Interaction of nickel hydroxocarbonate,ammonium paramolybdate,and ammonium metatungstate under mechanical activation

The interaction of nickel hydroxocarbonate, ammonium paramolybdate, and ammonium metatungstate (Ni: Mo: W = 3: 1: 1) is reported. Under mechanical activation conditions, nickel hydroxocarbonate particles undergo comminution and ammonium paramolybdate and ammonium metatungstate particles soften and aggregate. It is demonstrated by DTA, X-ray diffraction, and IR spectroscopy that heat treatment of the mechanically activated mixture at 400–450°C yields the salts NiMoO₄ and NiWO₄.     

Phase state and physicochemical properties of systems containing ammonium tungstate or ammonium vanadate, polyvinylpyrrolidone, and water

Isothermal sections of ammonium dodecatungstate-polyvinylpyrrolidone-water and ammonium vanadate-polyvinylpyrrolidone-water phase diagrams have been designed. The combination of visual or microscopic examination and refractive index and density measurements was employed in analysis. The fields of homogeneous polymer-salt solutions and a two-phase field in which a salt phase exists were found in the systems have been found in the systems. Exposure of the vanadate system to light increases the solubility of the salt. In the heterogeneous field of this system, colored precipitates appear because of the solvolysis of ammonium vanadate in combination with the photochemical reduction of the products     

The thermal decomposition of ammonium metavanadate,I

The stoichiometry of the various stages involved in the thermal decomposition of ammonium metavanadate has been shown to correspond to a stepwise decrease in the ratio of ammonia and water to V₂O₅, with V₂O₅ being the final product in vacuum, in air and in argon. In ammonia, VO₂ is formed. The actual stages and intermediates are dependent upon the prevailing atmosphere. Chemical analyses, together with infrared absorption spectra and X-ray powder data, have enabled the intermediates and products to be characterized and the structural changes involved in the decomposition to be discussed.

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Zusammenfassung Es wurde gezeigt, daß die verschiedenen Stufen in der thermischen Zersetzung von Ammoniummetavanadat dem stufenweisen stöchiometrischen Verlust von Ammonia und Wasser entsprechen. In Vakuum, Sauerstoff und Argon ist V₂O₅, in Ammoniak VO₂ das Endprodukt. Die Zwischenprodukte der einzelnen Stufen sind von der umgebenden Gasatmosphäre abhängig. Durch chemische, infrarot- und röntgenspektroskopische Analyse gelang es, diese zu charakterisieren und so die durch die Zersetzung hervorgerufenen strukturellen Umlagerungen zu deuten.

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Résumé On montre que les différentes étapes de la décomposition thermique du métavanadate d'ammonium correspondent à la diminution progressive de l'eau et de l'ammoniac par rapport à V₂O₅; cet oxyde constitue le produit final dans le vide, dans l'air et dans l'argon. Dans l'ammoniac, c'est VO₂ qui se forme. Les étapes respectives et les intermédiaires dépendent de l'atmosphère qui prévaut. A l'aide de l'analyse chimique, des spectres d'absorption infrarouge et des données de rayons X sur poudre, on a pu caractériser les intermédiaires et les produits formés, ainsi que les changements structuraux provoqués par la décomposition.

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, V₂O₅. , V₂O₅. . , , .

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We wish to acknowledge helpful comments from Prof. L. Glasser and Dr. N. H. Agnew and financial support from the National Institute for Metallurgy, Johannesburg, South Africa.     

Thermal depolarization in ammonium chloride crystals,I

The thermal depolarization of crystals of NH₄Cl polarized above the phase transition temperature (242.5K) by an applied electric field was studied in 13 crystals prepared under a variety of conditions in order to examine the effects of doping with divalent anions or cations and of acid or alkaline conditions during crystal growth. All the features found in crystals grown from solution also occur in a crystal grown from the vapor. We may conclude, therefore, that the depolarization effects observed are properties of crystalline NH₄Cl and are not due to water or urea occluded during crystal growth. Four main depolarizations were observed: one of these is ascribed to space charge and the other three are attributed to dipole relaxation processes. The activation energies for these are 0.58, 0.73, and 0.85 eV, respectively. The various doping experiments lead to the conclusion that one of these is favored by acid conditions and the presence of cation vacancies and the other two by alkaline conditions and the presence of anion vacancies. Specific models for the dipolar defects are formulated and discussed.     

The thermal decomposition of ammonium metavanadate,III

The kinetics and thermodynamics of the thermal decomposition of ammonium metavanadate (AMV) are combined with the structural information available for AMV, for the important decomposition intermediate, ammonium hexavanadate (AHV), and for vanadium pentoxide, the product of the decomposition in non-reducing atmospheres, to enable the atomic movements involved in the course of decomposition to be discussed in detail.The decomposition of AMV involves scission of the V-G chains in the AMV structure (accompanied by simultaneous evolution of gaseous ammonia and water) with subsequent rearrangement and cross-linking of discrete units, based on V₃O ₈ ^– , to form AHV. Further decomposition to V₂O₅ is a similar but less ordered process.

