The determination and application of 87Sr/86Sr ratio in verifying geographical origin of wheat

As ⁸⁷Sr/⁸⁶Sr ratio plays a significant role in authenticating the geographical origin of foodstuff, it is important to identify where the ⁸⁷Sr/⁸⁶Sr signature in food comes from, and the methods of ⁸⁷Sr/⁸⁶Sr ratio analysis in food and environmental samples. Wheat with three genotypes, soil and groundwater samples were collected from three regions of China during harvest time of 2014. The ⁸⁷Sr/⁸⁶Sr ratios in the samples were determined by thermal ionization mass spectrometer in order to investigate the possible source of ⁸⁷Sr/⁸⁶Sr in wheat, and the concentrations of Rb and Sr in wheat and soils were also detected by inductively coupled plasma mass spectrometry and combined with ⁸⁷Sr/⁸⁶Sr ratio in order to trace the geographical origin of wheat. The ⁸⁷Sr/⁸⁶Sr ratio, the contents Rb and Sr, and Rb/Sr ratio of wheat and soil samples showed significant differences among three regions. The ⁸⁷Sr/⁸⁶Sr ratios and the concentrations of Rb and Sr in soils were higher than those in corresponding wheat. The ⁸⁷Sr/⁸⁶Sr ratio in wheat was identical to that corresponding soil NH₄NO₃ extracts (labile fraction of soil) and groundwater. Wheat uptake more Rb than Sr. 3D distribution of ⁸⁷Sr/⁸⁶Sr, Rb and Sr could identify wheat samples from different regions clearly. The ⁸⁷Sr/⁸⁶Sr ratio of wheat reflects the ⁸⁷Sr/⁸⁶Sr ratio of the associated environment including soil and groundwater. It is expected that the use the parameters of ⁸⁷Sr/⁸⁶Sr ratio, the contents of Rb and Sr will allow to trace geographical origin of wheat. Copyright © 2017 John Wiley & Sons, Ltd.     

Rubidium gadolinium bis­(tungstate)

The structure of rubidium gadolinium bis­(tungstate), RbGd(WO₄)₂, has been determined. The crystal is built up from corner‐ and edge‐sharing WO₆ octa­hedral and GdO₈ polyhedral groups, giving rise to a Gd–WO₄ polyhedral backbone surrounding structural cavities filled with Rb⁺ cations. The Gd and Rb atoms lie on twofold axes.     

Hydrolysis of ammonium oxofluorotungstates: A F, O and W NMR study

Fluorine-19 and natural abundance ¹⁷O and ¹⁸³W NMR spectroscopy were employed for the characterization of aqueous solutions of (NH₄)₂WO₂F₄ and (NH₄)₃WO₃F₃. Dissolution of the (NH₄)₂WO₂F₄ complex is accompanied by its partial acid hydrolysis to give the trans(mer)-dimer, [W₂O₅F₆]⁴⁻, and unreacted cis-[WO₂F₄]²⁻. The cis(fac)-[W₂O₅F₆]⁴⁻ anion is the major soluble product resulting from the alkaline hydrolysis of (NH₄)₂WO₂F₄ along with the isolation of the solid (NH₄)₂WO₃F₂. In addition, the edge-bridging dimer, [W₂O₆F₄]⁴⁻, and the cyclic trimer, [W₃O₉F₆]⁶⁻, are also suggested as hydrolysis products. Decomposition of (NH₄)₃WO₃F₃ occurs in aqueous solution to give NH₄WO₃F.     

On the preparation of nanosized Al2(WO4)3 by a precipitation method

Nanosized aluminum tungstate, Al₂(WO₄)₃, is prepared by a precipitation reaction between Na₂WO₄ and Al(NO₃)₃. The structure of the precipitated composition is determined by powder XRD analysis, IR and ²⁷Al MAS NMR spectroscopy. The thermal properties are examined by DSC, DTA and TG analyses combined with gas evolved analysis. Particle sizes and morphology are examined by TEM analysis. Precipitation reaction leads to the formation of an amorphous composition, which consists of dimer and trimer aluminum hydroxide species and WO₄^2? groups. Finely dispersed particles with dimensions of about 25 nm are formed. The precipitated composition is decomposed to amorphous Al₂(WO₄)₃ immediately after H₂O release. At 630 °C, amorphous Al₂(WO₄)₃ crystallizes in an orthorhombic modification of Al₂(WO₄)₃, the enthalpy of crystallization being 58 kJ/mol. The nanosized particles remain intact after the crystallization of amorphous Al₂(WO₄)₃. A significant particle growth take places when nanosized Al₂(WO₄)₃ is heated from 600 to 800 °C.     

