Amélioration De L'aptitude Au Décochage Et Au Débourrage: Des Sables Liés Au selicate De Soude Et Durcis: Par Le Gaz Carbonique

Improvement In the aptitude to discharge and to unstop of sands binded with sodium silicate and hardened by carbon dioxide. Chemically hardened sands offer a large choice of moulding and coring processes by the use of organic and mineral compounds. The use of these binders requires a knowledge of associated risks, to obtain a reduced residual resistance (in order to facilitate the discharging and the unstopping of the parts) and for the success of the products.The aim of this study was to rationalise the utilisation conditions of sodium silicate moulded sands, with additives, hardened by carbon dioxide. This should minimize the eventual defects in the cast parts. Sand resistance is very important right after the casting; it makes more difficult the tasks of discharging and unstopping. The need to incorporate organic matter to the sands becomes a necessity. The role of the organic matter is to reduce the sand resistance. The use of silicate binder requires the identification of the mechanism of the mixture hardening by carbon dioxide. It also calls for a knowledge of the gel structure formation, and of the influence of certain parameters on the properties.The experimental part is concerned with a comparative study of the behaviour of these sands in the foundry.The factors influencing this behaviour are: grain size, carbon dioxide blowing-in time, binder rates, adjuvant ratios and mixing time, etc…A thermographie study was carried out in order to perform the experimental work in real conditions.The obtained results have led to the determination of the optimal values of the above-mentionned parameters. This allows to obtain the smallest residual resistance, hence to improve the discharging and unstopping processes.This approach is clearly exhaustive and shows all possible interactions of the adjuvants with sodium silicate and the considered sands.     

Variation De L'énergie Superficielle D'une Bentonite Par Traitement Chimique Et Thermique

Variation of surface energy of a bentonite by chemical and thermal treatments. The effect of an attack by hydrochloric acid and of thermal treatments on the dispersive surface energy, γ^d_s, and on the morphology index of a bentonite has been studied by inverse gas chromatography at infinite dilution. The results show that γ^d_s is very sensitive to two parameters: one is the atomic scale morphology of the clay material, the other one is the mineral impurity contents, mainly composed of alkaline and alkaline-earth oxides. The large increase of γ^d_s after a moderate treatment [t < 10 h, HC1 < 2N and thermal treatment temperature (TTT)≤300°C] is attributed to the bentonite purification and to the lateral surface appearence. However, a more severe treatment (t>10h, HC1 >3N et TTT > 500°C) destroys the lamellar structure of the montmorillonite and in this case the measured γ^d_s is attributed to the basal surface.     

Dosage De L′antimoine Dans Le Zinc Electrolytique Et Le Sulfate De Zinc

Abstract

Anmodic-stripping voltammetry at a haning-drop mercury electrode has been applied to the precise and accurate trace analysis of antominy in metalic zinc and in solutions of zinc sulfate. A sample preparation methos is described which obviates loss of antimony by voltalization. A mixture of zinc sulfate and 6M hydrochloricacid is used as supporting electrolyte, in order to enhance the separation o the closely spaced dissolution peaks of copper and antimony.     

La Méthylfluorone,réactif spécifique De L'antimoine

The purity of the methyl fluorone was controlled by the melting point of its acctyl derivative. Methyl fluorone is stable in the solid state, but not in ethyl alcohol solution. The solubility of the pure methyl fluorone which we prepared is 0.095% in ethyl alcohol, only a fifth of the solubility of the product used by P. Wenger, R. Duckert and Cl. Blancpain.We prefer the filter paper technique to that of a spotting plate or micro test tube. We were led to reject the use of tartaric solutions pH 4. recommended by the abovementioned authors, and prefer solutions in 1 N HCl.In employing the filter paper impregnated with a drop of the saturated alcoholic solution of methyl fluorone, antimony and molybdenum produce a colour change from yellow to red. germanium and tin a slight change from yellow to orange.If the filter paper is impregnated with a drop of acid solution (I N HCl) of methyl fluorone in alcohol, the sharpness of the reaction of antimony and molybdenum is appreciably increased, whilst the colouration due to germanium and tin do not interfere.By treating the spot with a few drops of H₂O₂ + HCl, the colouration due to molybdenum disappears and the reaction for antimony, which was selective, now becomes specific for this element.     

