Extraction of prussian blue into chloroform in the presence of ajatin

Extraction of Prussian Blue into chloroform in the presence of ajatin (dimethyl-lauryl-benzylammonium bromide) is proposed for the concentration and determination of ferrocyanide ion. Optimum concentrations of sulphuric acid and of ajatin have been established and the selectivity of the extraction has been investigated. Ways of eliminating some interferences are discussed.     

Extraction-spectrophotometric determination of small amounts of boron in copper metal and copper-base alloys with methylene blue

A sensitive and rapid spectrophotometric method for the determination of small amounts of boron in copper metal and some copper alloys is described. The method is based on the extraction of a BF(4)(-)-Methylene Blue complex into dichloroethane after decomposition of the sample with hydrogen peroxide and sulphuric acid. The optimum reaction conditions and the influence of alloying elements have been investigated. Boron contents in the range 0.00-0.1% can be determined with a relative error ranging from about 9 to 2%.     

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.     

The conductometric titration of carboxylic and phenolic acids in non-aqueous solutions: The resolution of acid mixtures and some practical applications

A detailed study has been made of non-aqueous conductometric titrations suitable for the resolution of acid mixtures. The optimum conditions for the various determinations with respect to base and solvent are extensively discussed. The applications include determinations of diphen-ylolpropane, naphthenic acids, perchloric acid and mixtures containing sulphuric acid.     

Potentiometric and visual titrations with bromamine-B

Bromamine-B is proposed as an oxidimetric titrant for potentiometric and visual end-point titrations of arsenic(II), hexacyanoferrate(II), antimony(III), hydroquinone, semicarbazide hydrochloride, isonicotinic acid hydrazide, hydrazine sulphate, ascorbic acid, phenylhydrazine hydrochloride and metol. Quinoline Yellow, naphthidine, dimethylnaphthidinedisulphonic acid, o-dianisidine, diphenylbenzidine, Variamine Blue, alpha-naphthoflavone, Amaranth, Methyl Orange and Methyl Red are proposed as indicators in macro and micro titrations of the reductants with bromamine-B. The transition potentials of Quinoline Yellow, naphthidine, dimethylnaphthidinedisulphonic acid, and o-dianisidine in the titration of ascorbic acid are reported. Arsenic(III) and hexacyanoferrate(II) are suggested for the standardization of bromamine-B solutions.     

Examples of the application of titration techniques in the process industry

Different titration techniques are used for analyses of the nitrating acids in three different industrial processes, namely in the production of glycerol trinitrate (nitrate ester,  C-ONO₂), trinitrotoluene (nitro group,  C-NO₂) and trimethylene trinitramine (nitramine, N-NO₂). The determination of the composition of the process acids, which consist mainly of water, nitric acid, sulphuric acid, acetic acid and hexamethylenetetramine with minor amounts of nitrous acid and ammonium nitrate, are complicated by the ability of the process acids to dissolve the product to various extents. Acid-base titrations as well as oxidation-reduction titrations and voltammetry are used to provide a rapid system for analysing the process acids.     

Comparison of sample preparation (extraction) techniques for phthalocyanine blue pigment types

Summary Two sample preparation methods, Soxhlet extraction and the perforation of solutions in conc. sulphuric acid were used and compared for PCDD and PCDF determination in phthalocyanine blue (Heliogen ® Blue) pigments. The Soxhlet extraction method gave lower recoveries for the penta to octachloro homologues. The PCDD/F-values (of isomers) determined with the perforation method were in the range of 0.1 to 3 ppb, mainly hexa, hepta and octachloro-homologues. The results for the tetrachloro-isomers were comparable in the range of precision obtained. Artefact formation during Soxhlet-extraction cannot be excluded. All the analyzed Heliogen Blue-Pigments showed PCDD and PCDF values below the values of the German Regulations (GefStoffV).Dedicated to Professor Dr.Dr. h.c. mult. E. O. Fischer on the occasion of his 75th birthday     

Mikrogrammverfahren zur bestimmung des organisch gebundenen stickstoffes nach der kjeldahlmethode

The proposed method gives a new way for the determination of nitrogen according to Kjeldahl and permits working on a microgram scale. The use of a receiver containing a known amount of strong acid or boric acid can be omitted. As indicators arc recommended : sodium salt of alizarin sulphonic acid (till 100 γ nitrogen) and methyl red (over 100γ nitrogen). The titrations were carried out with 0.004 n and 0.002 n sulphuric acid respectively. The results obtained with proteins, quinine, papaverine, pyramidon, taurine etc. are satisfactory.     

