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.     

Nitration et dosage de la phénylalanine

This paper comprises a study of the conditions for nitrating phenylalanine and an investigation of the compounds obtained, polarographic and chromatographic methods being employed. At the same time some nitrobenzoic acids that are found among the nitration products of nitrophenylalanine were examined by both these methods.A method has been proposed for the polarographic determination of phenylalanine, by means of which as little as 30γ of this substance can be detected in 10 ml solution. With concentrations between 2.4.10^-4M and 6.10^-3Mt, the error is less than 2.5%, with those of the order of 2.10^-5M it approaches 12%.     

Separation et dosage de traces de bore dans le silicium : Nouvelle méthode de séparation et de dosage de traces de bore. application au dosage du bore dans le silicium

A new method is described for the separation and determination of traces of boron by extraction of methylene blue fluoroborate by dichlorethane The method has been applied to the determination of traces of boron in silicon and silica     

Nouvelle méthode de dosage colorimétrique d'une très petite quantité de vanadium à l'aide de la formaldoxime

Résumé Là s'achève notre étude sur la coloration de vanadium quadrivalent avec la formaldoxime, et son application à l'analyse chimique. Cette coloration est la plus sensible parmi les réactions colorées de vanadium connues jusqu'à présent.L'influence de l'excès du réactif et de la température ainsi que celle de diverses substances ont été étudiées. On peut sans inconvénients, réduire la quantité d'échantillon, le réactif employé étant d'une très grande sensibilité.

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Summary This completes our study of the coloration produced by quadrivalent vanadium with formaldoxime and its application in analytical chemistry. This color reaction is the most sensitive among those of vanadium discovered hitherto. The influence of the excess of the reagent, of the temperature, as well as that of various substances have been investigated. Since the reagent is so very sensitive, there is no disadvantage in reducing the size of the sample.

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Zusammenfassung Die Farbreaktion von Vanadium (IV) mit Formaldoxim und ihre analytische Anwendung wurden untersucht. Sie ist unter den bisher bekannten Farbreaktionen des Vanadiums die empfindlichste. Der durch einen Überschuß an Reagens, durch die Temperatur und durch verschiedene Substanzen auf die Reaktion ausgeübte Einfluß wurde geprüft. Infolge der großen Empfindlichkeit des verwendeten Reagens läßt sich die Probemenge ohne Nachteil sehr gering halten.

     

Méthode pratique de dosage ampèrométrique du manganèse

A practical method is described .for thu determination of manganese by ampcrometnc titration.The Mn⁺² ion is oxidized quantitatively into Mn⁺³ (complex formation) by titration with permanganate in approximately neutral pyrophosphate solution. We have found that the end point of this Litration appears both very clearly and accurately by using a most simple electiometric device. A. platinum and a silver wire dipping in the solution are connected directly to a pointer galvanometer. The so revealed current remains very low during the titration and suddenly increases at the equivalence point.Tins titration can be effected quickly. The growing instability of the pointer usefully warns of approaching end point. There is practically no interference from foreign ions and theercfore the method can be applied widely and easily.     

Detection et dosage de trés petites quantités d'eau par la metéhode hygrophotographique

Some applications of a method called “hygrophotography” for the detection and determination of water are described. The method is suitable for the determination of small quantities of water in organic solvents, plants, soil samples, etc     

Méthode de dosage du nickel métallique en présence de composés oxydés de nickel dans des matières complexes (minerals)

During investigations on the behaviour of metallic nickel in HgCl₂-, KCN- and HCl-containing media, it was noticed in certain cases that nickel metal dissolution was achieved, while a mixture of nickel oxides remained absolutely unaltered.The working conditions were determined, and on the basis of the results obtained two methods have been developed for the determination of metallic nickel in the presence of nickel oxides in complex materials, including ores.These methods are described, in detail and the results of the experiments are given: they show that an accuracy of about 5 % can be obtained.     

Application de la chélatométrie au dosage des esters et chlorures de mono-esters oxaliques

Esters and chlorides of oxalic mono-esters can be estimated volumetrically. After saponification precipitation is carried out by means of a calcium chloride solution, the excess of which is measured by chelatometry.     

