A new approach to the reduction of sulfoxides to sulfides with 1,3-dithiane in the presence of electrophilic bromine as catalyst

A new, mild, and novel method is described for the efficient deoxygenation of sulfoxides to their corresponding sulfides with 1,3-dithiane at room temperature in the presence of catalytic amounts of N-bromosuccinimide (NBS), 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO), or Br(2) as the source of electrophilic bromine.     

p-4He elastic scattering at 2.68 GeV

The p-⁴He elastic differential cross section has been measured at a kinetic energy of 2.68 GeV. The momentum transfer region studied is t = 0.15–0.66 (GeV/c)². The cross section displays a shallow first minimum and shape very similar to recent data at 1 GeV.     

A new liquid membrane electrode for determination of vitamin B1 in multivitamin preparations

Summary A new liquid membrane electrode was developed which is highly selective and sensitive for vitamin B₁. It is based on the thiamine-picrolonate ion-pair complex as an electroactive material in nitrobenzene solvent. The electrode has a remarkable selectivity for vitamin B₁ in the presence of vitamins B₂, B₆, B₁₂ and nicotinamide. The results obtained for the determination of vitamin B₁ in various multivitamin preparations at levels as low as 1 g/ml show an average recovery of 98% (mean standard deviation 1.8%) and are favourably compared with those obtained by the official methods.

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Neue Flüssig-Membranelektrode zur Bestimmung von Vitamin B₁ in Multivitaminpräparaten

Zusammenfassung Eine neue, für Vitamin B₁ hochselektive Flüssig-Membranelektrode wurde entwickelt. Sie beruht auf dem Thiamin-Picrolonat-Ionenpaarkomplex als elektroaktives Material im Lösungsmittel Nitrobenzol. Die Elektrode besitzt eine beachtliche Selektivität für Vitamin B₁ in Gegenwart der Vitamine B₂, B₆, B₁₂ und Nicotinamid. Bei Bestimmungen in verschiedenen Multivitaminpräparaten mit Konzentrationen bis herab zu 1 g/ml erhielt man eine durchschnittliche Wiederfindung von 98% (mittlere Standardabweichung 1,8%). Die erhaltenen Resultate zeigen gute Übereinstimmung mit den nach amtlichen Methoden erhaltenen Werten.

     

Spectrophotometric determination of phosphorus and arsenic in pharmaceutical organic compounds

Summary A simple and accurate method is described for the microdeter-mination of phosphorus and arsenic in some pharmaceutical organic compounds. It is based on the conversion of phosphorus and arsenic into phosphate and arsenate ions respectively, followed by precipitation with quinoline and sodium molybdate reagents. The excess quinoline in the supernatant is spectrophotometrically measured at 312.5 nm in an ammonium acetate background of pH 5.5. The results obtained with 24 structurally different phosphorus and arsenic compounds show an average recovery of 99% and a mean standard deviation of ±1%. Excipients and diluents normally used in drug formulations do not interfere.

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Spektrophotometrische Bestimmung von Phosphor und Arsen in organischen Arzneimitteln

Zusammenfassung Eine einfache und genaue Methode zur Mikrobestimmung von Phosphor und Arsen in einigen organischen Arzneimitteln wurde angegeben. Sie beruht auf der Umsetzung des Phosphors zu Phosphat und des Arsens zu Arsenat sowie deren Fällung mit Chinolin und Natriummolybdat. Der Chinolinüberschuß wird spektrophotometrisch bei 312,5 nm in Ammonium-acetat bei pH 5,5 gemessen. Die mit 24 strukturell verschiedenen Phosphorbzw. Arsenverbindungen erhaltenen Resultate ergaben eine durchschnittliche Wiederfindungsrate von 99% und eine rel. Standardabweichung von ±1%. Arzneimittelträger und Verdünnungsmittel stören nicht.

     

Microdetermination of divalent sulphur in aliphatic compounds by visual titrimetry,potentiometry, and atomic absorption spectrometry

Summary Divalent sulphur in structurally different aliphatic compounds including thiols, sulphides, disulphides and thiocarbonyls is selectively determined by reaction with solid potassium hydroxide at 250–280° for 5–10 min, followed by addition of alkali plumbite whereby lead sulphide is stoichiometrically formed. The excess lead ions are measured by: (a) atomic absorption spectrometry at 217 nm; or (b) potentiometric titration with EDTA at pH 4.6 using the lead ion selective electrode; or (c) visual titration with EDTA using urotropine buffer and Xylenol Orange indicator. An average recovery of 99%, and a mean standard deviation of 0.9% are obtainable with samples down to 2 mg. Divalent sulphur in many aromatic compounds, and tetra- and hexa-valent sulphur in both aliphatic and aromatic compounds do not interfere.

