Thermal and infrared spectrum analyses of natural and synthetic andersonites

The thermal decompositions of natural and synthetic andersonites were studied. Two partly overlapping dehydration steps and three partly overlapping decarbonation steps were observed. The second dehydration and the first decarbonation steps also partly overlap. During decarbonation, the gradual formation of sodium diuranate and monoclinic and hexagonal phases in the Na₂U₂O₇-CaUO_4–x system was proved. The results were correlated with measured infrared spectra using site and factor group analysis and X-ray structure analysis. The chemical formula inferred for natural andersonite, Na₂Ca[UO₂(CO₃)₃] 5.6H₂O, agrees with that proposed for its synthetic analogue.

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Zusammenfassung Die thermische Zersetzung von natürlichem und synthetischem Andersonit wurde untersucht. Sie umfasst zwei teilweise überlappende Entwässerungs- und drei teilweise überlappende Decarboxylierungsstufen. Der zweite Entwässerungs- und der erste Decarboxylierungsschritt überlagern einander ebenfalls teilweise. Während der Decarboxylierung wird die allmähliche Bildung von Natriumdiuranat und monoklinen und hexagonalen Phasen des Systems Na₂U₂C₇-CaUO_4–x nachgewiesen. Die Ergebnisse wurden mit den gemessenen IR-Spektren unter Benutzung der site- und Faktor-Gruppenanalyse sowie Röntgenbeugungsuntersuchungen korreliert. Die für natürlichen Andersonit abgeleitete Formel Na₂Ca[UO₂(CO₃)₃].5,6H₂O stimmt mit der für synthetischen Andersonit vorgeschlagenen überein.

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. . . , Na₂U₂O₇-CaUO_4–x. . Na₂Ca[UO₂(CO₃)₃] 5,6₂, ** , .

     

TMA as a method of investigation of the phase structure of segmented polyurethanes

A complex of methodical approaches for investigating structural changes under the influence of temperature are presented on the basis of modern concepts of the domain structure of block copolymers. Effects of formation of structure due to phase segregation, crystallization processes and those of thermal homogenization have been considered in connection with the deformational properties of polymers. One and the same polymer appears to have quite different phase structures and properties when obtained by altering its thermal conditions. Thermomechanical analysis is shown to be a most efficient technique for investigating the changes in the phase structure of a wide series of polyether(ester)urethanes and -urethaneureas.

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Zusammenfassung Ein Komplex methodischer Näherungen zur Untersuchung von Strukturänderungen unter dem Einfluss von Wärme werden vorgeführt, welche auf den modernen Konzepten der Gebietstruktur von Block-Kopolymeren beruhen. Die Effekte der Strukturbildung durch Phasensegregation, Kristallisationsvorgänge und thermische Homogenisierung wurden im Zusammenhang mit den Deformationseigenschaften der Polymeren in Betracht gezogen. Das gleiche Polymer scheint ganz verschiedene Phasenstrukturen und Eigenschaften zu haben, wenn es unter veränderten thermischen Bedingungen erhalten wird. Es wird gezeigt, dass die thermomechanische Analyse eine sehr wirksame Technik zur Untersuchung der Phasenstrukturänderungen einer ganzen Reihe von Polyäther(ester)urethanen und -urethankarbamiden ist.

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Résumé On présente un ensemble de méthodes d'approximation pour l'étude des variations structurales sous l'influence de la température, reposant sur des concepts modernes sur la structure en domaine des copolymères en bloc.Les effets de la ségrégation des phases, de la cristallisation et de l'homogénéisation thermique ont été examinés en connexion avec les propriétés de déformation des polymères. La même polymère semble avoir des structures de phases et des propriétés tout à fait différentes, quand il est obtenu sous différentes conditions thermiques. On montre sur une large série de polyéther (ester)uréthanes et -uréthane urées que l'analyse thermomécanique est une technique très efficace pour étudier les variations de la structure des phases.

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- . , . , , . - .

     

Thiolactame als Reagenzien in der quantitativen Analyse. IX

Zusammenfassung Thiocaprolactam (T) eignet sich zur Goldbestimmung im Konzentrationsbereich 10 bis 130 g Au/ml mit einem Fehler von ±0,5g. Thiocaprolactam bildet mit [AuCl₄]^– eine Verbindung im molaren Verhältnis TAuCl=112, mit [AuJ₄]^– im molaren Verhältnis TAuJ=213. Dagegen bilden sich im System T:Au:Br zwei verschiedene Verbindungen: Ein Bromidkomplex mit höherem Goldgehalt TAu=12, der mit Chloroform extrahierbar ist, und eine sich als Niederschlag ausscheidende Verbindung mit dem Verhältnis TAuBr=112.