Br-掺杂Bi2WO6的水热法合成及其可见光催化性能

以Bi（NO₃）₃·5H₂O和Na₂WO₄·2H₂O为主要原料,采用水热法合成了纯相Bi₂WO₆,并对其进行非金属离子Br^-掺杂改性。采用XRD、SEM、TEM、XPS、Raman、PL和DRS研究了Br^-掺杂对Bi₂WO₆的物相结构、形貌和可见光催化性能的影响。结果表明,Br^-掺杂可有效提高Bi₂WO₆的可见光催化性能,当掺杂量（物质的量百分数）为8%时,溴掺杂Bi₂WO₆的光催化性能最好,可见光照射40 min后,可降解96.73%的罗丹明-B,与未掺杂Bi₂WO₆相比,其降解率提高了36.32%。     

Br~-掺杂Bi_2WO_6的水热法合成及其可见光催化性能

以Bi(NO_3)_3·5H_2O和Na_2WO_4·2H_2O为主要原料,采用水热法合成了纯相Bi_2WO_6,并对其进行非金属离子Br-掺杂改性。采用XRD、SEM、TEM、XPS、Raman、PL和DRS研究了Br~-掺杂对Bi_2WO_6的物相结构、形貌和可见光催化性能的影响。结果表明,Br-掺杂可有效提高Bi_2WO_6的可见光催化性能,当掺杂量(物质的量百分数)为8%时,溴掺杂Bi_2WO_6的光催化性能最好,可见光照射40 min后,可降解96.73%的罗丹明-B,与未掺杂Bi_2WO_6相比,其降解率提高了36.32%。     

Synthesis,structural characterization and reactivity of manganese tungstate nanoparticles in the oxidative degradation of methylene blue

Nanoparticles of manganese tungstate (MnWO₄) were prepared via an impregnation method using Mn(NO₃)₂·4H₂O and WO₃ as a source of Mn and W, respectively. The morphology of the manganese tungstate nanoparticles was studied in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). MnWO₄ nanoparticles showed severe catalytic performances for the degradation of organic dye (methylene blue, MB) in the presence of tert-butyl hydrogen peroxide, TBHP, as the oxidant at room temperature in water.     

The gravimetric determination of tungsten in tungstate solutions

A comparison is made between gravimetric methods for the determination of tungsten from tungstate solutions Precipitation of Hg₂WO₄ with Hg₂(NO₃)₂ in ammoniacal medium is used as reference methodPrecipitation of WO₃ with acids, followed by digestion, gives no quantitative results, the best method, using HClO₄, still gives rise to a negative error larger than 1%A survey of the organic reagents is given, of these, tannin is unsatisfactory (1.2%) Better results are obtained using benzidine (0.86%), o-tolidine (0.78%), phenazone (0.77%) and rhodamine B (0.70%) Only cinchonine (0.09%) and β-naphthoquinoline (0.06%) are to be recommended for the quantitative determination of tungsten from tungstate solutions     

Effect of MWO<Subscript>4</Subscript> (M = Ca,Sr, Ba) dispersion on the interfacial processes in (+/−)WO<Subscript>3</Subscript>|MWO<Subscript>4</Subscript>|WO<Subscript>3</Subscript>(−/+) cells and transport properties of metacomposite phases

We compare data on the reciprocal electrosurface transfer (EST) of WO₃ and MWO₄ components through WO₃|MWO₄ eutectic heterointerfaces using MWO₄ (M = Ca, Sr, Ba) samples prepared by standard ceramic technology (CER) and nitrate-organic technology (N/O); these samples considerably differ in both the grain size of precursor powders and the grain size of sintered ceramics. When an electric field is applied, the interpenetration of WO₃ and MWO₄ components occurs though WO₃|MWO₄ (M = Ca, Sr, Ba) heterointerfaces. The general ⁽⁻⁾WO₃ ↔ MWO₄ ⁽⁺⁾ intermigration pattern in the cells is not influenced by tungstate preparation technology. However, interpenetration rates are far greater for MW₄^N/O. The transport properties of {MWO₄ · xWO₃} two-phase eutectic metacomposites manufactured by both technologies were studied. Tungstate and composite manufacturing technologies have no radical influence on the electric properties (overall and partial conductivity, transference numbers) of the samples, only changing conductivity versus concentration relationships. Our data well fit the model of formation of a nonautonomous electrolytic interphase.     

