Caractérisation des couches minces de Cd1–xZnxS préparées par dépôt chimique

Cd_1–xZn_xS is an important material that can be used to make n-type window-layers for thin film heterojunction solar cells. After a theoretical study of the solution chemistry of cadmium and zinc sulphates, ammonia and thiourea corresponding to sulphurs precipitation, we have been interested in the study of the effect of some parameters (temperature and zinc concentration) on the deposition process of Cd_1–xZn_xS on a glass substrate. X-ray diffraction studies showed that this latter compound crystallises in a hexagonal wurtzite crystalline structure. The AFM analysis showed that a homogenous deposited film was obtained for x = 0.1. The different values of gap energy are in the range 2,42–2,50 eV for x values between 0.08 and 0.28.     

Microdétermination du zinc par chromatographie-colorimétrie

Résumé La détermination colorimétrique de zinc avec de la dithizone est une méthode excellente quand il s'agit de dissolutions pures de zinc; mais les résultats sont douteux en présence d'autres métaux, specialement de cuivre. Dans ce travail, nous proposons une méthode chromatographique sur papier pour la séparation totale du zinc, suivie de la dissolution de la tache et du dosage par colorimétrie avec la dithizone.

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Summary The dithizone colorimetric method for zinc is an excellent procedure when pure solutions of zinc are being used. However, the results are doubtful in the presence of other metals, particularly copper. In this study, a paper Chromatographic method is proposed for the complete separation of the zinc, followed by solution of the stain and colorimetric determination with dithizone.

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Zusammenfassung Die kolorimetrische Bestimmung des Zinks mit Dithizon bewährt sich ausgezeichnet, sofern es sich um reine Zinklösungen handelt; in Gegenwart anderer Metalle, besonders Kupfer, sind die Resultate aber unsicher. Daher wird eine vollständige papierchromatographische Abtrennung des Zinks vorgeschlagen, dessen Chromatogrammfleck gelöst und mit Dithizon kolorimetrisch bestimmt wird.

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Dédié à l'occasion du 100^me anniversaire de la naissance deFriedrich Emich.     

Dosage du silicium par précipitation du complexe silicomolybdique jaune par la quinoléine

The authors have studied the conditions of precipitation of complex silicomolybdic yellow by quinoline from the point of view of the determination of silicon.Under the conditions that produce complete development of the complex, the precipitation is itself quantitative in the presence of an excess of quinoline, the role of which is to make the precipitate insoluble in its formation surroundings. The precipitation of free molybdate is prevented by adding the quantity of acid necessary for complexing it.The precipitate thus obtained filters without difficulty, and only needs to be dried for 1 hour at 150° in order to attain constant weight. It corresponds then exactly to the formula: SiO₂.12MoO₃.4(C₉H₇N).2H₂O.     

Radiométrie thermique par absorption différentielle distribuée

Thermal detectors are based on converting the incident radiation into heat transfer. A differential distributed radiometer works by way of measuring the local temperature rises taking place upon a substrate featuring alternatively absorbent and reflecting areas. The center of each area is crossed with a thin thermoelectric chain whose hot and cold junctions are submitted to the superficial thermal field. This paper deals with performance of ideal structures, owing to a bidimensional analysis regarding homog-enous solid structures undergoing an alternatively distributed energy absorption.     

Spectres d'absorption détectés par effet photoacoustique en infrarouge par transformée de Fourier—applications à quelques médicaments

Photoacoustic detection in Fourier transform i.r. spectrometry has led to spectra obtained without sample preparation. This fact may be a very important advantage in biological applications, but these spectra are not directly in good agreement with transmission spectra. In the present work a simple mathematical correction treatment is presented which is in accord with the theory of the photoacoustic effect. This correction routine is applied to some drugs in view of a possible application to direct identification in pharmaceutical preparations.     

Ouverture régiosélective d'époxydes par Me3SiN3 catalysée par Ti[O.iPr]4

Ti[O-iPr]₄ catalyzes the ring opening reaction of functionnalized epoxides with Me₃SiN₃ in a highly regioselective manner.     

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.     