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Mikrobestimmung von zweiwertigem Schwefel in aliphatischen Verbindungen durch visuelle Maanalyse, Potentiometrie und Atomabsorptionsspektrometrie

Zusammenfassung Zweiwertiger Schwefel in verschieden strukturierten aliphatischen Verbindungen wie Thiolen, Sulfiden, Disulfiden und Thiocarbonylverbindungen, lät sich durch Umsetzung mit festem Kaliumhydroxid bei 250–280° C durch 10 min und Zugabe von Alkaliplumbit bestimmen, wobei Bleisulfid in stöchiometrischer Menge gebildet wird. Der Überschuß an Bleiionen wird gemessen: a) durch Atomabsorptionsspektrometrie bei 217 nm; b) durch potentiometrische Titration mit ÄDTA bei pH 4,6 mit einer bleiionenspezifischen Elektrode; oder c) durch visuelle Titration mit ÄDTA, Urotropin als Puffer und Xylenolorange als Indikator. Ein durchschnittliches Ergebnis von 99% und eine mittlere Standardabweichung von 0,9% sind bei Einwaagen von wenigstens 2 mg erreichbar. Zweiwertiger Schwefel in vielen aromatischen Verbindungen, vier- und sechswertiger Schwefel sowohl in aliphatischen als auch in aromatischen Verbindungen stört nicht.

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Based on a paper presented at the Euroanalysis III Conference, Dublin, August 20–25, 1978.     

Hyperfine interaction experienced by181Ta nuclei at the Hf site in HfFe2−xSix compounds through a decoupling experiment

The time-differential perturbed angular correlation (TDPAC) experiments involving the 133–482 keV γ-γ cascade in¹⁸¹Ta have been performed in the presence of an external magnetic field along the quantization axis to measure the hyperfine magnetic field experienced by¹⁸¹Ta nuclei at the Hf site in the pseudobinary compounds HfFe_2?xSi_x with x=0.1 and x=0.3. The hyperfine magnetic fields measured at 298 K are H_hf=133.1±12.0 kG in the cubic (C15) Laves phase compound HfFe_1.9Si_0.1 and H_hf=76.8±7.0 kG in the hexagonal (C14) Laves phase compound HfFe_1.7Si_0.3. The measured hyperfine fields are discussed within the framework of the Campbell-Blandin model.     

Mn55(p,p′γ)Mn55 reaction low proton energies

Angular distributions of gamma rays following the inelastic scattering of protons from Mn⁵⁵ have been measured at proton energies below 2.50 MeV. The mixture multipole orders for the transition 983→126 keV and 1,530→0 in Mn⁵⁵ have been obtained.     

Factorizations of the Complete Graph into C 5-Factors and 1-Factors

In this paper, we show that K_10n can be factored into C₅-factors and 1-factors for all non-negative integers and satisfying 2+=10n–1.Research partially supported by an NSF-AWM Mentoring Travel Grant     

The complexity of generating an exponentially distributed variate

We analyze in detail an almost optimal algorithm for generating an exponentially distributed variate. The algorithm is due to Knuth and Yao and relies on a method which goes back to J. von Neumann. It is shown here that it can generate k bits of an exponentially distributed variate using an average of about k + 5.67974692 coin flippings. This solves a problem left open by Knuth and Yao.     

Direct determination of benzylnitriles using the cyanide ion selective electrode

The response characteristics of the solid state cyanide ion selective electrode towards some benzylnitriles are investigated. In 10M KOH solution, the electrode exhibits nearly Nernstian response over the concentration range of 10^–2 to 10^–4 M of various substituted benzylnitriles with an anionic slope of 53–59 mV/concentration decade. The response time varies from 10 to 20 min depending on both the nature of the substituent group and the concentration of the nitrile compound. Direct potentiometric measurement of some nitrile compounds at the concentration level of 0.01 to 1 mg/ml shows an average recovery of 98.2% and a mean standard deviation of 2.3%. Many nitrogen functional groups do not interfere.