Étude des spectres vibrationnels des cyclotétraphosphates

The analysis of the infrared and Raman spectra of a number of cyclotetraphosphates shows that it is possible to characterize the cyclic anion P₄O⁴⁻₁₂. The number, positions and shapes of the infrared absorption bands observed in the symmetric stretching region provide an indication of the symmetry of the P₄O⁴⁻₁₂ ring in each compound.     

Étude critique des réactions des cations : Nickel

The authors have tried out the spot tests suggested for the cation nickel between 1937 and 1947. After a critical examination they recommend following the details of the second Report as drawn up by WENGER AND DUCKERT, in particular the use of the dioxime of 1:2-cyclohexanedione, known commercially under the name nioxime.     

Étude critique des réactions des cations : Cobalt

The authors have critically examined the reactions proposed for cobalt between 1937 and 1947. Their findings are in agreement with the conclusions, of the second Report (wenger and duckert). However, the reaction with potassium cyanate can be replaced by the closely similar test, using sodium thosulpliate, a more accessible reagent, there is no interference; from copper, iron and nickel.     

Étude critique des réactions des cations : Uranium

A critical examination has been made of all drop reactions proposed for uranium during the period 1937–1917. In view of the preparation of the fourth Report, it is proposed to retain only the micro-chemical reaction given by an alkaline thiocyanate and sparteine, even in presence of a large excess of iron.     

Étude ultrasonore de mélanges de polymères

Ultrasonic experiments have been performed on polyethylene/polystyrene blends of various compositions. Attenuation and velocity measurements were performed on samples made either by injection moulding or by compression. Attenuation varies through the same sample and variations are greater for compressed plates than for moulded plates. Velocities are of the same order of magnitude for both types of samples.     

Étude des Interactions du Zinc et de l'Or dans l'Étain Liquide

Abstract

Les auteurs ont étudié par voie électroehimique l'influence de faibles additions d'or sur les propriétés thermodynamiques du zinc en solution diluée dans l'étain fondu. Le paramètre d'interaction de Wagner ?_Zn ^Au et sa variation avec la température ont été déterminés dans l'intervalle de température 420–650°C: ?_Zn ^Au = 2.71 – 5.92. 10³/T.     

Étude critique des réactions des cations : Rhénium

For the reactions proposed for rhenium, the author is in agreement with the conclusions of the “Second Report” (wenger AND duckErt) with one exception, the microchemical test with pyridine seems preferable to that using acridine.     

Étude des effets de frottement sur la dynamique des ondes de densité de charge dans les systèmes unidimensionnels

In this work, we present the numerical simulation results of the dynamics of charge density waves in one-dimensional systems. With a classical model, we show that the threshold field depends on the friction coefficient of the system. From the threshold field variation versus impurities concentration, we show the existence of three different pinning regimes and we prove that the pinning regime in witch E_c ∝ n_i^4/3 is an intermediate regime between the weak pinning and the strong pinning one, in the sense of Fukuyama, Lee, Rice. We show also that the transition from one pinning regime to the other is continuous.     

Étude de la distribution des ions sur colonnes échangeuses

Résumé L'auteur étudie la distribution de divers ions seuls ou mélangés sur une résine cationique, par voie semimicro-analytique.

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Summary A column constructed from eight sacks filled with ion exchangers was used to study the distribution of metal ions of various valency from pure solutions or mixtures. If the chlorides of the metals are used in all cases, sodium and ammonium are retained in the first two sacks; magnesium and zinc in all sacks, especially in the first and sixth; iron and aluminium in all, particularly the first and sixth; nickel and cadmium in the first two, particularly the first; thorium in the first sack. These findings, which are independent of the atomic weight and valency, are possibly related to the formation of solvates and their various stabilities.

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Zusammenfassung Mit Hilfe einer Säule, die aus acht mit einem Ionenaustauscher gefüllten Säckchen bestand, wurde die Verteilung von Metallionen verschiedener Wertigkeit aus reinen Lösungen oder Gemischen untersucht. Verwendet man stets Chloride der betreffenden Metalle, so werden Natrium und Ammonium in den beiden ersten Säckchen, Magnesium und Zink in allen Säckchen, insbesondere im ersten und sechsten, Nickel und Cadmium in den beiden ersten, insbesondere im ersten, Eisen und Aluminium in allen, insbesondere im ersten und sechsten, Thorium im ersten Säckchen zurückgehalten. Diese von Atomgewicht und Wertigkeit unabhängigen Ergebnisse stehen möglicherweise mit der Bildung von Solvaten und deren verschiedener Stabilität im Zusammenhang.

     

Étude des propriétés viscoélastiques de quelques polyfluorure de vinylidène fondus

The rheological behaviour of molten poly(vinylidene fluoride) was studied in steady flow and dynamic flow. An attempt was made to correlate the experimental results with extrudability.     

