Dosage colorimétrique du fer

By developing a sensitive tint, it is possible to determine colorimetrically small quantities of iron without having recourse to a colorimeter. The proposed method is derived from that used for the determination of lead, by the dithizone method.     

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.     

Dosage colorimétrique du cuivre dans les aciers par l'acide rubéanique

The rapid colorimetric determination of copper has been studied by means of the coloured reactions of copper salts with dithio-oxamide or rubeanic acid. This method can be used for the determination of copper, contained in an impure state in steels, in the presence of iron and some alloy elements without first extracting in an acetic buffer medium, the iron being made complex by citric acid. The method can equally be applied to the determination of small quantities of copper in different metals and alloys. The accuracy obtained is about ± 2.5 % of the quantity of copper.     

Dosage colorimétrique du fer dans l′acide phosphorique et ses sels

In the presence of phosphoric acid and aliphatic hydroxides, reduction of trivalent iron by hydroxyalamine is very slow For colorimetric estimation with dipyridyl and ortho-phenanthroline, it is convenient to use hydrosulphite and to work at a pH of 5-6 in order to avoid the precipitation of sulphur resulting from an excess of this reducing agent At pH higher than 6 the colour develops more slowly     

Dosage colorimétrique du rhénium dans les produits naturels

Traces of rhenium, in the form of tetraphenylarsonium perrhenate, are extracted by chloroform, and determined absorptiometrically in the form of a complex thiocyanate in isoamyl alcohol solution.     

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.     

Dosage microgravimétrique et spectrophotométrique du calcium par la lorétine

Résumé Les auteurs ont élaboré une méthode semi-micro et micro-gravimétrique et une méthode spectrophotométrique pour le dosage du calcium par la lorétine. Après avoir établi le facteur analytique du lorétinate de calcium par voie gravimétrique et thermogravimétrique, ils ont démontré la possibilité de doser le calcium à l'échelle semi-micro gravimétrique pour des quantités allant de 5 mg à 50 mg, l'erreur moyenne étant de 0,35%. La méthode microgravimétrique permet de ramener la quantité minima à doser à 0,2 mg de calcium par ml, l'erreur moyenne étant de 0,45%. L'influence d'une série d'ions étrangers fut étudiée. La plupart ne gênent pas le dosage, même s'ils sont présents en quantités importantes. Par spectrophotométrie indirecte, notamment en redissolvant le lorétinate de calcium dans un excès d'une solution ferrique, les auteurs ont réussi à doser des quantités de calcium de l'ordre de 20g avec une erreur moyenne de 0,35%.

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Summary The authors have elaborated a method (semi-micro and micro-gravimetric) and also a spectrophotometric method for determining calcium by means of loretin. After establishing the analytical factor for calcium loretinate by the gravimetric and the thermogravimetric methods, they showed the possibility of determining calcium on the semimicro gravimetric scale for quantities ranging from 5 mg to 50 mg, the mean error being 0.35%. The microgravimetric method allows the minimum quantity to be determined to be reduced to 0.2 mg calcium per ml, the mean error being 0.45%. A study was made of the influence of a number of foreign ions. Most of them do not harm the determination, even though they are present in considerable amounts. By indirect spectrophotometry, notably by dissolving the calcium loretinate in an excess of ferric solution, the writers have succeeded in determining amounts of calcium of the order of 20g with a mean error of 0.35%.

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Zusammenfassung Die Verfasser haben eine semimikro- und eine mikrogravimetrische Methode und ein spektrophotometrisches Verfahren zur Bestimmung von Calcium mit Loretin (7-Jod-8-hydroxychinolin-5-sulfonsäure) ausgearbeitet. Nach Festlegung des Umrechnungsfaktors des Calciumloretinats auf gravimetrischem und thermogravimetrischem Wege wurde gezeigt, daß durch Semimikrogravimetrie Calciummengen von 5 bis 50 mg mit einem mittleren Fehler von 0,35% bestimmbar sind. Die mikrogravimetrische Methode eignet sieh für 0,2 mg Calcium/ml mit einem mittleren Fehler von 0,45%. Der Einfluß einer Reihe von Fremdionen wurde untersucht. Die meisten davon stören nicht, auch wenn sie in bedeutender Menge vorhanden sind. Durch indirekte Spektrophotometrie, nämlich durch Auflösen des Calciumloretinats in überschüssiger Eisen(III)lösung gelang es, Calciummengen in der Größenordnung von 20g mit einem mittleren Fehler von 0,35% zu bestimmen.

