Influence of water on the heat of hydrogen adsorption on nickel

Water and hydrogen adsorption on Ni-black has been studied by a microcalorimetric method. The heat of hydrogen adsorption is considerably different on clean surfaces and on those covered with 20–50% chemisorbed water. In the former case it varies between 33 and 8 kcal/mol, and in the latter between 26 and 4.6 kcal/mol. The decrease in the heat of hydrogen adsorption is related to the energy requirement of water desorption. On the hydrogen-covered catalyst surface no water adsorption occurs.

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Ni-. 20–50% . 33 8 /, - 26 4,6 /. . , , .

     

Crystallization of glasses in the system SiO2-Li2O-TiO2-Al2O3, investigated in situ at high temperature by XRD and DTA methods

The processes of crystallization of fibres (diameter 10–15m) and coarse powders (grain size 500–1000m) with four compositions in the system SiO₂-Li₂O-TiO₂-Al₂O₃ were studied by conventional and in situ high-temperature XRD, DTA, SEM and optical microscopy. Activation energies of crystallization and morphological indices were deduced from the kinetic curves obtained by recording the high-temperature XRD peak intensity as a function of time. The glass-ceramic fibres drawn from compositions which exhibit glass-inglass phase separation show prevailing not-oriented bulk crystallization, whereas prevailing surface crystallization was found for single-phase glass fibres. Homogeneously-dispersed crystallization was obtained on heating fibres of these compositions. The partially cocrystallized glass fibres of eutectic composition between Li-metasilicate and-spodumene gave rise to a very fine and homogeneously-dispersed sub-microstructure.

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Zusammenfassung Die Prozesse der Kristallisation von Fasern (Durchmesser 10–15m) und groben Pulvern (Korngröße 500–1000m) von SiO₂-LiO₂-TiO₂-Al₂O₃ in vier verschiedenen Zusammensetzungen wurden mittels herkömmlicher und in situ XRD, DTA, SEM und optischer Mikroskopie untersucht. Aktivierungsenergien der Kristallisation und morphologische Indices wurden aus den durch Registrierung der Intensität der Hochtemperatur-XRT-Peaks in Abhängigkeit von der Zeit erhaltenen kinetischen Kurven ermittelt. Die aus Gemischen einer die Glas-in-Glas-Phasentrennung bedingenden Zusammensetzung gezogenen Glas-Keramik-Fasern zeigen vorwiegend eine nicht-orientierte Bulk-Kristallisation, während vorherrschend Oberflächenkristallisation bei Einphasen-Glasfasern festgestellt wurde. Eine homogen verteilte Kristallisation wurde beim Erhitzen der Fasern dieser Zusammensetzungen erhalten. Bei partiell ko-kristallisierten Glasfasern einer eutektischen Mischung von Li-Metasilikat und (-Spodumen liegt eine sehr feine und homogen-disperse Submikrostruktur vor.

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( 10–15 ) ( 500–1000 ) SiO₂-Li₂O-iO₂AL₂O₃ , , . , - . , --, ë, - . - . — - - - .

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This work was supported by the Italian C. N. R., Progetto Finalizzato Chimica Fine e Secondaria — Sottoprogetto Metodologie.

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We are indebted to Dr. B. Locardi of Stazione Sperimentale del Vetro, Murano (Venice) for furnishing the initial glasses and fibres.

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We are also indebted to the G. Giacomello Institute (C. N. R., Rome) for furnishing the computer programme for the unit cell parameter refinement. Assistance by M. Pistolato and F. Venuda in the experimental work is gratefully acknowledged.     

Combined pulse microcatalytic and ESR studies of butylene oxidation on V-Mg oxide catalysts

Abstract The behavior of V–Mg oxide catalysts in both steady and non-steady state butylene oxidation has been examined.

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, .

     

A differential thermal analysis study of phase transitions in some mercury(II) carboxylates

Data are presented on the heats of phase changes and heat capacities for the even chain number mercury(II) carboxylates from octanoate to octadecanoate. The octanoate and dodecanoate melt directly to the liquid, while the decanoate and octadecanoate pass through a solid solid transition before melting to the liquid. The tetradecanoate and hexadecanoate pass through a mesophase before finally melting. It is proposed that this mesophase is aG (smectic) phase. Addition of mercuric oxide to the tetradecanoate and hexadecanoate causes the appearance of an additional mesophase. The results are explained in terms of theR theory of fused micellar phases.

