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91.
Horst Pietzner und Hans Werner 《Fresenius' Journal of Analytical Chemistry》1966,221(1):186-194
Zusammenfassung Es wird eine Goldbestimmung an sulfidischen Erzen für den Bereich von 0,05–5 ppm bei 20 g Einwaage beschrieben. Das Gold wird durch Salpetersäurebehandlung von den übrigen Metallen getrennt, mit Salzsäure/ Salpetersäure gelöst und mit Selen als innerem Standard und Tellur als Spurenfänger mittels Zinn(II)-chlorid gefällt. Der Niederschlag wird auf ein Membranfilter aufgezogen. Die Goldbestimmung erfolgt über den Impulsratenquotienten der Gold L- und Selen K-Linien. Die störende Molybdän K-Strahlung und die Comptonstreuung werden durch ein Zirkoniumblech auf dem Röhrenfenster unterdrückt. Der Variationskoeffizient beträgt 20% für 0,2–5 ppm und 53,6% für 0,05 ppm.
Herrn Prof. Dr.-Ing. habil. J. Hesemann zum 65. Geburtstag gewidmet. 相似文献
Summary A method is described for the determination of gold in sulphide ores within the concentration range of 0.05–5 ppm with sample weights of 20 g. Gold is separated from the other metals by treatment with nitric acid, dissolved by hydrochloric acid, containing some nitric acid, and is finally precipitated by stannous chloride applying selenium as internal standard and tellurium as collecting agent. The precipitate is mounted on a diaphragm filter and the determination of gold is carried out by X-ray analysis suppressing the disturbing Mo K radiation and compton scattering by a zirconium sheet-metal on the X-ray tube. The pulse rate quotient of the lines Au L /Se K is a function of the concentration of gold. The variation coefficient is 20% for 0.2–5 ppm and 53.6% for 0.05 ppm.
Herrn Prof. Dr.-Ing. habil. J. Hesemann zum 65. Geburtstag gewidmet. 相似文献
92.
Horst J. Klepp 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1980,31(5):657-662
Zusammenfassung Ein autonomer und konservativer Verband mit einem Freiheitsgrad wird betrachtet. Die potentielle Energie des Verbandes wird mit Hilfe der Heaviside Funktion ausgedrückt und ihre Ableitungen besitzen Unstetigkeitsstellen. Mit der potentiellen EnergieU wird eine DistributionU gebildet und die ersten zwei Ableitungen dieser Distribution bestimmt. In den DistributionenU undU erscheinen Funktionen und Werte welche mitV, K undR bezeichnet werden und welche es erlauben die Natur der Unstetigkeitsstellen zu bestimmen. In einer Ebene mit den Achsen OV und OR werden die Bereiche der stabilen und instabilen Gleichgewichtslagen dargestellt. Dir kritischen Fälle an den Grenzen der Bereiche werden mit Hilfe vonK untersucht. Abschließend wird ein Beispiel gebracht.
Summary An undamped autonomous system with one degree of freedom is considered. The potential energy of the system is expressed with the help of the Heaviside function and its derivatives possess points of discontinuity. With the potential energyU a distributionU is determined and the first and second differentiation of the distributionU are calculated. In the distributionsU andU appear functions and values denoted byV, K, R which permit to establish the nature of the points of discontinuity. In a plane with the axes OV and OR the regions of stable and instable equilibrium positions are represented. Critical cases on the boundaries between the different regions are analysed with the help ofK. An example is also considered.相似文献
93.
FTIR-spectroscopic investigations of catalytic reactions yield detailed information about the interaction of adsorbed molecules with the catalyst and kinetic data of the surface reaction, if the participating molecules show vibrations whose position and intensity in the IR-spectrum depend on the sorption state and the quantity adsorbed. In this paper, the possibilities and limitations of the method are represented by two examples. 相似文献
94.
The alkyl (aryl)-bishydroxymethylphosphines react with primary amines to give the title compounds. With optically active amines optically active phosphines are formed. 相似文献
95.
Woods M Zhang S Ebron VH Sherry AD 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(19):4634-4640
The lanthanide(III) complexes of three tetraamide DOTA bearing pyridyl, phenolic and hydroxypyridyl substituents have been studied by NMR, luminescence and cyclic voltammetry. The relaxivity profiles of the gadolinium complexes of the pyridyl and phenolic ligands were flat and essentially the same between pH 2 and 8. The hydroxypyridyl ligand, however, exhibited two regions of enhanced relaxivity. The small relaxivity enhancement (25 %) at lower pH (pH 2-4) has been attributed to an increase in the prototropic exchange of the coordinated water molecule while the slightly larger enhancement (84 %) at higher pH (pH 6-9) reflects deprotonation of the ligand amide protons. Deprotonation of the amides results in the formation of an intramolecular acid-base pair interaction with the phenolic protons and this, in turn, causes a highly organized second hydration sphere to come into effect, thereby increasing the relaxivity. The water relaxivity of the Gd(3+)-hydroxypyridyl complex is further enhanced upon binding to serum albumin. 相似文献
96.
