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.     

Étude sur le dosage colorimétrique de l'aluminium dans les aciers

Colorimetric determination of aluminium by means of a new reagent, stilbazo, is studied.The investigation leads to a method for the direct determination of aluminiumsteel alloys: nitrided steels, magnetic steels.The aluminium is determined by a technique consisting of electrolysis with mercury cathode, separation of titanium and vanadium, if present, by chloroform extraction of the complexes of these elements with cupferron, and, finally, colorimetric determination.During these experimental investigations, observations have been made concerning the influence of a number of elements on the reaction of aluminium with stilbazo. The reactions of vanadium with various reagents (dicyandiamidine, diantipyrylphenylmethane, a-benzoinoxime) and the silico-vanado-tungstic complex have been studied.     

Sur le dosage colorimétrique du fer

Sodium hypophosphite is proposed as a reducing agent for Fe⁺³ in the colorimetric determination of iron by a.a'-bipyridyl and by o-phenanthroline.     

Sur la réaction colorimétrique de l'aluminium avec la quinalizarine

The reaction between aluminium and quinalizarin has been studied, and some modifications have been made to the analytical procedure usually followed.The absorption curve of the Al-quinalizarin compound and that of quinalizarin alone have been drawn. We applied the continuous variations method in order to determine the structure and composition of the reaction product. The spectrophotometric readings have shown that the constituents of the coloured compound are bound in a definite ratio. 2:3.     

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.     

Dosage acidimétrique de l'ion aluminium

Acid titration of aluminium salts consists of two stages.1. Titration of the free acid. Complex ions are formed of aluminium with oxalatē of hydrofluorideions. 'I'he precipitation of aluminium hydroxide is retaided. Consequently the neutralisatiom of the free acid by the base is quite clear.2. Simultaneous titration of the acid and the aluminium ions. The solution with NaOH is neutralised until all the aluminium hydroxide is just precipitated. To avoid errors due to the formation of adsorption compounds, an excess of base is added and back-titrated with hydrochloric acid at the boiling point.These two titrations permit the determination of XXX acid and the aluminium content of the solution to approximately 0,3%.The influence of disturbing ions is studied.     

Sur le dosage colorimétrique du soufre libre

Résumé On fait une revue du dosage du soufre libre par échange du dissolvant en modifiant les conditions proposées précédemment pour obtenir une plus grande sensibilité. On essaie diverses solutions stabilisantes, mais on ne trouve pas d'améliorations notables.

---

Summary The determination of free sulfur has been reviewed. The conditions proposed previously have been modified by using other solvents in the hope of obtaining a greater sensitivity. Various stabilizing solutions have been tried but no notable improvement has been found.

---

Zusammenfassung Es wird über die Bestimmung von freiem Schwefel berichtet. Durch Wahl anderer Lösungsmittel und Veränderung früher vorgeschlagener Versuchsbedingungen wurde getrachtet, größere Empfindlichkeit zu erzielen. Verschiedene Lösungsmittel wurden zur Stabilisierung der kolloidalen Dispersion herangezogen, jedoch wurden keine bemerkenswerten Verbesserungen erreicht.

     

Dosage colorimétrique de l'uranium par le dibenzõylméthane

A colorimetric method for the determination of uranium by means of dibenzoylmcthane lias been studied and described.The complex is formed in aqueous pyridine in the presence of EDTA and tartaric acid; the optical density is measured at 415 mμ.Beer's Law applies; the sensitivity amounts to 0.005% uranium in the mineral.The method involves only one filtration and can be used in the presence of various impurities including Mo, W, V, Ge, Th, F and P.With a uranium content of more than 5% no single clement disturbs the determination. With a content of less than 0.5% the absolute error amounts to more than 0.01% only in the presence of 1% gold, 2% platinum or 10%, soluble strontium.The method described has been applied with completely satisfactory results to the analysis of pitchblende, antunite, thorianite, columbite, urano-thorianite, tantalite and carnotite containing from 0.05 to 25% uranium.     

Sur le dosage gravimétrique du sulfate de baryum en présence de fer

Résumé L'analyse par spectrographie infrarouge et par rayons X indique que le fer n'est pas combiné au sulfate de baryum précipité mais retenu fortement en quantités relativement faibles (1% au maximum), tout en colorant intensément le précipité. Il est très probable qu'il s'agisse d'une insertion sous forme d'oxyde à l'exclusion d'eau, d'oxhydriles et d'anions chlore.

---

Summary Analysis by infrared spectrography and byx-rays indicates that iron is not combined with precipitated barium sulfate but is held firmly in relatively small amounts (1% maximum), though strongly coloring the precipitate. It is very likely that this involves entrance in the form of anhydrons oxide, hydrated oxide and chlorine anions.

---

Zusammenfassung Infrarot- und röntgenspektrographische Analysen ergaben, daß Eisen mit Bariumsulfat bei dessen Fällung keine Verbindung bildet, daß aber relativ geringe Mengen (maximal 1%) sehr hartnäckig festgehalten werden. Dadurch wird der Niederschlag intensiv gefärbt. Wahrscheinlich handelt es sich um Einschlüsse des Eisens in Form des wasserfreien Oxyds und des Oxydhydrats und der Chlorionen.

     

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     

Méthode continue pour le dosage de l'acide carbonique en faibles concentrations

Low concentrations of carbon dioxide in gases can be determined by leading the gas over circulating water and measuring the conductivity.The method can be extended to the determination of the carbonic acid content of water by means of another closed circuit, of air, which is blown through the water sample.Concentrations of the order of 0.0001% in inert gases and 1 p.p.b. in water can be determined with reasonable accuracy.     

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.     

Étude et dosage polarographique de la di-dnp-histidine dosage de l'histidine

The di-DNP-histidine has been prepared, and studied polarographically.A standardization curve has been composed by means of which it is possible to estimate 1 γ of di-DNP-histidine in 1 ml.A method of estimating the histidine lias been established. It is allowed to react with an excess of DNFB. The excess is removed by extracting twice with ether. One can then determine polarographically the excess of DNFB, 01 the di-DNP-histidine formed, By this method up to 10 γ histidine can be determined.The error lies between 0.5 and 10% according to quantity.     

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.     

Dosage colorimétrique de faibles quantités de cérium dans l'uranium

After extraction of the iron and uranium thiocyanates by ethyl acetate, the solution is oxidised by ammonium persulphate (in the presence of silver nitrate). The absorption of this solution is measured at 360 mμ by comparison with that of an aliquot previously reduced with oxalic acid, which selectively reduces cerium and manganese to the low valences. The absorption of manganese is deduced from a measurement at 525 mμ. By this method I to 5γ/ml cerium can be determined with an error of less than 15%.     

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.     

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.     

Sur le dosage de chlorure en présence d'hypochlorite,chlorite et chlorate alcalins

A method has been developed for determining the chloride anion with silver nitrate in presence of the hypochlorite, chlorite and chlorate anions.The chlorate anion does not interfere with the determination. In the presence of chlorite anions the figures for Cl' are too low in acid media.The hypochlorite anion should be reduced to the Cl' anion by PENOT'S solution.