Méthode indépendante des propriétés locales pour le calcul des indices de rétention en Chromatographie en phase gazeuse à température programmée

Retention indices of some phthalates, separated by temperature-programmed gas chromatography, computed using B-spline interpolations are more consistent with the scheme of this retention parameter. In applying this technique to a mixture of reference n-alkanes, which two successive members do not defer of more than four carbon atoms, it is possible to recover classical retention indices.     

Spectres de vibration de monocristaux de paratoluidine à la température de l'hélium liquide

A comparative study is made of i.r. and Raman spectra of p-toluidine rhombic single crystals in the 0–200 cm⁻¹ range, at liquid helium temperature. No evidence of a phase transition up to room temperature has been found     

Séparation des isoméres de l'hexachlorocyclohexane par chromatographie en phase gaz

Hexachlorocyclohexane isomers can be separated by a glass bead technique with polypropylene glycol Niax 1025 as the stationary phase. The principal isomers separated are the γ-hexachloro-cyclohexane (Lindane isomer), the α, β, ε, and δ isomers and γ-heptachlorocyclohexane. The life of the glass bead column is short — about 20 days in constant use. A longer column life can be obtained by pretreatment of the glass beads.     

Étude générale sur la nature des tungstates formés à haute température au cours de diverses réactions à l'état solide

Résumé L'étude de la décomposition du paratungstate de sodium par la chaleur met en évidence la formation de tétratungstate Na₂W₄O₁₃ et de bitungstate Na₂W₂O₇. Ce dernier tungstate, existant seulement à l'état solide, présente un spectre d'absorption caractéristique. On peut l'obtenir pur en faisant agir l'anhydride tungstique sur le tungstate de sodium Na₂WO₄.

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Summary The study of the thermal decomposition of sodium paratungstate reveals the formation of sodium tetratungstate Na₂W₄O₁₃ and the bitungstate Na₂W₂O₇. The latter tungstate exists only in the solid state and gives a characteristic absorption spectrum. It may be obtained pure by causing tungstic anhydride to react with sodium tungstate Na₂WO₄.

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Zusammenfassung Das Studium der thermischen Zersetzung von Natriumparawolframat erwies die Bildung von Tetrawolframat Na₂W₄O₁₃ und von Biwolframat Na₂W₂O₇. Letzteres besteht nur in festem Zustand und bietet ein charakteristisches Spektrum. Man erhält es in reinem Zustand durch Einwirkung von Wolframtrioxyd auf Natriumwolframat Na₂WO₄.

     

Identification spécifique des acides aminés et des vitamines par l'indice de réfraction et la température eutectique: Application a la chromatographie sur papier et au contrôle

Refractive index and eutectic melting temperature of binary systems, together lead to specific identification of organic individuals and isomers. A number of vitamins and amino acids have been experimented with to that purpose. The result is that analysis of an entire spot of amino acids on paper becomes easy owing to these properties. An example using glumatic acids shows that better results on the composition of an entire spot on paper can be obtained by this analysis than by Chromatographie R_F values.     

Dépôt chimique en phase vapeur à basse température de revêtements dans le système V-C-N à partir de bis(arene)vanadium

Vanadium carbide coatings V₈C₇ have been deposited on steel substrates by MOCVD using bis(arene)vanadiums as precursors at temperatures lower than 550 °C. Addition of C₆Cl₆ in the gas phase allows to reduce the carbon content of the films to 13 at. %. These metal coatings exhibit the features of a metastable carbon-rich solid solution. Carbonitride V(C,N) and nitride δ-VN layers with only 5 at. % carbon have been deposited in the presence of NH₃. These reactive gas phases allow to grow almost all the phases of the V-C-N ternary diagram.     

Etude de la fluorescence du 9,9′-bianthryl en solutions liquides et en milieux polymériques rigides à la température ambiante

The fluorescence of 9,9′-bianthryl (9,9′BA) is very sensitive to the polarity of the solvent. This molecule exibits an intramolecular charge transfer state in polar medium. The study of the fluorescence of 9,9′BA, in liquid solutions, shows a strong dependency of the Stokes shift versus the dipole moment m of the aprotic lowly viscous solvent. Moreover, this compound exhibits in polyvinylacohol (PVA) an original anomalous behaviour.     

Comportement en frottement — usure d'un acier de travail à froid,avec et sans oxydation à basse température par la vapeur d'eau

Cutting tools are subjected to work, mechanical and tribological stresses, during the crushing of thermoplastics. The purpose of this work was to investigate the influence of a pre-existing oxide film on the friction process between the tool and the thermoplastic, during the crushing. Steam is employed for oxidizing the tools at 300°C.The experimental results showed that during the major part of the grinding non oxidized tools exhibit a severe oxidation wear and the thermoplastic transfers to the tools. The oxidation of the tools, notably in the case of steam, decreases the wear rate. The oxide thickness and addition element concentrations were determined by scanning transmission electron microscopy and energy dispersive X-Ray spectroscopy. The microanalysis confirmed the presence of oxygen, Fe, Si, Mg, N. These results are discussed in terms of addition element effects on the development of the microstructure of the oxide films and on the friction process.     

