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.     

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.     

Solochrome Violett R. S. as a new colorimetric reagent

Summary The reaction between molybdenum and the sulphonic acid azo dye Solochrome Violet R.S. has proved to be a suitable one for the microdetermination of Mo amounts covering the range of 0.3 to 10 ppm in purely aqueous solutions. The variation of extinction with concentration conforms satisfactorily with Beer's law throughout the whole range. Very many cations and anions do not interfere with such a determination. Ferric iron up to 2 mg per 25 ml is completely masked with ascorbic acid.Part II: Khalifa, H., and S. W. Bishara: Z. analyt. Chem. 178, 345 (1960).     

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.     

Reduction of selenious acid by hydrazine sulphate. Volumetric determination of selenium

Summary A volumetric method of estimating selenium, depending upon the reduction of selenious acid by excess hydrazine sulphate solution and titration of the excess against KIO₃ to the iodine monochloride end point, has been described. Determination of tellurium on these lines is suggested.The author is indebted to Professor S. S.Joshi for facilities and kind interest in the work. The award of a Scientific Man Power Committee Research Fellowship is also gratefully acknowledged.     

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.     

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).     

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.     

Diphenic acid as an analytical reagent

Summary Diphenic acid can separate thorium completely from moderate amounts of ferrous iron and titanium in almost neutral solutions. As the reagent forms quantitative precipitates with ferric iron and zirconium, workable methods for their separation from thorium and their co-determinations in a mixture with the help of this reagent have also been developed. The reagent can separate thorium from zirconium by precipitating the latter below p_h2, and the same from iron(ic) can be accomplished by the use of ascorbic acid as a masking agent. Ferric iron can be precipitated from solution containing ascorbic acid, by the ammonium salt of the reagent. A convenient process for the estimation and separation of zirconium, thorium, iron(ic) and titanium, when present in a mixture, has also been described, which involves the proper control ofph and the use of ascorbic acid as a complexing agent for ferric iron.My sincere thanks are due to Dr. A.K. Mukherjee of the Indian Association for the Cultivation of Science, Calcutta for his valuable suggestions and to Dr. A. K. Ghosal, Principal, Darjeeling Government College for providing laboratory facilities.     

Kinetic Spectrophotometric Determination of Ascorbic Acid in Pharmaceutical Samples by Oxidation of Ponceau 4R by Hydrogen Peroxide

A new sensitive and simple kinetic method is developed for determination of traces of ascorbic acid based on its activated effect on oxidation of trisodium‐2‐hydroxy‐1‐(4‐sulphonato‐1‐naphthylazo)naphthalene‐6,8‐disulphonato (red artificial color Ponceau 4R) by hydrogen peroxide, in the presence of Cu(II) as catalyst, in borate buffer. The reaction is followed spectrophotometrically by tracing the oxidation product at 478.4 nm within 1 min after addition of H₂O₂. The optimum reaction conditions are: borate buffer (pH = 11.00), Ponceau 4R (9.6·10^?6 mol/L), H₂O₂ (2·10^?2 mol/L), Cu(II) (8·10^?7 mol/L) at 22 °C. Following this procedure, ascorbic acid can be determined with a linear calibration graph up to 1.76 ng/mL and a detection limit of 0.28, based on 3S criterion. The relative error ranges between 6.77‐1.66% for the concentration interval of ascorbic acid 1.76‐17.61 ng/mL. The effects of certain foreign ions upon the reaction rate were determined for an assessment of the selectivity of the method. The method was applied for determination of ascorbic acid in pharmaceutical samples, and spectrophotometric method was used like an comparative method.     

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.     

Selektive und quantitative Bestimmung von Alkoxyl und Oxyalkylen in nieder- und hochmolekularen Substanzen

Zusammenfassung Es wurde eine Methode und Apparatur beschrieben, mit der Alkoxylgruppen (C₁-nC₄) und Oxyalkylengruppen (-OC₂H₄- und OC₃H₆-) selektiv und quantitativ bestimmt werden können. Die bei der JodwasserstoffsÄurespaltung (Zeisel) entstehenden Alkyljodide werden in einer KÄltefalle über Vermiculit oder bei Raumtemperatur über Kieselgel quantitativ festgehalten und die bei der Umsetzung entweichenden Reaktionsgase in einem Azotometer gesammelt.Nach dem Aufschlu\ werden die Alkyljodide an Trikresylphosphat auf Embacel und die Reaktionsgase an Squalan auf Sterchamol gas-chromatographisch getrennt und die Komponenten aufgrund ihrer Retentionszeit identifiziert.Die einzelnen Alkyljodidfraktionen werden quantitativ durch jodometrische Titration nach Vieböck und Brecher, die Gasfraktionen volumetrisch nach Janák bestimmt und daraus der Prozentgehalt der entsprechenden Alkoxyl- und Oxyalkylengruppen ausgerechnet.