Synthese Et Photochimie Des (Oxo-3)Butyl- α Et β -L-Arabinopyranosides

Abstract

(3-Oxo) butyl-l-arabinopyranosides undergo Norrish II type photocyclization giving hydroxyspiroketals with a low stereo-selectivity but with a greater reactivity for α -l-anomers according to stereoelectronic effects for the photolysis of axial anomeric hydrogens.     

De l'hydrogénation catalytique à la théorie chimique de la catalyse : Paul Sabatier,chimiste de génie,apôtre de la décentralisation

From catalytic hydrogenation to the chemical theory of the catalysis: Paul Sabatier, genius chemist, decentralization apostle. Paul Sabatier received the aggregation degree in the physical science in 1877 and received his doctorate in the physical science in 1880. In 1884, he was named to the chair of chemistry at Toulouse, when he was thirty, the minimum age for the position. Sabatier's initial researches were inorganic studies within the thermochemical tradition of Berthelot's laboratory. The Mond's preparation of nickel carbonyl instigated him to study gaseous molecules which might behave analogously to carbon monoxide: he succeeded in 1892 in fixing nitrogen peroxyde on copper, cobalt, nickel and iron. One year later he repeated the experience of Moissan and Moureu with unsaturated hydrocarbons and reduced nickel: he found that ethylene and acetylene were hydrogenated. With his student, J.-B. Senderens, he demonstrated the generality of his method to the hydrogenation of non-saturated and aromatic compounds, ketones, aldehydes, phenol, nitriles, nitrites, etc. In contrast of previous physical theories, Sabatier postulated that, in catalysis, a temporary, unstable intermediary between the catalyst and one of the reactants forms on the surface of the catalyst. He predicted the reversibility of the reaction: a catalyst of hydrogenation will be equally one of dehydrogenation. He was awarded the 1912 Nobel Prize in the same time with Victor Grignard. Paul Sabatier was a very reserved man. Elected Professor of chemistry at Toulouse in 1884, he was ever faithful to this town and turned down many offers of attractive positions in Paris. In 1913, he became the first scientist elected to one of six chairs newly created by the Academy for provincial members.     

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.     

Linéarisation et homogénéisation en viscoélasticité

Constitutive equations for non-linear viscoelastic materials are expressed first using a causal operator which relates a response function to any loading history. The corresponding tangent linear equations are then defined through the Fréchet derivative of this operator. This definition is used to propose a step-by-step treatment in view of the derivation of the overall behaviour of non-linear non-ageing viscoelastic heterogeneous materials.     

Géométrie de l'intermittence en turbulence développée

A geometrical interpretation of intermittency in fully developed turbulence is realized through an hierarchy of fractal structures Ω_p of dimensions Δ_p linked each other by the relations Ω_{p + 1} − Ω_p (i.e. Δ_{p + 1} < Δ_p) and γ = (Δ_{p + 1} − Δ_∞)/(Δ_p − Δ_∞) with γ = ((1 + 3/√8)^1/3 + (1 − 3/√8)^1/3)³ and Δ_∞ = 1 and Δ_∞ = 1. This is obtained by the introduction of an entropy jump, defined at the scale r, ΔS_p(r) = (Δ_{p + 1} − Δ_p) ln (r/r₀) characterizing the order level of each sub-structure Ω_p and verifying a linear relation ΔS_p(r) = γ ΔS_{p − 1}(r).     

Étude des propriétés des mélanges pebd régénéré / pebd vierge

This study is a contribution to the valorization of recycled low-density polyéthyléne (LDPE). First the characterization of five recycled LDPE produced from wastes coming from different sources was performed. The physical properties (density, melt flow index), chemical structure (Fourier transform infra-red spectroscopy) and mechanical properties (tensile strength and hardness) were investigated. The effect of the ratio of virgin LDPE on these physical and mechanical properties was studied in the case of the blends of recycled LDPE / virgin LDPE.     