(C2H10N2)[BPO4F2] — Strukturbeziehungen zwischen [BPO4F2]2— und [Si2O6]4— Colourless crystals of (C2H10N2)[BPO4F2] were prepared from mixture of ethylendiamine, H3BO3, BF3 · C2H5NH2, H3PO4 and HCl under mild hydrothermal conditions (220 °C). The crystal structure was determined by single crystal methods (triclinic, P1¯ (no. 2), a = 451.85(5) pm, b = 710.20(8) pm, c = 1210.2(2) pm, α = 86.08(1)°, β = 88.52(2)°, γ = 71.74(1)°, Z = 2) and contains infinite tetrahedral zweier‐single‐chains {[BPO4F2]2—} which are isoelectronic (48e—) with the polyanions {[Si2O6]4—} of the pyroxene family. 相似文献
97.
Gerhard Buchbauer Angela Fischlmayr Ernst Haslinger Wolfgang Robien Horst Völlenkle Carla Wassmann 《Monatshefte für Chemie / Chemical Monthly》1984,115(6-7):739-748
2-Hydroxy-13-oxo-tricyclo[7.3.1.02,7]tridecane derivatives can be obtained by reaction of cyclohexanone with alcohols under alkaline conditions. The unambiguous assignment of all signals of the1H-NMR- and13C-NMR-spectrum is possible by 2D-1H-13C-shift correlation and 2D-INADEQUATE. Compound1 crystallizes in space group P21/n witha=8.518 (1),b=14.789 (2),c=19.321 (2) Å, =94.91 (1)°,Z=8,D
c
=1.22 Mg cm–3. The structure refined toR=0.100 andR
w
=0.097 for 1719 observed reflections. Two independent molecules form centrosymmetric hydrogen-bonded dimers.Part V:Haslinger E.,Kalchhau-ser H.,Robien W.,Steindl H., Monatsh. Chem.115, 597 (1984). 相似文献
98.
Paul Von Ragu Schleyer Andrzej Sawaryn Alan E. Reed Pavel Hobza 《Journal of computational chemistry》1986,7(5):666-672
Electron correlation corrections have a considerable influence on the relative stabilities of lithium isocyanide ( 1 ), lithium cyanide ( 2 ), and the bridged form, 3 . While Hartree-Fock theory finds 1 to be most stable and 3 not to be a minimum, MP2/6-31G* optimization indicates 3 to be the global minimum. At higher levels employing full fourth-order Møller-Plesset theory and a quadruply split valence and polarized basis set (MP4STDQ/6-311+G*), 2 is only about 2 kcal/mol less stable than 1 and 3 , which are indicated to have nearly the same energy. LiNC thus is similar to C(Na)N and C(K)N, both of which are known to prefer T-shaped (bridged) structures in the gas phase. However, to an even greater extent than formerly realized, rotation of the lithium cation around the cyanide anion nucleus should be practically free. ΔH (LiCN) = 32.8 kcal/mol is estimated from the calculated lithium cation affinity of 151.2 kcal/mol. In addition, we find at the MP4SDTQ/6-31+G*//MP2/6-31G* level that the bridged form of NaCN is favored by 2–3 kcal/mol over the corresponding linear forms, which have nearly the same energy. 相似文献
99.
Johann-Peter Melder Klaus Weber Andreas Weiler Emmerich Sackers Hans Fritz Dieter Hunkler Horst Prinzbach 《Research on Chemical Intermediates》1996,22(7):667-702
Methodological alternatives for the preparation of highly strained, highly pyramidalized dodecahedrene 2 (Estr=87.3 kcal mol?1; ?=43.5°, MM2) and 1,16-dodecahedradiene 3 (Estr=105.3 kcal mol?1; ?=42.9°, MM2) have been explored, protection/deprotection strategies have been tested—with the eye on their utilization for the generation of higher unsaturated dodecahedranes (e.g. 1,4, 16-triene 4, 1,4,10 (14),16-tetraene 5). For the acquisition of preparative quantities of monoene 2 the “P2F” catalyzed cis-β-elimination in bromododecahedrane, of diene 3 the FVP fragmentation of a “twofold protected” precursor (bis-furan adduct) have become the protocols of choice, which both profit from the recent synthetic advances along the pagodane → dodecahedrane scheme. Because of unusually effective steric protection the highly tilted C=C double bonds of 2 (λmax (CH3CN) = 254 nm, ν C=C = 1658 cm?1, δC=C = 164.4) and 3 (δC=C = 170.5) enter into thermal stabilization pathways (dimerization, oligomerization) only at higher temperatures (for 2 ca. 50% consumption after 5 h at 100°C in a 3·10?3 molar toluene solution); extreme sensitivity to oxygen is primarily attributed to kinetically and thermodynamically promoted allylic hydrogen abstraction. 相似文献
100.
Perfluoroorgano tin and lead compounds can be prepared in high yields from the reactions of (CH3)3SnOCOCF3 and (CH3)3Pb(OCOCF3) with perfluoroorgano cadmium complexes. (CH3)3SiOCOCF3 reacts with (CF3)2Cd complexes — probably via the intermediate (CH3)3SiCF3 and CF2 elimination — to form (CH3)3SiF and CF3CdOCOCF3 complexes. While the reaction of (CF3)2Cd·D with (CH3)3SnONO2 yields CF3NO as the only volatile product, (Rf)2Cd·D (Rf C2F5, iC3F7) forms RfCdONO2·D and (CH3)3SnRf. The preparations and properties of the partly new compounds as well as the n.m.r. spectra are described. 相似文献