Kinetic studies on the foam separation of thorium (IV) with sodium lauryl sulphate

Summary The effects of pH, gas flow rate and collector concentration on the rate of thorium removal by foaming with sodium lauryl sulphate have been investigated. The obtained data indicate that only aged hydrated thorium oxide is removed by a flotation mechanism. All the other colloidal and condensed thorium species as well as the colloidal sublates which are formed between the dissolved thorium species and the collector anions appear to be removed by partition and their removal rates could be described by a reversible first-order rate equation. The obtained results are discussed in terms of thorium hydrolysis.

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Zusammenfassung Der Einfluß der pH-Werte, Gasdurchflußmengen und Kollektor-Konzentration auf die Geschwindigkeit der Entfernung des Thoriums durch Schaumbildung mit Natrium-Lauryl-Sulfat wurde untersucht. Die Ergebnisse zeigen, daß das gealterte, wässerige Thoriumoxid durch Flotations-Mechanismen entfernt wird. Die anderen kolloidalen und kondensierten Thorium-Spezien und auch die Kolloidalprodukte, die durch Reaktionen zwischen den gelösten Thoriumspezien und den Kollektor-Anionen formiert sind, sind durch die Verteilung entfernt worden. Die Entfernungsgeschwindigkeit kann beschrieben werden durch eine reversible 1. Ordnungs-Gleichung. Die Ergebnisse werden in Abhängigkeit einer ThoriumHydrolyse diskutiert.

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With 7 figures     

Development of Odorless Thiols and Sulfides and Their Applications to Organic Synthesis

Summary. Development of new odorless thiols (dodecanethiol, 4-n-heptylphenylmethanethiol, 4-trimethylsilylphenylmethanethiol, 4-trimethylsilylbenzenethiol) and an odorless sulfide (1-methylsulfanyldodecane) and their applications to dealkylation, Michael addition, Swern oxidation, and Corey-Kim oxidation are described.     

Hot atom chemistry in oxyanion targets,part II1: Recoil behaviour of56Mn in permanganates

Fractional precipitation techniques have been utilized to separate the lower valent and parent forms of⁵⁶Mn in permanganate targets and an attempt is made to study a few aspects of chemical stabilization of recoil⁵⁶Mn in permanganates. Ammonium permanganate, recoil behaviour of which has not been studied previously, is chosen as one of the targets along with the potassium permanganate for initial retention and also for isothermal annealing.⁵⁶Mn initial retentions of about 12% and about 4% are obtained for potassium and ammonium permanganate, respectively, by activation from a Ra–Be neutron source. A usual trend for KMnO₄ and the reduction of recoil fragments by ammonium ions in NH₄MnO₄ are seen through the isothermal annealing study.     

Indirect potentiometric titration of sulphamethoxazole in the presence of trimethoprim in co-trimazole tablets using copper based mercury film electrode

A simple and rapid indirect potentiometric titration of sulphamethoxazole in the presence of trimethoprim contained in co-trimazole tablets is described. The method is based on the formation of a complex of sulphamethoxazole with a known excess of silver ions and the titration of unreacted silver ion potentiometrically using an inexpensive lab-made copper based mercury film electrode (CBMFE). The titration conditions have been optimized for the determination of 1.0-10.0 mg of sulphamethoxazole in pure and dosage forms. The precision and accuracy of the method have been assessed by the application of lack of fit test and other statistical methods. Overall mean recovery and relative standard deviations obtained were 99.88% and 1.32% (n=7) respectively. No interference was caused by other excipients present in pharmaceutical dosage forms. The application of this method for sulphamethoxazole assay in the presence of trimethoprim in tablets was validated by the comparison of results obtained by the proposed method with that of the British Pharmacopoeia (BP) method using F- and t-statistical tests of significance.     

