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 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.     

Volumetric Studies In Oxidation-Reduction Reactions: Oxidation with ceric sulphate ferrous ethylenediamine sulphate method

Ceric sulphate has been used as an oxidizing agent in acid medium for the indirect volumetric determinations of ferrous ammonium sulphate, cuprous chloride, potassium thiocyanate, sodium thiosulpliate, sodiuin nitrite, hydrogen peroxide, sodium oxalate, hydroquinone and pyruvic acid. The excess of ceric sulphate added to each of the substances in acid medium was titrated with standard ferrous ethylenediamine sulphate solution using ferroin as an indicator.     

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.     

Sodium hypochlorite as volumetric reagent

Summary In presence of 5 N to 6 N hydrochloric acid, ferrous ethylenediamine sulphate was used as a reducing agent to determine indirectly potassium chlorate, potassium bromate, potassium metaperiodate, potassium dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide, ceric sulphate and chloramine-T. An excess of ferrous ethylenediamine sulphate added to each of the substances in the acid medium was titrated with a standard solution of sodium hypochlorite. Iodine monochloride was used as catalyst and preoxidizer and chloroform was used as an indicator. Chloroform was coloured violet owing to the liberation of iodine during the titration and became very pale yellow at the end-point because of the formation of iodine monochloride.Part I: See Z. analyt. Chem. 160, 429 (1958).     

Oxidimetric methods for the volumetric estimation of sulphite

1. The use of permanganate, ceric sulphate, and dichromate for the estimation of sulphite has been reinvestigated, although these reagents have heen discarded as useless by earlier investigators. By using catalysts under controlled acid concentration, we have been able to develop conditions for the quantitative oxidation of sulphite to sulphate at room temperature by any one of these oxidizing agents, avoiding the formation of dithionate. Copper sulphate and iodine monochlonde have been found useful as catalysts with potassium permanganate and dichromate; but only iodine monochloride with ceric sulphate. 2. Sodium sulphite is also oxidized quantitatively to sulphate at room temperature, when added to excess of sodium vanadate solution containing 5 to 6N hydrochloric acid and iodine monochloride as catalyst.     

Volumetric estimation of uranium-part III, with ceric sulphate

Summary The use of diphenylamine, diphenylbenzidine, diphenylamine sulphonate and N-phenylanthranilic acid as inside indicators in the titration of uranium IV salt with ceric sulphate has been investigated in detail. Experimental conditions have been defined under which these indicators function efficiently.     

Diethylenetetra-ammonium sulphatocerate as volumetric reagent: Iodine monochloride method. Indirect determinations

In presence of 4N to N hydrochloric acid, diethylenetetra-ammnonium sulphatocerate was used as a volumetric reagent to determine indirectly potassium iodate, potassium metaperiodate, potassium dichromate, potassium bromate, ceric sulphate, hydrogen peroxide, lead dioxide and chloramine-B by the iodine monochloride method. An excess of potassium iodide added to each of the substances in the acid medium was, titrated back with a standard solution of diethylene-tetra-ammonium suphatocerate. Chloroform was used as an indicator. It was coloured violet owing to the liberation of iodine during the titralion and became very pale yellow at the end-point because of the formation of iodine monochloride.     

Chlorpromazine hydrochloride as an analytical reagent : A new indicator for titrations with very dilute ceric sulphate solutions

Chlorpromazine hydrochloride is proposed as an indicator for the microtitration of iron(II), arsenic(III), ascorbic acid and hydroquinone with 0.0005–0.001 N ceric sulphate; the indicator blanks are small. The colorimetric déterminations of μg quantities of cerium(lV) and arsenic(III) using the same reagent are also described.     

Rapid decomposition of organic materials with acidic lithium sulphate flux containing catalysts, oxidizing agents or reducing agents, and Kjeldahl determination of nitrogen

Organic compounds and natural materials such as dimethylglyoxime, p-nitrophenol, alpha-nitroso-beta-naphthol, 4-(2-pyridylazo)-resorcinol, phenylhydrazine hydrochloride, monopyrazolone, residual fuel oil and coal can be rapidly decomposed in the melting state with various ratios of sulphuric acid-lithium sulphate (v/w) mixture containing catalysts, oxidizing agents or reducing agents such as elemental selenium powder, cupric sulphate, ceric sulphate and stannous sulphate. The quantitative recovery of nitrogen in the melting medium can be obtained with the Kjeldahl method.     

Continuous potentiometric determination of sulphate in a differential flow system

Continuous monitoring of sulphate in a differential flow system equipped with two lead ion-selective electrodes is described. All solutions contained 75% methanol and were adjusted to pH 4. In the flow cell, a standard solution of lead(II) is pumped past the first sensing electrode and is mixed with the sample stream containing sulphate in a small mixing chamber; the mixture containing excess of lead(II) and lead sulphate precipitate then flows through the second sensing electrode chamber. The potential difference depends on the sulphate content in the sample. The effects of lead electrode passivation and the interferences of calcium and chloride are discussed. The system is useful for routine sulphate determination in the range 30–400 mg l^-1 with an accuracy of ±5%     

Mercurous nitrate as a reductimetric reagent : The titration of various oxidising agents

It has been found that when excess of a solution containing ferrous ions is added to certain oxidising agents, the equivalent amount of ferric iron produced can be titrated accurately with mercurous nitrate, enabling the original oxidant to be assessed. Oxidising agents which have been determined in this way are potassium permanganate, potassium persulphate, ceric sulphate, sodium vanadate, potassium chlorate, hydrogen peroxide and potassium dichromate. The last substance provides a convenient primary standard for the standardisation of mercurous nitrate solutions.     

