The exceptional Lie group E<Subscript>8</Subscript>

No Abstract.  .     

Hydrogen-deuterium exchange in fused-silica capillary columns.

Ketones deuteriated alpha to the carbonyl have been observed to undergo significant isotope exchange on fused-silica capillary columns during gas chromatography-mass spectrometry. The residence time of the compounds on the column was found to influence the extent of isotope exchange. The degree of exchange was examined using a variety of columns and the isotope exchange was found to occur even with brand new columns. Conversion of the keto compounds into the methyloxime derivatives resulted in retention of the "correct" isotope content during gas chromatography-mass spectrometry.     

Highly fluorinated graphite prepared from graphite fluoride formed using BF3 catalyst

Fluorinated graphites (CF_0.47) were obtained by reaction at room temperature of fluorine gas with graphite in the presence of boron trifluoride and hydrogen fluoride as catalysts. Their thermal treatments under fluorine at temperatures up to 600 °C lead to a progressive increase of the fluorine level resulting in an highly fluorinated graphite (CF_1.02). Whatever the fluorination level, a stage one fluorine-graphite intercalation compound is obtained. The sp² carbon hybridization is maintained for treatment temperature below 300 °C and two types of structure coexist for T_T in the range 350-550 °C. Finally, above 550 °C, carbon hybridization is sp³.The resulting materials were studied by ¹¹B, ¹H, and ¹⁹F NMR and EPR at different experimental temperatures giving informations about the intercalated fluoride species, the temperature of their removal from the host fluorocarbon matrix, as well as their mobility.     

Determination of the ionization constants of weak electrolytes by capillary zone electrophoresis

Capillary zone electrophoresis in untreated fused silica capillaries has proved suitable for the determination of the ionization constants of weak electrolytes. Several fundamental equations relating the electrophoretic mobilities of ionized solutes to hydronium ion concentrations in the running electrolyte have been verified experimentally. The observed dependence of the electrophoretic mobilities of weak bases and ampholytes on the pH of the electrolyte showed good agreement with predicted behavior. The pK_a values calculated from electrophoretic mobility data obtained by capillary zone electrophoresis were reasonably close to those reported in the literature.     

Some aspects of the preparation,characterization and thermal decomposition of anisaldehyde Girard T complexes of some transition elements

Anisaldehyde Girard T complexes of Mn(II), Fe(III), Co(II) and Cu(II) with the general formula [MCl₂(AGT)₂]Cl₂ or [MCl₂(AGT)]Cl, where (AGT)=anisaldehyde carbohydrazone methyltrimethylammonium cation, H₃C-O-C₆H₄-CH=N-NHCOCH₂N⁺-(CH₃)₃ andM=Mn(II), Co(II), Fe(III) or Cu(II) were prepared. Elemental analysis, electrical conductance and IR spectra showed that the ligand coordinates with the studied metals in keto form through the azomethine and carbonyl groups. The molar conductances, electronic spectra and magnetic moments of the solid complexes were determined. The processes of thermal decomposition of these complexes were studied. From the analysis of the thermal decomposition curves obtained, the corresponding kinetic parametersn, E _a and logA were evaluated by two different methods and the effects of the central metal ions on the stabilities of the complexes are discussed.

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Zusammenfassung Es wurde die Herstellung und Isolierung von Anisaldehyd-G-T-Komplexen von Mn(II), Fe(III), Co(II) und Cu(II) der allgemeinen Formel [MCl₂(AGT)₂]Cl₂ oder [MCl₂(AGT)]Cl durchgeführt, wobei (AGT)=Anisaldehydcarbohydrazon-methyl-trimethyl-ammoniumkation H₃C-O-C₆H₄-CH=N-NHCOCH₂N⁺-(CH₃)₃ undM=Mn(II), Co(II), oder Fe(III) und Cu(II). Elementaranalyse, elektrische LeitfÄhigkeit und IR-Spektren zeigten, da\ der Ligand an den untersuchten Metallen in der Ketoform, über die Azomethin- und Carbonylgruppe koordiniert ist. Es wurden die molare LeitfÄhigkeit, Elektronenspektren und das magnetische Moment der festen Komplexe bestimmt. Der Vorgang der thermischen Zersetzung dieser Komplexe wurde untersucht. Durch Analyse der erhaltenen thermischen Zersetzungskurven wurden die entsprechenden kinetischen Parametern, E _a und logA durch zwei verschiedene Methoden ermittelt und weiterhin der Einflu\ des zentralen Metallions auf die StabilitÄt der Komplexe diskutiert.

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The authors would like to express their sincere thanks to Dr. F. I. M. Taha, Professor of Inorganic Chemistry and Head of the Chemistry Department, Faculty of Science, Mansoura University, for encouragement and useful discussions.     

Langmuir-Blodgett films of preformed polymers containing biphenyl groups

Polymers containing liquid crystal groups have been studied previously as waveguides, and they have been deposited as spacer materials with various chromophores to form alternating films However, only a few members of this group of materials have been studied in any detail, and very little structural information has been obtained so far. Therefore, a more detailed examination of these materials as mono- and multilayers was undertaken. A new group of materials including the same mesogenic group, polymeric sulfones, was also studied. The polymers gave steep isotherms with high collapse pressures, indicating good packing of the monolayers, and could be deposited to form thick multilayers. X-ray diffraction showed that an ordered multilayer was formed, and the effects of the polymers chemical nature on the structure of the LB films are discussed. It appears that the dominant factor in monolayer structure is the nature of the polymer backbone rather than that of the liquid crystal side chains, which play a secondary role.     

Colorimetric determination of pyridoxine in pharmaceutical preparations

Summary The USP method for the determination of pyridoxine hydrochloride in pharmaceutical preparations has been modified to increase the stability of the colour, the speed of determination and the sensitivity. The reaction is carried out in propan-2-ol medium instead of water triethanolamine is used as the buffer, and iodine is used as oxidant when necessary. The colour is stable for about 45 min, the sensitivity of the reaction is greatly increased and the method takes only about a fifth of the time of the USP method.

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Kolorimetrische Bestimmung von Pyridoxin in pharmazeutischen Präparaten

Zusammenfassung Die USP-Methode zur Bestimmung von Pyridoxinhydrochlorid in pharmazeutischen Präparaten wurde modifiziert, um die Beständigkeit der Farbe, die Geschwindigkeit der Bestimmung und deren Empfindlichkeit zu verbessern. Statt in Wasser wird die Reaktion in Propan-2-ol durchgeführt, wobei Triethanolamin als Puffer und Jod — wenn nötig — als Oxydationsmittel verwendet werden. Die Farbe ist ungefähr 45 min beständig, die Empfindlichkeit der Reaktion stark verbessert und die zur Durchführung der Methode erforderliche Zeit beträgt etwa ein Fünftel im Vergleich zur USP-Methode.