Determination of low-level residual ethylene oxide by using solid-phase microextraction and gas chromatography

Current methods of analysis for ethylene oxide (EO) in medical devices include headspace and simulated-use extractions followed by gas chromatography with either a packed or a capillary column. The quantitation limits are about 0.5-1.0 microg/g for a packed column and about 0.1-0.2 microg/g for a capillary column. The current allowable levels of EO on medical devices sterilized with EO gas as outlined in International Organization for Standardization (ISO) 10993-7 may be significantly reduced from current levels by applying the ISO Draft International Standard 10993-17 method for establishing allowable limits. This may require EO test methods with detection and quantitation limits that are much lower than those of the currently available methods. This paper describes a new method that was developed for the determination of low-level EO by solid-phase microextraction using the direct-immersion method. Factors such as temperature and stirring were found to affect absorption efficiency and absorption time. A low extraction temperature (about 6 degrees C) was found to be more efficient than room-temperature extraction. Stirring was found to reduce absorption time by about 50%. Under these conditions, detection and quantitation limits of 0.002 and 0.009 microg/g, respectively, were obtained by using a capillary column. As a result, this method makes compliance with lower EO limits feasible.     

Redox reactions of transient species formed during pulse radiolysis of 2-pyridine carboxaldehyde and 2-pyridine methanol in aqueous solutions

Rate constants for the reactions of e _aq ^? , H and OH radicals with 2-pyridine carboxaldehyde and 2-pyridine methanol have been determined by pulse radiolysis technique. Reactions of reducing radicals such as acetone ketyl radicals and CO₂ ^? with these compounds were also evaluated at various pHs. The species produced by the reaction of reducing radicals with these solutes was a strong reductant itself. While pyridinyl were produced in the case of 2-pyridine methanol, one-electron reduction of 2-pyridine carboxaldehyde led to the formation of PyCHOH radical. The one-electron reduction potential of PyCHOH radicals was estimated by establishing an equilibrium with MV⁺ radical cations to be ?0.6V vs NHE. OH radical reaction with 2-pyridine carboxaldehyde gave an OH adduct, while in the case of 2-pyridine methanol, OH radicals reacted partly by H-abstraction from the ?CH₂OH group. SO₄ ^? radical reaction with 2-pyridine carboxaldehyde produced a species which was reducing in nature. The rate constants for the reaction of e _aq ^? and OH radicals are compared with similar values obtained in the case of other 2-pyridine derivatives to see if there is any electron-inductive effect.     

Reactions with Carbo(heterylhydrazonoyl) Halides. I. Chemistry of Carbo(3-phenylpyrazol-5-yl-hydrazonoyl) Chlorides

The Carbo(3-phenylpyrazol-5-yl-hydrazonoyl) halides 1a , b react with active methylene compounds to yield the 1-(3-phenylpyrazol-5-yl)-pyrazole derivatives 2a – k (Scheme 1). The acyclic intermediates 3a , b could be isolated from reaction of 1a , b with acetylacetone, thus establishing the substitution mechanism for these reactions. Compounds 1a , b reacted with carbon disulfide, phenyl isothiocyanate, methyl cyanide, and with p-chlorobenzaldehyde to yield the corresponding heterocyclic derivatives 5 – 8 , respectively (Scheme 2). The behaviour of compounds 2 with hydrazine hydrate is reported.     

A new approach for the solid-phase synthesis of pyrrolo[2,1-c][1,4]benzodiazepines involving reductive cleavage

A methodology based on reductive cleavage followed by cyclization, for the solid-phase synthesis of pyrrolo[2,1-c][1,4]benzodiazepines employing DIBAL-H, is described.     

Nonfactorization and the decaysD s +→φπ +,φρ + andφl + ν l

Using the experimentally measured values ofx=A ₂(0)/A ₁(0) andy=V(0)/A ₁(0) and the measured ratiosR _st=Γ(D _s ⁺ →φl ⁺ ν _l)/Γ(D _ins ⁺ →φπ ⁺) andR _h=Γ(D _s ⁺ →φρ ⁺)/Γ(D _s ⁺ →φπ ⁺), we present evidence for significant nonfactorization contribution in the decay amplitude forD _s ⁺ →φπ ⁺. We analyze the role of nonfactorization inD _s ⁺ →φρ ⁺ and conclude that present data onR _h are consistent with factorization inD _s ⁺ →φρ ⁺. A measurement of polarization inD _s ⁺ →φρ ⁺ would greatly assist our analysis.