Hydrazine sulphate as reagent for titrimetric determination of vanadium(V) and chromium(VI)

Conditions have been developed for the direct titration of vanadium(V) and chromium(VI) with hydrazine sulphate, barium diphenylaminesulphonate being used as indicator and osmium tetroxide as catalyst.     

Bromometric determination of vanadium (V) by hydrazine

A method for the quantitative determination of vanadium(V), based on the reduction of vanadium(V) by hydrazine, has been described. The reduction is carried out in high concentration of hydrochloric acid and the excess hydrazine back-titrated against standard potassium bromate, using the dead-stop end-point procedure. Hydrazine is preferentially oxidized by bromate in presence of vanadium(IV). Accurate results have been obtained over a wide range of vanadium(V) concentration.     

Separation and determination of ruthenium by evolution with chromium(VI)-condensed phosphoric acid reagent

Ruthenium in various chemical forms can be evolved as the tetroxide from insoluble matrix materials by heating the sample with chromium(VI)-condensed phosphoric acid reagent (abbreviated as Cr(VI)-CPA). Because of its excellent decomposing power for various solid samples, condensed phosphoric acid is very useful in the chemical analysis of various insoluble materials, and when an oxidizing agent such as potassium dichromate is added in the CPA medium, drastic oxidation proceeds on heating. This method is now extended to the separation of ruthenium from marine sediments. During the reaction with Cr(VI)-CPA ruthenium tetroxide is evolved and collected in an absorbent solution of 6M hydrochloric acid and ethanol (1:1), and the ruthenium is then determined spectrophotometrically with thiourea or radiometrically by counting the beta or gamma-activity. Osmium, which can be evolved as the tetroxide by the same treatment, can be eliminated beforehand by heating the sample with Ce(IV)-CPA, which removes osmium but not ruthenium. The successive distillations by means of Ce(IV)-CPA and Cr(VI)-CPA give satisfactory results for the separation between osmium and ruthenium. This method might be useful for the separation of ruthenium in geochemical or neutron-activation analysis.     

Titrimetric determination of vanadium(IV) with DCTA

Vanadium(IV) has been determined by DCTA titration conductometrically, spectrophotometrically and visually (with Alizarin Red S, Gallein and Catechol Violet as indicators at pH 4.0, 4.2 and 4.5-4.6 respectively). The interference of nickel, copper, lead, aluminium and thorium can be removed, and the method utilized for the analysis of binary mixtures of vanadium(IV) with nickel, copper or thorium.     

Titrimetric determination of vanadium(IV) with cerium (IV)sulphate at room temperature using ferroin as indicator

A procedure has been developed for the visual titrimetric determination of vanadium(IV) with cerium(IV) sulphate, using ferroin is redox indicator. The method has been extended to the determination of iron(II) and vanadium(IV) in mixtures.     

Titrimetric determination of U(iv) alone and in mixtures with V(IV), Mn(II), Ce(III) and Fe(II)

Summary A rapid and accurate method is described for the potentiometric determination of uranium(IV) with permanganate at room temperature using trace amounts of ortho-phosphoric acid as a catalyst. The procedure has been extended for the differential potentiometric determination of mixtures with vanadium, manganese or cerium. The methods are easy, non-time consuming and free from interference by a large number of foreign ions. Conditions are also developed for the differential photometric determination of uranium and iron in mixtures.Based on these procedures, a differential titrimetric procedure has been developed for determination of iron(III), vanadium(V), chromium(VI) and manganese(VII) [or cerium(IV)] in a single solution at room temperature. This procedure has also been tested on Bureau of Standard samples.

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Titrimetrische Bestimmung von U(IV) allein und in Mischungen mit V(IV), Mn(II), Ce(III) und Fe(II)Anwendung auf die Analyse von Stählen und Legierungen

Zusammenfassung Eine schnelle und genaue Methode wird beschrieben zur potentiometrischen Bestimmung von Uran(IV) mit Permanganat bei Raumtemperatur unter Verwendung von Spuren Orthophosphorsäure als Katalysator. Das Verfahren wurde auf die differentialpotentiometrische Bestimmung im Gemisch mit V, Mn und Ce ausgedehnt. Die rasch und einfach ausführbare Methode wird durch zahlreiche Fremdionen nicht gestört. Eine differentialphotometrische Bestimmung von U(IV) und Fe(II) im Gemisch wird ebenfalls angegeben, außerdem eine differentialtitrimetrische Bestimmung von Fe(III), V(V), Cr(VI), Mn(VII) [oder Ce(IV)] in einer Lösung. Anwendungsbeispiele für Stähle und Legierungen werden beschrieben.

     

Platinum catalyzed reduction of uranium(VI) with hydrazine in sulfuric acid media

The process of platinum-catalyzed uranium(VI) reduction with hydrazine in sulfuric acid media has been studied. The influence of sulfuric acid and hydrazine concentrations, and temperature on the reaction rate were investigated. A new reaction mechanism is proposed. The process allows to obtain pure U(IV) sulfate solutions with concentrations of up to 0.3 mol·l^–1. Further increase of initial U(VI) concentrations is limited by the reductant solubility in sulfuric acid media.     

A new oxidimetric reagent-potassium dichromate in a strong phosphoric acid medium-VIII Potentiometric titration of molybdenum(VI) and vanadium(V)

A new titrimetric method is described for the determination of molybdenum(VI) involving prior reduction to Mo(V) with an excess of Fe(II) in a concentrated phosphoric acid solution, followed by titration with dichromate. The titration can be done at room temperature and without protective atmosphere. Uranium interferes, but vanadium may be determined simultaneously.     