Analyse cytologique de l'expression d'un épitope porté par les glycoprotéines excrétées par Candida albicans

The present study concerns an epitope identified by a monoclonal IgM, named 5B2, generated against the parasitic phase of Candida albicans. The epitope was previously shown to be carried by excreted C. albicans glycoproteins and to be present in the sera of patients suffering from systemic candidiasis. The cytological analysis of the epitope expression was investigated in 3 different yeast strains: the C. albicans strain from which 5B2 was generated (VW.32); a C. albicans mutant, deficient in cell wall mannans (KD.102); and a Sacchromyces cerevisiae strain. Immunofluorescence assays using IgM-5B2 showed discontinoous labelling with the VW.32 strain and no labelling with the 2 other yeast strains; however, the superficial structures of the 3 strains reacted homogeneously with ConA. Ultrastructural immunodetection experiments performed with the VW.32 cells, using gold-conjugated monoclonal antibody, revealed the presence of the epitope in the vacuolo-vesicular system, the periphery of the cytoplasm, the periplasmic space and the cell wall. Under the same conditions, cells from the KD.102 strain only exhibited weak cytoplasmic labelling whereas the presence of the epitope in S. cerevisiae blastoconidia was restricted to the vesicles. Competition and double labelling experiments with IgM and ConA showed that the epitope, distributed on the great majority of VW.32 glycoproteins, is shared by a lesser proportion of the KD.102 glycoproteins and only by some vesicular glycoproteins of S. cerevisiae. Inhibition of the N-glycosylation process of the VW.32 strain by tunicamycin resulted in the absence of cytokinesis and germ tube formation. In such cells, epitope 5B2 was no longer expressed on the bud surface. These cytological results concerning the C. albicans epitope are discussed in relation to recent, more general biochemical data on the yeast glycosylation process.     

Analyse élémentaire organique par diffusion de l'hydrogéne á travers la silice et par carbonisation

Résumé En mettant á profit les découvertes des savants français du début de ce siécle sur la perméabilité de la silice fondue pour l'hydrogéne, l'oxygéne et l'azote, nous avons montré que le dosage á l'échelle ultramicro de l'hydrogéne, de l'oxygéne par voie directe, du carbone et du squelette oxydo-carboné d'une molécule d'un même échantillon de substance contenant carbone, hydrogéne et oxygéne, était possible, avec des moyens extrêmement modestes.

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Summary By taking advantage of the discoveries made at the beginning of this century by French scientists with respect to the permeability of fused silica to hydrogen, oxygen, and nitrogen, we have shown that the determination on the ultramicro scale of hydrogen, oxygen by the direct way, and of carbon and of the oxydo-carbonaceous skeleton of a molecule is possible employing the same sample of a substance containing carbon, hydrogen, and oxygen, and by means of extremely modest equipment.

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Zusammenfassung Die zu Beginn dieses Jahrhunderts von französischen Autoren entdeckte Durchlässigkeit von Quarzglas für Wasserstoff, Sauerstoff und Stickstoff bei hohen Temperaturen bietet die Grundlage zur direkten ultramikroanalytischen Bestimmung von Wasserstoff und Sauerstoff. In der gleichen Einwaage einer aus C, H und O bestehenden Substanz lassen sich mit einfachen Mitteln auch der Kohlenstoffgehalt und der von Wasserstoff befreite Rest des Moleküls bestimmen.

     

Dosage indirect du potassium par complexométrie

An indirect complexometric method for the determination of potassium is described Potassium is precipitated is perchlorate, which is reduced to chloride Silver chloride is treated with tetracyano nickelate, nickel being titrated chelatometrically     

Le dosage indirect du molybdéne par voie complexométrique

The classical method for the determination of molybdenum is long and requires special precautions. A. simple and speedy method is given for indirect determinations of molybdenum. The separation of molybdenum (in the form. of calcium, molybdate) is obtained by precipitation with calcium chloride. The precipitate is dissolved on adding hot 1 : 1 HCl. On evaporating the solution one obtains molybdenic acid and calcium chloride. In determining the calcium complexometrically one also determines indirectly the molybdenum. This method can be used for the ores and alloys of molybdenum.     

