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.     

Gravimetric estimation of bismuth as bismuthyl dichromate

Summary Conditions are described for the quantitative precipitation of bismuthyl dichromate, (BiO)₂Cr₂O₇, and the suitability of this reaction for the gravimetric estimation of bismuth is shown. The use of arsenious oxide as a primary standard for the iodometric titration of excess chromate is emphasised.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.     

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.     

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.     

Oxidations with potassium permanganate in the presence of fluoride

Summary The titration of ferrous iron in presence of fluoride ions in acid medium gives fleeting end points and erroneous results. A method is deviced to overcome this difficulty by oxidising the ferrous with an excess of KMnO₄ in alkaline medium. After mixing the reactants the excess of KMnO₄ is reduced by an excess of Hg₂ ²⁺ ions in presence of H₂SO₄ and fluoride. The remaining mercurous is then titrated with standard KMnO₄ solution.Part III: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 174, 418 (1960).     

Oxidations with potassium permanganate in the presence of fluoride

Summary Quadrivalent selenium can be determined with fair accuracy by mixing with an excess of KMnO₄ in the presence of 25–75 ml of 2% NaF solution and 4–7 ml of 9 N sulfuric acid. After leaving the reaction mixture for 10–30 minutes the excess KMnO₄ is estimated by one of the following procedures: A) Titration of the excess KMnO₄ with monovalent mercury, B) Adding an excess of Hg₂ ²⁺ solution to react with the excess KMnO₄ followed by titrating the excess mercurous with KMnO₄ solution.Part I: Issa, I. M., and M. Hamdy, Z. analyt. Chem. 172, 94 (1980).     

Oxidations with potassium permanganate in the presence of fluoride

Summary Trivalent chromium and quadrivalent vanadium can be determined with fair accuracy by a method consisting in mixing either with an excess of KMnO₄ in the presence of 0.3 to 1.8 M alkali hydroxide. After leaving the mixture for 5 min, the solution is acidified with sulphuric acid and mixed with 50 to 75 ml of 2% NaF solution. An excess of monovalent mercury Hg₂ ²⁺ solution is then added, the solution heated to 40° C and then titrated with KMnO₄ solution in the presence of Cu²⁺ ions to conceal the pink manganic fluoride colour.Part II: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 172, 162 (1960).     

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.).     

Oxidation with manganate solutions

Summary The reaction between Tl⁺ solutions and manganate is sluggish. In the titration of Tl⁺ with manganate solution the end points are always attained earlier than the theoretical. When the reaction is accelerated by NaCl and heating to 45–50° C the end points were found to be concordant with the theoretical values. Titration of manganate with Tl⁺ solutions gives accurate results in presence of telluric acid but not in its absence. It is also possible to determine Tl⁺ by oxidation with an excess of K₂MnO₄ using arsenite as a back titrant for excess oxidant.Part III: Issa, I. M., and M. G. E. Allam: Z. analyt. Chem. 175, 103 (1960).     

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.

---

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.

---

---

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.     

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.     

Determination of cobalt as tellurite

Summary Cobalt has been determined gravimetrically by precipitation as cobalt tellurite and by titration of the excess tellurite added. Effect of temperature of drying and addition of excess of tellurite was studied. Composition of the cobalt tellurite has also been determined.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 gratefully acknowledged.     

Thermal properties of amphiphilic biodegradable triblock copolymer of <Emphasis Type="SmallCaps">l</Emphasis>,<Emphasis Type="SmallCaps">l</Emphasis>-lactide and ethylene glycol

Samples of poly(l,l-lactide)-block-poly(ethylene glycol)-block-poly(l,l-lactide) (PLLA-PEG-PLLA) were synthesized from l,l-lactide polymerization using stannous 2-ethylhexanoate, Sn(Oct)₂ as initiator and di-hydroxy-terminated poly(ethylene glycol) (PEG) (M _n  = 4000 g mol⁻¹) as co-initiator. The chemical linkage between the PEG segment and the PLA segments was characterized by Fourier transform infrared spectroscopy (FTIR). Thermogravimetry analysis (TG) revealed the copolymers composition and was capable to show the deleterious effect of an excess of Sn(Oct)₂ in the polymer thermal stability, while Differential Scanning Calorimetry (DSC) allowed the observation of the miscibility between the PLLA and PEG segments in the different copolymers.     

