Oxidation of organic substances with compounds of trivalent manganese: XXIII. Preparation,stability, and determination of the titer of standard solutions of the fluoride complex of trivalent manganese

A method of preparation of 10^?2 ?10^?3M standard solutions of the fluoride complex of manganese(III) by the reaction of manganese(II) with permanganate in a medium of potassium fluoride acidified with sulfuric acid has been developed. It has been found that in a medium of 1 M sulfuric acid, 0.5 M manganese(II) sulfate, and 0.1 M potassium fluoride these solutions are sufficiently stable for both direct and indirect titrimetric determinations. The titer was determined using potassium iodide as a primary standard and potentiometric, bipotentiometric, or biamperometric titration.     

2-Nitrodiphenylamine as a versatile high-potential reversible oxidation-reduction indicator

The use of 2-nitrodiphenylamine as a reversible indicator has been investigated in the titration of iron(II) with cerium(IV) sulphate, potassium dichromate and sodium vanadate in sulphuric acid media. Accurate results can be obtained with cerium(IV) sulphate in 0.5–5.0 M acid, with potassium dichromate in 5.0–7.0 M acid, and with sodium vanadate in 5.0–7.5 M acid. With cerium(IV) sulphate the titrations are preferably conducted in 2.0 M sulphuric acid or in a 1.0 M. sulphuric acid-1.0 M pechloric acid medium. Tungstic acid, acetic acid, arsenic(III) and manganese(II) do not interfere. In titrations of iron(II) with dichromate and vanadate, the colour changes at the end-point are much more vivid with 2-nitrodiphenylamine than with ferroin.     

Use of tetravalent manganese in solutions of sulfuric acid as an oxidant for the direct titration of nitrite

Conditions have been worked out for the direct titration of nitrite with manganese(IV) sulfate using ferroin as indicator. The method is suitable for the estimation of 8–60 mg of sodium nitrite with a standard deviation of 0.04, in an acidity range of 0.3 to 0.6 M. The special feature of this method lies in the reagent's association with acid and its relatively higher redox potential.     

The oxidation of benzidine, o,o′-tolidine and o,o′-dianisidine by manganese dioxide

The oxidation of benzidine, o,o′-tolidine, and o,o′-dianisidine by manganese dioxide was studied in an acidic medium. It has been shown that the studied substances are quantitatively oxidized by the reagent to the corresponding quinonediimines and that this reaction can be utilized for the indirect titrimetric determination of benzidine and o,o′-tolidine, based either on ferrometric titration of unconsumed manganese dioxide or on ascorbinometric titration of the quinonediimine formed.     

Selective separations by reactive ion exchange : Part III. Preconcentration and separation of oxo anions

A new procedure for simultaneous preconcentration, separation, and determination of permanganate, chromate and vanadate was developed for aqueous solutions containing p.p.b. levels of these anions (and molybdate). The presence of other (non-complexing) ions in p.p.m. concentrations did not interfere. The procedure consisted of reactive adsorption of all three anions as their reduced cations, on iron(II)-treated resin, followed by elution of vanadium(IV) with 0.01 M HNO₃/H₂O₂, manganese(II) with 0.35 M HCl, and chromium(III) with 4M HCl. Concentration factors of 40 were obtained with 1-l “samples” 10 p.p.b. concentrations were determined with standard deviations of 4–5 % by a.a.s. and conventional spectrophotometry.     

Titration of antimony(III) with cerium(IV) sulphate and diphenylamine and its derivatives as reversible indicators

Diphenylamine, barium diphenylamine sulphonate, N-phenylanthranilic acid and 2-nitrodiphenylamine have been investigated as reversible indicators for the titration of antimony(III) with cerium(IV) sulphate in 0.5–2 M sulphuric acid medium. Diphenylamine is the most satisfactory in titrations of antimony(III) in chloride-free solutions, e.g. of potassium antimonyl tartrate. Even low chloride concentrations affect the indicator action of N-phenyl-anthranilic acid or 2-nitrodiphenylamine, but diphenylamine is satisfactory in 1 M hydrochloric acid media. Iodine catalyst is necessary to accelerate the reduction of the oxidized indicator by antimony(III). The indicator colour change is vivid and the colour of the oxidized indicator is stable. Titrations of antimony(III) in mixtures with iron(II) and arsenic(III) are also considered.     

Oxidation of organic compounds by tervalent manganese compounds: IX. Determination of the titer of hexaquomanganese(III) ion standard solutions in perchloric acid

Optimum conditions have been found for the determination of the titer of 0.005 N solutions of hexaquomanganese(III) ion by potentiometric titration of ferrous chloride. The accuracy and reproducibility of this method were studied. A new method of determining the titer of dilute solutions of hexaquomanganese(III) ion has been proposed, using potassium iodide as a primary standard. The optimum conditions for this titration have been found and its applicability to the determination of the titer of 0.005, 0.001, and 0.0005 N solutions has been verified.     