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Zusammenfassung Daten der Phasenübergangswärmen und Wärmekapazitäten der Quecksilber(II)karboxylate mit geradzahligen Kohlenstoffatomen vom Oktanat bis Oktadekanat angegeben. Oktanat und Dodekanat schmelzen unmittelbar zur Flüssigkeit, während Dekanat und Oktadekanat durch einen Fest-Fest-übergang in den flüssigen Zustand übergeführt werden. Tetradekanat und Hexadekanat werden über eine Mesophase endgültig geschmolzen. Es wird für diese Mesophase die Struktur einer smektischen G-Phase vorgeschlagen. Der Zusatz von Quecksilberoxid zum Tetradekanat und Hexadekanat verursacht das Auftreten einer zusätzlichen Mesophase. Die Ergebnisse werden durch die R-Theorie geschmolzener Micellarphasen erklärt.

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Résumé On présente des données sur les chaleurs des changements de phase et les chaleurs spécifiques des carboxylates de mercure(II), mÊme à longue chaÎne carbonée, de l'octylate à l'octadécanoate. L'octylate et le dodécanoate conduisent directement au liquide par fusion tandis que le décanoate et l'octadécanoate subissent une transition solide-solide avant de fondre. Le tétradécanoate et l'hexadécanoate passent par une mésophase avant la fusion finale. On propose pour cette mésophase une structure smectique (G). L'addition d'oxyde de mercure au tétradécanoate et à l'hexadécanoate donne une mésophase additionnelle. On explique les résultats en se référant à la théorie R des phases micellaires fondues.

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(II) . , - . . , () . . P .

     

Nonisothermal kinetics of zinc oxide nonstoichiometrization

The results obtained by studying zinc oxide non-stoichiometrization are presented. The kinetic parameters values under nonisothermal conditions were calculated too. Both the nonstoichiometric zinc oxide composition and the kinetic parameter values are depending on the generating substances.

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Zusammenfassung Die Ergebnisse der Untersuchungen der Nichtstöchiometrisierung von Zinkoxid werden vorgeführt.Die Werte der kinetischen Parameter unter nicht-isothermen Bedingungen wurden eben falls berechnet.Sowohl die nichtstöchiometrische Zusammensetzung des Zinkoxids als auch die Werte der kinetischen Parameter hängen von der das Phänomen auslösenden Substanz ab.

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Résumé On présente les résultats d'une étude sur la formation d'oxyde de zinc non-stchiométrique. Les valeurs des paramètres cinétiques en conditions non-isothermes sont égale ment calculées. La composition de l'oxyde de zinc non-stchiométrique ainsi que les valeurs des paramètres cinétiques dépendent du composé de départ.

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, , . .

     

A TPR study of SiO2-supported Ru?Ag catalysts

A H₂ chemisorption and TPR study of Ru–Ag/SiO₂ catalysts reveals that after oxidation at 373 K this systems behaves like Ru–Cu/SiO₂. High temperature oxidation, however, does not result in the separation of the metal like in the Ru–Cu case but in the redispersion of Ag on top of the Ru particles.

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H₂ Ru–Ag/SiO₂ , 373 Ru–Cu/SiO₂. , , , Ru–Cu, Ag Ru.

     

Quality control of the cure process of thermosetting resins by means of differential scanning calorimetry

Calorimetric and rheological characterizations of thermosetting resin formulations containing a novalac epoxy resin hardened with 60 to 120 parts per hundred of methylated maleic acid adduct anhydride are described. The calorimetrically determined epoxy conversion has been related to the gelation limits theoretically calculated from Flory's non-linear copolymerization theory and experimentally verified in rheological tests.

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Zusammenfassung Die kalorimetrische und rheologische Charakterisierung der Ansätze von hitzhärtbarem Harz wird beschrieben. Die Ansätze enthalten ein mit 60–120% methyliertem Maleinsäure-Adduktanhydrid gehärtetes Novolackepoxidharz. Die kalorimetrisch bestimmte Epoxid-konversion wurde auf die theoretisch aus der nicht-linearen Flory'schen Kopolymerisationstheorie berechneten und experimentell durch rheologische Tests bestätigten Erstarrungsgrenzen bezogen.

