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941.
Summary Three polarographic micro-methods are described for the determination of sulphur in organic compounds after oxygen-flask combustion. The products are converted into sulphuric acid by oxidation with hydrogen peroxide, the excess of which is expelled through boiling. The methods are based upon allowing the sulphuric acid to react with an excess of barium iodate or bromate, then recording polarographically the cathodic reduction wave of the iodate or bromate ion. The bromate methods are superior to the iodate method being simpler and more rapid, and the results are correct to within ca. ±0.5%.
Zusammenfassung Drei polarographische Mikromethoden zur Bestimmung von Schwefel in organischen Verbindungen nach deren Verbrennung im Sauerstoffkolben wurden beschrieben. Die Verbrennungsprodukte werden durch Oxydation mit Wasserstoffperoxid in Schwefelsäure umgesetzt. Der Überschuß des Oxydationsmittels wird durch Kochen zerstört. Die Schwefelsäure läßt man mit überschüssigem Bariumjodat oder -bromat reagieren und mißt dann polarographisch die kathodische Reduktionswelle des Jodats oder Bromats. Die Bromatmethode ist der Jodatmethode überlegen, da sie einfacher und rascher zu Resultaten führt, die innerhalb ±0,5% korrekt sind.相似文献
942.
N. S. Vul'fson V. A. Puchkov Yu. V. Denisov B. V. Rozynov V. N. Bochkarev M. M. Shemyakin Yu. A. Ovchinnikov V. K. Antonov 《Chemistry of Heterocyclic Compounds》1967,2(4):468-474
Analysis of mass-spectra of various 2, 5-diketopiperazines gives the basic fragmentation rules for their molecular ions, and the effects of nature and positions of substituents on the process.Mass-spectrometry Laboratory of the Institute of the Chemistry of Natural Compounds.Antibiotics Chemistry Laboratory of the Institute of the Chemistry of Natural Compounds. 相似文献
943.
N. Thornton Lipscomb Edwin C. Weber 《Journal of polymer science. Part A, Polymer chemistry》1967,5(4):779-784
Studies have been made of the γ-radiation-induced polymerization of methyl methacrylate in bulk, in the solid state at a temperature of ?65°C. and a radiation intensity of 346,000 rad/hr. The reaction was found to have an extremely long induction period (~50 hr.) when pure monomer was used, and to be first-order with respect to polymer concentration. This first-order dependency was confirmed by a series of irradiations in which 0.6% poly(methyl methacrylate) was dissolved in the monomer before irradiation. These irradiations showed no induction period. Nuclear magnetic resonance spectroscopy indicated a much more heterotactic polymer than that obtained in the liquid state at ?49°C. 相似文献
944.
8-Methylquinoline-5-carboxylic acid was obtained by the Skraup reaction from 3-amino-p-toluic acid or by hydrolysis of 5-cyano-8-methylquinoline.
The latter was synthesized by the Rosenmund-von Braun reaction from 5-bromo-8-methylquinoline, which was obtained by bromination
of 8-methylquinoline in the presence of silver sulfate. Bromination in the side chain of 8-methylquinoline-5-carboxylic acid
and its nitrile was studied.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 366–368, March, 1980. 相似文献
945.
Sharutin V. V. Egorova I. V. Sharutina O. K. Ivanenko T. K. Gatilov Yu. V. Adonin N. A. Starichenko V. F. 《Russian Journal of Coordination Chemistry》2003,29(7):462-467
The reaction between triphenylbismuth, hydrogen peroxide, and 3,4,5-trifluorobenzoic or pentafluorobenzoic acid (molar ratio 1 : 1 : 2, respectively) in ether gave triphenylbismuth bis(3,4,5-trifluorobenzoate) (I) and triphenylbismuth bis(pentafluorobenzoate) (II) in 74 and 89% yields, respectively. The structures of compounds I and II were established by X-ray diffraction. The Bi atoms have a distorted trigonal-bipyramidal coordination with acylate groups in the axial positions. The OBiO angles are 170.2(2)° and 171.5(2)° in I and II, respectively. The Bi–C(Ph)eq bond lengths vary in the range of 2.187(6)–2.204(5) Å, the Bi–O(acyl) lengths are 2.256(5) Å in I, and 2.281(5) and 2.318(5) Å in II. In the crystals I and II, the Bi and carbonyl O atoms are involved in intramolecular interactions (Bi···O(=C) 2.926(5)–3.176(5) Å), which increase the equatorial CBiC angles on the side of these contacts to 136.2(3)° and 138.6(2)° in I and II, respectively. 相似文献
946.
A. L. Podkorytov S. R. Kudakaeva E. V. Sokolova S. A. Shtin D. N. Ashikhmin 《Russian Journal of Inorganic Chemistry》2006,51(1):46-50
The main features of the synthesis of (Pb1-x
Srx)2Nb2O7 and (Pb1-x
Bax)2Nb2O7 pyrochlore solid solutions were determined using isothermal thermogravimetry in tandem with formal-kinetic analysis. The
stability and electron-transport properties of the triple niobates were studied, which allowed us to test them as electrode-active
materials for membranes in ion-selective electrodes (ISEs). 相似文献
947.
Yu. I. Dikanskii O. A. Nechaeva A. R. Zakinyan N. Yu. Konstantinova 《Colloid Journal》2007,69(6):691-694
Structural transformations and relevant changes in the magnetic and optical properties of magnetosensitive emulsions based on magnetic fluids are experimentally studied. Peculiarities of the changes in the magnetic susceptibility of emulsions associated with the deformation of their microdroplets and the effect of phase inversion (the transformation of dispersions of magnetic droplets in nonmagnetic media into dispersions of nonmagnetic droplets in magnetic fluids) are established. Optical effects occurring in magnetic emulsions under the combined action of a shear flow and a magnetic field are studied. It is concluded that optically active composition media may be developed on the basis of magnetic fluids. 相似文献
948.
Megalios EG Kapsalis N Paschalidis J Papathanasiou AG Boudouvis AG 《Journal of colloid and interface science》2005,288(2):508-512
In this paper, a novel optical device for measuring the deformation of liquid free surfaces is presented. The device employs a laser beam, which can be focused on any chosen location on the free surface. The key measurement is of the intensity of the beam reflected from a location on the free surface where the deformation exhibits a local extremum. The optics of the device is so designed as to measure a maximum intensity when the distance between the focusing lens and the selected point on the free surface is equal to the focal length, thus enabling a height measurement. The device is tested in ferrofluid pools where the height of the spikes of the normal field instability is measured. The simplicity of the suggested technique enables the fabrication of a quite cheap device for measuring surface deformation of nontransparent liquids, which provides good accuracy and reproducibility. 相似文献
949.
The reactions of iodine monochloride and iodine monobromide with a tetraalkyltin (butyl) and a tetraaryltin (phenyl) have been studied with a view to establishing their utility as routes to organotin chlorides and bromides respectively. Rapid high yield syntheses of the triorganotin bromides, diorganotin dichlorides and trialkyltin chloride were achieved. Some further suggestions are made on the mechanism of interhalogen fission of tincarbon bonds. 相似文献
950.
Extraction and subsequent recovery, in four separate fractions, of naphthenic acids, alkylphenols, pyrrollic compounds and nitrogen bases can be made from petroleum products using macroporous ion-exchange resins. Distinctive features of the technique are the use of dissolved gases in polar solvents as eluants and the application of the carbonate form of anion-exchange resins. The transition metal form of a macroreticular cation exchanger is shown to extract ligands from non-aqueous systems and a specific application to petroleum analysis is given. 相似文献