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Zusammenfassung Die Kinetik und thermische Zersetzung von Ammoniummetavanadat (AMV) wurden mit der zu erhaltenden Information über die Strukturen des AMV, des wichtigen Zwischenproduktes der Zersetzung, des Ammoniumhexavanadats (AHV) sowie des Vanadiumpentoxids verbunden. Das in nichtreduzierenden Atmosphären erhaltene Zersetzungsprodukt wurde eingehend erörtert um die in der Zersetzung mit inbegriffenen Atombewegungen zu studieren.Bei der Zersetzung von AMV spielt eine Spaltung der V- O-Ketten in der Struktur des AMV mit (welche durch eine gleichzeitige Entwicklung von gasförmigen Ammoniak und Wasser begleitet wird), dieser folgt eine Neuordnung und Raumvernetzung diskreter Einheiten auf V₃O ₈ ^– -Basis um zur Bildung von AHV zu führen. Die weitere Zersetzung zu V₂O₆ ist ein ähnlicher, obwohl weniger geordneter Vorgang.

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Résumé On a rapproché les données structurales du métavanadate d'ammonium (MVA) avec celles relatives à la cinétique et à la thermodynamique de la décomposition thermique du MVA, pour étudier le produit intermédiaire important de la décomposition, l'hexavanadate d'ammonium (HVA) et le pentoxyde de vanadium. On discute en détail le produit de la décomposition obtenu en atmosphère non réductrice afin d'obtenir des données sur les mouvements atomiques mis en jeu pendant la décomposition.La décomposition du MVA s'effectue avec scission des chaines V—O dans la structure du MVA, accompagnée d'un dégagement de gaz ammoniac et d'eau et suivie d'un réarrangement et d'une réticulation d'unités discrètes V₃O ₈ ^– , pour former HVA. La décomposition ultérieure en V₂O₅ suit un processus similaire mais moins bien ordonné.

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() , , ( ) . , . - ( ) , V₃O ₈ ^– . V₂O₅ , .

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Financial support from the National Institute for Metallurgy, Johannesburg, and the South African Council for Scientific and Industrial Research is gratefully acknowledged.     

Thermal analysis of ammonium,mono-, di- and triethanolammonium alginates

Thermal behaviour of ammonium (NH₄alg), mono- (MEAalg), di- (DEAalg) and triethanolammonium (TEAalg) salts of alginic acid (Halg) was investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). Salts were prepared by the direct reaction of alginic acid with the ammonium hydroxide and with the respective ethanolamines. After preparation the compounds were lyophilized during 24 h and characterized by FTIR spectroscopy and elemental analysis (C, H and N). Under air the compounds exhibited three successive thermal decomposition steps: dehydration, decomposition of the polymeric matrix and finally, burning of carbonaceous residue. Under nitrogen two steps (dehydration and decomposition) were observed. The stability order of this series of compounds was: TEAalg this series of compounds was: TEAalg<DEAalg<NH₄alg<Halg≈MEAalg. DSC curves between –50 and 150°C did not show any thermal events suggesting that after lyophilization probably non-freezing type water is present in the system.     

Thermal decomposition of ammonium monochloroacetate and ammonium monochloroacetate silicomolybdate

Journal of Thermal Analysis and Calorimetry - Les anomalies que nous avons observées, dans le cas de l'oxydation de fils de nickel, peuvent s'interpréter en faisant appel à...     

Volumetric properties of ammonium nitrate in N,N-dimethylformamide

The densities of the ammonium nitrate in N,N-dimethylformamide (DMF) mixtures were measured at T = (308.15 to 348.15) K for different ammonium nitrate molalities in the range from (0 to 6.8404) mol·kg⁻¹. From the obtained density data, volumetric properties (apparent molar volumes and partial molar volumes) have been evaluated and discussed in the term of respective ionic and dipole interactions. From the apparent molar volume, determined at various temperatures, the apparent molar expansibility and the coefficients of thermal expansion were also calculated.     

Indirect complexometric titration of potassium,rubidium, cesium,thallium and ammonium

A titrimetric method using EDTA for the determination of potassium, rubidium, cesium, thallium and ammonium has been developed. These cations are precipitated as M₂Ag[Co(NO₂)₆] and the blue cobalt thiocyanate complex in acetone-water mixed system is titrated with EDTA. Milligram quantities have been determined in the present work     

Small angle neutron scattering studies on micellar systems part 1. Ammonium octanoate,ammonium decanoate and ammonium perfluoroocatanoate

Small angle neutron scattering has been used to examine the size and shape of micelles of ammonium octanoate, ammonium decanoate and ammonium perfluoro-octanoate. Ammonium octanoate was found to form micelles with a micellar weight of 1640 and ammonium decanoate with a micellar weight of 12,576; both materials appeared to form spherical micelles. Ammonium perfluoro-octanoate formed micelles with a micellar weight of 17,610. Evidence from the scattering experiments suggested that the micelles were cylindrical and a model for the micelle is proposed.     

