Effect of sodium oxide doping on solid-solid interactions between V2O5 AND Al2O3

A V₂O₅/Al₂O₃ mixed solids sample was prepared with a molar ratio of 0.41 Na₂O (4 and 10 mol%) was added in the form of sodium nitrate prior to calcination in air in the temperature range 500–1000C. Solid-solid interactions between V₂O₅ and Al₂O₃ were studied using DTA and TG curves and their derivatives together with XRD techniques.The results obtained showed that Na₂O interacted with V₂O₅ at temperatures starting from 500C to yield a sodium/vanadium compound, Na_0.3V₂O₅ which remained stable and decomposed in part by heating at 1000C. V₂O₅ exists in orthorhombic and monoclinic forms in the case of pure mixed solids and those containing 4 mol% of Na₂O and preheated at 500C, and in monoclinic form in the case of the mixed solid doped with 10 mol% of Na₂O.Heating of pure and doped mixed oxide solids at 650C resulted in the conversion of most of the V₂O₅ into AlVO₄. Doping with sodium oxide enhanced the solid-solid interaction between V₂O₅ and Al₂O₃ at 650C to produce AlVO₄. The produced AlVO₄ decomposed completely on heating at 700C to form -Al₂O₃ and V₂O₅, (orthorhombic and monoclinic forms).The presence of Na₂O was found to decrease the relative intensity of the diffraction lines of -Al₂O₃ (corundum) produced at 750C which indicated some kind of hindrance of the crystallization process.Heating of pure and doped mixed solids at 1000C resulted in a further crystallization of acorundum together with V₂O₅ and sodium vanadate, Na_0.3V₂O₅. However, the intensities of diffraction lines relative to those of the sodium vanadium compound were found to decrease markedly by heating at 1000C, indicating partial thermal decomposition into vanadium and aluminium oxides.     

The Interaction of O2, NO,and N2O with Surface Defects of Dispersed Titanium Dioxide

A combined study of intrinsic structural defects in reduced TiO₂ was performed using mass spectrometry, optical diffuse-reflectance spectroscopy, and UV photoelectron spectroscopy (UPS). It was found that the reduction of TiO₂ resulted in the appearance of absorption in the region 0.50 h 3.50 eV (400 2500 nm), which is formed by absorption due to free electrons (a continuum at h 1.50 eV), local centers—Ti³⁺ ions (a band at 2.00 eV), and oxygen vacancies (bands at 1.17, 2.81, and 2.55 eV). The spectrum of induced occupied electronic states in the forbidden gap and the position of oxygen vacancy levels with respect to the Fermi level were determined by UPS. The absorption of reduced TiO₂ was stable on the sample to T = 800 K in a vacuum; however, it weakened in contact with O₂, NO, and N₂O molecules beginning at T = 300 K (surface sites) and T 400 K (subsurface sites) as a result of filling oxygen vacancies with atomic oxygen in the course of dissociative adsorption. The adsorption complexes formed by the interaction of O₂, NO, and N₂O with defects were analyzed by temperature-programmed desorption. The distribution of sites over the energies of oxygen binding was found with the use of a nonuniform surface model, and specific oxygen adsorption species were revealed. It was found that the irradiation of TiO₂ activates the formation and decay of sites and results in the formation of specific O₂ and N₂O adsorption species.     

Polarographic Determination of Lovastatin in the Presence of H2O2 in Pharmaceuticals, Human Urine and Serum

The polarographic reduction and catalytic behavior of lovastatin are studied by polarography and cyclic voltammetry. The reduction wave of lovastatin appears at ca. –1.49V (vs. SCE) in 0.16molL^–1 Na₂B₄O₇–KH₂PO₄ (pH=7.4) supporting electrolyte containing 20% ethanol. It is ascribed to a 2e^–, 2H⁺ addition to the carbonyl group on lactone ring. If H₂O₂ is present, the reduction wave is catalyzed to produce a polarographic catalytic wave. Based on the catalytic wave, a novel method for the determination of lovastatin is proposed. A rectilinear calibration curve of the catalytic wave was obtained for lovastatin concentration in the range 1.5×10^–8 to 1.0×10^–6molL^–1. The peak current of the catalytic wave is ca. 12 times higher than that of the corresponding reduction wave. The detection limit is 8.0×10^–9molL^–1. The proposed method is simpler, faster and more sensitive than the known methods for lovastatin analysis, and can be applied to the direct determination of lovastatin in pharmaceuticals, urine and serum without preliminary separation.     