Étude par diffraction des rayons X,par résonance magnétique nucléaire 31P en phase solide et par spectrométrie infrarouge des hydroxyapatites mixtes cadmium–strontium

X-ray powder diffraction, solid-state ³¹P-MAS-NMR and IR spectroscopy of cadmium–strontium mixed hydroxyapatites. Strontium–cadmium hydroxyapatite solid solutions Cd_xSr_(10–x)(PO₄)₆(OH)₂ were prepared in aqueous medium. They were characterized by X-ray powder diffraction, ³¹P-MAS-NMR and IR spectroscopic analyses. The structural refinement, by X-ray powder pattern fitting (Rietveld method), indicates the limits of strontium–cadmium solid solutions (x≤4) and allows us to determine the cadmium repartition in the apatite cell. Through the progressive replacement of Sr²⁺ (r=1.32 Å) by the smaller cation Cd²⁺ (r=1.09 Å), all interatomic distances decrease according to the decrease of the cell parameters. However, contrary to what could be expected from the coordinance of the metallic sites S₁ (hexacoordination) and S₂ (heptacoordination) the small cadmium cation does not preferentially occupy the four sites S₁: it is almost statistically distributed over both sites, with a slight preference for S₂. The ³¹P- solid-state-NMR of the pure phases Sr₁₀(PO₄)₆(OH)₂ and Cd₁₀(PO₄)₆(OH)₂ reveals a moderate chemical shift anisotropy (≈20 ppm) corresponding to slight distortion of the phosphate tetrahedron. This observation holds also for the mixed species where the surrounding of the phosphate anion is expected to change significantly when substituting Cd for Sr. Through the progressive replacement of strontium by cadmium, the isotropic signal moves regularly to high frequency, according to the deshielding observed for Cd₁₀(PO₄)₆(OH)₂ (δ_iso=12.2 ppm) with respect to Sr₁₀(PO₄)₆(OH)₂ (δ_iso=2.9 ppm). Moreover the isotropic signal broadens considerably because of unresolved chemical shift distributions in the highly disordered material. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAShydroxyapatite / Rietveld refinement / ³¹P-MAS-NMR / cadmium / strontium / phosphate     

Dosage microgravimétrique et spectrophotométrique du calcium par la lorétine

Résumé Les auteurs ont élaboré une méthode semi-micro et micro-gravimétrique et une méthode spectrophotométrique pour le dosage du calcium par la lorétine. Après avoir établi le facteur analytique du lorétinate de calcium par voie gravimétrique et thermogravimétrique, ils ont démontré la possibilité de doser le calcium à l'échelle semi-micro gravimétrique pour des quantités allant de 5 mg à 50 mg, l'erreur moyenne étant de 0,35%. La méthode microgravimétrique permet de ramener la quantité minima à doser à 0,2 mg de calcium par ml, l'erreur moyenne étant de 0,45%. L'influence d'une série d'ions étrangers fut étudiée. La plupart ne gênent pas le dosage, même s'ils sont présents en quantités importantes. Par spectrophotométrie indirecte, notamment en redissolvant le lorétinate de calcium dans un excès d'une solution ferrique, les auteurs ont réussi à doser des quantités de calcium de l'ordre de 20g avec une erreur moyenne de 0,35%.

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Summary The authors have elaborated a method (semi-micro and micro-gravimetric) and also a spectrophotometric method for determining calcium by means of loretin. After establishing the analytical factor for calcium loretinate by the gravimetric and the thermogravimetric methods, they showed the possibility of determining calcium on the semimicro gravimetric scale for quantities ranging from 5 mg to 50 mg, the mean error being 0.35%. The microgravimetric method allows the minimum quantity to be determined to be reduced to 0.2 mg calcium per ml, the mean error being 0.45%. A study was made of the influence of a number of foreign ions. Most of them do not harm the determination, even though they are present in considerable amounts. By indirect spectrophotometry, notably by dissolving the calcium loretinate in an excess of ferric solution, the writers have succeeded in determining amounts of calcium of the order of 20g with a mean error of 0.35%.