     

Un dosage colorimétrique du cuivre

A rapid colorimetric method for the determination of copper has been established by dissolving anhydrous copper (II) chloride in a solution of potassium thiocyanate in acetone. The complex produced has a red colour and allows the determination to be carried out by spectrophotometry.     

Dosage spectrophotométrique du molybdène par l'o-phénanthroline

Under certain conditions, o-phenanthroline and its derivatives, as well as 2,2',2′-terpyridyl, form relatively unstable red complexes with molybdenum(Vl) in presence of molybdenum(V). o-Phenanthroline is most sensitive, the molecular extinction coefficient being 6,290 at the absorption maximum (508 mμ). Beer's law is valid for the range 2–9 μg Mo/ml.     

Dosage colorimétrique précis de la silice applications

A method is described for the colorimetric determination of silica as silicomolybdate. Conditions have been established for determining major amounts of silica with an accuracy of about 0.5%.The method has been applied to the analysis of compounds rich in silica and for the determination of silica in compounds containing fluorine.     

Utilisation de l'acide phénylarsonique en turbidimétrie: Dosage du tantale

A turbidimetric method is described for the determination of tantalum with phenylarsonic acid. The method is fast and rarely requires preliminary separation. The only interfering elements are zirconium and niobium when present in molar ratios greater than Nb : Ta = 1 and Zr : Ta = 5.     

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.

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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.

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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 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%.     

Dosage indirect du potassium par complexométrie

An indirect complexometric method for the determination of potassium is described Potassium is precipitated is perchlorate, which is reduced to chloride Silver chloride is treated with tetracyano nickelate, nickel being titrated chelatometrically     

Dosage de l'histidine: Étude polarographique et dosage du dinitrofluorobenzene

After polarographic study and determination of dinitrofluorobenzene at varying pH and determination of a number of electron exchanges (n), standardization curves have been constructed at pH 5 and 10. They allow the estimation of DNFB to a concentration of 1γ/ml with a precision of 4–7%. The curve shows 2 or 3 leaps, according to pH.. The E_{$\text{1}\text{2}$} of the first two are less than 1 volt.     

Dosage du silicium par précipitation du complexe silicomolybdique jaune par la quinoléine

The authors have studied the conditions of precipitation of complex silicomolybdic yellow by quinoline from the point of view of the determination of silicon.Under the conditions that produce complete development of the complex, the precipitation is itself quantitative in the presence of an excess of quinoline, the role of which is to make the precipitate insoluble in its formation surroundings. The precipitation of free molybdate is prevented by adding the quantity of acid necessary for complexing it.The precipitate thus obtained filters without difficulty, and only needs to be dried for 1 hour at 150° in order to attain constant weight. It corresponds then exactly to the formula: SiO₂.12MoO₃.4(C₉H₇N).2H₂O.     

Dosage gravimétrique rapide du béryllium dans les béryls

After attacking the beryl by fusing the powdered mineral with sodium peroxide and eliminating silica, beryllium is precipitated directly in the filtrate by mono-ammonium phosphate in the presence of complexon II or ethylene diamino-tetraacetic acid.Complexon II forms complexes and retains in the solution the other metals contained in beryl, but permits the quantitative precipitation of ammonium phosphate and beryllium which is calcined at 1000° and weighed out as beryllium pyrophosphate, Be2P2O7.     

Dosage colorimétrique de l'antimoine dans les zincs,aluminiums et étains et dans leurs alliages

The colorimetric method using methyl violet is applied to the determination of antimony in zinc, aluminium, tin, and in their alloys.Applying the method to the determination of small quantities of antimony, the following domains of strengths are covered : Zinc alloys : Sb < 0.015 % Aluminium alloys : Sb < 0.030 % Tin : Sb < 0.15 %The amounts of metal used in the determination can be decreased in order to raise the maximum of these strengths, and conversely the latter can be lowered, with the correlative increase in the sensitivity of the determination, increasing conveniently the importance of the aliquot parts withdrawn in the course of the analysis.     

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.