Triterpene glycosides and their genins fromThalictrum foetidum. V. Structure of cyclofoetoside B

A new glycoside (cyclofoetoside B) (I) has been isolated from the epigeal part of the plantThalictrum foetidum L. (Ranunculaceae). On the basis of chemical transformations and with the aid of physicochemical characteristics it has been established that cyclofoetoside B is 24S-cycloartane-3, 16, 24, 25, 29-pentaol 3-O--L-arabinopyranoside 16-O-[O--L-rhamnopyranoside-(1 6)--D-glucopyranoside], C₄₇-H₈₀O₁₇, mp 194–197°C (methanol); [] _D ²⁴ +15.7 ± 2° (c 0.88; pyridine). The enzymatic hydrolysis of (I) has yielded cyclofoetigenin B (III), 24S-cycloartane-3,16,24,25,29-pentaol 16-O--D-glucopyranoside, (IV), C₃₆H₆₂O₁₀, mp 223–225°C (acetone), [] _D ²⁴ +37 ± 2° (c 0.97; methanol) and 24S-cycloartane-3,16,24,25,29-pentaol 16-O-[O--L-rhamnopyranosyl-(1 6)--D-glucopyranoside, C₄₂H₇₂O₁₄, mp 229–231°C (methanol), [] _D ³⁰ +41 ± 2° (c 0.7; methanol). Details of the IR and¹H and¹³C NMR spectra of the compounds are given.Irkutsk Institute of Organic Chemistry, Academy of Sciences of the USSR. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Trashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 341–345, May–June, 1986.     

Selective Kinetic Determination of Cu2+ with Tetraazamacrocyclic Bis(Methylphosphonate) Ligand (Dipon)

A new macrocyclic ligand, 1,4,8,11-tetraazacyclotetradecane-1,8-bis(methylphosphonic acid) (refered to as dipon) exhibits high thermodynamic and kinetic selectivity for Cu²⁺ compared to other transition metal ions. The initial-rate method (=310nm, pH=3.75, c_L4.6×10^–3molL^–1) was chosen as an optimal experimental approach in order to achieve maximum sensitivity of determination. The dynamic range of the method is (5–200)×10^–6molL^–1, and the detection limit is 2.5×10^–6molL^–1. A standard addition procedure was applied to the kinetic determination of Cu²⁺ to eliminate the effect of interfering ions (e.g. Zn²⁺, Ca²⁺, Mg²⁺, Cd²⁺, Pb²⁺, Mn²⁺, Co²⁺, Ni²⁺, HCO^–₃, Cl^–, SO₄^2–, etc.). The method was tested on artificial and real samples (alloys, pure and spiked mineral water) and gave satisfactory results which are in agreement with the values for some certified materials. The advantage of the proposed method is rapidity, simplicity and robustness in the presence of other metal ions.     

Effect of Thermal Activation of Supported Catalysts Pt/MeOx,Where MOx = Al2O3, CeO2, La2O3, and ZrO2, for Complete Oxidation

A sharp increase in the atomic catalytic activity (ACA) of supported platinum catalysts in the model reaction of n-pentane complete oxidation is found on going from the preliminary calcination temperature of 500–600°C to a temperature of 700°C. ACA increases by an order of magnitude for the Pt/-Al₂O₃ system, 3 times for Pt/ZrO₂, and 1.5 times for Pt/CeO₂. The per-gram activities of all catalysts decrease because of a decrease in the dispersion of supported platinum with an increase in the temperature of preliminary calcination.     

Non-Aqueous Capillary Electrophoresis with Indirect Photometric Detection for Direct Analysis of Pb2+, Zn2+ and Cd2+ Ions

A new approach, based on non-aqueous capillary electrophoresis separation and indirect photometric detection, was established for the determination of the transition metal ions Pb²⁺, Zn²⁺ and Cd²⁺. Under optimized conditions, the method produced baseline separation of these three metal ions. The linear range and detection limits were 1050µM, 1.9µM for Cd²⁺; 1050µM, 2.1µM for Zn²⁺; and 20100µM, 3.8µM for Pb²⁺, respectively.     

Iron Catalysis of SO2 Oxidation in the Atmosphere

The mechanisms of SO₂ oxidation catalyzed by iron ions in the droplet phase of the convective cloud in the lower atmosphere were examined. The relations of the catalytic SO₂ decrease to the concentration of the iron ions and to the intensity of fluxes to the droplet of the OH _(g) and HO _2(g) radicals were characterized. The determining role of the replacement of the low-reactive HO _2(g)(O^– _2(aq)) radical by the reactive SO^– _5(aq) radical in the sulfite medium during daytime was revealed. This process occurred due to the coupling of the decay of the radicals and their regeneration in the liquid-phase reactions O^– _2(aq) + FeOH²⁺ _(aq) Fe²⁺ _(aq) + OH^– _(aq) + O_2(aq), HSO^– _5(aq) + Fe²⁺ _(aq) FeOH²⁺ _(aq) + SO^– _4(aq)HSO ₃ ^- _(aq),O_{2 (aq)} SO^– _5(aq).     