Determination of manganese in uranium by ion exchange and square-wave polarography

Traces of manganese in uranium and its compounds can be determined by ion-exchange separation and square-wave polarography. When a 9 M hydrochloric acid solution of the sample is introduced into a column of strongly basic anion-exchange resin, manganese can be quantitatively separated from uranium by cluting with 9 M hydrochloric acid. The determination of the separated manganese by square-wave polarography is performed in 1 M potassium hydroxide-0.4 M triethanolamine solution with an excellent sensitivity. The lower limit of the method is 0.5 p.p.m. of manganese.     

Complex formation of MnII with tetra(p-tert-butyl)thiacalix[4]arene acid in aqueous solutions of surfactants and polymers

The formation of manganese(II) complexes with different stereoisomers of tetraacid based on p-tert-butylthiacalix[4]arene in water, in micellar solutions of nonionogenic surfactants, and in polymer solutions was studied. The formation of complexes with different degrees of ligand protonation was revealed by pH-metric titration and nuclear magnetic relaxation. On the basis of experimental data, the composition and stability constants of the solubilized complexes of stereoisomers of thiacalixarene acid with manganese(II) ions were determined using mathematical simulation methods. The manganese thiacalixarene complexes are unstable in solutions, especially upon the addition of calcium cations and in the presence of nitrilotriacetic acid.     

Coulometric generation of molybdenum(v)

Molybdenum (V) was generated at a platinum cathode from 0.7 M molybdenum(VI) in 4 M sulfuric acid. A current efficiency of 99.9% was attained. A limiting current density of 0.05 mA/cm²/mM was found. The formal potential of the Mo(VI)–Mo(V) couple in 4 M sulfuric acid was determined to be ca. 0.55 V vs. N.H.E. Chromium(VI) solutions were titrated over a wide range of sample size and generating current. Amperometric titration curves were interpreted from current-voltage curves. Titrations could be performed in the presence of oxygen at the 1μeq. level. The effect of nitrate, perchlorate, orthophosphate, and chloride ions on the titration was determined.     

硫酸亚铁铵滴定法测定锰渣中的锰含量

研究了高氯酸氧化-硫酸亚铁铵滴定法测定锰渣中锰含量的主要影响因素。采用磷酸分解试样,通过控制试样质量和磷酸用量的比例,优化确定了最佳溶样温度和溶样时间,探讨了放置冷却时间对测定结果的影响程度,分析了共存离子的干扰。建立了硫酸亚铁铵滴定法测定锰渣中的锰含量的方法,方法用于对锰渣标准物质和样品进行分析,测定结果的相对标准偏差为0.21%～0.35%,准确度和精密度均能满足锰渣中锰含量的分析要求。     

Dosage de l'acidite libre dans les solutions aqueuses concentrees de plutonium(IV)

A method for the determination of free acidity in concentrated aqueous solutions of plutonium (IV) is described. The plutonium-EDTA complex is formed by addition of the calcium-EDTA complex and the neutralization titration with sodium hydroxide is followed potentiometrically, the equivalence point being determined by a graphical method. The relative standard deviation is 1%. Uranium and iron in small amounts do not interfere. The method is applicable to solutions which are ca, 1 N in acid and which contain up to 200 g Pu/l.     

Electrically generated lead(IV) acetate and manganese(III) acetate as reagents for coulometric redox titrations in acetic acid

Summary The conditions were investigated for electrochemical generation of lead(IV) acetate in acetic acid by oxidation of lead(II) acetate on a lead dioxide electrode and on a platinum electrode. Bivalent manganese ions are quantitatively oxidized on a platinum electrode to the tervalent state in the same solvent. Coulometric titration methods for the determination of small amounts of hydroquinone in acetic acid were developed on the basis of the electrically generated oxidizing agents. Better results were obtained in titration with electrogenerated manganese(III) acetate. The titration end-point was detected by the biamperometric method. Suitable redox indicators were found.

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Zusammenfassung Die Bedingungen zur elektrochemischen Pb(IV)-Acetatherstellung aus Pb(II)-Acetat in Eisessig durch Oxydation an der Blei(IV)-oxid-Elektrode und an der Pt-Anode wurden untersucht. Auch Mn(II)-Ionen wurden in diesem Lösungsmittel quantitativ zu Mn(III) an der Pt-Elektrode oxydiert. Mit diesen auf elektrochemischem Wege erhaltenen Oxydationsmitteln wurden coulometrische Titrationsmethoden für die Bestimmung kleiner Hydrochinonmengen ausgearbeitet. Bessere Resultate wurden mit Mn(III)-Acetat erhalten. Die Endpunktbestimmung wurde durch biamperometrische Anzeige oder mit Hilfe visueller Redoxindikatoren durchgeführt.

     

The oscillopolarographic determination of uranium and thorium in supporting electrolytes containing cupferron

Uranium(VI and IV) and thorium(IV) give cathodic indentations in supporting electrolytes prepared from 0.1M perchloric acid, 0.5 M ammonium thiocyanate and 5·10^-3M cupferron (solution A) or from 0.1 M succinic-succinate buffer pH 4, 0.1 M sodium chloride, 10^-3M cupferron and 0.05% gelatine (solution B). The uranium indentation on the dE/dt = f(E) curve (Q=0.75 and 0.73) permits its detection at the 3·10^-7M level. The thorium indentation (Q=0.78) permits its detection at the 4·10^-7M level in solution B. Methods for the elimination of interfering ions for the uranium determination are described. In the determination of thorium, Ga(III), Fe(III), Ti(IV) and U(VI) interfere.     

