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.     

Sur les réactions des ions du plutonium avec l'acide éthylénediaminotétracétique

The behavior of plutonium ions in a solution of trilon B was investigate At pH 3–5 plutonmin(VI) is reduced to plutonium(V) and a (I I) complex of plutonium(V) and trilon B is formed Withi excess trilon B a plutonium(lV ) -trilon B complex is formed after some time     

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 argentométrique de l'anion phosphorique

1. In aqueous solutions of phosphoric acid or alcali phosphates, the PO₄^-3can be determined by potentiometric titraition with silver nitrate PO₄^-3 + 3 Ag⁺ ár unAg₃PO₄↓The pH value of the solution is maintained about 9 by using borax-buffer 2 The determination of phosphate ion is also possible by precipitation of Ag₃PO₄ with an excess of silver nitrate, the pH of the solution is adjusted between 7 and 8 by using a new buffer mixture containing NH₄⁺, NHXXX, and Ag⁺. After diluting the solution up to a known volume and filtering through dry filter paper, the excess of silver is determined by potentiometric titration with potassium bromide. This method gives very good results, it is applicable in the presence of Mg⁺² and Ca⁺². The presence of Fe⁺³ and Al⁺³ hinders the determination of the phosphate ion. 3. The properties of the ,,ammonium-silverdiamme” buffer system are described. This buffer contains NH₄⁺, NH₃ and Ag⁺ (the latter in excess with regard to NH₃)     

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.     

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.     

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.     

Séparation de traces de fluorure des sels d'aluminium(III) par échangeurs d'ions

A method is proposed for the separation of aluminium(III) fluoride by chromatographie by means of an anion exchanger in alkaline medium, The methode is applicable to a minimum of 100 p.p.m. of fluoride in the aluminium.     

La séparation du scandium,du lanthane et de l'yttrium

The behaviour of scandium on a resin column has been studied and an efficient separation of scandium, lanthanum and yttrium has been effected using citric acid at different pH's. The hysteresis phenomenon which accompanies the adsorption of scandium and its importance for calculations, based on the theory of levels, are discussed.     

Étude de la formation du complexe silicomolybdique application au dosage du silicium dans l'aluminium

The authors have examined the application of the reaction in which the yellow silicomolybdate complex is formed to the estimation of silicon.Among other things, it was established that the development of the complex is complete and rapid in the cold between pH 4.0 and pH 1.0.The rate of formation of the complex decreases rapidly above this pH but can, to a certain extent, be compensated by raising the temperature and the concentration of molybdate.The Lambert-Beer law is followed between 3650 and 5000 A only when the light is strictly monochromatic. At wave-lengths longer than 4000 A and at pH below 3, a supplementary absorption appears which is without doubt due to a chemical transformation of the molybdate in acid solution.     

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     

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.     

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 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.     

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.     

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.     

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.     

La détermination rapide du calcium et du magnésium dans l'eau de mer

A rapid method is described for the determination of calcium and magnesium in sea. water. The classical gravimetric methods are very lengthy and are susceptible to errors if used for sea-water. The two alkaline earths are determined by complexometric titration using complexen III (disodium ethylenediaminetetra-acetate) as reagent and two indicators (murexide and ériochrome black T) for the determination of calcium and for the sum of Ca⁺² and Mg⁺² ions. The quantity of magnesium is obtained by difference. While the classical gravimetric methods take at least 24 hours, these two determinations can be effected in 1 hour, giving satisfactory accuracy.     

Contribution à l'étude des méthodes de dosages électrotitrimétriques

The author establishes a general equation for the polarisation curve of an oxidation-reduction system taking into account the kinetics of reactions and concentration polarisation, and shows how it can be applied to the interpretation of titration curves obtained by the dead-stop end-point method of Foulk and Bawden and by the derivative method of Reilley, Cooke and Furman.