Leaching of uranium with the H2O2-Na2SO4-H2SO4 (HSS) system and the efficiency of Acigol Lake water

The applicability of a new leaching method, the HSS (H₂O₂-Na₂SO₄-H₂SO₄) system, in the extraction of uranium from Saricaolu-Bergama Region low grade ore, and the efficiency of Acigol Lake (Denizli)-Turkey water as a natural source of Na₂SO₄ has been investigated. The effect of H₂SO₄ concentration, temperature, leaching time, H₂O₂ and Na₂SO₄ concentrations and the amount of Acigol Lake water on the extraction of uranium was examined. HSS was found suitable for the extraction of uranium from Saricaolu-Bergama Region samples and it was observed that the acid consumption could be decreased by adding Na₂SO₄.     

Kristallstruktur von Trisilber(I)amidosulfat Monohydrat,Ag3SO3N · H2O

An X-ray crystal structure analysis of yellow Ag₃SO₃N · H₂O was carried out at room temperature:M=435.69, monoclinic, P2₁/n,a=11.628 (5) Å,b=8.058 (4) Å,c=12.034 (5) Å, =86.49 (3)°,V=1125.5 ų,Z=8,d _x =5.142 Mgm^–3, MoK, =0.71069 Å (graphite monochromator), =10.5 mm^–1,R=5.44%,R _w =5.85% (877 reflections, 118 parameters). The structure contains Ag planes with Ag-Ag distances shorter than in metallic silver. The nitrogen atoms of the SO₃N anion are covalently bonded to 4Ag atoms of these Ag planes, thus assuming the extraordinary coordination number of 5. The five crystallographically independent Ag atoms forming the Ag planes have approximate linear N-Ag-N coordination. In addition, the structure contains two Ag atoms which are ionically coordinated to 4 resp. 5O atoms of SO₃N and water. The colour-structure correlation of Ag(I) compounds with colourless anions is discussed.

Herrn Prof. Dr. mult.V. Gutmann zum 65. Geburtstag gewidmet.     

Synthesis and Application of a Novel Poly(Acryl-p-Toluenesulfonamideamidine-p-Toluenesulfonylamide) Chelating Fiber for Preconcentration and Separation of Trace Noble Metal Ions from Solution Samples

A novel poly(acryl-p-toluenesulfonamideamidine-p-toluenesulfonylamide) chelating fiber containing S, N and O elements was synthesized from polyacrylonitrile fiber and p-toluenesulfonamide and used for the preconcentration and separation for traces of Ru(III), Rh(III), Au(III) and Pd(IV) ions from waste water and ore sample solution. The synthesis of this fiber was simple and rapid. The results indicate that 100ngmL^–1 of these ions can be quantitatively enriched by the chelating fiber at a flow rate of 6mLmin^–1 and a pH of 4 and desorbed quantitatively with 20mL of 6molL^–1 HCl and 5% CS(NH₂)₂ solution at 50°C (with recovery>95%). A 50 to 1000-fold excess of Ca²⁺, Mg²⁺, Mn²⁺, Co²⁺, Fe³⁺, Cu²⁺, Zn²⁺, and Al³⁺ ions caused little interference in the concentration and determination of the analyzed ions. When the fiber had been reused twenty times, the recoveries of the ions enriched by the fiber were still over 96%. The saturated adsorption capacities of the fiber were in the range of 22–96mgg^–1. The relative standard deviation (RSD) of the method was between 0.70% and 0.84%. Recoveries of a standard added to actual samples were in range of 95–101%. The results obtained for these ions in real solution samples were basically in agreement with the given values, the average errors being below 5.0%. FT-IR spectra show that the existence of –SO₂–Ar, HN=C–NH–, O=C–NH– and –NH–SO₂ functional groups are verified in the chelating fiber. The experiments show that the method is rapid, precise, simple and convenient.     

Influence of substituents on hydrogenation of nitro groups in aromatic hydrocarbons catalyzed by rhenium thiocomplexes

Homogeneous hydrogenation studies of (NO₂)_1–2–C₆H_3–4–L nitro compounds (where L=–H,–NH₂,–COOH,–CHO,–OH,–CH₃ and –CH=CH–COOH) catalyzed by Re₂S₆TThio₃Cl₂ in dimethylformamide solutions at and T=343 K, have revealed that the reaction is enhanced by electron-acceptor substitutents and hindered by electron-donor ones.