ESI-QIMS Investigation of Sr,Rb, and Crown Ether Mixture Solutions

The isotope distribution of Sr, alternatively ⁸⁷Sr/⁸⁶Sr ratio frequently reported in geologic investigations, is obtained by direct electrospray ionization of aqueous samples containing Sr(II), Rb(I) with added 18-crown-6 (18c6) [1,4,7,10,13,16-Hexaoxacyclooctadecane C₁₂H₂₄O₆ m/z 264.3]. At relatively high concentrations of Sr and Rb, we observed favorable formation of Sr²⁺(18c6)₂ and Rb⁺(18c6) rather than Sr²⁺(18c6) complexes. Significant Sr²⁺(18c6)₂ suppression observed in post column addition of samples into water solvent disappeared when formic acid was present in the carrier solvent. Electrospray ionization-quadrupole-ion trap mass spectrometry (ESI-QITMS) successfully obtained the expected isotope distribution of Sr showing no interference from Rb without chromatographic separation of ⁸⁷Sr and ⁸⁷Rb necessary in ICP-MS studies.     

High-pressure Raman study of Al2(WO4)3

A high-pressure Raman scattering study of the tungstate Al₂(WO₄)₃ is presented. This study showed the onset of two reversible phase transitions at 0.28±0.07 and 2.8±0.1 GPa. The pressure evolution of Raman bands provides strong evidences that both the transitions involve rotations/tilts of nearly rigid tungstate tetrahedra and that the structure of the stable phase in the 0.28-2.8 GPa range may be the same as the structure of the ambient pressure, low-temperature monoclinic (C_2h⁵) ferroelastic phase of Al₂(WO₄)₃.     

The fluorination of scheelite with ammonium bifluoride

The interaction of scheelite with ammonium bifluoride was studied. It was shown that sheelite reacts with NH₄HF₂ at room temperature, in contrast with tungstic oxide and other tungsten compounds. Two complexes are formed (NH₄)₃WO₃F₃ and the previously unknown (NH₄)₂WO₃F₂. The compounds obtained were fluorinated to (NH₄)₃WO₂F₅ (endothermic peaks at 170° and 90°C, respectively).Cubic monocrystals of (NH₄)₃WO₂F₅ were obtained. The cubic form is unstable and underwent a lattice transformation at room temperature to the more stable tetragonal form, which was transformed reversibly into the cubic form at 140°C. The thermal decomposition of (NH₄)₂WO₃F₂ was studied.

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Zusammenfassung Es wird die Wechselwirkung von Scheelit und Ammoniumhydrogenfluorid untersucht. Im Gegensatz zu Wolframoxid und anderen Wolframverbindungen geht Scheelit mit Ammoniumhydrogenfluorid bei Raumtemperatur eine chemische Reaktion ein, wobei zwei verschiedene Komplexe gebildet werden: (NH₄)WO₃F₃ und der bisher unbekannte Komplex (NH₄)₂WO₃F₂. Die erhaltenen Verbindungen werden zu (NH₄)₃WO₂F₅ fluoriert (endotherme Peaks bei 170° bzw. 90°C).Man erhält die kubischen Einkristalle (NH₄)₃WO₂F₅. Die unstabile kubische Form wandelte sich bei Raumtemperatur in die stabilere tetragonale Form um, die bei 140°C reversibel wieder in die kubische Form überführt werden kann.Es wird weiterhin die thermische Zersetzung von (NH₄)₂WO₃F₂. untersucht.

     

(NH4)6Nd(NO3)9, ein ammoniumreiches ternäres Lanthanidnitrat mit einsamen Nitrationen: (NH4)6[Nd(NO3)6](NO3)3

(NH₄)₆Nd(NO₃)₉, A Ternary Ammonium-Rich Lanthanide Nitrate with Lonesome Nitrate Ions: (NH₄)₆[Nd(NO₃)₆](NO₃)₃ . Single crystals of the ternary ammonium neodymium nitrate (NH₄)₆Nd(NO₃)₉ are obtained from a solution of Nd₂O₃ in a melt of NH₄NO₃. In the crystal structure (monoclinic, C 2/c, Z = 4, a = 1 775.1(4), b = 912.7(3), c = 2 072.3(5) pm; β = 125.56(1)°; R = 0.059, R_w = 0.036) the Nd³⁺ ion is surrounded by six bidentate nitrate ligands so that anionic units [Nd(NO₃)₆]^3? are formed. The units are isolated, but they are incorporated in layers parallel to (010). The structure is held together by a network of hydrogen bonds, built up by NH₄⁺ and NO₃^? ions lying between the layers. Due to the structure, the compound may be described as a double salt like (NH₄)₃[Nd(NO₃)₆] · 3 NH₄NO₃ or, better, as (NH₄)₆[Nd(NO₃)₆](NO₃)₃.     