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Zusammenfassung Die Verfasser haben eine semimikro- und eine mikrogravimetrische Methode und ein spektrophotometrisches Verfahren zur Bestimmung von Calcium mit Loretin (7-Jod-8-hydroxychinolin-5-sulfonsäure) ausgearbeitet. Nach Festlegung des Umrechnungsfaktors des Calciumloretinats auf gravimetrischem und thermogravimetrischem Wege wurde gezeigt, daß durch Semimikrogravimetrie Calciummengen von 5 bis 50 mg mit einem mittleren Fehler von 0,35% bestimmbar sind. Die mikrogravimetrische Methode eignet sieh für 0,2 mg Calcium/ml mit einem mittleren Fehler von 0,45%. Der Einfluß einer Reihe von Fremdionen wurde untersucht. Die meisten davon stören nicht, auch wenn sie in bedeutender Menge vorhanden sind. Durch indirekte Spektrophotometrie, nämlich durch Auflösen des Calciumloretinats in überschüssiger Eisen(III)lösung gelang es, Calciummengen in der Größenordnung von 20g mit einem mittleren Fehler von 0,35% zu bestimmen.

     

Modélisation numérique des milieux granulaires par l'approche du bipotentiel

A 2D numerical simulation of the contact dynamics is presented: moving rigid circular cylinders can run into themselves or into surrounding walls and are subjected to friction forces during these collisions. The interaction between cylinders is described by the unilateral contact law with Coulomb's friction. Using the contact bipotential leads to an algorithm of resolution based on a predictor-corrector scheme by projection on friction cone and a convergence criterion based on the estimator of relative error in constitutive law. The applications show the convergence and the robustness of the algorithm.     

La Micro-Détermination du Béryllium par la fluorimétrie du complexe Morin-Be

Résumé Les conditions optimales du microdosage du Béryllium par la réaction du Morin sont déterminées (spécialement l'influence de la concentration en alcool) de même que la formule du composé fluorescent: Be₃(Mor)₂.

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Summary The optimal conditions for the micro-determination of beryllium by Morin are determined, particularly the influence of alcohol. The fluorescent compound was found to have the composition Be₃(Mor)₂.

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Zusammenfassung Die optimalen Arbeitsbedingungen für die Mikrobestimmung von Beryllium als Morinat wurden unter besonderer Berücksichtigung des Einflusses der Alkoholkonzentration festgelegt. Die Zusammensetzung der fluoreszierenden Verbindung entspricht der Formel Be₃(Mor)₂.

     

Sémi-microdosage de quelques constituants du lait par séparation chromatographique

Résumé La complexité de l'état physique dans lequel se trouvent les constituants du lait à l'état naturel fait de leur séparation un problème difficilement soluble, surtout quand il s'agit d'analyser de petites quantités.Une séparation des constituants du lait est possible sur une colonne d'alumine hydratée.Le mécanisme de cette séparation réside dans un échange d'ions, résultant des propriétés conférées par la couche de graisse déposée sur le grain d'alumine hydraté.Le lactose, le premier constituant recueilli, passe par simple filtration indifféremment duh de l'alumine.Les protéides sont élués par une solution alcaline. Leh de l'alumine a une grande influence à la fois sur leur adsorption et sur leur élution. Une alumine acide retient la presque totalité des protéines, tandis qu'une alumine neutre ou légèrement alcaline en permet une élution facile.Dans les conditions de nos expériences l'alumine employée ne peut adsorber qu'une quantité déterminée de protéines. L'excès passe immédiatement dans le filtrat. Ainsi, l'on peut différencier deux fractions protéiques qui sont récoltées après le passage du lait dans la colonne: l'une dans le filtrat, quand la colonne est déjà saturée, l'autre dans l'éluat alcalin.Les phosphates minéraux sont élués par une solution acide; leur rétention n'est pas influencée par leh de la colonne.

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Summary The complexity of the physical state, in which the constituents of milk occur naturally, makes their separation a difficult problem, particularly when small quantities are to be analyzed. The constituents of milk can be separated on a column of hydrated alumina.The mechanism of this separation resides in an exchange of ions resulting from properties conferred by the layer of fat deposited on the grains of hydrated alumina.Lactose, the first constituent collected, passes through by simple filtration, indifferent to theh of the alumina.The proteins are eluted by means of an alkaline solution. Theh of the alumina has a large influence both on their adsorption and elution. An acidic alumina retains practically all of the proteins, whereas a neutral or slightly alkaline alumina makes their elution easy.Under the conditions of the author's experiments, the alumina employed could adsorb only a determinate quantity of proteins. The excess immediately passed into the filtrate. It is thus possible to differentiate two protein fractions, which are collected after the passage of the milk through the column: one in the filtrate, when the column is already saturated, the other in the alkaline eluate.The mineral phosphates are eluted by an acid solution; their retention is not influenced by theh of the column.

