Definitizable extensions of positive symmetric operators in a Krein space

The Friedrichs extension and the Krein extension of a positive operator in a Krein space are characterized in terms of their spectral functions in a Krein space.     

Kinetics and mechanism of the formation of poly[(1,1,3,3-tetramethyldisiloxanyl)ethylene] and poly(methyldecylsiloxane) by hydrosilylation

The kinetics of the formation of poly(carbosiloxane), as well as of alkyl-substituted poly(siloxane), by Karstedt's catalyst catalyzed hydrosilylation were investigated. Linear poly(carbosiloxane), poly[(1,1,3,3-tetramethyldisiloxanyl)ethylene], (PTMDSE), was obtained by hydrosilylation of 1,3-divinyltetramethyldisiloxane (DVTMDS) and 1,1,3,3-tetramethyldisiloxane (TMDS), while alkyl-substituted poly(siloxane), poly(methyldecylsiloxane), (PMDS), was synthesized by hydrosilylation of poly(methylhydrosiloxane) (PMHS) and 1-decene. To investigate the kinetics of PTMDSE formation, two series of experiments were performed at reaction temperatures ranging from 25 to 56 °C and with catalyst concentrations ranging from 7.0 × 10⁻⁶ to 3.1 × 10⁻⁵ mol Pt/mol CHCH₂. A series of experiments was performed at reaction temperatures ranging from 28 to 48 °C, with catalyst concentrations of 7.0 ×10⁻⁶ mol of Pt per mol of CHCH₂, when kinetics of PMDS formation was investigated. All reactions were carried out in bulk, with equimolar amounts of the reacting Si H and CHCH₂ groups. The course of the reactions was monitored by following the disappearance of the Si H bands using quantitative infrared spectroscopy. The results obtained showed typical first order kinetics for the PTMDSE formation, consistent with the proposed reaction mechanism. In the case of PMDS an induction period occurred at lower reaction temperatures, but disappeared at 44 °C and the rate of Si H conversion also started to follow the first-order kinetics. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2246–2258, 2007     

Application of the ring oven method to the determination of dyestuffs

Summary The Weisz ring oven method has been applied to the semiquantitative determination of indigo carmine, erythrosin A, amaranth O, new coccine, Victoria blau B, tartrazine, azorubin S, alizarin S, eosin, light green SF, Guinea green B, fuchsin, eriochrome black T, saphranine, ponceau 3 R, cyanine, gelborange S, and methyl violet 6 B. The amount of dye needed ranges from 0.5 to 20g, and the error is generally less than 5%. The method has been used for the determination of azorubin S, methyl violet 6 B, tartrazine, and amaranth O in various materials.

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Zusammenfassung Die Ringofenmethode vonWeisz wurde für die semiquantitative Bestimmung folgender Farbstoffe angewendet: Indigocarmin, Erythrosin A, Amaranth O, Neucoccin, Viktoria blau B, Tartrazin, Azorubin S, Alizarin S, Eosin, Lichtgrün SF, Guineagrün B, Fuchsin, Eriochromschwarz T, Saphranin, Ponceau 3 R, Cyanin, Gelborange S und Methylviolett 6 B. Die dazu nötige Farbstoffmenge beträgt 0,5 bis 20g, der Fehler ist im allgemeinen geringer als 5%. Die Methode wurde für die Bestimmung von Azorubin S, Methylviolett 6 B, Tartrazin und Amaranth O in verschiedenen Materialien angewendet.

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Résumé On a appliqué la méthode du four annulaire deWeisz au dosage semi-quantitatif du carmin d'indigo, de l'érythrosine A, de l'amaranthe O, de la coccine nouvelle, du bleu Victoria B, de la tartrazine, de l'azorubine S, de l'alizarine S, de l'éosine, du vert lumière SF, du vert Guinée B, de la fuchsine, du noir ériochrome T, de la safranine, du ponceau 3 R, de l'orangé jaune, de la cyanine S et du violet de méthyle 6 B. La quantité de colorant nécessaire va de 0,5 à 20g et l'erreur est généralement inférieure à 5%. On a appliqué la méthode au dosage de l'azorubine S, du violet de méthyle 6 B, de la tartrazine et de l'amaranthe O dans diverses substances.

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We wish to thank Mrs.Lidija Pfendt of the Faculty of Sciences in the University of Belgrade for doing the spectrophotometric analyses.     

The application of levulinic acid and 5-nitro-2-furylmethylene diacetate in the total synthesis of some novel biologically active (5-nitro-2-furyl)azomethines

Summary The syntheses andin vitro antibacterial and antifungal evaluation of certain (5-nitro-2-furyl)azomethines with different heterocyclic nuclei are described.

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Die Anwendung von Lävulinsäure und 5-Nitro-2-furylmethylendiacetat in der Totalsynthese einiger neuer biologisch aktiver (5-Nitro-2-furyl)azomethine

Zusammenfassung Es wird die Synthese und diein-vitro-antibakterielle und antifungale Wirksamkeit für bestimmte (5-Nitro-2-furyl)azomethine mit verschiedenen heterocyclischen Kernen beschrieben.

