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951.
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.
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. 相似文献
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.
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.
, V2O5. , V2O5. . , , .
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. 相似文献
952.
J. Franz und B. Melichar 《Fresenius' Journal of Analytical Chemistry》1965,214(6):430-433
Zusammenfassung Die spektrophotometrische Bestimmung von p-Nitro-m-kresol bei 400 nm wurde zum Zweck eines frühzeitigen und empfindlichen Nachweises der Exposition, sowie zur Untersuchung des Metabolismus von Metation (Folithion, Sumithion) modifiziert. Nach der sauren Hydrolyse von Harn beseitigt man die Harnpigmente durch Oxydation mit H2O2 und durch Abtrennung von p-Nitro-m-kresolat durch Ausschütteln mit Acetonitril aus 5 n Natronlauge. Die Ausbeute der Rückgewinnung bei einer Konzentration von 0,5 ppm p-Nitro-m-kresol betrug 97,3±6,3%, bei 5 ppm 92,6±2,4%. Bei stark pigmentierten Harnen (insbesondere tierischer Herkunft) wird eine weitere Reinigung vorgenommen und zwar durch die Beseitigung der Abbauprodukte mit Oxalatpuffer aus Toluol. Die Ausbeute betrÄgt bei 0,5 ppm 86,5±5,1%, bei 5 ppm 85,2±3,1%. Die untere Bestimmungsgrenze liegt bei 1,5 g p-Nitro-m-kresol in 10 ml Harn (0,15 ppm).
Summary The early and sensitive detection of an exposure to Metation (Folithion, Sumithion) has been performed by a modified spectrophotometric determination of p-nitro-m-cresol in the urine at 400nm. After acid hydrolysis of the urine the pigments are removed by means of oxidation with H2O2 and separation of p-nitro-m-cresol by extraction from 5 N NaOH solution into acetonitrile. The recovery of p-nitro-m-cresol was 97.3±6.3% and 92.6±2.4% with concentrations of 0.5 ppm and 5 ppm, respectively. Further purification is required for highly pigmented urines (especially of animal origin), viz., the removal of decomposition products by extraction from toluene solution into oxalate buffer. 86.5±5.1% and 85.2±3.1% have been recovered with concentrations of 0.5 ppm and 5 ppm, respectively. The lower limit of determination is 1.5 g of p-nitro-m-cresol in 10 ml of urine (0.15 ppm).相似文献
953.
M. B. Bogacki M. Wiśniewski J. Szymanowski 《Journal of Radioanalytical and Nuclear Chemistry》1998,228(1-2):57-61
Extraction of arsenic(V) from sulfuric acid solutions with various extractants in multistage counter-current extraction-stripping systems was compared. The extraction ability of the extractants studied showed the following order: ENIM 100>TBP=CYANEX 923>2-methylhexanol. The extraction depends significantly on the number of extraction stages and the phase ratios in extraction. The effects of the number of stripping stages and the phase ratio in stripping are less important. 相似文献
954.
N. P. Elinov G. A. Vitovskaya E. P. Anan'eva Yu. B. Maryukhta 《Chemistry of Natural Compounds》1986,21(6):704-708
The structure of an extracellular mannan formed by the yeastBullera tsugae has been studied. It has been shown that the repeating unit of this polysaccharide contains -(13)- and -(14)-bound D-mannopyranose residues in equimolar ratio. A comparison has been made of the polymer under investigation with the extracellular mannan from a yeast of the genusRhodotorula.
Leningrad Institute of Pharmaceutical Chemistry. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 746–750, November–December, 1985. 相似文献
955.
Use of a novel coupling reagent, N,N-bis[2-oxo-3-oxazolidinyl]phosphorodiamidic chloride (BOPDC) in the synthesis of oligodeoxyribonucleotides is described. This reagent allows the synthesis of phosphotriesters in high yields (70–80%) without detectable side reactions. Synthesis of a hexanucleotide, d(A-A-C-C-C-G) is presented as an example. 相似文献
956.