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.     

Identification spécifique des acides aminés et des vitamines par l'indice de réfraction et la température eutectique: Application a la chromatographie sur papier et au contrôle

Refractive index and eutectic melting temperature of binary systems, together lead to specific identification of organic individuals and isomers. A number of vitamins and amino acids have been experimented with to that purpose. The result is that analysis of an entire spot of amino acids on paper becomes easy owing to these properties. An example using glumatic acids shows that better results on the composition of an entire spot on paper can be obtained by this analysis than by Chromatographie R_F values.     

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.     

Un réactif spécifique du germanium: la phénylfluorone

Based on the action of methyl fluorone on Ge(IV) the use of this reagent for the detection of germanium is described. It is necessary to treat with 6N HCl to make this reaction specific.However, another derivative of fluorone, namely phenyl fluorone, is still better for identifying Ge(IV). By placing a drop of the solution under test, previously strongly acidified (3 N to 6N in HCl), on a phenyl fluorone reagent paper and adding 2 or 3 drops of 6 N HNO₃, a. sensitive and specific reaction for germanium is obtained.The only interfering ions are those of strong oxidising agents (Ce⁺⁴, Cr⁺⁶, Mn⁺⁷, etc.) which destroy the reagents and must be eliminated in the first place.Other ions and ions of the group of the sulphides soluble in alkalisulfides do not interfere, even in the proportion of 100 parts by weight, to 1 of Ge. The limit of dilution is about 10^-5.5.     

Le microdosage de l'azote amidé etα aminé par la méthode aux acides chlorhydrique et nitrique concentrés

Résumé L'étude de la réaction du mélange acides chlorhydrique et nitrique concentrés sur les acides-monoaminés monocarboxylés a montré que celle-ci s'effectue d'après le schéma: R-CHNH₂-COOH + HCl + HNO₃ = R-CHCl-COOH + N₂O + 2 H₂O.L'étude quantitative de cette réaction a, en particulier, montré que le volume de gaz recueilli correspond rigoureusement à l'azote aminé de la molécule. Cette constatation nous a permis, lorsque la molécule n'est pas susceptible de donner des réactions secondaires avec l'acide nitrique, de développer à l'échelle micro une méthode simple et précise de dosage de l'azote aminé des acides-aminés et des acides-aminosulfonique ainsi que de l'azote amidé des amides et des sulfonamides.

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Summary The study of the reaction of a mixture of concentrated hydrochloric acid and nitric acid on the mono-carboxylated monamines has shown that it proceeds: R—CHNH₂—COOH + HCl + HNO₃ = R—CHCl—COOH + N₂O + 2 H₂O.The quantitative study of this reaction has proved, in particular, that the volume of gas collected corresponds rigorously to the amine nitrogen of the molecule. This finding has made it possible for the authors, provided the molecule is not susceptible to yielding secondary reactions with nitric acid, to develop on the microscale, a simple and precise method of determining the amine nitrogen of amino acids and aminosulfonic acids, as well as the amide nitrogen of amides and sulfonamides.

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Zusammenfassung Das Studium der Umsetzung eines Gemisches von konzentrierter Salzsäure und Salpetersäure mit-Monoaminomonocarbonsäuren ergab die Erkenntnis folgenden Reaktionsablaufes: R—CHNH₂—COOH + HCl + HNO₃ = R—CHCl—COOH + N₂O + 2 H₂O. Die quantitative Untersuchung dieser Reaktion ergab im besonderen, daß das erhaltene Gasvolumen dem vorhandenen Aminostickstoff genau entspricht. Sofern die Substanz keiner Sekundärreaktion mit Salpetersäure unterliegt, ermöglichte diese Feststellung die Ausarbeitung einer einfachen und genauen Mikrobestimmung des Aminostickstoffes in-Aminosäuren und-Aminosulfonsäuren und ebenfalls des Amidostickstoffes in Amiden und Sulfonamiden.

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Actuellement chargé de cours à l'Institut Agronomique de l'Etat à Gembloux.

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Avec 1 figure.     