     

Semiquantitative determination of micro amounts of phenols using the ring colorimetry method

Summary The semiquantitative determination of micro amounts of pyrocatechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, andp-nitrophenol using the Weisz ring colorimetry method has been described. The results obtained deviated, on an average, from those calculated by about 4% and the amount of phenol required for one determination was about 4 g.

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Zusammenfassung Die halbquantitative Bestimmung von Mikromengen Brenzcatechin, Resorcin, Hydrochinon, Pyrogallol, Phloroglucin und p-Nitrophenol mit Hilfe der vonWeisz angegebenen Ringkolorimetrie wurde beschrieben. Die Resultate weichen von den berechneten Werten durchschnittlich um etwa 4% ab, wobei für eine Bestimmung etwa 4 g benötigt werden.

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Résumé On décrit le dosage semiquantitatif de microquantités de pyrocatéchol, résorcinol, hydroquinone, pyrogallol, phloroglucinol etp-nitrophénol, à l'aide de la méthode colorimétrique annulaire deWeisz. Les résultats obtenus se sont écartés, en moyenne, d'environ 4% d'avec ceux calculés et la quantité de phénol nécessaire pour un dosage s'élevait à 4 g environ.

     

Electrochemical generation of manganese(III) and behaviour of the generated oxidant in acetic acid in the presence of perchlorate ions

Summary Research was carried out to determine conditions for the anodic generation of manganese(III) with high current efficiency in solutions of sodium perchlorate in acetic acid, and to examine the behaviour of the oxidant thus generated. The effects of water and acetic anhydride on current efficiency in the generation of the oxidant was also examined. The formal redox potential of the Mn(III)/ Mn(II) system is decreased with increasing concentrations of sodium acetate in the solution. The effect of sodium perchlorate and perchloric acid concentrations is the reverse. Procedures for coulometric titrations of a number of substances with the generated oxidant were developed, end point being detected using biamperometric and potentiometric methods. Perchloric acid accelerates the oxidation of certain substances with manganese(III) in acetic acid and increases the sensitivity of end-point detection using the potentiometric method.

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Elektrochemische Erzeugung von Mangan(III) und das Verhalten dieses Oxydationsmittels in Essigsäure bei Gegenwart von Perchlorat

Zusammenfassung Die Bedingungen der anodischen Erzeugung von Mangan(III) mit hoher Stromausbeute in Essigsäure, nach Zugabe von Natriumperchlorat wurden untersucht; das elektrochemische Verhalten des so dargestellten Oxydationsmittels wurde ebenfalls untersucht. Der Einfluß von Wasser und Essigsäureanhydrid auf die prozentuelle Stromausbeute des erwähnten Oxydationsmittels wurde verfolgt. Das Formalredoxpotential des Systems Mn(III)/ Mn(II) sinkt bei Erhöhung der Konzentration an Natriumacetat in der Lösung. Perchlorsäure wie auch Natriumperchlorat üben eine entgegengesetzte Wirkung aus und führen zur Steigerung des Formalredoxpotentials bei Erhöhung ihrer Konzentration. Verfahren zur coulometrischen Titration verschiedener Substanzen mittels biamperometrischer oder potentiometrischer Erfassung des Titrationsendpunktes wurden ausgearbeitet. In Gegenwart von Perchlorsäure wächst die Geschwindigkeit der Oxydation einiger Substanzen in Essigsäure in Gegenwart von Mn(III) und auch die Empfindlichkeit der Endpunktbestimmung verbessert sich.

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Presented at the 9th International Symposium on Microchemical Techniques, Amsterdam, August 28–September 2, 1983.     

Thermal study and mechanism of Ag2S oxidation in air

The results of thermal study and mechanism of the oxidation process of synthetic Ag₂S in air are presented in this article based on the comparative analysis of DTA and XRD results, as well as by constructed phase stability diagrams (PSD) for the Ag–S–O system.     

New Insight on Carbon Dioxide-Mediated Hydrogen Production**

A new approach to hydrogen production from water is described. This simple method is based on carbon dioxide-mediated water decomposition under UV radiation. The water contained dissolved sodium hydroxide, and the solution was saturated with gaseous carbon dioxide. During saturation, the pH decreased from about 11.5 to 7–8. The formed bicarbonate and carbonate ions acted as scavengers for hydroxyl radicals, preventing the recombination of hydroxyl and hydrogen radicals and prioritizing hydrogen gas formation. In the presented method, not yet reported in the literature, hydrogen production is combined with carbon dioxide. For the best system with alkaline water (0.2 m NaOH) saturated with CO₂ under UV-C, the hydrogen production amounted to 0.6 μmol h⁻¹ during 24 h of radiation.     

Sums and Limits of Generalized Direct Families of Algebras

In this paper we introduce a generalization of direct families of algebras and we study their limits and sums. In the case of generalized direct families of algebras carried by idempotent algebras we investigate some subdirect decompositions of their sums. The results that we obtain generalize various results given by J.L. Chrislock and T. Tamura [2], M. iri and S. Bogdanovi [3-7], H. Mitsch [13], M. Petrich [14-16], B.M. Schein [23-24] and others.Supported by Grant 04M03B of RFNS through Math. Inst. SANU