La Rhéoturbidimétrie

Résumé L'état d'agrégation des particules de certaines solutions colloïdales dépend de la valeur du gradient de vitesse qui règne dans ces solutions et de la durée de l'écoulement. On décrit un appareil qui permet de mesurer les variations correspondantes de la turbidité. Les solutions examinées sont placées entre deux cylindres coaxiaux dont l'entrefer constitute la chambre de mesure proprement dite. Le gradient de vitesse est imposé par la rotation du cylindre intérieur. La partie optique et électrique du rhéoturbidimétre est contenue dans un chariot mobile afin de faciliter le nettoyage et le remplissage de la chambre de mesure. Une série d'exemples relatifs à des solutions aqueuses de virus de la mosaïque du tabac et de sérum albumine de buf native ou dénaturée montre les principaux cas susceptibles de se produire selon que l'agrégation provoquée par l'écoulement est ou non réversible en fonction du gradient de vitesse.

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Zusammenfassung Der Aggregationszustand der Teilchen gewisser kolloidaler Lösungen hängt vom Geschwindigkeitsgradienten ab, der während der Dauer des Fließens in der Lösung herrscht. Ein Gerät wird beschrieben, das die entsprechenden Veränderungen in der Trübung zu messen gestattet. Die Lösungen befinden sich zwischen zwei koaxialen Zylindern, deren Zwischenraum die Meßkammer darstellt. Der innere Zylinder rotiert. Die optische und elektrische Anordnung des Rheoturbidimeters ist beweglich angeordnet, um Reinigung und Füllung der Meßkammer zu erleichtern. Eine Reihe von Relativmessungen an vorhandenen Lösungen von Tabakmosaikvirus und Rinderserumalbumin, natives und denaturiertes, zeigen die wesentlichen Fälle, die auftreten und bei denen Aggregation durch Fließen hervorgerufen wird, die reversibel oder nicht reversibel als Funktion des Geschwindigkeitsgradienten ist.

     

Etude polarographique du méthyl-phényl-dodécyl-triméthylammonium (désogène)

Rèsumè Le méthyl-phényl-dodécyl-triméthylammonium (désogène), donne une vague polarographique caractéristique, en utilisant comme électrolyte de support l'hydroxyde de tétraméthylammonium, le CILi ou le ClK.Les propriétés de cette vague ont été étudiées en fonction de la concentration du saponium. La loi d'Ilkovi est vérifiée.Deux électrons interviennent dans la réduction du saponium.

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Summary The cationic detergent désogène (methyl-phenyl-dodecyl-trimethylammonium) gives a characteristic polarographic wave in LiCl or in tetramethylammonium solution. The wave seems to correspond to a 2 electronprocess, following Ilkovi's law at low concentrations. A typical adsorption maximum, proceeded by a prewave wich does not follow the Ilkovi' law is found at higher concentrations. At high ionic strength this maximum disappears.

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Zusammenfassung Das kationische Detergens Désogène (Methylphenyl-Dodeeyl-Trimethylammonium) gibt in Lithiumchlorid- oder in Tetramethylammoniumhydroxydlösung eine charakteristische polarographische Welle. Diese scheint einem 2-Elektronen-Prozeß zu entsprechen und folgt bei niederen Konzentrationen dem Gesetz von Ilkovi. Ein typisches Adsorptionsmaximum, dem eine dem Ilkovi-Gesetz nicht folgende Welle vorangeht, findet sich bei höheren Konzentrationen. Dieses Maximum verschwindet bei hoher Ionenkonzentration.

