Potentiometric studies in oxidation-reduction reactions: Oxidation with chloramine-b. indirect determinations

Chloramine-B has been used as an oxidising agent to determine indirectly potassium iodate, potassium metaperiodate, potassium, bromate, potassium dichromate, hydrogen peroxide, chloramine-T and potassium permanganate by a potentiometric method. An excess of potassium iodide added to each of the substances in an acid medium is titrated back with a standard solution of chloramine-B, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Studies in oxidation-reduction reactions: Oxidation with chloramine-b,iodine monochloride method

Chloramine-B has been used as an oxidizing agent in hydrochloric acid medium for the volumetric estimations of potassium iodide, arsenious oxide, tartar-emetic, mercurous chloride, stannous chloride, potassium thiocyanate, ferrous ammonium sulphate, hydrazine sulphate and hydroquinone, using iodine monochloride as a catalyst and pre-oxidizer. Chloroform is used as an indicator. It is coloured pink owing to the liberation of iodine during the titration and becomes light pale yellow at the end-point because of the formation of iodine monochloride.     

Volumetric studies in oxidation-reduction reactions: Oxidation with chloramine-t. indirect determinations

Chloramine-T has been used as an oxidizing agent in hydrochloric acid medium for the indirect volumetric determination of hydrogen peroxide, lead dioxide, selenium dioxide, sodium formate, potassium meta-periodate, potassium permanganate and potassium dichromate using iodine monochloride as a catalyst, prcoxidizer and an indicator. Chloroform is coloured pink owing to the liberation of iodine during the titration and becomes very pale yellow at the end-point because of the formation of iodine monochloride.     

Potentiometric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate indirect determinations

Ferrous ethylenediamine sulphate has been used as a reducing agent to determine indirectly potassium dichromate, hydrogen peroxide, potassium permanganate, potassium persulphate, potassium chlorate, potassium bromate, and ceric sulphate by a potentiometric method. An excess of ferrous ethylenediamine sulphate added to each of the substances in an acid medium is titrated with a standard solution of potassium permanganate, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Volumetric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate indirect determinations

Ferrous ethylenediamine sulphate has been. used as a reducing agent in acid medium for the indirect volumetric estimations of potassium chlorate, potassium bromate, potassium metaperiodate, potassium, dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide and ceric sulphate. The excess of ferrous ethylenediamine sulphate added to each of the substances was titrated with standard potassium permanganate and also with. standard potassium dichromate solution. In case of potassium bromate or potassium metaperiodate the end-point was not sharp in potassium dichromate titrations; while accurate volumetric observations were made with standard potassium permanganate solution.     

Volumetric studies in oxidation-reduction reactions: Oxidation with chloramine-t. iodine monochloride method

Chloramine-T has been used as an oxidizing agent in hydrochloric acid medium' for the volumetric estimations of potassium iodide, hydrazine sulphate, arscnious oxide, stannous chloride, mercurous chloride, tartar-emetic, potassium thiocyanate and ferrous ammonium sulphate, using iodine monochloride as a catalyst and pre-oxidizer. Chloroform is used as an indicator. It is coloured pink owing to the liberation of iodine during the titration and becomes very pale yellow at the end-point because of the formation of iodine monochloride.     

Volumetric studies in oxidation-reduction reactions : Oxidation with sodium hypochlorite iodine monochloride method

Alkaline sodium hypochlorite was used as an oxidant to determine arsenious oxide, hydrazine sulphate, ferrous ammonium sulphate, stannous chloride, sodium sulphite, potassium iodide, mercurous chloride, thallous chloride and tartar emetic, by a volumetric method, using iodine monochloride as catalyst and preoxidizer. During these titrations, the normality of the solution with respect to hydrochloric acid was kept between 5N and 7N, Chloroform was used as an indicator. Its pink colour due to the liberation of iodine during the titration turns very pale yellow at the end-point because of the formation of iodine monochloride     

Volumetric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate ceric sulphate method

Ferrous ethylenediamine sulphate has been used as a reducing agent in acid medium for the indirect volumetric estimations of potassium chlorate, potassium bromate, potassium metaperiodate, potassium dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide and ceric sulphate. The excess of ferrous ethylenediamine sulphate added to each of the substances in acid medium was titrated with standard ceric sulphate solution using ferroin as an indicator.     