Synthese,Struktur und Thermolyse der ternären Ammoniumnitrate (NH4)3[M2(NO3)(9] (M  La?Gd)

Synthesis, Structure, and Thermolysis of the (NH₄)₃[M₂(NO₃)₉] (M ? La? Gd) The ternary ammonium nitrates (NH₄)₃[M₂(NO₃)₉] (M ? La-Gd) are obtained as single crystals from a solution of the respective sesquioxides in a melt of NH₄NO₃ and sublimation of the excess NH₄NO₃. In the crystal structure of (NH₄)₃[Pr₂(NO₃)₉] (cubic, P4₃32, Z = 4, a = 1 377.0(1) pm, R = 0.038, R_w = 0.023) Pr³⁺ is surrounded by six bidentate nitrate ligands of which three are bridging to neighbouring Pr³⁺ ions. This results in a branched folded chain, held together by the NH₄⁺ ions which occupy cavities in the structure. (NH₄)₃[Pr₂(NO₃)₉] is the first intermediate product of the thermal decomposition of (NH₄)₂[Pr(NO₃)₅(H₂O)₂] · 2H₂O.     

The2 E↔4 A 2 transition in tetragonal Cr3+ complexes

The² E⁴ A ₂ absorption and emission spectra of [Cr(NH₃)₅(NO₃)](NO₃)₂, [Cr(NH₃)₅(NO₂)] ·(NO₃)₂, and [Cr(NH₃)₅(H₂O)](NO₃)₃ microcrystals have been recorded at 77°K. Tetragonal²E splittings are 209, 188 and 87 cm^–1, respectively. An analysis of the limited vibronic structure has been made and compared to the results for the parent octahedral complex, [Cr(NH₃)₆](NO₃)₃. Vibrations of approximately 270 and 700 cm^–1 are prominent.

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Zusammenfassung Die² E⁴ A ₂ Absorptions- und Emissionsspektren von [Cr(NH₃)₅(NO₃)](NO₃)₂-, [Cr(NH₃)₅ (NO₂)](NO₃)₂- und [Cr(NH₃)₅(H₂O)](NO₃)₃-Mikrokristallen werden für 77° angegeben. Die tetragonalen² E Aufspaltungen sind209, 188 bzw. 87 cm^–1. Eine Analyse der begrenzten vibronischen Struktur wurde vorgenommen und mit den Resultaten für den oktaedrischen Stammkomplex, [Cr(NH₃)₆](NO₃)₃ verglichen. Schwingungen von etwa 270 und 700 cm^–1 treten besonders hervor.

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Résumé Les spectres d'émission et d'absorption² E⁴ A ₂ de microcristaux de [Cr(NH₃)₅(NO₃)](NO₃)₂, [Cr(NH₃)₅(NO₂)](NO₃)₂ et [Cr(NH₃)₅(H₂O)](NO₃)₃ ont été enregistrés à 77° K. Les écartements tétragonaux² E sont respectivement 209, 188 et 87 cm^–1. Une analyse de la structure vibronique limitée a été effectuée et comparée aux résultats pour le complexe octaédral parent [Cr(NH₃)₆](NO₃)₃. Les vibrations au voisinage de 270 et 700 cm^–1 émergent.

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This contribution is dedicated to the memory of Prof. Hans-Ludwig Schläfer, a stimulating colleague and valued friend.     

WO_3对MnO_x-CeO_2/ZrO_2-TiO_2整体式催化剂NH_3选择性催化还原NO_x性能的影响

以ZrO2-TiO2为载体,MnOx-CeO2为活性组分,WO3为助剂制备了MnOx-CeO2/WO3/ZrO2-TiO2整体式催化剂,考察了添加不同质量分数的WO3对低温氨选择性催化还原(NH3-SCR)氮氧化物反应性能的影响.通过低温N2吸附-脱附,X射线衍射(XRD),X射线光电子能谱(XPS),NH3程序升温脱附(NH3-TPD)等手段对催化剂进行表征.实验结果表明,与未添加WO3的催化剂相比,含有10.0%(w)WO3的催化剂具有较好的织构性能,且具有较多的中强酸位,较好的氧化性能,表现出良好的NH3-SCR活性和较宽的活性温度窗口(空速为10000h-1时,在144-374℃之间,NOx转化率为90%以上),该催化剂在低温净化氮氧化物中具有潜在的应用前景.     