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(NO₂)_1–2–C₆H_3–4–L, L=–H,–NH₂,–COOH,–CHO,–OH,–CH₃,–CH=CH–COOH, Re₂S₆Thio₃Cl₂ 343 . , .

     

Determination of Attogram Quantities of Silver via Quenching of the Solid Substrate Room-Temperature Phosphorescence of Rhodamine B Based on the Catalysis of its Oxidation by Potassium Persulfate

A new method of SS-RTP for the determination of trace silver has been established. This method is based on the fact that Ag⁺, when activated by ,-bipyridyl (bipy) in a media of HAc–NaAc (pH=4.9), can catalyze the reaction of Rhodamine B (RhoB) oxidized by K₂S₂O₈, thus causing the Solid Substrate Room-Temperature Phosphorescence (SS-RTP) of RhoB to be quenched. The activating efficiency of bipy is 6.7 times higher than that of o-phenanthroline (phen). The reduction of the phosphorescence intensity (I_p) of RhoB is directly proportional to the concentration of Ag⁺ ions in the range of 1.6016.0agspot^–1 (0.40µLspot^–1). The regression equation of the working curve can be expressed as I_p=18.78+5.100m_Ag+ (agspot^–1) (r=0.9994, n=6), the detection limit is 0.28agspot^–1. This rapid, accurate and sensitive method has been successfully applied to the determination of trace silver in tea and human hair samples, and the results agree well with the Atomic Absorption Spectroscopy (AAS) method. The mechanism of the catalyzing reaction is also discussed.     

A Simple Procedure for Decomposition of Human Hair Using Polypropylene Vials for Selenium Determination by Hydride Generation Atomic Absorption Spectrometry

Two procedures for wet decomposition of human hair samples were compared for selenium determination by hydride generation atomic absorption spectrometry (HGAAS). These procedures involve treatment with HNO₃/H₂O₂ and H₂SO₄/HNO₃, respectively, using small disposable polypropylene (PP) vials. Analytical steps from weighing to dilution were performed in the same individual PP vial. After sample weighing (10±3mg) and reagent addition, decomposition was performed in a conventional oven (20h, 100°C). Addition of sulfamic acid prior to HGAAS measurements was necessary to minimize interference due to residual nitrogen oxides from the decomposition step. The accuracy was estimated using certified hair reference analysis which yielded an agreement higher than 97% (recovery tests). The absolute limit of detection was 1.2ng (3 s; n=10), corresponding to 0.12µgg^–1 in the dry sample.     

Field and field-gradient polarizabilities of H2O

Using a charge-perturbation approach, all components of the polarizability tensors , , A, B, and C for H₂O have been evaluated at the SCF level and, with the exception of and B, at the MC SCF level of approximation. This is the first such comprehensive evaluation of the electrical properties of water.Member of the Ottawa-Carleton Chemistry Institute     

Single Crystal Growth,Crystal Structure and Thermal Behaviour of Mercury(II) Pyrophosphate Dihydrate

Summary. Colourless single crystals of Hg₂P₂O₇(H₂O)₂ up to 0.4 mm in length were grown by a diffusion technique starting from aqueous solutions of Na₄P₂O₇ and Hg(NO₃)₂. The crystal structure is isotypic with that of Ca₂P₂O₇(H₂O)₂ and was determined from a four-circle diffractometer data set (space group , Z=2, a=6.9374(7), b=7.4396(8), c=7.9863(7)Å, =84.685(8), =75.158(8), =72.818(8)°, 2413 structure factors, 132 parameters, R[F ²>2(F ²)]=0.0181, wR(F ² all)= 0.0384). Hg₂P₂O₇(H₂O)₂ is composed of approximately eclipsed P₂O₇ ^4– anions and distorted [HgO₆] octahedra and [HgO₇] pentagonal bipyramids as the main building units. The structure is stabilized by inter-water hydrogen bonding and by hydrogen bonding between terminal pyrophosphate oxygen atoms and the water molecules. The P–O distances to the terminal oxygen atoms range from 1.501(4) to 1.536(3)Å, with an average of 1.522Å; the mean distance of 1.615Å to the bridging O atom is considerably longer with an (O–P–O) bridging angle of 123.44(19)°. Both Hg atoms have two short Hg–O bonds around 2.17Å and additional bonds ranging from 2.381(3) to 2.708(4)Å. Upon heating above 160°C, both crystal water molecules are released simultaneously and anhydrous Hg₂P₂O₇ is formed which is stable up to ca. 660°C. Above this temperature the material decomposes completely.     

