions have been studied potentiometrically (25 °C, I=3.0 mol⋅dm⁻³ KCl ionic medium) and by spectrophotometric measurements. Application of the least-squares computer program LETAGROP to the experimental emf (H) data, taking into account the hydrolytic V(III) species and the binary V³⁺–picolinic acid and V³⁺–dipicolinic acid complexes, shows that under the investigated conditions the following ternary complexes are formed: [V(dipic)(pic)], [V(dipic)(pic)(OH)]⁻ and [V(dipic)(pic)₂]⁻. The stability constants of the ternary complexes were determined by potentiometric measurements whereas the spectrophotometric measurements were done in order to obtain a qualitative characterization of the complexes formed in aqueous solution.     

On the Intrinsic Volumes of Ions in Aqueous Solutions

Various methods that have been proposed in the literature for the estimation of the intrinsic volumes of electrolytes in aqueous solutions are briefly discussed. Most of these depend on the radii of the constituent ions. A method that is independent of the radii but requires a long extrapolation from the temperatures involved in salt melts is also mentioned. A new method is developed here, independent of ionic radii, which employs the partial molar volumes of salts in their concentrated solutions (and is, therefore, limited to highly soluble salts). These are extrapolated to a virtual concentration at which all the water present is as closely packed as possible, hence no longer capable of being electrostricted. The resulting intrinsic volumes of salts are reasonable when compared to other estimates of these quantities.     

Extraction Kinetics of Copper Ions from Aqueous Solutions with a Mixture of Oleic Acid and Triethanolamine

Solvent extraction of copper(II) ions from aqueous solutions with a mixture of oleic acid and triethanolamine in kerosene is studied.     

The State of Copper Ions in Aqueous and Aqueous Ammonia Solutions of Copper Acetate

Stabilization of Cu²⁺ ions in aqueous and aqueous ammonia solutions of copper acetate was studied for a wide range of ammonia concentrations. The structure of copper acetate hydrate complexes was shown to markedly change upon dissolution in water. In aqueous solutions, copper is stabilized as strongly bound Cu²⁺ associates (dimers) in a distorted octahedral environment composed of water molecules and acetate groups oxygen atoms in equatorial positions with strong exchange interaction via acetate groups. In solutions of copper acetate in aqueous ammonia, the concentration of ammonia has a crucial effect on the ordering of Cu²⁺ ions in associates. At high ammonia concentration, disordered copper tetra-ammoniate associates with the \({d_{{x^2} - {y^2}}}\) ground state are formed, whereas at low ammonia concentration, bulky Cu²⁺ ion associate structures are generated, with the \({d_{{x^2} - {y^2}}}\) ground state, hydroxyl groups in the equatorial plane, and water molecules in the axial positions.     

Formation of Methyl Iodide in the Radiolysis of Aqueous Cesium Iodide and Acetic Acid Solutions

Volatile compounds of radioactive iodine, including methyl iodide, are released into the environment in the cases of serious accidents at nuclear power plants. The aim of this study was to find a conceivable mechanism of the radiation-chemical formation of methyl iodide in aerated aqueous solutions of cesium iodide and acetic acid. This provides the basis for subsequent investigations aimed at preventing the formation of methyl iodide. The radiation-chemical yield of methyl iodide formation in 10^–3M CsI solutions containing CH₃COOH (0.1 mol/l) decreased with increasing the pH. This fact is primarily explained by a decrease in the steady-state concentration of molecular iodine with increasing the pH. An increase in the pH of irradiated solutions up to pH 9 was found not only to prevent the formation of methyl iodide but also to enhance its radiation-chemical degradation.     

Electrical Conductance Studies in Aqueous Solutions with Aspartic Ions

Conductivity measurements of dilute aqueous solutions of DL-aspartic acid, potassium-DL-aspartate and magnesium-DL-aspartate were performed in the 288.15 to 323.15 K temperature range. The limiting molar conductances of aspartate anions, λ ⁰(HAsp⁻,T) and the dissociation constants of aspartic acid, K ₂(T) were derived by use of the Debye-Hückel equation for the activity coefficients and the Onsager, and Quint and Viallard conductivity equations.     

Electrical Conductance Studies in Aqueous Solutions with Glutamic Ions

Conductivity measurements in dilute aqueous solutions of L-glutamic acid, DL-glutamic acid, sodium-L-glutamate and magnesium-L-glutamate, were performed in the 288.15 to 323.15 K temperature range. The limiting molar conductivities of glutamic anions, λ ^o(HGlu⁻,T) and the dissociation constants of glutamic acid, K ₂(T) were derived by the use of the Debye–Hückel equation for the activity coefficients and the Onsager, and Quint and Viallard conductivity equations.     

Study of Silver(I) Complex Formation with Some Thiourea Derivatives in Aqueous Solution

Russian Journal of General Chemistry - The equilibrium processes of the formation of mononuclear and some binuclear silver(I) complexes with thiourea, N-acetylthiourea, thiosemicarbazide,...     

Electrical Conductance Studies in Aqueous Solutions with Ascorbate Ions

Conductivity measurements in dilute aqueous solutions of L-ascorbic acid, sodium-L-ascorbate, magnesium-L-ascorbate, calcium-L-ascorbate and ferrous-L-ascorbate were performed in the (288.15 to 323.15) K temperature range. The limiting molar conductances of the ascorbic anion, λ^∘(HAsc⁻, T), and the dissociation constants of ascorbic acid, K(T), were derived by the use of the Debye-Hückel equation for the activity coefficients and the Onsager and Quint and Viallard conductivity equations.     

Formation of Hydrogen Peroxide under the Action of Microwave Radiation in Aqueous Solutions of Vanadyl and Permanganate Ions

Russian Journal of Applied Chemistry - The amount of hydrogen peroxide formed in aqueous solutions directly in the course of microwave irradiation is considerably larger than the amounts detected...