Oxydation électrochimique de l'ion thiocyanique. Application aux dosages et ä l'étude des réactions

The author has examined the rate of reaction of the system thiocyan ate/sulphate and cyanide, by means of the current/anode potential curves obtained during the electrolytic oxidation of thiocyanate in an acid medium.Corresponding with the minimum current detectable under our experimental conditions, we find a potential which agrees well with that determined by a classical potentiométrie method, and checked chemically. Consequently, it can be used to predict the chemical reactions taking place.From these curves, the relation between the anodic potential, the intensity of the electrolytic current, and the activity of the SCN^- ions has been deduced. These methods have been applied in a new method of investigating reactions in solution, viz. the potentiometry at constant current other than zero.     

Contribution á l'étude de la séparation des terres rares de fission par l'acide éthylènediaminetétraacétique

In the present paper, the authors investigate the conditions for a rapid and if possible analytical separation of a mixture Y-Eu-Pm-Ce for quantities of a few milligrams.Elution curves are given in function of the pH, which is the main influencing factor.A separation at pH 3.05 gives the best results.     

Séparation niobium-tantale contribution à l'étude de l'électrophorése sur papier

A study has been made of the separation of Nb and Ta on a micro-scale by paper electrophoresis, using oxalic and citric complexes and different buffer solutions.A fairly good separation is obtained by using oxalic complexes and, as buffer solution, a mixture of citric acid and potassium citrate of pH 3.42 and ionic strength 0.4.Different factors influencing the displacement of ions by paper electrophorcsis have been examined. It is shown that, if saturation currents are minimized, the displacement is practically proportional to the time of electrophoresis, and more difficult separations become possible using longer strips.     

Contribution à l'étude des émissions radioélectriques aurorales de Jupiter

We study the radioelectric emissions of Jupiter in the frequency range 1–40 MHz with the decametric observatory of Nançay and the Wind spacecraft. A wake in front of Io explains the Φ_Io/CML chart. An appropriate coordinate system shows that the Ioontrolled emissions occur mainly when Io is located in the northern magnetic hemisphere of Jupiter.     

Étude comparée de quelques méthodes de dosage de l'acide salicylique dans le sérum sanguin

If one deproteinises blood serum by sodium tungstate and sulphuric acid, the excess tungstate impedes the formation of the colourless complex of salicylic acid with the iron. The intervening reactions are not yet well understood. One can use this method if a sufficient concentration of iron is present to eliminate all the tungstate; but the method then becomes slow and delicate. It is shown finally that the most satisfactory method consists of extracting the salicylic acid by dichlorethylene and then bringing it again into aqueous solution by means of a ferric solution.     

Prévision des courbes de dosages potentiométriques

The knowledge of polarisation curves can be used to explain the facts observed in the neighbourhood of the equivalent point in the course of potentiometric determinations as well as the anomalies presented by certain determination curves.It is also possible to interpret the role of a “potential mediator” during the determinations of oxido-reduction potentials.     

Application de la chromatographie sur échangeur d'ions a l'étude de la composition des aliments en acides amines

A detailed procedure is presented for the determination of the amino acid composition of foods by chromatography of the hydrolysates on columns of Dowex-50 by the method of Moore and Stein. Nearly all of the common amino acids can be determined. The measurement of methionine, however, is complicated by partial oxidation of the amino acid to the sulfoxide during acid hydrolysis. A satisfactory chromatographic method for tryptophan has not been obtained as yet. Cross-reference is given to the auxiliary development of a Chromatographic method for the determination of cystine (in the presence of carbohydrate) as cysteic acid and to the utilization of these combined techniques in the analysis of several foods of importance in human and animal nutrition.     

Contribution au microdosage titrimétrique de l'iode organique

Simultaneous microdetermination of carbon, hdrogen and iodine in organic substances is practically possible on a five milligramme sample. The two first mentioned elements are gravimetrically deetermined, iodine being titrated. The available results are quite good.New calibration technique of capillary instruments enables precise titration of very small quantities of Iodine. It will help to improve precision of this determination.     

Détermination de l'ion chlorhydrique dans de l'eau condensée

The titration of chloride with Hg⁺² according to CLARKE allows the determination of lower concentrations as was possible according to MOHR. The greater sharpness of the endpoint at lower concentrations and the use of a more dilute Hg+2 solution permit a further lowering of the concentration limit down to 0.05 mg Cl^-/l, when using a calibration curve, the remarkable form of which perhaps may be attributed to the formation of HgCl₂.2HgO. This sensibility allows a suitable chloride determination in boiler condensates and the wetness determination of steam.     

