A new solvent system for the separation of Th4+, UO 2 2+ and Zr4+ in the presence of common anions by thin-layer chromatography

Summary A TLC method has been developed for separating Th⁴⁺, UO₂ ²⁺ and Zr⁴⁺ in the presence of some common anions using a dimethylamine/acetone/formic acid mobile phase. Capacity factors, separation factors and resolution for the separation of Th⁴⁺ from UO₂ ²⁺ have been evaluated. The effect of the pH of the sample on R_F values of Th⁴⁺, UO₂ ²⁺, Ni²⁺ and Cu²⁺ has also been examined.     

Ion-exchange chromatography using vanadyl and vandate salts as mobile phases with indirect detection

Summary Vanadyl sulfate, VOSO₄, was characterized as the mobile phase for the ion exchange separation of Li⁺, Na⁺, NH ₄ ⁺ , and K⁺ using indirect photometric detection at 254 nm. Detection limits ranged from 0.2 ppm for Li⁺ to 1 ppm for K⁺. Indirect electrochemical detection of these separated cations by reduction of VO (II) to V³⁺ was compared to spectrophotometric detection. The potential of the vanadate species, HVO ₄ ^2– , for the separation of F^–, Cl^–, and SO ₄ ^2– , with indirect photometric detection was also demonstrated.     

Enthalpies of crystallization of equilibrium solid phases occurring in the system KNO3−NH4NO3−H2O at 298.15 K

The concentration dependencies of the differential enthalpies of solution along several crystallization paths in the above mentioned system were measured. On this basis enthalpies of crystallization of equilibrium solid phases occurring there were calculated.     

Enthalpy of solution and effect of temperature on activity coefficients in MSO4−H2SO4−H2O system

Results of calorimetric determination of integral enthalpies of solution of some hydrates (monohydrates and heptahydrates) of 3d transition metal sulphates such as FeSO₄, NiSO₄ and MnSO₄ in three-component systems at sulphuric acid concentrations up to 2M are reported. Measured values of integral enthalpies of solution are the basis for calculation of activity coefficient temperature dependences according to Pitzer's model.     

Correlation of the position of the bond functions in H-X with electronegativity

S type Gaussian bond functions are optimized for HF, H₂O, NH₃, and CH₄. The optimization is carried out with respect to the exponent and position in the H-X bond. The position is found to correlate well with the electronegativity of Pauling and Allred-Rochow.     

Quantitative determination of gas mixture composition by gas chromatography—New approach

Summary A new method has been developed for the quantitative determination of gas mixture composition where air penetration during gas sample collection would lead to erroneous results. It requires the use of a stationary phase that separates gas sample components and the air and involves 4–5 analyses of samples of equal volumes containing different amounts of air. By graphical extrapolation of the air peak area (S _air ) as a function of the peak areas of the individual components (S _comp ) the areas for these components in the absence of air can be obtained forS _air =0. Using calibration curves for the pure gas components the true quantitative composition of the gas mixture is estimated.     

Nitrite formation in aerated aqueous azide solutions: A radiation chemical study

Gamma radiolysis of oxygenated 1–10 mM azide solutions was carried out at various pH values. In oxygenated 10 mM azide solutions, H₂O₂ and NO ₂ ⁻ were observed as radiolytic products while NH3 was not. The concentration of H₂O₂ reached its maximum level at a dose of 1 kGy, whereas NO ₂ ⁻ yield increased non-linearly beyond 2 kGy in this system. Both in aerated and oxygenated systems, G(NO ₂ ⁻ ) and G(H₂O₂) were found to vary with N ₃ ⁻ concentration. The yield of NO ₂ ⁻ was found to be dependent on both dose rate and pH. On pulse radiolysis, NO ₂ ⁻ was found as a radiolytic product in aerated 1 mM azide solution at pH 6.8. In this system the intermediate generated exhibits absorbance around 250 nm. The overall results obtained during the present study reveal that in presence of both reducing radical (mainly e _aq ⁻ ) and oxygen, N ₃ ⁻ produced an intermediate possibly NH₂O ₂ ^• radical, which is the prime source for NO ₂ ⁻ generation.     