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Summary A new method and apparatus is described for the selective and quantitative determination of alkoxyl (C₁-nC₄) and oxyalkylene groups (-OC₂H₄- and -OC₃H₆-). The alkyl iodides, generated by cleavage with boiling hydroiodic acid, are collected in a freezing trap over vermiculite or over silica gel and the reaction gases are passed into an azotometer by the carrier gas.After the reaction the alkyl iodides are separated gaschromatographically by tricresylphosphate on embacel and the reaction gases by squalane on sterchamol, and the components are identified by their retention times.The quantitative determination of alkyl iodides is performed iodometrically according to Vieböck and Brecher and the gas fractions are determined volumetrically according to Janák. The results obtained are equivalent to the percentage of the individual alkoxyl and oxyalkylen groups.

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Den Herren H. Leffringhausen und W. Mann danke ich auch an dieser Stelle für die eifrige Mithilfe bei der Ausarbeitung der Methoden, und Herrn E. Heil für gegebene RatschlÄge bei der Einrichtung der Gastrennung.     

Exploiting Sulphide Generation and Gas Diffusion Separation in a Flow System for Indirect Sulphite Determination in Wines and Fruit Juices

A flow system for sulphite determination in wines and fruit juice samples has been developed exploiting H₂S generation and gas diffusion separation. The composed sandwich gas diffusion cell was coupled in the flow manifold to permit sulphite reduction to H₂S and H₂S diffusion through a microporous PTFE membrane to produce methylene blue resulting from the reaction with N,N-dimethylphenylene diamine (DMPD) and Fe³⁺. The flow parameters were optimized, and the best results were obtained by using NaOH solution for H₂S collection. Interferences of H₂S, CO₂ and ascorbic acid were evaluated. Limits of detection (3σ) for the free and total sulfite were calculated at 0.12 and 0.25 mg L⁻¹, respectively. The results obtained by the proposed process were in agreement with the reference methods for a 95% confidence level.     

Detection of halogenated organic compounds using immobilized thermophilic dehalogenase

Environmental pollutants containing halogenated organic compounds can cause a plethora of health problems. Detection, quantification, and eventual remediation of halogenated pollutants in the environment are important to human well-being. Toward this end, we previously identified a haloacid dehalogenase, L-HAD_ST, from the thermophile Sulfolobus tokodaii. This thermophilic enzyme is extremely stable and catalyzes, stereospecifically, the dehalogenation of l-2-haloacids. In the current study, we covalently linked L-HAD_ST to an N-hydroxysuccinimidyl Sepharose resin to construct a highly specific sensor with long shelf life for the detection of l-2-haloacids. The enzyme-modified resin was packed into disposable columns. Samples containing l-2-haloacids were first incubated in the column, and were then collected to quantify the chloride produced through the breakdown of the substrate. The optimum pH of the immobilized enzyme is around 9.5, similar to that of the soluble protein. Its catalytic activity increased with temperature up to the highest temperature measured (50 °C). The resin could be fully regenerated after multiple reaction cycles and retained 70% of the initial activity after being stored at 4 °C for 6 months. The L-HAD_ST-modified resin could be used to breakdown and quantify l-2-haloacids spiked in the simulated environmental samples, indicating dehalogenases from extremophiles can potentially be employed in the detection and decontamination of l-2-haloacids.     

Synthesis of LiCoO<Subscript>2</Subscript> by <Emphasis Type="SmallCaps">l</Emphasis>-apple acid assisted sol–gel method and its electrochemical behavior in aqueous lithium-ion battery

The synthesis process of LiCoO₂ prepared by l-apple acid (l-HOOCCH(OH)CH₂COOH) assisted sol–gel method is studied by using Fourier transforms infrared spectroscopy, mass spectroscopy, simultaneous thermogravimetric and differential thermal analysis, X-ray diffraction analysis, and elemental analysis. The results show that lithium and cobalt ions are trapped homogeneously on an atomic scale throughout the precursor. Lithium carbonate and Co₃O₄ are intermediate products during heat treatment of the precursor. Moreover, the kinetics for formation of LiCoO₂ by l-apple acid assisted sol–gel method is faster than the case of the conventional solid-state reaction between lithium carbonate and Co₃O₄. In comparison with the solid-state reaction, the sol–gel method significantly shortens the required reaction time for synthesizing LiCoO₂, and also reduces the particle size. In the electrochemical test, it is found that the specific discharge/charge capacities as well as the coulomb efficiency substantially increase with increasing the calcination temperature. It is considered that LiCoO₂ with a good-layered structure facilitates the insertion and de-insertion of lithium ions in aqueous electrolyte. As a result, the combination of the sol–gel method with proper calcination processes is highly successful in producing LiCoO₂ powders with large specific capacity and good cycle performance in aqueous lithium-ion battery.     

