Determination of bismuth by selenious acid

Summary Bismuth is shown to be precipitated quantitatively as bismuth selenite by boiling an almost neutral solution of bismuth nitrate and excess selenious acid. The excess H₂SeO₃ is determined iodometrically by standard thiosulphate or arsenious oxide solution. Alternatively, the precipitated selenite may be dried at 105–110° C and weighed as Bi₂(SeO₃)₃.Sincere thanks of the authors are due to Prof. S. S. Joshi for research facilities and to Dr. G. S. Deshmukh for keen interest in the work.     

Determination of ascorbic acid by potassium iodate

Summary Results are given for a two stage oxidation in the ascorbic acid-KIO₃ reaction under controlled conditions of acidity. The first step corresponds to the Landolt reaction and the second end point is obtained by the classical Andrews method. The reproducibility and accuracy of the results calculated on the basis of the two successive end points constitute an interesting new feature of this redox reaction involving the use of KIO₃ as a primary standard for the determination of ascorbic acid.Our sincere thanks are due to Professor S. S. Joshi for kind interest in the work and to the National Institute of Sciences of India for award of a Research Fellowship to one of us (G. S. D.).     

Iodometric determination of potassium permanganate by arsenious oxide following iodide reduction in presence of borax-boric acid buffer and barium chloride

Summary An iodometric method for the determination of potassium permananate is described following its reduction to MnO₂ in presence of boraxboric acid buffer at PH 8–10 by iodide and titration of the liberated iodine with standard arsenious oxide solution. Excess BaCl₂ is added to coagulate the colloidal MnO₂ whose otherwise partial reduction by iodide is prevented thereby.Sincere thanks of the authors are due to Prof. S. S. Joshi, for his kind interest in the work.     

Iodine monochloride end point in the oxidation of thiocyanate by permanganate. Determination of cerium

Summary A new volumetric method for cerium determination based on the quantitative reduction of Ce(SO₄)₂ by excess potassium thiocyanate and titration of the excess with standard KMnO₄ to the ICl end point has been described.Sincere thanks of the authors are due to Professor S. S. Joshi for facilities and kind interest in the work. The award of a U. P. Scientific Research Committee Scholarship to one of us (M.K.J.) is also gratefully acknowledged.     

Conductometric estimation of thorium in dilute thorium chloride

Summary Conductometric titrations of thorium chloride against oxalic acid, ammonium oxalate and silver nitrate have been carried out at high dilutions (0.001, 0.0005 and 0.00033 M) of the chloride. Oxalic acid is found to be a suitable titrant for rapid estimation of thorium, the minimum error being +0.5%. The other titrants do not give good results. The titrations with ammonium oxalate indicate the step-wise ionisation of ThCl₄ into ThCl₂ ²⁺, ThCl³⁺ and Th⁴⁺. For mixtures of thorium chloride and cerous chloride, only the equivalence point corresponding to complete precipitation of both thorium and cerium is indicated.The authors express their sincere thanks to Prof. S. S.Joshi for his keen interest in this work and to Dr. G. S.Deshmukh for his advice and help in so many ways during the progress of these studies.     

Oxidation of thiocyanate by alkaline ferricyanide

Summary Oxidation of KSCN by alkaline K₃Fe(CN)₆ in presence of osmic acid has been studied quantitatively. The reaction proceeds at a measurable rate at ordinary temperature but is accelerated on refluxing the system on a water bath for a short time. The stoichiometry of the redox process suggests the formation of cyanate and sulphate as the products of oxidation. The quantity of thiocyanate is calculated by estimating the ferrocyanide formed and the ferricyanide consumed in terms of Ce(SO₄)₂ and Na₂S₂O₃ respectively. A kinetic study of the above reaction is under investigation.Sincere thanks of the author are due to Prof. S. S. Joshi for facilities and kind interest in the work. The award of a Scientific Man Power Committee Research Scholarship is also gratefully acknowledged.     

Extrahierte Verbindungen von Gallium, Indium und Thallium in Verteilungssystemen mit Tributylphosphat, Cyclohexanon und Isobutylmethylketon

Zusammenfassung Das Verteilungsverhalten der Halogenide und Halogenometallate von Gallium, Indium und Thallium mit den drei Solventien (S) Tributylphosphat (TBP), Cyclohexanon (Cyclo) und Isobutylmethylketon (IBMK) wurde untersucht. Die extrahierten Verbindungen wurden nach der Geradenmethode nach Asmus, der logarithmischen Methode nach McKay, der Methode der kontinuierlichen Variation, durch Analyse der beiden Phasen und durch konduktometrische Extraktionstitration nachgewiesen. Identifiziert wurden folgende Verbindungen: [GaCl₄]^–·2 S, Ga-(SCN) ₃·3 TBP, [Ga(SCN)₄]^–·2 TBP, [InCl₄]^–·2 TBP, [InBr₄]^–·2TBP, [InBr₄]·x Cyclo, [InBr₄]^–·x IBMK, [InJ₄]^–·2 S, In(SCN)₃·3 TBP, [In(SCN)₄]^–·2 TBP, TlCl₃·1 TBP, [TlCl₄]^–·2 S, TlBr₃·1 TBP, [Tl-Br₄] ^–·2 S, TlJ₃·x TBP und [TlJ₄]^–·xS. Wegen der nicht eindeutig definierten Oxydationsstufe von Thalliumjodiden ergaben sich bei den Versuchen experimentelle Schwierigkeiten. Daher wurde in diesem System zusätzlich das radioaktive Isotop ²⁰⁴Thallium verwendet.