Rôle des ponts disulfure dans le repliement en épingle à cheveux de l’androctonine. Relations structure–activité

Androctonin is a 25-residue antibacterial peptide extracted from the hemolymph of the scorpion Androctonus australis. In order to understand the structural requirements for hairpin fold and for interactions with the bacterial membrane, we have analysed the chemical shifts and the nOes of three synthetic androctonin mutants for which the disulfide bridges were selectively removed.     

Étude de réactions à l'état solide entre l'arbre de Saturne et des sels contenant le groupement XO3

Résumé Le plomb utilisé sous forme d'arbre de Saturne possède une grande réactivité et permet de réduire les nitrates en nitrites. Il s'agit d'une réaction à l'état solide, débutant dès la température ordinaire. On a pu caractériser ainsi la présence de nitrites en mélangeant le plomb avec les nitrates de lithium, sodium, potassium, césium, cuivre, argent, magnésium, calcium, strontium, baryum, zinc, thallium, plomb, cobalt et nickel.

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Summary Lead used in the form of the lead tree has great reactivity and is able to reduce nitrates to nitrites. This involves a solid state reaction and starts at room temperature. In this way it is possible to detect the presence of nitrites after mixing the lead with the following nitrates — Li, Na, K, Cs, Cu, Ag, Mg, Ca, Sr, Ba, Zn, Tl, Pb, Co, Ni.

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Zusammenfassung In der Form des Bleibaumes ist Pb sehr reaktionsfähig und reduziert Nitrat zu Nitrit. Dabei handelt es sich um eine Festkörperreaktion, die bei gewöhnlicher Temperatur einsetzt. Nach Vermengen von Blei mit den Nitraten von Li, Na, K, Cs, Cu, Ag, Mg, Ca, Sr, Ba, Zn, Th, Pb, Co und Ni konnte die Anwesenheit von Nitrit festgestellt werden.

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En l'honneur du ProfesseurA. A. Benedetti-Pichler, pour son 70^e anniversaire.     

Decontamination chimique. II. Oxydation de composés soufrés en milieu micellaire: rôle de la lipophilie des substrats

Chemical decontamination of toxic compounds (warfare agents and pesticides) is of increasing importance. Oxidation of sulphur-containing model toxic agents in micellar media (in water or binary systems) was investigated through the relationship between the reactivity/ selectivity and the lipophilicity (log P)) of the model.Two substrates with lipophilicities close to that of mustard seem to be the best suited for miming the degradation of the toxin. The micellar medium composed of cetylpyridinium chloride and of the binary system water/ formamide (1:1; vol/vol) gave the best results: quantitative yield with over 90 % of the product in the form of sulphoxide.     

De l'analyse de la résistance interne par perçage à la détermination du profil de dureté des aciers traités en surface

The thrust measured during a drilling test is related to the hardness of the material tested. When the test is performed on a superficially heat-treated specimen, the results do not exactly correspond to the hardness profile obtained by the Vickers micro hardness technique. The difference is due to the integration of heterogeneous resistance along the cutting edge of the conic drill. By discretising the drilled thickness, we have developed an algorithm yielding the hardness of each elemental thickness. Results are very close to those obtained by Vickers hardness profile measurements.     

Mécanismes de corrosion sous contrainte par l'iode dans le zirconium et le zircaloy-4. Transposition aux conditions dtnteraction pastille-gaine dans les réacteurs à eau pressurisée

The aim of tnis work was to explain the very rapid cladding rupture occuring by iodine-induced Stress Corrosion Cracking, by means of a study of parameters specific to Pellet-Cladding Interaction loadings in Pressurized-Water Reactors (neutron irradiation and recoil implantation).     

Forces de la répulsion dans la spectroscopie vibrationelle—II. L'influence combinée d'attraction et de répulsion entre les particules sur les profils des composantes isotropes des lignes vibrationelles à l'exemple des systèmes ioniques

Mutual effect of interparticle attraction and repulsion on isotropic Raman line contours and time correlation functions was studied. The theory of Burshtein et al. [Chem. Phys. Lett. 83, 335 (1981); 100, 155 (1983); Spectrochim. Acta 43A, 483 (1987)] was used, and broadening caused by repulsion forces was defined more precisely. The discussion of the results obtained was made with special reference to ionic systems (molten salts and salt glasses).     

Transmission de l'effet de substituant à travers les systèmes insaturés-IV. Utilisation des relations de type Hammett avec les paramètres spectroscopiques i.r. et RMN pour la détermination des conformations de cétones α, β-éthyléniques aromatiques

The i.r. stretching frequencies of the carbonyl group and the chemical shift of the ethylenic proton in three series of α,β-unsaturated ketones, 3-substituted-5,5-dimethyl-2-cyclohexen-1-ones s-trans p-substituted-4-aryl-3-buten-2-ones and p-substituted-3-aryl-5,5-dimethyl-2-cyclo-hexen-1-ones, have been analysed using correlations with Hammett type substituent constants. The comparison of parameters ϱ of these correlations allows us to obtain quantitative information on the conformation of the last series of ketones. In this series, the dihedral angle between the aromatic ring and the plane of enonic system varies inversely with the resonance donor effect of substituent (0° for p-NH₂, 38° for NO₂).