     

Méthodes de concentration préalable dans la détermination spectrochimique d'éléments à l'état de trace

Résumé La concentration préalable est très intéressante en vue des déterminations analytiques des traces d'éléments qui, en très petite concentration, se trouvent dans les sols de culture, les engrais chimiques, et commes des impuretés, ou des petites quantités des éléments, dans des alliages ou d'autres divers matériaux. Pour cette sorte de microdosage, nous avons spécialement choisi les méthodes spectrochimiques, comme celles les plus convenables pour la détermination simultanée de plusieurs éléments dans les échantillons étudiés. Avec cette concentration préalable des traces d'éléments on obtient dans des méthodes spectrochimiques, l'élimination la plus grande possible des éléments principales qui peuvent troubler ou bien déguiser les lignes appropriées pour le dosage des traces d'éléments. Des divers techniques utilisées pour la concentration préalable nous avons poursuivi spécialement celles qui basent sur l'emploi des réactifs chimiques appropriés, aussi bien qu'à cause de leur spécificité de la précipitation, aussi bien qu'à cause des procès de coprécipitation ou trainage qu'elles provoquent. Parmi les méthodes qui employent des réactifs organiques on a étudié, entre autres, la détermination spectrographique quantitative de petites quantités de bismuth comprises dans des alliages ternaires en base de plomb. On a employé le cupferron comme un réactif sélectif qui précipite le bismuth en présence de plomb et de cadmium, après avoir étudié la zone optime deph (0,5–1,5) dans laquelle ceci est possible. On a aussi étudié la détermination spectrochimique des traces de baryum à l'égard des diverses problèmes, en concentrant préalablement le baryum moyennant un procès de trainage ou coprécipitation provoqué par le ion sulfate en présence de plomb, qui s'ajoute excessivement, et que nous employons comme étalon interne spectral. Cette méthode a été employée pour le dosage de baryum dans certains procès d'adsorption, étudiés dans nos laboratoires.

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Summary The preliminary concentration is of great interest with regard to analytical determinations of traces of elements which occur at very low concentrations in agricultural soils, chemical fertilizers, and as impurities, or of minute quantities of elements in alloys or other divers materials. For this kind of microdetermination, we have especially chosen spectrochemical methods as being the most convenient for the simultaneous determination of several elements in the samples studied. With this preliminary concentration of traces of elements, there is obtained in the spectrochemical methods, the greatest possible elimination of the principal elements which may interfere with or entirely disguise the appropriate lines to be followed for determining the traces of elements. Among the various techniques employed for the preliminary concentration, we have followed especially those which are based on the use of appropriate chemical reagents, both because of there specific precipitating action, or because of the process of coprecipitation or entrainment which they provoke. Among the methods, which utilize organic reagents, there have been studied, for instance, the spectrographic quantitative determination of small quantities of bismuth contained in ternary alloys containing principally lead. Cupferron has been used as a selective reagent, which precipitates bismuth in the presence of lead and cadmium, after establishing the optimalph zone (0,5–1,5) in which this separation is possible. A study has also been made of the spectrochemical determination of barium by means of an entrainment of coprecipitation process brought about by sulfate ion in the presence of lead, added in excess, and which we have used as an internal spectral standard. This method has been used for the determination of barium in certain adsorption processes studied on our laboratories.