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Thiolactams as reagents in quantitative analysis. IX

Summary Thiocaprolactam (T) is suitable for the determination of gold in the concentration range 10–130g Au/ml with an error of ±0.5g. Thiocaprolactam yields with [AuCl₄]^– a compound in the molar ratio TAuCl=112, with [Aul₄]^– in the molar ratio TAuI=213. On the other hand various compounds result in the system TAu Br. The molar ratio in the case of the bromide complex has a higher gold content, namely TAu=12; this product is extractable with chloroform and a compound that comes down as a precipitate shows the ratioT Au Br=112.

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Herrn Dr.K. Czerepko möchte ich hiermit meinen Dank für die Diskussion der Ergebnisse aussprechen.     

Dimerization of N-methylanabasine in the presence of metallic sodium

In a study of the dimerization of N-methylanabasine in the presence of metallic sodium under conditions for the dimerization of pyridine, it was found that the reaction does not take place at room temperature while at 50–70° C it leads to the formation of,-di(1-methylpiperid-2-yl)-,-bipyridyl. Oxidation of the latter yielded 4,4-bipyridyl-5, 5-dicarboxylic acid, the decarboxylation of which gave,-bipyridyl.     

Mean configurational distribution function for the steady state and stern-volmer representation

A slight discrepancy appears between the treatment of the steady state of diffusion controlled bimolecular quenching of excited species either by the pair model or by the continuum model. A simplifying assumption is pointed out which helps to solve the steady state case but which is responsible for the discrepancy. The error involved is of small importance considering the experimental accuracy.

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- , . , , . , .

     

Condensation of acetals of aromatic β-keto aldehydes with ketones and phenols

Pyrylium salts with a free (active) position and different kinds of substituents in the, positions of the pyrylium ring were obtained by the reaction of acetals of aroylacetaldehydes with ketones and phenols.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1163–1165, September, 1972.     

Thermal decompositions of (NH4)2WSe4 and (NH4)3VS4 under normal and reduced nitrogen pressures

A method is devised by modification of the author's previous method. Thermoanalytical data are transformed to equivalent isothermal ones, and linear relations are utilized to elucidate the mechanism and the pre-exponential factor, instead of curvefitting. Advantages are illustrated by applying this method to the decomposition of polycaprolactam.

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Zusammenfassung Es wurde eine neue Methode durch Modifizierung der früheren Methode des Autors entwickelt. Bei der neuen Methode werden die thermoanalytischen Daten in isotherme umgewandelt und anstatt der Kurven-Anpassung der vorhergehenden Methode werden lineare Zusammenhänge zur Klärung des Mechanismus und des pre-exponentiellen Faktors eingesetzt. Die Vorteile der neuen Methode werden durch ihre Anwendung bei der Untersuchung der Zersetzung von Polycaprolactan veranschaulicht.

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Résumé La méthode précédemment proposée par l'auteur est modifiée. La nouvelle méthode qui est présentée transforme les données thermoanalytiques en données isothermes équivalentes et utilise des relations linéaires pour établir le mécanisme et le facteur pré-exponentiel au lieu de la méthode antérieure avec ajustement des courbes. Les avantages de cette nouvelle méthode sont illustrés en l'appliquant à la décomposition du polycaprolactane.

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, , , , , . .

     

Two-dimensional model of a rough surface and spatial distribution of the desorbed species

We consider the angular distribution (AD) of species desorbed from a rough surface described by various distribution functions (DF) of the surface topography. It is shown that the width of the AD of the desorbed flow depends mainly on the roughness coefficient and is almost independent of the DF, except for the indirect dependence through . It is established that the secondary reflection of desorbed species from an uneven surface (with 1.2) has no appreciable effect on the form of the AD. Taking two models as examples, it is shown that anisotropy in the surface topology leads to anisotropy in the AD of the desorbed species.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2699–2704, December, 1990.     