The propagation rate of polystyryl-barium was studied in THF at 20°, in the presence of small amounts of lithium chloride. These kinetic results furnish a new method for the determination of triple ion formation in both mono- and α,ω-dicarbanionic polystyryl-barium. The constant of triple ion association of monocarbanionic (PS?)2Ba, KT, was found to be 3.7 × 105 l M?1, close to the value calculated from published data. The triple ion association constant of α,ω-dicarbanionic PS2?Ba2+, KDT, is about 1.2 × 106 l M?1. Taking into account the cyclic structure of α,ω-dicarbanionic PS2?Ba2+ and a statistical factor 3 between KT and KDT, it is concluded that mono- and dicarbanionic polystyryl-barium have similar abilities for triple ion formation. Nevertheless, stronger associations are observed for dicarbanionic oligomers with a degree of polymerization lower than 5–7. 相似文献
957.
A. A. Nishanov B. Tashkhodzhaev I. M. Usupova M. N. Sultankhodzhaev 《Chemistry of Natural Compounds》1992,28(5):466-469
The known alkaloid lepenine and the new diterpene alkaloid akirine have been isolated from the epigeal part ofAconitum kirinense Nakai. To establish the structure of akirine, its spectral characteristics have been studied and an x-ray structural analysis has been made. It is 1α,8β-dihydroxy-16β-methoxy-9β,14β-methylenedioxy-3β,4β-epoxy-N-ethylaconitane — the first diterpene alkaloid with a lycoctonine skeleton containing a 9,14-methylenedioxy group and a β-oriented substituent at C14. 相似文献
958.
O. Yu. Rekhlova B. Tashkhodzhaev V. I. Andrianov A. I. Saidkhodzhaev G. V. Sagitdinova N. G. Furmanova 《Chemistry of Natural Compounds》1991,26(6):643-647
The spatial structure of the sesquiterpene humulane alcohol juniferol, which is represented in the crystal by two conformers, IA and IB, differing by the conformation of the C2...C9 section, has been established by the x-ray structural method. The strain energies of the conformers have been calculated by the method of molecular mechanics. The barrier to the interconversion of the conformers by rotation of the C2...C9 section has been calculated; it amounts to 7–8 kcal/mole. This value of the transformation barrier permits the assumption that the two conformers also exist in solution, their interconversion being hindered.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Crystallography, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 757–762, November–December, 1990. 相似文献
959.
B. G. Kovalev K. Loftstedt S. F. Nedopekina A. M. Sorochinskaya K. S. Artokhin E. A. Nesterov É. Viik 《Chemistry of Natural Compounds》1991,27(4):503-506
Four components have been isolated from an extract of the sex pheromone of the mothHeliothis maritima and have been identified: hexadecanal, hexadec-cis-11-enal, hexadec-cis-9-enal, and hexadec-cis-11-en-1-ol.
All-Union Scientific-Research Institute for Biological Methods of Plant Protection, Kishinev. Don Zonal Scientific-Research
Institute of Agriculture. Don Scientific-Production Combine. Ecology Division of Lund University, Lund, Sweden. Translated
from Khimiya Priorodnykh Soedinenii, No. 4, pp. 574–577, July–August, 1991. 相似文献
960.
B. S. Shasha D. Trimnell F. H. Otey 《Journal of polymer science. Part A, Polymer chemistry》1981,19(8):1891-1899
A simple method of encapsulating water-insoluble pesticides in a starch matrix is described. The method consists of mixing the pesticide with alkali starch followed by precipitation with a calcium chloride solution. A starch–calcium adduct that entraps the pesticide in small cells within granular particles is formed. Liquid and solid pesticides were successfully encapsulated by the new method. By use of the herbicide trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl) benzenamine] as core material more than 90% recovery and encapsulation was achieved. Use of acid-modified starches and flours resulted in a lower percentage of encapsulation. Effective encapsulation was also achieved by replacing calcium chloride with strontium chloride or barium chloride. 相似文献