The determination of sulphate in fertilizers by atomic absorption spectrometry

Methods are described for the determination of sulphate in superphosphate fertilizers. Barium sulphate precipitated from an acidified EDTA solution is filtered onto a membrane filter and redissolved in ammoniacal EDTA, and the barium equivalent to the sulphate is determined by atomic absorption spectrometry. Alternatively, after precipitation of calcium as oxalate during sample solution preparation, and by following a similar sulphate precipitation technique, excess of barium is determined in the filtrate. No interferences were encountered when a nitrous oxide—acetylene flame was used with a potassium ionization buffer.     

A new design of lead amalgam/lead sulphate electrode for potentiometric measurement of sulphate

A new lead amalgam/lead sulphate electrode has been developed which is easy to handle and can be used in a simple measuring cell. Its electrochemical characteristics have been tested in two different cell systems. The potentials obtained were very stable, and reproducible within +/-0.04 mV. The electrode exhibited a Nernstian response to sulphate and its calculated standard potential (-350.68 +/- 0.13 mV) agreed very closely with that recorded in the literature.     

Studies in bivalent chromium salts

Summary It has been shown that chromous solution can be standardised with the help of potassium dichromate, sulphatocerate, potassium iodate, bromate and periodate solutions. N-phenylanthranilic acid, ferroin and diphenylbenzidine serve as reversible indicators for the titrations of potassium dichromate and ceric sulphate against chromous solution.The authors are indebted to Dr. R. N. Singh, Professor of Chemistry, B. R. College, Agra, for his kind encouragement and for providing laboratory facilities.Part II: See Z. anal. Chem. 158, 189 (1957).     

Oxidative determination of thiosulphate by alkaline ferricyanide using osmium tetroxide as a catalyst

Summary The catalytic action of osmium tetroxide has been utilised in the determination of thiosulphate by oxidation to sulphate with alkaline ferricyanide. Both direct and indirect procedures were developed. In the former the titration was carried out either ways using amperometric detection. In the latter, both the excess ferricyanide and ferrocyanide formed, were determined by arsenious oxide or iodometrically with thiosulphate, and by ceric sulphate respectively. The high conversion factor, availability of alternate procedures, use of potassium ferricyanide as a standard oxidant with a high molecular weight are characteristic features of this redox procedure.     

Standardization of titanous chloride and sulphate solutions

It is confirmed that the presence of iron as impurity in titanous chloride and sulphate solutions invalidates the use of potassium dichromate as a standard substance. Methods of overcoming this interference and of preparing iron-free titanous salt solutions are discussed and reasons are given for preferring titanous chloride to titanous sulphate for most purposes.     

Inhibition of copper corrosion in acidic sulphate media by eco-friendly amino acid compound

This investigation aimed to study a “green” non-toxic biodegradable copper corrosion inhibitor in an acidic sodium sulphate solution. The methods used in the investigation of cysteine as a copper corrosion inhibitor in an acidic sodium sulphate solution were: potentiodynamic measurements, open circuit potential measurements, and chronoamperometric measurements. Optical microscopy was used in addition to electrochemical methods. Potentiodynamic measurements show that cysteine has good inhibitory properties in an acidic medium. Polarisation curves indicate that the presence of cysteine in a sulphate solution decreases the current density and that using various cysteine concentrations results in the formation of a protective film on the surface of the electrode due to the formation of the Cu(I)-cys complex. These results are confirmed by chronoamperometric measurements. Furthermore, it is clear from microphotographs that a protective film does form on copper electrode in the presence of cysteine. The Langmuir adsorption isotherm indicates that cysteine is chemisorbed on the surface of the electrode.     

Amperometric titration of cerium(iii) with ferricyanide

Milligram and larger quantities of cerous cerium may be determined accurately and precisely, even in the presence of large amounts of ceric salts, by amperometric titration in 3 to 4M potassium carbonate solution with potassium ferricyanide. A rotating platinum microelectrode held at the potential of the saturated calomel electrode is recommended.     

Titration of oxalic acid with cerium sulphate at room temperature using ferroïn as internal indicator

Evidence is presented to show that, contrary to the statements of earlier workers, the reaction between ceric sulphate and oxalic acid is quite rapid in hydrochloric acid medium specially in the presence of iodine monochloride as catalyst. We have now found that the need for a temperature of 50° in the cerimetric titration of oxalic acid using ferroïn as indicator is not due to the sluggishness of the reaction between oxalic acid and Ce^IV (as believed by Willard and Young) but because of the slow reaction between oxidised ferroïn and oxalic acid in the presence of sulphate ion derived from eerie sulphate. Conditions have now been developed for the titration of oxalic acid with eerie sulphate at room temperature in lN hydrochloric acid medium using ferroïn as indicator, and barium ion as scavenger for sulphate ion, which latter markedly retards the reaction between oxalic acid and oxidised ferroïn, as well as that between oxalic acid and Ce^IV. The method now developed has several advantages over that prescribed by Willard and Young because it avoids the high temperature of 50°, where the ferroïn indicator is found to undergo some dissociation. It also avoids the use of the iodine monochloride catalyst.