Triphenylmethane dyes as redox indicators in dichrometry

Summary The use of some triphenylmethane dyes, Erioglaucine A, Eriogreen B, Xylenecyanol FF, Setoglaucine O, Setocyanine Supra, Fast Green FCF, and Night Blue as redox indicators in the dichrometric titration of iron(II), ferrocyanide, uranium(IV), molybdenum(V), and hydroquinone in hydrochloric acid, sulphuric acid and perchloric acid media has been studied. Conditions for the satisfactory titrations employing these indicators have been established.

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Triphenylmethanfarbstoffe als Redoxindicatoren bei Titrationen mit Dichromat

Zusammenfassung Bei der Titration von Eisen(II), Hexacyanoferrat(II), Uran(IV), Molybdän(V) und Hydrochinon mit Dichromat in salz-, schwefeloder perchlorsaurer Lösung wurden folgende Triphenylmethanfarbstoffe als Indicatoren verwendet: Erioglaucin A, Eriogrün B, Xylolcyanol FF, Setoglaucin O, Setocyanin Supra, Echtgrün FCF und Nachtblau. Die entsprechenden Titrationsbedingungen werden mitgeteilt.

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We are grateful to the Council of Scientific & Industrial Research, India, for the award of a Junior Research Fellowship to one of us (V. V. S. E. D.).     

Titration of methylene blue with chloromolybdate(III)

The reaction of Methylene Blue with aquomolybdenum(III) chloride and chloromolyb-date(III) in hydrochloric acid media has been investigated. Chloromolybdate(III) can be satisfactorily used as a reductometric titrant for Methylene Blue in 6-8M hydrochloric acid medium. The end-point can be detected either potentiometrically or visually. Aquomolybdenum(III) chloride is not useful as a titrant for this estimation.     

Some triphenylmethane dyes as redox indicators in the titration of antimony(III) with cerium(IV) sulphate

Erioglaucine A, Eriogreen B, Patent Blue and Xylene Cyanol FF work satisfactorily for the titration of Sb(III) with Ce(IV) in 1-2N sulphuric acid medium with iodine as catalyst. In hydrochloric acid medium the colour of the oxidized dye is very evanescent but is very much improved in intensity and stability by the addition of manganese(II) sulphate; no catalyst is needed.     

Colour changes of chemical indicators-VI: metallochromic indicators for direct chelometric titrations of zinc

Eriochrome Blue SE, Eriochrome Red B, Naphthylazoxine 6S, SNAZOXS, and Zincon have been studied in order to find optimum conditions for their use as metallochromic indicators in direct visual chelometric titrations of zinc. The sharpness of the indicator transitions has been investigated by means of photometric titrations and the colour quality has been specified with the aid of the C.I.E. chromaticity systems. Zincon and Eriochrome Blue SE have been found to be the most convenient for visual titrations of zinc.     

Separation of molybdenum from interfering elements by extraction as phosphomolybdenum blue

A simple method is described for the separation of molybdenum from titanium, zirconium, chromium, manganese, iron, cobalt, nickel, uranium and aluminium in a wide variety of samples in <30 min. Phosphomolybdenum blue is produced by boiling for 2 min a molybdate solution containing phosphate to give Mo/P = 20-37 (w/w) with hydrazine sulphate in 0.1N sulphuric acid. The volume and acidity are adjusted to give a molybdenum concentration of 0.6-5 my/ml in 0.4-0.5N sulphuric acid. The phosphomolybdenum blue is 99.5% extracted with methyl isobutyl ketone in a single extraction. The residual molybdenum and hydrazine in the aqueous phase are oxidized with a few drops of liquid bromine and the molybdenum is quantitatively extracted with the same solvent from 1N sulphuric acid as its reddish brown thiosulphato complex. The molybdenum is stripped by ammonia-hydrogen peroxide solution. The back-extract is heated to boiling and filtered to remove the insoluble hydroxides of traces of accompanying elements. The thiosulphate in the filtrate is destroyed by boiling for 4-5 min with excess of hydrogen peroxide in slightly ammoniacal medium. The molybdenum is determined finally by cerimetry or other standard methods.     