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Zusammenfassung Die vorhergehende Anreicherung hat für die analytische Bestimmung von Spurenelementen in Ackerböden und im Kunstdünger oder von geringsten Beimengungen und Verunreinigungen in Legierungen oder sonstigem Material große Bedeutung. Wir verwenden für solche Mikrobestimmungen vor allem spektralanalytische Methoden, da sie sich für die gleichzeitige Bestimmung mehrerer Elemente in einer Probe am besten eignen. Mit einer solchen der Spektralanalyse vorangehenden Anreicherung erzielt man die größtmögliche Entfernung der Hauptbestandteile, die die zur spektralanalytischen Bestimmung der Spuren geeigneten Linien stören oder sogar überdecken können. Von den verschiedenen zur Anreicherung geeigneten Verfahren verwenden wir vor allem die mit Hilfe von chemischen Reagenzien, sei es daß sich diese zufolge ihrer Spezifität hierzu besonders eignen, sei es weil sie bei der Niederschlagsbildung die gesuchten Elemente mit ausfällen oder mitschleppen. Unter Zuhilfenahme organischer Reagenzien studierten wir unter anderem die spektralanalytische Bestimmung kleiner Mengen Wismuth, wie sie sich in Legierungen auf Bleibasis finden. Wir verwendeten hierfür als selektives Reagens Cupferron, welches Wismuth in Gegenwart von Blei und Cadmium ausfällt. Als geeignetstesph-Bereich hierfür wurde 0,5 bis 1,5 bestimmt. Weiters untersuchten wir die spektralanalytische Bestimmung von Bariumspuren mit Rücksicht auf gewisse Problemstellungen, indem wir das Barium vorher mit Sulfationen gleichzeitig mit Blei ausfällten, welches im Überschuß zugefügt und von uns als Vergleichssubstanz verwendet wurde. Diese Methode wurde zur Bariumbestimmung bei gewissen Adsorptionsversuchen verwendet, die in unserem Laboratorium durchgeführt werden.

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Avec 4 figures.     

Récentes réalisations en analyse thermogravimétrique

Résumé Récentes applications en chimie minérale de la thermogravimétrie, en association avec d'autres techniques comme l'analyse thermique différentielle, les rayons X, la spectrographie d'absorption infrarouge, etc.

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Summary Recent applications in inorganic chemistry of thermogravimetry, in association with other techniques such as differential thermal analysis, X-rays, infra red absorption, etc.

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Zusammenfassung Eine Übersicht über neuere Anwendungsmöglichkeiten der Thermogravimetrie in der anorganischen Chemie wird gegeben. Die Verbindung mit anderen Verfahren, wie IR-Spektrographie, thermische Differenzanalyse, Röntgenanalyse u. dgl., wird erörtert.

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Conférence donnée à Luton, le 16 avril 1962     

Modélisation multiphasique de matériaux renforcés par inclusions linéaires

Making use of the virtual work method, a mechanical multiphase model for reinforced materials is developed. Matrix and reinforcement are continuously distributed. In modelling the internal forces, account is taken of the ‘continuous’ and ‘curvilinearharacteristics of the matrix and reinforcements, and of their interaction. The corresponding equations of motion and associated boundary conditions are deduced for each phase by applying the virtual work principle. Such a multiphase model is a suitable framework for dealing with problems in which imperfect bonding between matrix and reinforcements should be taken into account.     

Propriétés thermoélectriques du sélénium liquide pur et dopé à i'lode

Abstract

On a étudié le pouvoir thermoélectrique du sélénium en fonction de la température pour des échantillons de puretés diverses et dopés ayantn subi divers cyles thermiques. II varie beaucoup, passant d'un signe à l'autre; le dopage à l'iode tend à donner une conductibilité de type p.

Thermoelectric power of selenium vs temperature has been studies for samples of variable purity or doped having undergone various thermal treatments. Large variations appear, with either sign; doping with iodine favours p-type conduction.     

Influence du cérium dans l'hydrogénation sélective du cinnamaldéhyde en présence de catalyseurs cobalt supportés

The study of the cinnamaldehyde hydrogenation over supported cobalt catalysts shows that the addition of cerium to cobalt increases the selectivity to unsaturated alcohol without decrease of the activity. Moreover the support has an important effect over the catalytic properties of the mixed cobalt-cerium system; active carbons clearly lead to the most active catalysts. If the calcination step does not modify the catalytic properties, the reduction step has a decisive effect, i.e. after a reduction with hydrogen at low temperature, a selectivity to unsaturated alcohol of 95 % is obtained at a conversion of 90 %. The preparation method, especially the order of addition of the elements (cobalt and cerium) to the support (C_L2S) also has an important effect, both on the activity and the selectivity. The first step of ceria dispersion on the support leads to the most efficient catalyst. The study of the catalysts reducibility and the electron microscopy micrographs show that in that case, the cobalt and cerium dispersion are much more important than that observed with another preparation.