A study of Co/Mo/Al2O3 hydrodesulphurization catalysts and related model compounds byxps and x-ray absorption spectroscopy (xanes andexafs )

A detailed investigation of sulphided Co/Mo/Al₂O₃ catalysts, their oxide precursors and several model oxides and sulphides of cobalt and molybdenum has been carried out using x-ray photoelectron spectroscopy and x-ray absorption spectroscopy (xanes andexafs). Octahedrally coordinated Co(II) and Mo(IV) are shown to be present in a sulphidic environment on the surfaces of these catalysts. The surface species contain an excess of sulphur, probably involving disulphide linkages. The surface compositions of the catalysts examined conform to the general formula Co¹¹ Mo _2n ^IV (2n + 3)S ₂ ²⁻ (2n -2)S²⁻.     

Neue Methoden zur Gehaltsbestimmung von Indolyl-3-brenztraubens?ure

Zusammenfassung Es werden 3 Methoden zur quantitativen Bestimmung der Indolyl-3-brenztraubensäure über ihren mit Diazomethan gewonnenen Methylester beschrieben, wobei die Lösung des Methylesters mit Dichlorphenolin-dophenol oxydiert wird. Bei der Methode A wird der Überschuß des Oxy-dationsmittels titrimetrisch mit Fe^II(NH₄)₂(SO₄)₂ zurückgemessen, bei der Methode B wird die Extinktionsabnahme des Oxydationsmittels in verdünnter propanolischer Lösung bei 635 nm gemessen. Bei Methode C wird der bei der Oxydation aus dem Indolyl-3-brenztraubensäuremethylester gebildete grüne Farbstoff mit Amylalkohol extrahiert und die Absorption bei 662 nm gemessen. Diese Methode ist für die Untersuchung von Rein- und Rohpräparaten am besten geeignet.

---

Summary Three methods are described for the estimation of indole-3-pyruvic acid using the methyl ester of the acid, which is oxidized by dichlorphenolindophenol. In method A the excess of DCPIP is determined titrimetrically by Fe^II(NH₄)₂(SO₄)₂, in method B the decrease of the extinction of the oxidizing agent in diluted propanolic solution is measured at 635 nm, in method C the green oxidation product of the methyl ester formed during the reaction is extracted by n-pentanol and the absorption is determined spectrophotometrieally at 662 nm. This latter method is the most suitable one for the analysis of pure preparations and crude products.

---

---

Ich danke Herrn Professor Dr. M. Steiner für die Untersützung der Arbeit durch Mittel des Institutes; Fräulein S. Ritter und Herrn E. Fritz für die Mitarbeit bei den Versuchen.     

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.     

Titration of AsO43? ions with 0.1 M magnesium sulphate solution in the presence of Ca2+, Mg2+, Fe3+, Cu2+ ions and some other foreign substances

Summary For the convenient and sufficiently accurate determination of AsO₄ ^3– ions in technical products containing different filling, suspending and colouring materials, as well as impurities—e.g. for the assay of arsenate containing plant protecting materials—the following procedure is recommended.About 5 g of the sample is dissolved, resp. extracted with 4 N hydrochloric acid, and aliquots of the clear filtrate are titrated after elimination of the interfering metal ions by combining them with complexing agents (potassium cyanide and disodium ethylenediamin tetraacetic acid) in a properly buffered medium. The titration with 0.1 M MgSO₄ solution is conducted in the presence of eriochrome black T solution as indicator, first time for eliminating the excess of EDTA added, and afterwards to determine the AsO₄ ^3– ions, after adding about 40% of ethanol.The procedure may be useful chiefly for serial routine analyses.The authors are indebted to engineer L. Fokássy, department leader at the State Institute for Agricultural Quality Control, as well as to engineeress P. Fodor and Mr. Gy. Josepovits, scientific collaborators of the Research Institute for Plant Protection, for kindly supplying some of the samples for the experiments.     

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.