Ultrasound-promoted synthesis of 2-amino-6-(arylthio)-4-arylpyridine-3,5-dicarbonitriles using ZrOCl2·8H2O/NaNH2 as the catalyst in the ionic liquid [bmim]BF4 at room temperature

We herein present an efficient and environmentally benign protocol for the synthesis of 2-amino-6-(arylthio)-4-arylpyridine-3,5-dicarbonitrile derivatives via the three-component condensation of a variety of aldehydes, arylthiols, and malononitrile catalyzed by ZrOCl₂·8H₂O/NaNH₂ (20 mol %) in the ionic liquid [bmim]BF₄ under ultrasound irradiation at room temperature.     

Influence of support acidity on electronic state of platinum in oxide systems promoted by SO4 2− anions

The electronic state of platinum supported on SO₄/ZrO₂, SO₄/TiO₂, SO₄/Al₂O₃, and SO₄/SiO₂ systems and on systems unpromoted by sulfur was investigated by diffuse-reflectance IR spectroscopy using CO as the probe molecule. The introduction of SO₄ ²⁻ anions increases the electron deficit on platinum particles. This suppresses the formation of bridging CO complexes with the metal, leads to the high-frequency shift of absorption maxima of CO adsorbed in the linear form, and stabilizes positively charged metal species (Pt^δ+ and Pt⁺) during the reduction process. The formation of the positively charged species includes the interaction between the acidic protons and the metal particles yielding [Pt−H]^δ+ adducts. The extent of the influence of the support on the electronic state of the metal increases in the series SO₄/SiO₂<SO₄/Al₂O₃<SO₄/TiO₂<SO₄/ZrO₂ in parallel with an increase in the strength of the acid sites in the system. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1094–1099, June, 1998.     

Gas chromatographic analysis of C2−C16 dicarboxylic acids esterified in aqueous solutions as n-propyl esters

Summary C₂−C₁₆ dicarboxylic acids were esterified in aqueous solution in the presence of sulfuric acid. Esterification in water/n-propanol mixtures with mole ratios between 0.03 and 2.21 can be utilized for the quantitative determination of dicarboxylic acids by gas chromatography. The presence of water does not interfere at water/n-propanol mole ratios below 0.45. For mole ratios above 0.45 anhydrous sodium sulfate has been used for binding the water. The mole ratio range tested was 0.12–0.99 for anhydrous sodium sulfate/water, and 0.16–2.55 for sulfuric acid/anhydrous sodium sulfate.     

一步水热合成Cu-SAPO-34选择性催化丙烯还原氮氧化物

采用一步法水热合成不同Cu/Al比的Cu-SAPO-34催化剂,并对其丙烯选择性催化还原NO（C₃H₆-SCR）性能进行了研究。通过N₂吸附-脱附、X射线衍射（XRD）、X射线光电子能谱（XPS）、程序升温还原（H₂-TPR）和原位漫反射傅里叶变换红外光谱（In situ DRIFTS）等研究手段对催化剂进行表征,考察Cu-SAPO-34中Cu物种含量对催化剂的物理化学性质和反应活性的影响。结果表明,当铜负载量为2.76%~4.12%（w/w）时,Cu-SAPO-34催化剂在富氧条件下300~400℃内表现出非常有吸引力的C₃H₆-SCR活性,可实现~100%的脱硝效率和~100%的N₂选择性。原位红外光谱研究表明,Cu-SAPO-34分子筛骨架上孤立的Cu²⁺离子是NO吸附和活化形成NO₂^-/NO₃^-中间物种的主要活性位,并通过C₃H₆-SCR反应过程中Cu²⁺/Cu⁺氧化还原循环来实现Cu²⁺离子的持续供给。     

Synthesis of derivatives of 4-amino-2-trifluoromethylnicotinic acid

The method for the synthesis of ethyl 4-R-amino-2-trifluoromethylnicotinates from a diphenylboron complex of ethyl 2-acetyl-3-amino-4,4,4-trifluorobut-2-enoate was developed.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2221–2223, October, 2004.     