Potentiometric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate ceric sulphate method

Ferrous ethylenediamine sulphate has been used as a reducing agent to determine indirectly potassium permanganate, ceric sulphate, potassium chlorate, hydrogen peroxide, potassium persulphate, potassium dichromate and potassium bromate by a potentiometric method. An excess of ferrous ethylenediamine sulphate added to each of the substances in acid medium was titrated with a standard solution of ceric sulphate, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Studies on the oxygen atom transfer reactions of peroxomonosulfate: Oxidation of glycolic acid

The kinetics of oxidation of glycolic acid, an α‐hydroxy acid, by peroxomonosulfate (PMS) was studied in the presence of Ni(II) and Cu(II) ions and in acidic pH range 4.05–5.89. The metal glycolate, not the glycolic acid (GLYCA), is oxidized by PMS. The rate is first order in [PMS] and metal ion concentrations. The oxidation of nickel glycolate is zero‐order in [GLYCA] and inverse first order in [H⁺]. The increase of [GLYCA] decreases the rate in copper glycolate, and the rate constants initially increase and then remain constant with pH. The results suggest that the metal glycolate ML⁺ reacts with PMS through a metal‐peroxide intermediate, which transforms slowly into a hydroperoxide intermediate by the oxygen atom transfer to hydroxyl group of the chelated GLYCA. The effect of hydrogen ion concentrations on k_obs suggests that the structure of the metal‐peroxide intermediates may be different in Ni(II) and Cu(II) glycolates. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 41: 160–167, 2009     

Studies on the oxygen atom transfer reactions of peroxomonosulfate: Oxidation of lactic acid

Kinetics of oxidation of lactic acid by peroxomonosulfate (PMS) catalyzed by Ni(II) ions has been studied in aqueous buffered (sodium acetate‐acetic acid) medium. The reaction follows first order in [PMS] and [Ni(II)] and inverse first order in [H⁺]. The effect of pH on the rate suggests that both HSO and SO are the active forms of the oxidant. The intermolecular reaction between HSO and nickel lactate results in hydroperoxide intermediate in the rate‐limiting step. The deprotonated form of PMS, SO, gives a lactate‐nickel‐peroxomonosulfate intermediate, which then undergoes intramolecular oxidation–reduction reaction. The thermodynamic parameters also support the kinetic scheme. Comparison with (nickel) glycolate shows that the electron‐donating methyl group in lactic acid enhances the nucleophilic interaction of the α‐hydroxyl group. A suitable mechanistic scheme is also proposed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 449–454, 2009     

Kinetic determinations of reactants utilizing uncatalyzed reactions

Kinetic-based determinations of reactants utilizing uncatalyzed chemical reactions do not match the polularity of catalytic methods for the determination of catalysts (particularly transition metal ions) or reactants (e.g., in enzymatic reactions) and this reflects on the scarcity of reviews on the topic. In some cases, however, advances in instrumentation and data manipulation provide competitive alternatives to nonkinetic-based methods for single as well as multispecies determinations. Such advances are reviewed here and applications illustrated.     

A simple device for determinations using Landolt reactions

Summary A device has been described which permits several Landolt reactions to be initiated simultaneously. All solutions remain at the same temperature, and mixing is rapid. This device improves the precision and the convenience of determinations using Landolt reactions.

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Zusammenfassung Eine Anordnung zur gleichzeitigen Ingangsetzung mehrerer Landolt-Reaktionen wurde beschrieben. Alle Lösungen werden bei gleicher Temperatur gehalten und rasch gemischt. Dadurch wird die Genauigkeit von Analysen mit Hilfe von Landolt-Reaktionen verbessert.

     

Error-compensated kinetic determinations by detecting the reagent in successive reactions

An error-compensated algorithm based on detecting the reagent in successive reactions is proposed. The algorithm was first studied by using simulated data and it was found that it performed well in compensating for the system error and eliminating random noise. Then the algorithm was examined by applying it to the determination of epinephrine and norepinephrine under different experimental conditions. The results revealed that the algorithm compensated errors produced not only by the changes of rate constants, but also by the variation of equilibrium signals.     