Evaluation of energy distribution on a heterogeneous surface from heat of adsorption and its application to the ammonia/Na-Y zeolite system

The— function (energy level function) which represents surface heterogeneity was derived from theq— function (experimental heat function) in the case of reversible adsorption. The Langmuir equation was extended and applied to the procedure of calculations. An iterative calculation led to the most probable— function by setting theq— function and adsorption temperature. As an example for actual cases, the— function of Na-Y zeolite was calculated from theq— function obtained by the measurement of heats of adsorption of ammonia at 373 K. The— function thus derived seemed to be consistent with the positional distribution of sodium ions.     

Low-temperature oxidative chlorination of methane over supported platinum chloride catalyst

The Pt^II (catalyst)+Pt^IV (oxidant) system with a deficiency of Cl ligands is active in the oxidative chlorination of alkanes not only in aqueous solutions but also in the SiO₂-supported state. In heterogeneous as well as in homogeneous conditions, the reaction proceeds at 100°C through platinum-alkyl intermediates.

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: Pt^II- Pt^IV- Cl-, , SiO₂. , , 100° - .

     

Salt effects in the reaction of hexacyanoferrate(II) with periodate

The effects of various salts on the kinetics of ferrocyanide oxidation by periodate are reported. The reaction exhibits salt effects of low specificity at low concentrations of the added salts (<0.1 M). At higher concentrations, the effectiveness order for alkaline cations is Li⁺>K⁺>Na⁺ and tetralkylammonium ions have a comparable (Et₄N⁺) or even greater (Me₄N⁺) accelerating effects than alkaline cations.

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. (<0,1 M) . : Li⁺>K⁺>Na⁺. (Et₄ N⁺) (Me₄ N⁺) , .

     

Synthesis of cis-1,4-bifunctional derivatives of an isoprene δ-sultone

Conclusions The stereospecific transformation of a,-unsaturated -sultone into derivatives of (Z)-4-hydroxy-2-methylbut-2-ene-1-sulfonic acid has been carried out.For the preliminary report see [1].Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1354–1358, June, 1981.     

A new improved expression for gamma-ray detection efficiency of Ge(Li) detectors

In the present paper, a new improved expression for -ray detection efficiency of Ge(Li) detectors, ⁰ , is given. It is represented as a continuous function of x (viz. E ^–1) with a maximum and decreases very rapidly to a small positive value as -ray energy, E, drops to 40 keV or lower, but slowly as E rises to 1.7 MeV or higher. Since it can well represent the whole physical process of the -ray detection, this expression may be one of the simplest and most precise representations, for ⁰ at the present time.     

The reactivity of TiO2 with different preparation histories in solid-state reactions in CaSO2-TiO2 systems

Influences of the preparation histories of TiO₂ on its reactivity in solid-state reactions in CaSO₂-TiO₂ systems were studied by means of TG, DTA and isothermal kinetic experiments.In order to estimate the reactivities of solids, it was necessary to note the behaviors in the initial reaction step in the selected reaction system. It was concluded that the reactivity of TiO₂ was dependent on the structure difference due to the different preparation histories, and the greater the stability of the anatase form, up to higher temperature, the higher the reactivity of TiO₂.

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Zusammenfassung Der Einfluß der Herstellungsgeschichten von TiO₂ auf seine Reaktivität bei der Festphasenreaktion im System CaSO₄-TiO₂ wurde durch TG, DTA und isotherme kinetische Versuche untersucht.Zur Abschätzung der Reaktivität der Festkörper mußte ihr Verhalten während des Anfangsschrittes der Reaktion im gewählten System beobachtet werden. Es wurde gefolgert, daß die Reaktivität des TiO₂ von den durch verschiedene Herstellungsgeschichten verursachten Strukturdifferenzen abhängt und bis zu höheren Temperaturen umso stabiler in der Anatas-Form ist, je höher die Reaktivität des TiO₂ ist.

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Résumé On a étudié par TG, ATD et expériences cinétiques isothermes l'influence du mode de préparation de TiO₂ sur sa réactivité lors de la réaction en phase solide des systèmes CaSO₄-TiO₂.Afin d'estimer la réactivité des solides, il a été nécessaire d'observer leurs comportements lors de l'étape initiale de la réaction dans le système réactionnel choisi. On en a conclu que la réactivité de TiO₂ dépend des différences de structure dues aux différents modes de préparation et que ce composé est d'autant plus stable, à températures élevées, sous la forme d'anatase, que la réactivité de TiO₂ est forte.