Détermination de traces de manganèse urinaire après extraction à l'aide de 2,2,6,6-tétraméthylheptane-3,5-dione et dosage par spectrométrie d'absorption atomique

A procedure has been developed for the determination of urinary manganese by flameless atomic absorption spectrometry. The method was checked initially with solutions of manganese(II) before it was applied to mineralized urine (HNO₃—H₂SO₄). Manganese, probably in the trivalent state, is extracted with 0.5 M dipivaloylmethane in methyl isobutyl ketone at pH 10.6 in the presence of n-butylamine. This reagent has good stability and a low limit of detection is obtained. Precision and reproducibility are excellent.     

Spectrophotometric determination of thiocyanate ions in stratal waters

The formation of [FeSCN]²⁺ complex in hydrochloric and sulfuric acid medium was studied by spectrophotometry using iron(III) sulfate and ammonium iron(III) sulfate solutions as reactants. A method for the determination of 10–200 μg SCN^? in 25 mL water solutions containing ammonium iron(III) sulfate in sulfuric acid medium was developed; its determination limit is 2.6 μg (P = 0.99, n = 9). The method was applied for the analysis of model water samples with macro- and micro-component compositions similar to that of water from the Arigol licensed area. Operational control of the accuracy rate was performed by the standard addition method. The developed method can be applied to analyze water samples containing 1–90 mg/L thiocyanate ions.     

Bestimmung des Faktors von Hydrochinonlösungen mit Kaliumbichromat als Standard

Zusammenfassung Zur Bestimmung des Faktors von Hydrochinonmaßlösungen unter Verwendung von Kaliumdichromat als Urtitersubstanz wurde vorgeschlagen, in 12-m Phosphorsäure Dichromat mit Mangan(II)-salz unter Bildung des Phosphatkomplexes des dreiwertigen Mangans zu reduzieren. Der genannte Komplex wird dann mit Hydrochinonmaßlösung unter Anwendung einer Platin-Indikationselektrode und einer gesättigten Kalomelbezugselektrode titriert. Genaue Ergebnisse wurden selbst bei der Titration 10^–3-n Lösungen erzielt.

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Determination of the factor of hydroquinone solutions with potassium bichromate as standard

Summary The determination of the factor of standard solutions of hydroquinone with employment as primary standard of potassium bichromate was proposed; this procedure involves the reduction of dichromate in 12M phosphoric acid with manganese(II) with production of the phosphate complex of trivalent manganese. This complex is titrated with hydroquinone solution using a platinum-indication electrode and a saturated calomel reference electrode. Precise results were obtained even in the titration of 10N solutions.

     

Analytical applications of thio. seleno and telluroethers: Part V. Titrimetric determination of palladium with sodium ethylene-bis-(thioglycolate)

Palladium solutions can be titrated visually and spectrophotometrically with sodium ethylene-bis (thioglycolate). Titrations were done in 2.5 M perchloric acid with nitroso-R salt as indicator. Palladium was determined in the range 5.0–30 mg (visual titration) and 2.0–10 mg (spectrophotometric titration): the tolerance for diverse ions is good, particularly with the spectrophotometric end-point. The probable structure of the isolated complex is given.     

The determination of antimony in natural waters with particular reference to sea water

A procedure is described for the determination of antimony in natural waters at concentrations down to 0.1 μg/l or less. The element is concentrated by coprecipitation with hydrous manganese dioxide (produced by the reaction of permanganate with ethanol). It is separated from manganese, iron and interfering elements by extraction from 5 M sulphuric acid, 0.01 M with respect to iodide, using methyl isobutyl ketone. After back-extraction with 0.4 M hydrochloric acid, it is determined photometrically using rhodamine B. The overall chemical yield of the process is measured radiochemically and amounts to ca. 80%. Sea water samples from the Irish Sea were found to contain 0.13–0.40 μg Sb/l.     

Direct potentiometric titration of thiosulfate,thiourea, and ascorbic acid with lodate using an iodide ion-selective electrode

A potentiometric method has been developed for the semi-automatic direct titration of thiourea, thiosulfate, and ascorbic acid with potassium iodate in strongly acidic solutions using an iodide ion-selective electrode to monitor the reaction and locate the endpoint. The method is simple, fast, precise, and accurate. Amounts ranging from 0.15–1.5 mg of thiourea (3.9 × 10^?4–3.9 × 10^?3, M), 0.3–3.0 mg of thiosulfate (5.4 × 10^?4–5.4 × 10^?3, M), and 0.5–5.0 mg of ascorbic acid (5.7 × 10^?4–5.7 × 10^?3, M) have been determined with an average error of about 1%. The method has been applied to the determination of ascorbic acid in tablets. Results checked closely with those obtained with a standard titrimetric method.