Comparative DFT study of crystalline ammonium perchlorate and ammonium dinitramide

The electronic structure, vibrational properties, absorption spectra, and thermodynamic properties of crystalline ammonium perchlorate (AP) and ammonium dinitramide (ADN) have been comparatively studied using density functional theory in the local density approximation. The results shows that the p states for the two solids play a very important role in their chemical reaction. From the low frequency to high frequency region, ADN has more motion modes for the vibrational frequencies than AP. The absorption spectra of AP and ADN display a few, strong bands in the fundamental absorption region. The thermodynamic properties show that ADN is easier to decompose than AP as the temperature increases.     

Reactions of bismuth iodide with ammonium,phosphonium, and bismuthonium salts

The reactions of ammonium, phosphonium, and bismuthonium salts with bismuth iodide were used to synthesize a series of complex compounds with bismuth-containing anions: [(HOC₂H₄)₃NH]⁺ ₄[Bi₄I₁₆]^4?, [Ph₃EtP] ₃ ⁺ [Bi₂I₉]^3?, and [Ph₄Bi] ₃ ⁺ [Bi₅I₁₈]^3?. X-ray diffraction data show that the nitrogen atoms in the two types of crystallographically independent cations of the nitrogen-containing complex possess a distorted tetrahedral coordination [the CNC angles are 110.3(9)°–113.2(9)°]. In the tetranuclear centrosymmetric [Bi₄I₁₆]^4? anion, the bismuth atoms have an octahedral coordination: Two types of groups, BiI₂ and BiI₃, are bound with one another by four μ₂-and two μ₃-iodine bridges (the Bi-I-μ₂, Bi-I-μ₃, and Bi-I-μ₁ distances are 3.1296(10), 3.2808(8); 3.3210(8) and 2.8670(8)–2.9108(9) Å, respectively). The coordination of the phosphorus atom in the [Ph₃EtP]⁺ cations of the phosphorus-containing complex is close to tetrahedral (the CPC angles are 107.5°–114.1°). In the binuclear [Bi₂I₉]^3? anions, the bismuth atoms have an octahedral coordination. The axial I-Bi-I angles are 167.52(2)°, 169.84(2)°, and 174.97(2)°. The terminal BiI₃ fragments [Bi²-I^7,8,9 2.9238(7), 2.9236(7), and 2.9522(7) Å] are in the eclipsed conformation.     

Thermal studies on lithium,sodium, potassium and ammonium monomethyl violurates

A study of the ammonium and some alkaline salts of monomethyl violuric acid by TG and DSC is described. These salts form hydrates in all cases and are, with some exceptions, very soluble in water.     

Comparison of the ammonium oxalate extraction of fertilizer for K2O, method 983.02, with the ammonium citrate/EDTA extraction, method 993.31

The direct available method for phosphorus in fertilizers, Method 960.03, is an Official Method for extraction of both P2O5 and K2O. Because K2O is much more soluble and easier to extract than P2O5, the conditions of the extraction procedure are set for efficient extraction of P2O5, and the extraction of K2O is, in effect, a bonus. In 1993, a modified extraction procedure, using an extractant of ammonium citrate/ethylenediaminetetraacetic acid (EDTA) solution, was evaluated for P2O5 and then collaboratively studied. This now-modified extraction procedure for phosphorus is Official Method 993.31, which is used extensively as an alternative to Method 960.03 for phosphorus because it is less labor-intensive. Method 993.31 was also evaluated in our laboratory for K2O extraction, but it was never formally collaboratively studied for K2O. To demonstrate the suitability of Method 993.31 as an extraction procedure for K2O, as well as P2O5 in fertilizers, Method 993.31 extraction for K2O was compared with Method 983.02, the traditional ammonium oxalate extraction procedure for K2O. A wide range of fertilizer samples was extracted by using both procedures. The t-test for samples containing < 30% K2O had a t-value of 1.23 and a probability of 0.22, which indicates there was no significant difference in the results obtained by the 2 extraction methods. The t-test for samples containing > 30% K2O had a t-value of 0.30 and a probability of 0.77, also indicating no significant difference. It is recommended that Method 983.02 be modified to include the ammonium citrate/EDTA extraction procedure as an additional option for extraction of K2O from commercial fertilizers.     

Thermoanalytical studies of natural potassium, sodium and ammonium alunites

Dynamic and controlled rate thermal analysis (CRTA) has been used to characterise alunites of formula [M(Al)₃(SO₄)₂(OH)₆] where M⁺ is the cations K⁺, Na⁺ or NH₄ ⁺. Thermal decomposition occurs in a series of steps: (a) dehydration, (b) well-defined dehydroxylation and (c) desulphation. CRTA offers a better resolution and a more detailed interpretation of water formation processes via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. Constant-rate decomposition processes of water formation reveal the subtle nature of dehydration and dehydroxylation.