High electrochemiluminescence intensity of the Ru(bpy)3 2+/oxalate system on a platinum net electrode

A new method for enhancing the electrochemiluminescence (ECL) intensity of the Ru(bpy)₃ ²⁺/ oxalate system is presented. When a platinum net was used as a working electrode and a platinum foil as an auxiliary electrode, the ECL intensity of the system was enhanced greatly. In addition, a cathodic peak appeared at 0.18 V (vs. SCE) on a platinum net electrode, and ECL of the system was observed at 0.18 V.     

Usy supported Pt-bearing SO42?/ZrO2 catalysts promoted by Cr for hydroisomerization of n -heptane

The Pt-bearing SO₄ ²⁻/ZrO₂ catalysts doped with Cr and supported on USY zeolite were prepared by impregnation, and characterized by XRD and IR spectroscopy of pyridine adsorption. Their catalytic activities were evaluated in the hydroisomerization of n-heptane with a fixed-bed atmospheric reactor. The Cr-promoted catalysts exhibited much higher catalytic activity and selectivity for isomerization products than the catalysts without the Cr dopant. Both the conversion and selectivity were discussed in relation with the physicochemical properties of catalysts.     

Spectrophotometric studies of 4-(2-hydroxy-4-substituted-azobenzene)-2-methyl-quinolines as reagents for the determination of silver

Summary The spectroscopic behaviour of some quinoline azo dyes has been studied. A simple, rapid, accurate, and sensitive method for the spectrophotometric microdetermination of Ag(I) ions using the title compounds is given. The conditions for the formation of the coloured complexes are obeyed up to 26 µg·ml^–1; the optimum concentration range for application of theRingbom method is 2.5–23 µg·ml^–1. The molar absorptivity and theSandell sensitivity have also been calculated. The method proved to be successful in determining Ag⁺ in photography fixing solutions. The results agreed satisfactorily with those obtained using standard atomic absorption spectroscopy.

---

Spectrophotometrische Untersuchungen von 4-(2-Hydroxy-4-subst.-azobenzol)-2-methylchinolinen als Reagentien zur Silberbestimmung

Zusammenfassung Das spektroskopische Verhalten einiger Chinolin-Azofarbstoffe wurde untersucht. Eine einfache, rasche, genaue und empfindliche Methode zur spektrophotometrischen Mikrobestimmung von Silbert(I)-Ionen mittels der Titelverbindungen wird vorgestellt. Die Bedingungen zur Bildung der gefärbten Komplexe werden bis zu einer Maximalkonzentration von 26 µg·ml^–1 erfüllt; der optimale Konzentrationsbereich zur Anwendung derRingbom-Methode liegt zwischen 2.5 und 23 µg·ml^–1. Die molare Absorption und die Empfindlichkeit nachSandell wurden ebenfalls berechnet. Die Methode wurde erfolgreich zur Bestimmung von Ag⁺ in photographischen Fixierlösungen eingesetzt. Die Ergebnisse stimmen in zufriedenstellender Weise mit durch Atomabsorptionsspektroskopie erhaltenen überein.

     

The effect of experimental methods and measurement conditions on values of the kinetic parameters of [Co(NH3)6]2(C2O4)3·4H2O

Using the thermal decomposition of [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O as a basis, the paper presents results which show how computed values of kinetic parameters are influenced by experimental conditions (ambient atmosphere, sample mass, linear heating rate) when using the non-isothermal methods and the Coats-Redfern (CR) modified equation. It also illustrates the influence of the experimental methods i.e. non-isothermal and isothermal (conventional) methods and also a quasiisothermal-isobaric one which can be recognised as equivalent to Constant Rate Thermal Analysis (CRTA). The results obtained have confirmed the significant influence of the experimental parameters as well as that of the experimental method used on the estimated values of kinetic parameters. The correlation between activation energy (E) and sample mass (m) or heating rate (β) is generally of a linear nature:E=a+bx     