Hydrolysis of [Pt(dien)H2O]2+ and [Pd(dien)H2O]2+ complexes in water

The hydrolysis of the [Pt(dien)H₂O]²⁺ and [Pd(dien)H₂O]²⁺ complexes has been investigated by potentiometry at 298 K, in 0.1 mol dm^–3 aqueous NaClO₄. Least-squares treatment of the data obtained indicates the formation of mononuclear and -hydroxo-bridged dinuclear complexes with stability constants: log ₁₁ = –6.94 for [Pt(dien)OH]⁺, log ₁₁ = –7.16 for [Pd(dien)OH]⁺, and also log ₂₂ = –9.37 for [Pt₂(dien)₂(OH)₂]²⁺ and log ₂₂ = –10.56 for [Pd₂(dien)₂(OH)₂]²⁺. At pH values > 5.5, formation of the dimer becomes significant for the Pt^II complex, and at pH > 6.5 for the Pd^II complex. These results have been analyzed in relation to the antitumor activity of Pt^II complexes.     

Symmetry functions adapted to the subgroup chain U(7) ⊃ SO(7) ⊃ G2 ⊃ SO(3) ⊃ G

Summary In this paper the Lie algebra technique is used to construct symmetry functions adapted to the subgroup chain U(7) SO(7) G ₂ SO(3) G, which is one of symmetry group chains appearing in the weak ligand field scheme for f ^N ions. The functions are expressed in terms of the Gelfand states.     

Laser-spectroscopic laboratory studies of atmospheric aqueous phase free radical chemistry

Nitrate radical (NO₃) reactions with benzene (R-1), toluene (R-2), p-xylene (R-3), p-cresol (R-4) and mesitylene (R-5) have been studied by laser photolysis/long path laser absorption (LP-LPLA) in aqueous solution. Rate constants of k₁=(4.0±0.6) 10⁸, k₂=(1.2±0.3)10⁹, k₃=(1.6±0.1)10⁹, k₄= (8.4±2.3)10⁸ and k₅=(1.3±0.3)10⁹ lmol^-1s^-1 were obtained at T=298 K. In addition, reaction rate coefficients for SO^-₅+Fe²⁺prod. (R-6) and SO^-₅+Mn²⁺prod. (R-7) of k₆=(4.3±2.4) 10⁷ lmol^-1s^-1 and k₇=(4.6±1.0)10⁶ lmol^-1s^-1 (T=298 K, I0) have been obtained by the application of laser photolysis/UV-VIS broadband diode array spectroscopy. A new laser photolysis/UV-long path laser absorption experiment has been applied to study the reaction of the Cl^-₂ radical anion with dissolved sulfur(IV). For the reactions Cl^-₂+HSO^-₃2Cl^-+H⁺+SO^-₃ (R-8) and Cl^-₂+SO^2-₃2Cl^-+SO^-₃ (R-9) rate coefficients of k₈=(1.7±0.2)10⁸ lmol^-1s^-1 (T=298 K, I0) and of k₉=(6.2±0.3)10⁷ lmol^-1s^-1 (T=279 K, I0) were obtained.     

Potentiometric Studies on Binary and Ternary Complexes of Di- and Trivalent Metal Ions Involving Some Hydroxamic Acids, Amino Acids, and Nucleic Acid Components

Summary. Formation of binary and ternary complexes of Cu^II, Co^II, Ni^II, Zn^II, Fe^III, Al^III, and Cr^III metal ions with some selected aliphatic and aromatic hydroxamic acids and some biologically important amino acids or nucleic acid components was investigated using the potentiometric technique at 25°C and I=0.10moldm^–3 NaNO₃. The acid-base properties of the ligands were investigated and discussed. The acidity constants of the ligands were determined and used for determining the stability constants of the complexes formed in aqueous medium under the experimental conditions. The ternary complex formation was found to occur in a stepwise manner. The stability constants of these binary and ternary systems were calculated. The order of stability of the ternary complexes in terms of the nature of hydroxamic acid, amino acid, nucleic acid component and metal ions was investigated and discussed as well as the values of log K and log X for the ternary systems. The concentration distribution of the various complex species in solution was evaluated. In addition, evaluation of the effect of temperature of the medium on the stability of the ternary system M^III – benzohydroxamic acid – L-histidine or adenine (M^III=Fe^III, Al^III, and Cr^III) has been studied. The thermodynamic parameters were calculated and discussed.