Analyse des alliages légersá base d'aluminium par les méthodes spectrophotométriques II

Colorimetric methods of analysis of light alloys of aluminium have been examined by the spectrophotometric method.In particular, four methods of determination of iron have been studied. The method which makes use of sulphophenyl pyrazolone carboxylic acid is recommended; the accuracy is of the same order as that of the phenanthroline method; the reagent is a much used product and is less expensive than phenanthroline.Simple and rapid methods are proposed for the determination of chromium, cobalt and titanium, and studies have been made leading to relatively new and original techniques for bismuth, tin and zirconium.     

Application de la diphényl-acroléine à l'analyse fonctionnelle

In highly acid alcoholic medium, diphenyl-acrolein develops a red colour with m-diphenols, in the cold. This reaction, which makes it possible to carry out determinations, has a sensitivity of one μg. Under the same conditions, yellow colouring is obtained with methylenes in the α position of a carboxyl or with primary aromatic amino groups. Various condensation products have been isolated.     

Dosage complexométrique de bromures et d'iodures en présence l'un de l'autre

Bromides and iodides are determined simultaneously by precipitation as silver halide In another aliquot, silver halides are oxidized, bromine being liberated, the iodate formed is then reduced to iodide which precipitates. The silver precipitates are treated with ammoniacal tetracyano nickelate and displaced nickel is determined complexometrically Bromide is determined by difference     

Généralisation de la méthode d'analyse de thorpe et application au dosage de l'isomère y dans l'hexachlorcyclohexane technique

The author presents a generalization of THORPE'S method for the analysis of complex mixtures and describes an application of it to the determination of the γ-isomer in technical hexachlorcyclohexane. This method has the advantage of not requiring expensive apparatus.Portions of the materials under examination are treated with CH₃OH at 20° C in such a way as to obtain, on the one hand, a solution saturated with regard to the (α + β ) isomers and, on the other hand, a solution saturated with regard to the (α + β + γ) isomers. Having determined tlie amounts of the products dissolved inthese solutions, the solubilities in CH₃OH enable the contents of the (α + β) and the γ-isomers to be calculated.     

Nouvelle méthode de mesure électrotitrimétrique1,2

The new method that we propose permits direct measurments of the speed of evolulion dE/de of an electromotive force.The application of this technique to electrometric titratons allows us to detect directly and accurately a great number of potentiometric, conductometric,and even amperometric titrations.     

Contribution à l'étude du mécanisme de mûrissement de résines polyesters insaturées en présence de MgO

The thickening process for unsaturated polyester resin in styrene monomer and with magnesium oxide (MgO) has been evaluated by gel permeation chromatography (GPC). The GPC analysis n tetrahydrofuran (THF) shows that with time the distribution shifts towards higher molecular weight. This effect disappears when the products are analysed in a polar solvent. The process of thickening is attributed to the formation of reversible ionic association. The existence of strong ionic bonds in the final products is confirmed by the presence of a rubber-like plateau in dynamic mechanical properties. The effects of water and magnesium oxide concentrations are given.     

Sur le dosage colorimétrique de l'antimoine au violet de méthyle

The oxidation technique using ceric sulphate and methyl violet as colouring reagent is very suitable for the détermination of antimony, but it is necessary to use benzene and not amyl acetate as extraction medium, since the latter tends to extract the coloration itself.     

Principes de l'iodimétrie absorptiométrique

A general method for the determination of oxidising or reducing agents has been investigated It is based on the measurement of the absorption of the spectrum of the 1₃^- complex Oxidizing agents may be determined by thu oxidation of iodide into I₃^-, reducing agents by reduction of I₃^-For a right application of this method one must have (a) all the iodine present in the state of 1₃^-, (b) the iodine produced by autoxidation of the iodide ion in negligible quantity Theconstants of the chief equilibria in which 13- is involved (equilibrium with I₂,I_2Br-,I₂Cl^-, IOH) and the kinetics of the autoxidation of the iodide ion in the presence and the absence of the catalyst Cu⁺² have been reinvestigated The acquned information enabled us to determine the general conditions of Applicability of this method and the realization of special analyses, The limit of detection by this method is 2.10^-7 gram equivalent of oxidizing or reducing agent per liter when absorptions are measured through a 5 cm layer.