Calcul de chiralité quantitative par la méthode des moindres carrés

It is shown how the root mean square chiral index is computed without enumerating all the permutations of a set of n atoms. As an example, the quantitative measure of chirality is achieved for various helicene derivatives. It is also shown that the chiral index of a protein backbone is computable without enumeration.     

Une nouvelle méthode de dosage colorimétrique de l'oxygène dissous dans l'eau

Résumé Nous avons présenté une nouvelle méthode de dosage colorimétrique de l'oxygène dissous dans l'eau. Cette méthode est basée sur la réaction de la solution décolorée de manganèse-formaldoxime. La réduction de la solution du dérivé manganique de la formaldoxime est exécutée avec succès à l'aide de la poudre de zinc. Les appareils peuvent être construits facilement et tous les réactifs nécessaires sont d'usage courant. La coloration est stable et les matières comme nitrate, nitrite, fer ferreux, matières organiques etc. ne font pas obstacle dans cette méthode.

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Summary A new method is given for the determination of oxygen dissolved in water. This colorimetric method uses the decolorized solution of manganeseformaldoxime. The reduction of the solution of the manganic derivative of formaldoxime is successfully accomplished by means of zinc powder. The apparatus is easily constructed and all the needed reagents are readily available. The color is stable and no interference arises because of the presence of such materials as nitrate, nitrite, iron (II), organic matter, etc.

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Zusammenfassung Eine neue Methode der kolorimetrischen Bestimmung von in Wasser gelöstem Sauerstoff wird angegeben. Sie beruht auf der Reaktion einer entfärbten Lösung von Mangan(I)-Formaldoxim mit Sauerstoff. Die Reduktion einer Mangan(II)-Formaldoxim-Lösung läßt sich mit Hilfe von Zinkpulver gut durchführen. Der dazu nötige Apparat ist leicht herstellbar, die dazu erforderlichen Reagenzien von üblicher Qualität. Die bei der Reaktion entstehende Färbung ist stabil. Nitrat, Nitrit, zweiwertiges Eisen, organische Substanzen usw. stören die Methode nicht.

     

Application de la chélatométrie au dosage du fluor dans les composés organiques

Fluorine bound in organic matter can be determined volumetrically, after decomposition with sodium peroxide, by precipitation by means of a calcium chloride solution, the excess of which is measured chelatometncally     

Sur une nouvelle méthode de dosage gravimétrique du tungstène

Résumé Cette étude nous a conduit, d'une part à mettre au point un procédé de dosage du tungstène sous forme de tungstate purpuréocobaltique, d'autre part à enregistrer les spectres d'absorption infrarouge des divers tungstates précipités à différentspH, purs ou en mélanges afin de les identifier. A ce point de vue la technique infrarouge se montre plus sensible que l'analyse chimique. Nous avons également entrepris l'étude des spectres dans la région 15 à 25 et nous espérons que les résultats de ces études nous aideront à connaître la structure de ces composés à l'état solide, structure encore bien mal connue.

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Summary This study has taken two directions. It has led to a procedure for determining tungsten as purpureo cobalti tungstate, and to the recording of the infra red absorption spectra of various tungstates precipitated at different p_H values, either pure or in mixtures, in order to identify them. From this point of view, the infra red technique has proved more sensitive than the chemical analysis. We have also undertaken the study of spectra in the region 15–25 and we trust that these results will aid us to discover the structure of these compounds in the solid state, structures which as yet are imperfectly known.

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Zusammenfassung Die vorstehenden Untersuchungen führten einerseits zur Ausarbeitung einer Methode zur Bestimmung des Wolframs ais ChlorpurpureokobaltWolframat, anderseits. zur Bestimmung der Infrarotspektren einiger bei verschiedenem pn gefällter Wolframate zu dem Zweck, sie in reinem Zustand oder in Gemischen zu identifizieren. Hierfür erwies sich die Infrarotteohnik empfindlicher als die chemische Analyse. Welters haben wir auch die Spektren im Bereich von 15 bis 25 untersucht und hoffen, da die Ergebnisse dieser Untersuchungen zur Aufklärung der Struktur dieser Verbindungen im festen Zustand dienen können, die bis jetzt noch ziemlioh wenig bekannt ist.