Spectrophotometric determination of vanadium (V) with 2-naphthohydroxamic acid

2-Naphthohydroxamic acid in methanol gives an intense and stable red-orange color with vanadium (V), sensitive to 0.009 μg V/cm², for log I₀/I = 0.001 abs. unit at wavelength 450 mμ. The value for σ is ±0.006 a.u., equivalent to ±0.08 p.p.m. V. The colored complex obeys Beer's law over the range 1–10 p.p.m. vanadium. The absorbance (in 1-cm cell) at 10 p.p.m. was so great that no data were obtained at higher concentrations. Under the conditions of the reaction, the combining ratio of vanadium and 2-naphthohydroxamic acid appears to be 1 to 2. Optimum conditions for the use of 2-naphthohydroxamic acid as a spectrophotometric reagent for vanadium-(V) were established; the procedure was applied to the determination of vanadium in steels and non-ferrous alloys with good precision and accuracy.     

Extract-photometric determination of vanadium(V) with 3-indole-acetohydroxamic acid

Summary A spectrophotometric study has been carried out of the violet complex 3-indole-acetohydroxamic acid-vanadium extracted into a solution of trioctylmethyl-ammonium chloride in toluene [_max 525 nm; =5381 l mol^–1 cm^–1; stoichiometry 1:3 (metal:reagent)]. A new method for the extract-spectrophotometric determination of V⁵⁺ in the range of 2–7 g/g is proposed and interferences by foreign ions were investigated. The method has been satisfactorily applied to the determination of vanadium(V) in fuel oil. The relative error is ±2.9%.     

Extraction of rhenium(VII) and molybdenum(VI) with hexabutyltriamide of phosphoric acid from acid media

Extraction of rhenium(VII) and molybdenum(VI) from sulfuric, hydrochloric, and nitric acid solutions with hexabutyltriamide of phosphoric acid was studied. The influence exerted on the extraction of Re(VII) and Mo(VI) by the nature and concentration of an acid in the aqueous phase, temperature, time of contact between phases, and concentration of the extracting agent in the organic phase was analyzed. Isotherms of extraction of rhenium(VII) and molybdenum(VI) with solutions of hexabutyltriamide phosphoric acid in kerosene were obtained, the composition of the complexes being extracted was determined, the enthalpies and entropies were evaluated, and the concentration constants of extraction of the metals were found.     

Titrimetric determination of vanadium (IV) with potassium permanganate at the room temperature, using phosphoric acid as catalyst and ferroin as internal indicator

Summary The observation that the reaction between vanadium(IV) and potassium permanganate is catalyzed by ortho phosphoric acid at the room temperature has been utilized to develop a new procedure for the titrimetric determination of vanadium(IV). In the absence of chromium(III) and other coloured ions the end point can be detected making use of the colour of permanganate itself, and applying the necessary correction. This procedure cannot, however, be employed for titrations with 0.01 N potassium permanganate when the use of ferroin must be resorted to indicate the end point. The use of ferroin in macro titrations helps to eliminate the correction and the interference of coloured ions like chromium(III) up to a reasonable limit. Titrations without the use of the ferroin indicator can be carried out within a wider range of acidity viz. 0.1 N to 1.0 N.

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Zusammenfassung Ein neues Verfahren zur titrimetrischen Bestimmung von Vanadium-(IV) wird auf den katalytischen Einfluß gegründet, den Orthophosphorsäure bei Zimmertemperatur auf die Reaktion zwischen V^IV und KMnO₄ ausübt. Bei Abwesenheit von Cr^III und anderen gefärbten Ionen kann der Endpunkt durch die Eigenfarbe des Permanganats festgestellt werden, wobei eine Korrektur erforderlich ist. Für kleinere Vanadiumgehalte (Titration mit 0,01 n KMnO₄-Lösung) wird die Verwendung von Ferroin als Indicator empfohlen, wobei die Notwendigkeit einer Korrektur sowie der Einfluß störender Ionen bis zu bestimmten Grenzen vermieden wird. Titrationen ohne Indicator können bei einem Säuregehalt von 0,1 n–1 n ausgeführt werden.

     

New specific methods for the detection of chromium(VI) and vanadium(V) using primaquin

Summary New specific methods have been developed for the detection of chromium(VI) and of vanadium(V), based on the formation of a purple color with primaquin in concentrated sulfuric acid solution. The identification limits and dilution limits have been determined to be 0.05g, 11 000 000 for chromium(VI) and 0.1g, 1500 000 for vanadium(V) respectively.

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Neue spezifische Methoden zum Nachweis von Cr(VI) und V(V) mit Primachin

Zusammenfassung Die neu ausgearbeiteten Methoden sind spezifisch und beruhen auf der Bildung einer Purpur-Färbung mit Primachin in konz. Schwefelsäure. Die Nachweisgrenzen und Verdünnungsgrenzen betragen 0,05g bzw. 11 000 000 für Cr(VI) und 0,1g bzw. 1500 000 für V(V).

     

Simultaneous polarographic determination of micro amounts of vanadium(V) and molybdenum(VI)

A simple and sensitive polarographic method has been developed for the determination of micro quantities of vanadium(V) and molybdenum(VI), based on the reduction of bromate, which is catalysed by these metal ions in the presence of 2,4-dihydroxyacetophenone oxime. Interference by various cations and anions has been investigated.