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181.
Dipl.-Ing. Dr. O. Hinterhofer 《Monatshefte für Chemie / Chemical Monthly》1974,105(2):279-290
The selective chlorination of a m/p-xylene mixture, followed by distillation of the unreacted p-xylene, leaves a residue containing up to 90% of monochlorinated m-xylenes. m-Xylene is recovered from the latter by heterogeneous catalytic hydrogenolysis in the gas-phase. It was found that the hydrogenolysis on certain noble metal catalysts proceeds according to an ionic reaction mechanism at temperatures below a definite temperature range. At temperatures above this range hydrogenolysis follows a radical reaction mechanism. 相似文献
182.
Dr. Rud Wegsheider 《Monatshefte für Chemie / Chemical Monthly》1896,17(1):111-120
Zusammenfassung Zu den früher von mir angeführten Gründen, welche für die aufgestellten Formeln der isomeren Opiansäureester sprechen, sind noch in erster Linie das Verhalten gegen Phenylhydrazin, sowie nach Versuchen Liebermann's das Verhalten gegen -Naphtylamin und Semicarbazid, in zweiter Linie das Verhalten gegen fuchsinschwefelige Säure, Diazobenzol-p-Sulfosäure und vielleicht auch das Verhalten gegen Essigsäureanhydrid und Natriumacetat hinzuzufügen. Da somit die Constitution der Opiansäureester genügend feststeht, ist eine Überprüfung der Beobachtungen Stabil's über die Ester der Phtalaldehydsäure wünschenswerth.Die Aldehydreactionen mit Resorcin und mit Nitroprussidnatrium versagen bei der Opiansäure und ihren Estern; auch die anderen oben erwähnten Farbenreactionen sind hier von geringem Werth. 相似文献
183.
Mechanism of Thermal Dehydration of Sodium Dihydrogenphosphate The thermal dehydration of sodium dihydrogenphosphate (P1) to sodium cyclotriphosphate (CP3) and sodium polyphosphate, the so-called Maddrell's salt (MS), is controlled by nucleation and crystallization of CP3 and MS, respectively. The wellknown influence of various formation conditions on the CP3:MS product ratio is caused by amorphous and crystalline intermediate phases and their ability to form CP3 or MS nuclei. On seeding P1 with CP3 or MS the dehydration proceeds structure-controlled via dihydrogendiphosphate to pure CP3 or pure MS. The particularities of thermal dehydration of crystalline sodium dihydrogendiphosphate, and also the dehydration and reorganization of sodium phosphate glasses (Na:P = 1:1) with different mean chain lengths, under formation of CP3 or MS are described. 相似文献
184.
Semiconductor quantum dots (QD) are nanometer-sized crystals with unique photochemical and photophysical properties that are not available from either isolated molecules or bulk solids. In comparison with organic dyes and fluorescent proteins, QD are emerging as a new class of fluorescent labels with improved brightness, resistance against photobleaching and multicolor fluorescence emission. These properties could improve the sensitivity of biological detection and imaging by at least 10- to 100-fold. Further development in high-quality near-infrared-emitting QD should allow ultrasensitive and multicolor imaging of molecular targets in deep tissue and living animals. Here, we discuss recent developments in QD synthesis and bioconjugation, applications in molecular and cellular imaging as well as promising directions for future research. 相似文献
185.
The stoichiometry and structure of acetophenone benzoylhydrazone and acetophenone salicoylhydrazone chelates with some divalent metal ions are studied by conductometric titration and visible and infra-red absorption spectrophotometry. The results are supported by analysis of the solid complexes. The infra-red study revealed that coordination occurs through C=O and C=N groups. The shift in the C=O and C=N bands is utilised for the determination of bond lengths. 相似文献
186.
Summary The effects of pH, gas flow rate and collector concentration on the rate of thorium removal by foaming with sodium lauryl sulphate have been investigated. The obtained data indicate that only aged hydrated thorium oxide is removed by a flotation mechanism. All the other colloidal and condensed thorium species as well as the colloidal sublates which are formed between the dissolved thorium species and the collector anions appear to be removed by partition and their removal rates could be described by a reversible first-order rate equation. The obtained results are discussed in terms of thorium hydrolysis.
With 7 figures 相似文献
Zusammenfassung Der Einfluß der pH-Werte, Gasdurchflußmengen und Kollektor-Konzentration auf die Geschwindigkeit der Entfernung des Thoriums durch Schaumbildung mit Natrium-Lauryl-Sulfat wurde untersucht. Die Ergebnisse zeigen, daß das gealterte, wässerige Thoriumoxid durch Flotations-Mechanismen entfernt wird. Die anderen kolloidalen und kondensierten Thorium-Spezien und auch die Kolloidalprodukte, die durch Reaktionen zwischen den gelösten Thoriumspezien und den Kollektor-Anionen formiert sind, sind durch die Verteilung entfernt worden. Die Entfernungsgeschwindigkeit kann beschrieben werden durch eine reversible 1. Ordnungs-Gleichung. Die Ergebnisse werden in Abhängigkeit einer ThoriumHydrolyse diskutiert.
With 7 figures 相似文献
187.
Thermal analysis supported by kinetic calculations was applied exhaustively to these compounds. Under dynamic conditions, tetrafluorometallates(III), which as intermediates, could not be isolated, for the first three compounds. In each case, the final step was the pure metal(III) fluoride. Ammonium hexafluorochromate(III) decomposed directly to the pure chromium(III) fluoride. The decomposition rate of all compounds slowed down towards the end, probably for kinetic reasons. Polymorphic transitions of ammonium hexafluorotitanate(III) were observed at 35 and 100°C. Ammoniumhexafluoroscandate(III) underwent polymorphic transition at 47°C. The decomposition patterns for all these compounds were similar. Conditions for the preparation of pure ammonium tetrafluorometallates(III) of Sc, Ti and V are described. 相似文献
188.
Subash C. Raghu Sheela Berchmans Dr. Kanala L. Phani Dr. Venkatraman Yegnaraman Dr. 《化学:亚洲杂志》2007,2(6):775-781
This paper describes the formation of catalytically active thin films of Pt, Pt/Au, and Pt/Ru on gold substrates stabilized by amine‐terminated polyamidoamine (PAMAM) dendrimers. A monolayer of dendrimer is initially self‐assembled on the gold substrate, which serves as a template for the growth of catalytically active thin films. As dendrimers contain tens to hundreds of functional groups at the periphery, the aggregate strength of the multidentate interactions with the gold substrate leads to the formation of robust films. The films were found to exhibit high catalytic activity for the oxidation of small hydrocarbons such as methanol. Such films offer versatility and scope for the design of effective electrocatalysts, especially in the context of microfuel cells and “dendrichips”; hence, they could find applications in the fields of sensors, fuel cells, and waste‐water treatment. 相似文献
189.
The sulfonation of anthracene yields a variety of products and byproducts by different reaction paths depending on the reaction conditions. While trying to reduce the number of products formed by sulfonation under mild conditions, a new reaction was found: under certain sulfonation conditions anthracene is not sulfonated but reacts to form oligoanthrylenes. The highest average molecular weight of a fraction, insoluble in benzene, is about 3,000. 相似文献
190.