Rearrangement of a trishomocubane derivative to a tetracyclo[6.3.0.02,6.03,10]undec-4-ene

Reaction of 8,8,11,11-tetrafluoropentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane with idio trimethylsilane leads to the expectedd ₃-trishomocubane derivative, but reaction with the more electrophilic boron tribromide yields a tetracyclo[6.3.0.0^2,6.0^3,10]undec-4-ene derivative which was characterized by X-ray diffraction. The most easily visualized pathway for this transformation would be an initial rearrangement of the starting material to ad ₃-trishomocubane followed by additional bond breaking to form the undec-4-ene compound. Molecular mechanics calculations indicate the brominatedd ₃-trishomocubane is about 4 kcal/mol more stable than the brominated undec-4-ene molecule and the associated carbonium ions show the same ordering. These data would indicate an alternate reaction pathway must be operative; however, semiempirical calculations predict the reverse ordering of the above energies.     

Stereoselective Synthesis and Complexation of a New Chiral Hybrid Phosphine-Phosphine Oxide Ligand from (S)-(+)-Prolinol

Abstract

The synthesis and the complex formation of chiral heterotopic ligands with two different binding sites each capable of bonding a different type of metal are described. The action of bis(dimethylamino) aryl phosphine on (S)-(+)-prolinol gives rise to the kinetic stereoisomer (2S,4S)-2-phenyl-1,3,2-oxazaphospholidine 1 and the thermodynamic stereoisomer (2R,4S)-2-phenyl-1,3,2-oxazaphospholidine 2. 1 is then totally converted into 2 at the end of the reaction. The Michaelis Arbuzov reaction of 2 with benzylbromide affords (R_p)-benzylaryl-(2-(S)-bromomethyl pyrrolidine-1-yl) phosphine oxide 3 in 80% yield. Compound 3 is an ideal chiral precursor for the synthesis of chiral hybrid phosphine-phosphine oxide ligands. The bromide atom is smoothly displaced by lithium diphenylphosphide to afford in 80% yield (R_p)-benzylaryl-(2-(S)-diphenylphosphinomethylpyrrolidine-1-yl) phosphine oxide 5. These reaction are proved to be totally stereoselective : the Michaelis Arbuzov reaction does not change the configuration at C2 in the proline ring. The relative configuration (R_p) of 5 (aryl = phenyl) was determinated by X-ray diffraction, from the known configuration of (S)-(+)-prolinol.     

Simultaneous dual wavelength spectrophotometric determination of citric and ascorbic acids using an artificial neural network

In this study, a very simple spectrophotometric method for the simultaneous determination of citric and ascorbic acid based on the reaction of these acids with a copper(II)-ammonia complex is presented. The Cu²⁺-NH₃ complex (with λ_max = 600 nm) was decomposed by citrate ion and formed a Cu²⁺-citrate complex (with λ_max = 740 nm). On the other hand, during the reaction of ascorbic acid with copper(II)-ammonia complex, ascorbic acid is oxidized and the copper(II)-ammonia complex is reduced to the copper(I)-ammonia complex and the absorbance decreases to 600 nm. Although there is a spectral overlap between the absorbance spectra of complexes Cu²⁺-NH₃ and Cu²⁺-citrate, they have been simultaneously determined using an artificial neural network (ANN). The absorbances at 600 and 740 nm were used as the input layer. The ANN architectures were different for citric and ascorbic acid. The output of the citric acid ANN architecture was used as an input node for the ascorbic acid ANN architecture. This modification improves the capability of the ascorbic acid ANN model for the prediction of ascorbic acid concentrations. The dynamic ranges for citric and ascorbic acid were 1.0–125.0 and 1.0–35.0 mM, respectively. Finally, the proposed method was successfully applied to the determination of citric and ascorbic acids in vitamin C tablets and some powdered drink mixes. The text was submitted by the authors in English.     

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.