Échelles caractéristiques des domaines tourbillonnaires apparaissant près des irrégularités des frontières

The possibility of the formation of a vortex domain of finite size near complex boundaries is analysed. For the proposed model, when such a scenario is attainable, the curve configuration delimiting the non-zero vorticity domain is found. This curve represents an approximate solution of an integral-differential equation obtained using the proposed model. It is shown that the vorticity level is a function of the characteristic dimension of the vortex domain, which depends on the size of the obstacle and is a homogeneous function of the Reynolds number.     

Étude expérimentale de l'instabilité du sillage d'une sphère

The transition from steady to periodic flow in the wake of a sphere is studied in the Reynolds number range [150, 400]. The vortex shedding frequency as well as variation of amplitude and phase of oscillation have been measured.     

Étude analytique de la viscosité turbulente à l'aide du modèle K-L

From the K-L turbulence model proposed by Lewellen [1], an analytical expression of turbulence macroscale is established. This expression, obtained with the hypothesis of a null horizontal pressure gradient, can be used for inertial or Couette flow. This formulation is better than the classical linear expression and, moreover, this analytical computation and numerical computations are in a good agreement.     

Structure Cristalline de L'Éthylènediammonium HydroxyÉthylidènebisphosphonate

The organic complex salt [H 3 N--CH 2 --CH 2 --NH 3 ][C(CH 3 )(OH)(PO 3 H 2 )(PO 3 H)] 2 is obtained by reaction between the hydroxyethylidenebisphosphonic acid (HEBP) and the ethylenediamine (EDA) in aqueous medium. This compound, the first where the cation is an organic base, crystallizes with the monoclinic space group P2 1 / c (n°;14) and a = 6.867(1) Å, b = 11.665(2) Å, c = 10.977(2) Å, g = 101.85(4)°;, V = 861.2(2) Å 3 , Z = 2. The cohesion of the crystal structure is assumed exclusively by a dense network of hydrogen bonds between two HEDP m and between one HEDP m and one EDA 2+ .     

Étude mécanistique et structurale des résines R/F

The follow-up of the advance of the reaction of polymerization of resorcinol with formaldehyde in acid or basic medium by NMR shows that the structure of the obtained xerogel in both cases is the same one. Indeed, the junction between the aromatic nuclei is of type OCH₂OCH₂. While basing itself on the structure of the xerogel, we propose the mechanism for the polymerization reaction between resorcinol and formaldehyde.     

Étude de la rétention des sels monovalents et bivalents par nanofiltration

Study of the retention of monovalent and bivalent salts by nanofiltration. The objective of this work was to study the influence of applied pressure, solution concentration and conversion rate on the salts retention by nanofiltration. Our study showed that the bivalent ions SO₄^2– are better retained than the monovalent ions F^–, Cl^– and I^– by nanofiltration. We also observed that the small ions F^– and Mg²⁺ are better retained than the big ions Cl^–, Ca²⁺, and I^– by effect of solvation. In spite of the bigger size of ion Ba²⁺ compared to Ca²⁺, Ba²⁺ is better retained than Ca²⁺; this is due to the effect of pressure. We also noticed that the increase of the (NH₄)₂SO₄ concentration and of the conversion rate leads to a decrease in the retention of SO₄^2–. To cite this article: A. Abouzaid et al., C. R. Chimie 6 (2003).     

Étude thermodynamique du système compatible polyfluorure de vinylidène-polyméthacrylate d'éthyle par chromatographie gaz-liquide

The thermodynamics of interaction between poly(ethyl methacrylate) and poly(vinylidene fluoride) have been studied by gas-liquid chromatography on their homogeneous blends (40 < PVDF < 80% by weight) in the liquid state (t > 140°C) using a variety of probes covering a wide range of polarity and of affinity for the polymers. The average and most representative interaction parameter χ₂₃′ (Flory-Huggins) is estimated as −0.32 ± 0.09, showing only slight sensitivity to temperature between 160 and 200°C and composition of the blend. The purely interactional χ₂₃ parameter (Prigogine-Flory-Patterson) is strongly negative (χ₂₃ = −6.5 J/cm³) as a result of dipolar and hydrogen bond interactions between the polymers.     

Introduction a l'étude des sels basiques insolubles: Étude des courbes de précipitation des sels basiques insolubles. Produits de solubilité des sels basiques et des hydroxydes

A critical study of curves of precipitation of basic salts by alkali hydroxides shows that the irregularities observed on these curves do not always permit the deduction of the constitution of the salt. They indicate nevertheless the appearance of a new phase and this observation explains, in particular, the important number of wrongly defined basic salts which have been observed.The theory of the titre curves leads to the proposal of formulas permitting the calculation of solubility products of basic salts and even those of hydroxides which were determined very accurately by other methods.