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Extracted compounds of gallium, indium and thallium in distribution systems with tributyl phosphate, cyclohexanone and isobutylmethylketone

The behaviour of distribution of the halides and halogenometallates of gallium, indium and thallium with the three solvents (S) tributylphosphate (TBP), cyclohexanone (Cyclo) and isobutylmethylketone (IBMK) are investigated. The extracted compounds are detected with the straight-line method of Asmus, the logarithmic method of McKay, the method of continuous variation, by analysis of the two phases, and with the conductometric extraction-titration. The following compounds were identified: [GaCl₄]^–·2S, Ga(SCN)₃·3TBP, [Ga(SCN)₄]^–·2TBP, [InCl₄]^–·2TBP, [InBr₄]^–·2TBP, [InBr₄]·x Cyclo, [InBr₄]^–·x IBMK, [InJ₄]^– ·2S, In(SCN)₃·3TBP, [In(SCN)₄]^–·2TBP, TlCl₃·1TBP, [TlCl₄]^–·2S, TlBr₃ ·1TBP, [TlBr₄]^–·2S, TlJ₃·x TBP and [TlJ₄]^–·x S. The not unequivocally defined stage of oxidation of thallium iodides resulted in experimental difficulties. Thus, in this system the radioactive isotope ²⁰⁴thallium was additionally used.

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Herrn Professor Dr. E. Asmus zum 60. Geburtstag gewidmet.

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Wie danken Herrn Priv.-Doz. Dr. H. Nickel für die freundliche Unterstützung bei den in der KFA Jülich durchgeführten radioaktiven Messungen.     

Coordination complexes of l-azetidine-2-carboxylic acid with platinum(II) and palladium(II)

Summary The complexes K[Pt(l-aze)Cl₂, [Pt(l-aze)₂] and [Pd(l-aze)₂] (l-aze = l-azetidine-2-carboxylate) were prepared. X-ray structures show that [Pt(l-aze)₂] and [Pd(l-aze)₂] are isomorphous, having a planar tetragonal geometry with a trans configuration around the Pt and Pd atoms. Slight puckerings of the MN(1)N(11)O(11) chelate ring (M = Pt or Pd) and the azetidine ring were observed. The circular dichroism (c.d.) spectra of the complexes in aqueous solution agree with the structures found in the solid state as far as the hexadecant rule is concerned, giving, for the trans configuration of [M(l-ia)₂] (where ia = imino acid), the profile of the c.d. signs for the three predominant d-d transitions as: +,-,-. I.r., conductivity and n.m.r. measurements are also reported and are in accord with the proposed structures.     

Determination of the primary structure and carboxyl p<Emphasis Type="Italic">K</Emphasis><Subscript>A</Subscript>s of heparin-derived oligosaccharides by band-selective homonuclear-decoupled two-dimensional <Superscript>1</Superscript>H NMR

Determination of the structure of heparin-derived oligosaccharides by ¹H NMR is challenging because resonances for all but the anomeric protons cover less than 2 ppm. By taking advantage of increased dispersion of resonances for the anomeric H¹ protons at low pD and the superior resolution of band-selective, homonuclear-decoupled (BASHD) two-dimensional ¹H NMR, the primary structure of the heparin-derived octasaccharide ∆UA(2S)-[(1 → 4)-GlcNS(6S)-(1 → 4)-IdoA(2S)-]₃-(1 → 4)-GlcNS(6S) has been determined, where ∆UA(2S) is 2-O-sulfated ∆^4,5-unsaturated uronic acid, GlcNS(6S) is 6-O-sulfated, N-sulfated β-d-glucosamine and IdoA(2S) is 2-O-sulfated α-l-iduronic acid. The spectrum was assigned, and the sites of N- and O-sulfation and the conformation of each uronic acid residue were established, with chemical shift data obtained from BASHD-TOCSY spectra, while the sequence of the monosaccharide residues in the octasaccharide was determined from inter-residue NOEs in BASHD-NOESY spectra. Acid dissociation constants were determined for each carboxylic acid group of the octasaccharide, as well as for related tetra- and hexasaccharides, from chemical shift–pD titration curves. Chemical shift–pD titration curves were obtained for each carboxylic acid group from sub-spectra taken from BASHD-TOCSY spectra that were measured as a function of pD. The pK _As of the carboxylic acid groups of the ∆UA(2S) residues are less than those of the IdoA(2S) residues, and the pK _As of the carboxylic acid groups of the IdoA(2S) residues for a given oligosaccharide are similar in magnitude. Relative acidities of the carboxylic acid groups of each oligosaccharide were calculated from chemical shift data by a pH-independent method.     