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C , TiO₂ CaSO₄-TiO₂. , . , TiO₂ , TiO₂.

     

α,β-Butenolides

,-Dibromo--('-carbethoxyacetony)-^,-butenolide (I) reacts with amines in diethyl ether solution to give -bromo-amino--('-carbethoxyacetony)-^,-butenolides. Compounds n are converted to -bromo-amino--('-carbethoxyacetony)-^,-butenolides on reaction with amines. The corresponding arylhydrazones (VI and VII) are obtained by the reaction of I and II with p-nitro- and 2,4-dinitrophenylhydrazines. Compound I reacts with phenylhydrazine to give furopyridazine VIII.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 867–871, July, 1972.     

On theC v toC p conversion for solid linear macromolecules

TheC _v toC _p conversion for solid linear macromolecules via the Nernst-Lindemann equationC _p -C _v =A ₀,C _p ² T/T_m is discussed on hand of data for 10 crystals and seven glasses. An average value ofA ₀=(5.11±2.41) · 10^–3 mol K J^–1 was calculated if the mole is assumed to refer to heavy atoms only. ThisA ₀ is numerically equal to the original Nernst—Lindemann constant.

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Zusammenfassung An Hand von sich auf 10 Kristalle und 7 Gläser beziehenden Daten wird die Umrechnung vonC _v -inC _p -Werte für feste lineare Makromoleküle mittels der Nernst-Lindemann-GleichungC _p -C _v =A ₀ C _p ² T/T _m diskutiert. Ein Durchschnittswert vonA ₀=(5.11±2.41) · 10^–3 mol K J^–1 wurde unter der Annahme berechnet, daß sich das Mol nur auf schwere Atome bezieht. DieserA ₀-Wert ist numerisch gleich der ursprünglichen Nerns-Lindemann-Konstanten.

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10 , - C _v C _p , —C _p –C _v = _{0 p} ² / . , , ₀ (5.11±2.41) · 10^–3 · ^–1. ₀ — .

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Support by the National Science Foundation, Polymers Program (Grant No. DMR 83-17097) is gratefully acknowledged.     

Spin conversion of positronium in paramagnetic solutions studied by age-momentum-correlation method

Correlated measurement of the lifetime and of the lineshape of the 511 keV annihilation radiation of positrons (age-momentum correlation, AMOC) has become a powerful tool for investigating reactions of positron or positronium in condensed matter as a function of time. The beam-based ⁺ AMOC method installed at the Stuttgart relativistic positron beam facility (E _kin ^e+ 4MeV) offers substantial advantages over the conventional E coincidence technique resulting in a fast data taking due to the unity detection efficiency of the ⁺ scintillator which provides the start signal for the lifetime measurement. In this paper the application of AMOC to positronium chemistry is illustrated by the study of spin conversion of positronium in the system methanol/HTEMPO as a function of HTEMPO (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, a paramagnetic solute) concentration. The same technique can be applied to other systems and other reactions in positronium chemistry, e. g., oxidation or complex formation.     

Calculation of adsorption heats of nitric oxide on ruthenium by the bond interaction method

Chemisorption heats of nitric oxide on Ru(0001) and Ru(1010) planes have been calculated by the bond interaction method. It is shown that the calculated values correlate well with TPD data.

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(000I) (I0I0) . , .

     

Chitosan–Carrageenan Gels

Phase behavior of the systems during the formation of polyelectrolyte complexes obtained by mixing of aqueous solutions of chitosan and -, -, or -carrageenan was studied. The gelation was shown to occur throughout the whole bulk solution at chitosan and -carrageenan concentrations higher than 0.1 and 0.3 wt %, respectively. At lower polysaccharide concentrations, the polyelectrolyte complexes precipitated. The study was performed at the polysaccharide concentrations not higher than 1 wt %. The gel systems were investigated by the dynamic rheology method. The mechanical characteristics of -carrageenan-containing gels were found to be mainly governed by the chitosan content; the viscosity of these gels was independent of temperature. Gels obtained with - and -carrageenans were sensitive to temperature because of the helix–coil conformational transitions in their molecules. The mechanical strength and stiffness of gels increase in the ––-carrageenan series. This effect was explained by the formation of additional crosslinks by double helixes of - and -carrageenan molecules.