Study of the oxidation-reduction reactions of manganese and cobalt in alkaline triethanolamine medium

Summary It has been found that in alkaline triethanolamine medium the complex of bivalent manganese is oxidised by hexacyanoferrate(III), hydrogen peroxide or lead dioxide to the red-coloured complex of Mn^IV, which can be titrated potentiometrically with ferrous salt solution (Mn^IV Mn^III and Mn^III Mn^II). The stability of this complex has been studied in dependence on the oxidant employed, and it has been found that lead dioxide is best suited for this oxidation process. Similarly the oxidation of the complex Co^II Co^III has been studied in the same medium, and conditions have been found for the reductometric determination of the Co^III complex formed.The possibilities for determining manganese in the presence of cobalt and of other accompanying elements are discussed. The results obtained have been applied to the determination of manganese in ores and alloys.

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Zusammenfassung Bei Untersuchungen zum Oxydations-Reduktions-Verhalten von Mangan und Kobalt in alkalischer Triäthanolaminlösung wurde gefunden, daß der Mn^II-Komplex durch Hexacyanoferrat(III), Wasserstoffperoxid oder Bleidioxid zum rotgefärbten Mn^IV-Komplex oxydiert wird, der potentiometrisch mit, Fe^II-Lösung titriert werden kann (Mn^IV Mn^III; Mn^III Mn^II). Die Stabilität des Komplexes wurde in Abhängigkeit von der Art des Oxydationsmittels geprüft und Bleidioxid als am günstigsten gefunden. Analog wurden auch die Oxydation des Co^II- zum Co^III-Komplex untersucht und Bedingungen zur reduktometrischen Bestimmung des letzteren ausgearbeitet. Die Möglichkeiten zur Manganbestimmung in Gegenwart von Kobalt sowie anderen Begleitelementen werden diskutiert, und als praktische Anwendung wird die Manganbestimmung in Erzen und Legierungen beschrieben.

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Dedicated to Prof. Dr. M. von Stackelberg on his 70th birthday.     

Differential electrolytic potentiometry, a detector in flow injection analysis for oxidation-reduction reactions

For the first time, differential electropotentiometry (DEP) is coupled with the flow injection analysis (FIA) technique for detection of oxidation–reduction reactions, and is utilized for quantitative determination of vitamin C in pharmaceutical preparations using 1.0×10⁻³-M cerium(IV) in 0.50-M sulfuric acid as carrier. Two similar platinum electrodes were employed and polarized by a constant current. Optimization by the univariate method was carried out and the optimum conditions for current density, flow rate, sample size and concentration of sulfuric acid were 4 mA, 0.93 ml min⁻¹, 140 μl and 0.25 M, respectively. Vitamin C was determined in the concentration range 100–300 ppm with 0.9987 correlation coefficient and 1.9 standard deviation. The method was applied to the determination of vitamin C in pharmaceutical preparations and no excipient was found to pose any interference thus rendering the method suitable for determination of the drug in pharmaceutical preparations. The accuracy of the method was determined by comparison with the BP standard method.     

The application of oscillating chemical reactions to analytical determinations

Oscillating chemical reactions, which are far from equilibrium, are extremely sensitive to certain species and may provide new analytical methods using the regular oscillations as well as the non-equilibrium stationary state after system bifurcation. This review of their application to analytical chemistry from 2005 to 2012 includes other appropriate references. Both organic and inorganic analytes are included.     

Oxidation reactions of azines.

Condensation of 2-([2.2]paracyclophan-4-yl)propene with formaldehyde and amines gave 4-paracyclophanyl substituted -piperidols which were readily dehydrated to the corresponding tetrahydropyridines. N-Methyl substituted 4-paracyclophanyltetrahydropyridine has been oxidized to the corresponding piperidin-2-one.For communication 2, see [1]. This article is also communication 4 in the series Synthesis, structure and biological activity of [2.2]paracyclophanes (for communication 3, see [2]).Russian University of National Friendship, Moscow 117198. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 653–658, May, 1997,