Determination of thiocyanate by potassium bromate

Summary Estimation of thiocyanate, based on its titration with standard KBrO₃ solution in presence of 1.5–3.0 N hydrochloric acid, is described. The end point is determined either potentiometrically or with methyl orange as indicator.Sincere thanks of the author are due to Professor S. S. Joshi for research facilities.     

Gleichzeitige Bestimmung von Sulfit und Sulfid in sulfathaltigen Gemischen

Zusammenfassung Sulfit- und Sulfidschwefel werden in einer Entwicklungsapparatur nacheinander als SO₂ und H₂S ausgetrieben und nach bekannten Methoden acidimetrisch bzw. jodometrisch titriert. Zur Zersetzung der Sulfite dient 20%ige Perchlorsäure, die bei Gegenwart von HgCl₂ kein H₂S frei macht. Zur Zersetzung der Sulfide werden anschließend SnCl₂ und HCl zugefügt.

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Summary A method has been developed for the simultaneous determination of sulphite and sulphide in sulphates. The sulphites are decomposed by 20% perchloric acid in presence of mercuric chloride which prevents evolution of hydrogen sulphide. Sulphur dioxide is absorbed in alkaline hydrogen peroxide, an excess is back-titrated by acid. The sulphides are then decomposed by stannous chloride and hydrochloric acid. The hydrogen sulphide is absorbed in cadmium acetate solution and titrated with iodine.

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Wir danken der Deutschen Forschungsgemeinschaft und dem Verband der Chemischen Industrie (Fonds der Chemie) für die Förderung der Arbeit durch Sachbeihilfen sowie Frau E.-M. Rinne und Frl. H. Schirra für ihre verständnisvolle und sorgfältige Mitarbeit.     

Iodometric estimation of cerium(IV) by arsenious oxide

Summary Determination of cerium(IV), depending upon its reduction to cerium-(III) by KI and titration of the liberated iodine with standard arsenious oxide solution in a suitably adjusted p_H range, is described.Sincere thanks of the author are due to Professor S. S. Joshi for research facilities.     

Conductometric and ph studies on cobalt tellurite

Summary Conductometric and p_H titration procedures for the determination of cobalt over a wide range of concentrations of cobalt solutions are described. Direct, as well as reverse titration procedure are shown to be possible and the effect of varying ethanol concentrations is reported. Both conductometric and p_H studies lend support to the 11 molar ratio of Co and Te.Sincere thanks of the authors are due to Prof. S. S. Joshi, D. Sc. (London), Head of the Chemistry Department for keen interest and facilities. The award of a scholarship to one of us (V.D.A.) by the Ministry of Scientific Research and Cultural Affairs is also acknowledged.     

Sodium alizarin-3-sulphonate as a chromophoric reagent

Summary A method for the colorimetric determination of hexavalent tungsten with Alizarin Red S has been described. The composition of the coloured chelate is MKe₂ and the wave length of maximum absorption is 470 nm. The colour reaction is almost instantaneous. The coloured complex conforms to Beer's Law over tungsten concentration of 0.37 to 13.3 ppm. The suitable p_H for the measurement is 3.5 to 5.8 and temperature has no effect on the intensity of the colour. The sensitivity is 0.037 g/cm² (Sandell) and 0.37 g/cm² (practical) based on an absorption of 0.01 unit. The interference of added foreign ions has also been investigated and most of the common ions are found to interfere and should, therefore, be removed before determination of tungsten is made.

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Zusammenfassung Es wird eine Methode zur colorimetrischen Bestimmung von Wolfram(VI) mit Alizarinrot S beschrieben. Die Zusammensetzung des Farbkomplexes ist MeAliz₂, das Absorptionsmaximum liegt bei 470 nm. Die Farbreaktion verläuft fast augenblicklich und gehorcht dem Beer'schen Gesetz im Bereich von 0,37–13,3 ppm Wolfram. Der günstigste p_H-Bereich liegt zwischen 3,5 und 5,8. Die Temperatur ist ohne Einfluß auf die Farbintensität. Die Empfindlichkeit beträgt 0,037 g/cm² (Sandell) bzw. praktisch 0,37 g/cm² (Absorption 0,01 Einheiten). Da die meisten Fremdionen stören, müssen sie vor der Bestimmung abgetrennt werden.

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Part I: Banerji, S. K., and A. K. Dey: Z. analyt. Chem. 179, 30 (1961).     

Electrometric end points in the oxidation of thiocyanate by permanganate. Determination of cerium

Summary Oxidation of thiocyanate by standard permanganate using electrometric end points is shown to be quantitative in 1.5–2.5N HCl medium and in the presence of ICl as catalyst. A method of estimating cerium(IV), based upon its reduction to cerium(III) by excess KSCN and potentiometric titration of the excess against KMnO₄, is also described.Sincere thanks of the author are due to Prof. S. S. Joshi for research facilities.     

Eine neue Methode zur Darstellung von Thiozuckern

Zusammenfassung Durch direkte Einwirkung von H₂S in dimethylformamid aufPictetsches Anhydrid kann aus Glucose in fast quantitativer Ausbeute 1-Thio-d-glucopyranose erhalten werden.