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Zusammenfassung Die verwickelten physikalischen Verhältnisse unter den Bestandteilen der Milch im natürlichen Zustand macht deren Trennung zu einem schwierigen Problem, besonders wenn es sich um die Analyse kleiner Mengen handelt. Diese Trennung wird durch Verwendung einer Säule von Aluminiumoxydhydrat ermöglicht. Der Trennungsmechanismus beruht auf einem Ionenaustausch zufolge jener Umstände, die sich aus der Bindung des Fettes an das gekörnte Adsorptionsmittel ergeben. Die Lactose, der zuerst erhältliche Bestandteil, passiert das Aluminiumoxyd unabhängig vomh. Die Proteide werden alkalisch eluiert. Dash des Aluminiumoxyds ist von großem Einfluß auf deren Adsorption und Elution. Saures Aluminiumoxyd hält das Eiweiß fast zur Gänze zurück, während neutrales oder schwach basisches Aluminiumoxyd die Elution erleichtert. Unter den von uns gewählten Versuchsbedingungen kann das verwendete Aluminiumoxyd nur eine bestimmte Menge der Eiweißkörper adsorbieren. Der Überschuß geht unmittelbar ins Filtrat. So lassen sich zwei Eiweißfraktionen unterscheiden, von denen sich die eine nach der Sättigung der Trennsäule im Filtrat, die andere im Eluat findet. Das anorganische Phosphat wird sauer eluiert; dessen Adsorption wird durch dash der Kolonne nicht beeinflußt.

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Avec 10 figures.     

La détermination indirecte du tungsténe dans les minerais par voie complexométrique

The determination of tungsten by gravimetric methods is time-consuming and requires special precautions. A simple and rapid method is described for the indirect determination of tungsten in minerals by means of complexometric titration.The separation of tungsten (in the form of sodium, tungstate) is obtained by precipitation of this soluble salt by means of calcium chloride. The precipitate of calcium tungstate is filtered and decomposed into calcium chloride and tungstic acid (insoluble) by treating with concentrated hydrochloric acid.The filtrate is made alkaline and serves for the titration with a 0.1M solution of Complexon III. One ml of this solution corresponds to 23.1867 mg of WO₃. This determination of Lungyten takes 3 to 4 hours.     

Étude du mécanisme de polymérisation de l'acide silicique par potentiométre

Ionization and solubility of silicic acid with variation of pH and concentration of silicic acid are studied by potentiometric measurements. Two characteristic points appear on titration plots: the first point occurs at pH = 3 with formation of the ionized silicic acid; the second at pH = 7 is interpreted as revealing monomeric species. Diverse species of ionized silicic acid are in sols between pH = 3 and 7; the sols contain the smallest species of polymer for pH < 6 and show an optimum of polymerization for pH ≥ 6.     

La détermination du vanadium par la méthode spectrophotométrique en solution non-aqueuse

On mixing small quantities of an aqueous solution of vanadium, containing hydrogen peroxide and acidified with HCl, with anhydrous dioxan containing gaseous hydrogen chloride in molar concentration, an intense red-yellow colour appears, in the presence of as little as 5 μg/ml vanadium.If a drop of salicylic aldehyde is added to the solution thus obtained, the colour changes to violet-blue, which shows an absorption maximum at 565 mμ, clearly visible even with 1 μg/ml vanadium.This reaction, though a sensitive method for the detection of vanadium, is not suitable for quantitative measurement of this substance because the small quantity of water introduced in the form of the vanadium solution hydrolyses the coloured compounds.Very good results can be obtained by dissolving the dry residue (at 100°C) of the solution under examination in 0.2 ml of N HCl in 2% aqueous H₂O₂ solution, and then in 5 ml of a solution made up of 40% acetic anhydride containing gaseous HCl (1 N), 40% glacial acetic acid, and 20% methyl Salicylate.By this method as little as 1 μg of vanadium can be determined.Co, Mo, and W, interfere; the other elements do not.