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, - . -, , , .

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Financial and scientific support by the CNR Progetto Chimica Fine e Secondaria and the Societa Italiana Resine (SIR) is gratefully acknowledged.     

Influence of lanthanum on K/Fe/silicalite-2 catalyst in CO+H2

The promotion of a K/Fe/silicalite-2 catalyst with lanthanum increases the selectivity of C₂–C₄ olefin and conversion of carbon monoxide. The influence of lanthanum on the catalyst has been characterized by TPR, TPD and XPS techniques. The suitable lanthanum content in the chemical composition of the catalyst is determined.

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K/Fe/-2 C₂–C₄ . , . .

     

Approaches to the synthesis of pregn-5-en-3β,21-diol-20-one-[16,17α-d]-2'-methyloxazoline

Conclusions Two independent methods were found for the preparation of pregn-5-en-3,21-diol-[16,-17-d]-2'-methyloxazoline: 1) by cis-opening of the aziridine ring of the 3;16,17;21-triacetate of 16,17-epiminopregn-5-en-3,21-diol-20-one and 2) by the 21-hydroxylation of pregn-5-en-3-o1-20-one-[16,17-d]-2'-methyloxazoline using iodosobenzoyl diacetate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2138–2141, September, 1984.     

The composition of volatile and particulate hydrocarbons in urban air

Summary The hydrocarbon composition of the particle and gas phases in the urban atmosphere has been studied by filtration and parallel adsorption on active charcoal and polyurethane foam (PUF). Gas chromatography (GC) and GC coupled to mass spectrometry (GC-MS) have been used for the analysis of the organic matter extracts obtained with each system. In the case of the particle and PUF samples these extracts were fractionated into aliphatic and aromatic compounds. This approach has allowed to identify up to 247 hydrocarbon molecules showing that C0–C5 alkylbenzenes are the major compounds in the charcoal extracts whereas C14–C23 n-alkanes, C0–C4 alkylnaphthalenes, C0–C4 alkylbiphenyls and C3–C5 alkylbenzenes are those predominantly found in the PUF materials. The particles essentially contain C17–C38 n-alkanes and parent polycyclic aromatic hydrocarbons (PAH). These qualitative differences are paralleled by a progressive concentration decrease from the more to the less volatile hydrocarbons. Thus, the total charcoal extracts average 80 g/m³, the PUF compounds represent 4 /m³ and the particle hydrocarbons 0.7 g/m³. These latter airborne materials are essentially composed of petrogenic residues 0.6 g/m³ (aliphatic fraction) whereas the pyrolytic PAH only involve 0.08 g/m³.     

Thermische Eigenschaften und Aufschlussreaktionen von Natriummetaphosphat

Zusammenfassung Die thermischen Eigenschaften des Natriummetaphosphats sowie die Aufschlußreaktion zwischen Natriummetaphosphat und Natriumchlorid wurden durch Thermogravimetrie, Differentialthermoanalyse, Dilatometrie und Thermogasanalyse untersucht. Hierbei wurden die Zusammenhänge zwischen der Gewichtszunahme beim Schmelzen von NaPO₃, der Art der Atmosphäre und dem Verlauf der Reaktion zwischen Natriummetaphosphat und Natriumchlorid beobachtet.

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The thermal behaviour of sodium metaphosphate and the reaction thereof with sodium chloride have been investigated by thermogravimetry, differential thermal analysis, dilatometry and thermo-gas-analysis. Relationship has been established between the weight increase of NaPO₃ in the course of melting, the nature of the atmosphere and the proceeding of the reaction with NaCl.

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Résumé On a étudié par ATG, ATD, dilatométrie et analyse de la phase gazeuse les propriétés thermiques du métaphosphate de sodium et la réaction chlorure de sodium-métaphosphate de sodium. On a pu trouver une corrélation entre l'augmentation de poids de NaPO₃ lors de la fusion, la nature de l'atmosphère et la réaction NaPO₃-NaCl.

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NaPO₃-NaCl , , . NaPO₃, NaPO₃-NaCl.