Preparation of ferric tungstate and its catalytic behavior toward methanol

Pure ferric tungstate, Fe₂(WO₄)₃, has been prepared and characterized for the first time. Ferric tungstate has a structure very similar to that of ferric molybdate with a unit cell volume about 1.5% larger. Decomposition to Fe₂WO₆ and WO₃ occurs at about 600°C. Ferric tungstate was tested as a catalyst for the selective oxidation of methanol and shown to have very different properties from ferric molybdate for this reaction. Whereas over the molybdate the predominant reaction is oxidation of methanol to formaldehyde, over the tungstate it is dehydration to dimethyl ether.     

Synthesis and Crystal Structure of Alkali Metal and Ammonium Nitratocuprates(II): M3[Cu(NO3)4](NO3) (M = K,NH4, Rb) and Cs2[Cu(NO3)4]

Blue crystals of metal nitratocuprates(II), M₃[Cu(NO₃)₄](NO₃) (M = K ( I ), NH₄ ( II ), Rb ( III )) and Cs₂[Cu(NO₃)₄] ( IV ) were synthesized from Cu(NO₃)₂ · 3 H₂O and MNO₃ by heating at 100–140 °C during 3–12 h. X-ray single crystal structures for isotypic I and II reveal the presence of the [Cu(NO₃)₄]^2– and NO₃^– anions and M⁺ cations. Structure IV contains [Cu(NO₃)₄]^2– and Cs⁺. In structures I , II , and IV , Cu atoms have a square-planar coordination [CuO₄] with short Cu–O distances of 1.92–2.00 Å, the oxygen atoms belonging to four different NO₃ groups. Each coordinated NO₃ group is a nonsymmetrical bidentate ligand with the second, longer Cu–O distance from 2.38 to 2.74 Å. Rubidium derivative III was shown to be isotypic to I on the basis of unit cell dimensions and symmetry. Eight-coordinate metal(II) environment in tetranitrates is compared for transition metals with different electronic configurations.     

A New Predictive Equation for the Surface Tensions of Aqueous Mixed Ionic Solutions Conforming to the Linear Isopiestic Relation

The linear isopiestic relation has been used, together with the fundamental Butler equations, to establish a new simple predictive equation for the surface tensions of the mixed ionic solutions. This newly proposed equation can provide the surface tensions of multicomponent solutions using only the data of the corresponding binary subsystems of equal water activity. No binary interaction parameters are required. The predictive capability of the equation has been tested by comparing with the experimental data of the surface tensions for the systems HCl–LiCl–H₂O, HCl–NaClO₄–H₂O, HCl–CaCl₂–H₂O, HCl–SrCl₂–H₂O, HCl–BaCl₂–H₂O, LiCl–NaCl–H₂O, LiCl–KCl–H₂O, NaCl–KCl–H₂O, KNO₃–NH₄NO₃–H₂O, and LiCl–NaCl–KCl–H₂O at 298.15 K; KNO₃–NH₄Cl–H₂O, KBr–Sr(NO₃)₂–H₂O, NaNO₃–Sr(NO₃)₂–H₂O, NaNO₃ –(NH₄)₂SO₄–H₂O, KNO₃–Sr(NO₃)₂– H₂O, NH₄Cl–Sr(NO₃)₂–H₂O, NH₄Cl– (NH₄)₂SO₄–H₂O, KBr–KCl–H₂O, KBr–KCl–NH₄Cl–H₂O, KBr–KNO₃– Sr(NO₃)₂–H₂O, KBr–NH₄Cl–Sr(NO₃)₂–H₂O, KNO₃–NH₄Cl–Sr(NO₃)₂–H₂O, and NH₄Cl–(NH₄)₂SO₄–NaNO₃–H₂O at 291.15 K; and KBr–NaBr–H₂O at temperatures from 283.15 to 308.15 K. The agreement is generally quite good.     

209Bi NQR study of bismuth(III) complexes

Potassium pentafluorobismuthate(III), nitrate-chloride Bi^III complexes MBiCl₃NO₃ (M=K, (NH₂)₂CNH₂), sulfate-chloride Bi^III complexes MBiCl₂SO₄ (M=K, Rb, NH₄, (NH₂(₂CNH₂), and Bi^III complexonates with the anions of ethylenediaminetetraacetic acid M[Bi(edta)]₂·nH₂O (M=Mg, Ca, Ni, Cd) and nitrilotriacetic acid Bi(nta)·2H₂O, and Bi(nta)·3thio·H₂O (thio is thiourea) were studied by²⁰⁹Bi NQR spectroscopy. A second-order phase transition was observed in K₂BiF₅ at 100 K. The compounds Bi(nta)·2H₂O, (NH₂)₂CNH₂BiCl₃NO₃, and MBiCl₂SO₄ (M=K, NH₄) are piezoelectrics. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2237–2240, November, 1998.