Determination of indium and thallium in indium-thallium alloys

The thallium-indium alloys were dissolved in sulphuric acid (1 + 1). In this medium thallium remained in the univalent state and could be determined directly, without a separation, by an oxidation-reduction titration with potassium bromate. The indium was determined directly with an EDTA titration. Ascorbic acid was added to maintain the thallium in the univalent state, which did not interfere. Ascorbic acid also masked any interfering tervalent thallium by effectively reducing it to the univalent state. Sharp end-points were obtained for both titrations, which were carried out in the temperature range of 50-95 degrees . The method offers excellent precision and accuracy.     

Simultaneous spectrophotometric determination of thymol blue, semimethylthymol blue and methylthymol blue II. Monitoring of the syntheses of semimethylthymol blue and methylthymol blue

A new version of the direct spectrophotometric method for the simultaneous determination of Thymol Blue, Semimethylthymol Blue (SMTB) and Methylthymol Blue (MTB) was developed and used for monitoring syntheses of SMTB and MTB.     

Fluorometric titration of calcium, magnesium and iron using calcein blue as indicator

Calcium, magnesium and iron can be determined by successive fluorometric titration without separation. Calcium is titrated directly with EGTA at a pH 13; magnesium is determined by a substitution reaction with copper-EDTA complex at a pH of about 11 ; and iron is titrated directly with EDTA in the presence of hydrogen peroxide at a pH of 10.5, after destroying its triethanolamine complex. Calcein Blue serves as an indicator in all of the titrations and as a fluorescent standard. The end-points are sharp and the accuracy is good for various proportions of the metal ions. The method is simple, reproducible and inexpensive. Standard solutions of ions, limestone, cement and serum samples have been analysed by the proposed method.     

Sequential oxidimetric determination of thallium(I) and (III)

The reaction between thallium(III) and oxalic acid in sulphuric acid medium has been investigated. Spectrophotometric results show that thallium(III) can be quantitatively reduced to thallium(I) with oxalic acid in aqueous medium when heated to near boiling point. Conditions for the estimation of the excess of oxalic acid with cerium(IV) sulphate in the presence of thallium(I) and for the estimation of a mixture of thallium(I) and thallium(III) have been investigated. The method is simpler than many other redox methods reported for the determination of thallium(III) and is free from many interferences encountered in these titrations. The reagents are cheap and quite stable.     

Studies on methylthymol blue-I Separation and purification of methylthymol blue and semimethylthymol blue

The metallochromic indicator Methylthymol Blue was purified chromatographically with cellulose and ion-exchange resin columns. The monosubstituted product of the reaction, Semimethylthymol Blue, was also separated and purified, and can also be used for the colorimetric determination of metals. There are not marked differences between the infrared spectra of Methylthymol Blue and Semimethylthymol Blue. The purities of Methylthymol Blue and Semimethylthymol Blue finally obtained were above 97% and 90% respectively. In acidic medium Methylthymol Blue forms 1:1 greyish blue and 1:2 pure blue chelates with copper(II) whilst Semimethylthymol Blue forms only 1:1 orange chelates with bivalent metals. The molar absorptivities at 435 mmu are 1.89 (+/- 0.03) x 10(4) for Methylthymol Blue at pH 5.00 and 1.76 (+/- 0.03) x 10(4) for Semimethylthymol Blue at pH 5.45.     

Simple conditions for the use of ferroin indicator in cerimetric titrations of antimony(III) alone and in mixtures with arsenic(III)

The titration of antimony(III) with cerium(V) sulphate in the presence of ferroin indicator at room temperature is entirely satisfactory in media consisting of 50% ($\text{v}\text{v}$) acetic acid and 1–3 M hydrochloric acid. In the absence of acetic acid, ferroin reacts with the antimony(V) formed in the very early stages, to give a sparingly soluble red complex, which remains in suspension and resists oxidation by cerium(IV). This titration provides a rational method for sequential visual titrations of antimony(III) and arsenic(III). The composition of the ferroin-antimony(V) complex is discussed. Titrations of antimony(III) in 0.5–1 M sulphuric acid medium do not require acetic acid but need iodine monochloride catalyst.     

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.