Syntheses, crystal structures and Raman spectra of Ba(BF4)(PF6), Ba(BF4)(AsF6) and Ba2(BF4)2(AsF6)(H3F4); the first examples of metal salts containing simultaneously tetrahedral BF4 and octahedral AF6 anions

In the system BaF₂/BF₃/PF₅/anhydrous hydrogen fluoride (aHF) a compound Ba(BF₄)(PF₆) was isolated and characterized by Raman spectroscopy and X-ray diffraction on the single crystal. Ba(BF₄)(PF₆) crystallizes in a hexagonal space group with a=10.2251(4) Å, c=6.1535(4) Å, V=557.17(5) Å³ at 200 K, and Z=3. Both crystallographically independent Ba atoms possess coordination polyhedra in the shape of tri-capped trigonal prisms, which include F atoms from BF₄⁻ and PF₆⁻ anions. In the analogous system with AsF₅ instead of PF₅ the compound Ba(BF₄)(AsF₆) was isolated and characterized. It crystallizes in an orthorhombic Pnma space group with a=10.415(2) Å, b=6.325(3) Å, c=11.8297(17) Å, V=779.3(4) Å³ at 200 K, and Z=4. The coordination around Ba atom is in the shape of slightly distorted tri-capped trigonal prism which includes five F atoms from AsF₆⁻ and four F atoms from BF₄⁻ anions. When the system BaF₂/BF₃/AsF₅/aHF is made basic with an extra addition of BaF₂, the compound Ba₂(BF₄)₂(AsF₆)(H₃F₄) was obtained. It crystallizes in a hexagonal P6₃/mmc space group with a=6.8709(9) Å, c=17.327(8) Å, V=708.4(4) Å³ at 200 K, and Z=2. The barium environment in the shape of tetra-capped distorted trigonal prism involves 10 F atoms from four BF₄⁻, three AsF₆⁻ and three H₃F₄⁻ anions. All F atoms, except the central atom in H₃F₄ moiety, act as μ₂-bridges yielding a complex 3-D structural network.     

One-step synthesis of 5-acetyl-2-amino-4-aryl-3-cyano-4H-pyrano[3,2-b]indoles. Molecular and crystal structure of 5-acetyl-2-amino-4-(4"-chloro-3"-nitrophenyl)-3-cyano-4H-pyrano[3,2-b]indole

A one-step procedure was developed for the synthesis of 5-acetyl-2-amino-4-aryl-3-cyano-4H-pyrano[3,2-b]indoles involving the three-component reaction of 1-acetylindol-3(2H)-one with aromatic aldehydes and malononitrile in ethanol in the presence of triethylamine as the catalyst. The structure of 5-acetyl-2-amino-4-(4"-chloro-3"-nitrophenyl)-3-cyano-4H-pyrano[3,2-b]indole was established by X-ray diffraction analysis.     

Aqueous solution of phosphoric acid as the stationary liquid phase for selective separation of fatty acids under conditions of steam chromatography

An aqueous solution of phosphoric acid was used as a selective stationary liquid phase for the separation of volatile fatty acids under conditions of steam chromatography. Organic acids C₂–C₈ are eluted from the column as symmetric peaks, and the order of their elution is reverse to that observed commonly on other phases. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 497–499, March, 1997.     

Theoretical study of electric field gradients at nitrogen nuclei in HNO,CH3NO and C2H3NO

Electric field gradients (EFGs) at the nitrogen nuclei of nitroxyl, nitrosomethane and nitrosoethylene were calculated by employing the complete-active-space self-consistent field (CASSCF), internally contracted multireference configuration interaction (icMRCI) and single-configuration coupled-cluster (CC) methods with correlation-consistent basis sets at the levels of attainable accuracy. Changes in the pσ and pπ atomic orbital populations were used to rationalize the differences between the N EFG tensor components related to the nitroso compound and separate nitric oxide. Calculated ¹⁴N nuclear quadrupole coupling constants were found in reasonable accord with experimental values. Comparison of electric dipole moments and potential energy characteristics with external values served to testify to good overall quality of the wave functions used in our calculations.