     

The kinetics of Ln2O3 Hydration under mild conditions

The kinetics of Ln₂O₃ hydration (Ln=Sm, Ho, Yb, Lu) have been studied at room temperature and atmospheric pressure, as have the influence of the activation temperature and the method of preparation of the oxides.The best correlation coefficients are obtained for a diffusion mechanism. If a structural relationship between the C-Ln₂O₃ and their precursors is considered, the possibility arises of the existence of defect planes in the oxides prepared from the hydroxide and carbonate. This facilitates the hydration process through a diffusion mechanism in the case of the rare earth sesquioxides prepared from the above precursors.

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Zusammenfassung Die Kinetik der Hydratisierung von Ln₂O₃ (Ln=Sm, Ho, Yb, Lu) wurde bei Raumtemperatur und atmosphärischem Druck bezüglich des Einflusses der Aktivierungstemperatur und der Art der Darstellung der Oxide untersucht. Die besten Korrelationskoeffizienten werden für einen Diffusionsmechanismus erhalten. Wenn die strukturelle Beziehung zwischen den C-Ln₂O₃ in Betracht gezogen wird, so ergibt sich die Möglichkeit der Existenz von defekten Gitterebenen in den aus Hydroxiden und Carbonaten hergestellten Oxiden. Dies erleichtert den Hydratisierungsprozeß durch einen Diffusionsmechanismus im Falle von aus den oben genannten Vorstufen hergestellten Sesquioxiden der Seltenen Erdmetalle.

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Ln₂O₃, Ln=Sm, Ho, Yb, Lu, . . , , . .

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We thank the CAICYT (Project No. 1377/82) for financial support.     

Steroid glycosides from the starfish Crossaster papposus

The following have been isolated from the starfishCrossaster papposus and characterized: the new glycoside (24S)-5-cholestane-3,4,6,8,15,24-hexaol 24-O-[O-(2,4-di-O-methyl--D-xylopyranosyl)-(1 5)--L-arabinofuranoside] (crossasteoside P₄) and the previously known attenuatoside B-1.Pacific Ocean Institute of Bioorganic Chemistry, Far-Eastern Scientific Center, Russian Academy of Sciences, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 257–260, March–April, 1993.     

Fast Atom Bombardment Mass Spectroscopic Investigation of Inclusion Complexes of Cyclodextrins with 4-Nitrophenol and Benzoic Acid

Mixtures of -, -, and -cyclodextrins and 4-nitrophenol (or benzoic acid) were investigated by means of fast atom bombardment mass spectroscopy. In the gas phase, inclusion complexes of -, , and -cyclodextrins with 4-nitrophenolate and benzoate, which have a 1 : 1 cyclodextrin–guest stoichiometry, were observed in negative-ion mode. In addition, guest anions, clusters of two and three guest molecules, and guest–matrix complexes were observed.     

Diastereoselective methylation of ls-α-phenylethyl-Δ9,10-octahydroquinol-4-one

The methylation of the lithium derivative of ls--phenylethyl-^9,10-octahydroquinol-4-one under kinetic-control conditions at –70 °C in hexane is highly diastereoselective and leads to (+)-ls--phenylethyl-3-methyl-^9,10-octahydroquinol-4-one in 90% optical yield.Communication 2 in the series Metallation of cis-enamino ketones. See [1] for Communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 389–392, March, 1984.     

Differential pulse voltammetric methods for the simultaneous estimation of uranium-iron and uranium-cadmium mixtures in solution

Differential pulse voltammetric methods have been developed for the simultaneous estimation of the constituents of uranium-iron and uranium-cadmium mixtures in solution. A mixture of 1M H₃PO₄–1M KH₂PO₄ (with a pH1.5), was found to be the most ideal supporting electrolyte for both methods, among many that were evaluated for their suitability. In uranium-iron mixtures the calibration for iron was found to be linear up to 150 g ml^–1 (r²=0.9986), while that of uranium up to 500 g ml^–1 (r²=0.999). Iron at 6.7 g ml^–1 level could be determined in the presence of 800 fold uranium (wt/wt) without significant interference. Uranium at 21 g ml^–1 level could be analyzed with 5-fold iron (wt/wt). This upper limit of iron was due to the precipitation of iron as phosphate. In the case of uranium — cadmium mixtures, cadmium calibration for cadmium was found to be linear up to 1300 g ml^–1 (r²=0.9993). Concentration levels of 4.6 g ml^–1 Cd could be determined at a 500-fold excess (wt/wt) of uranium. Uranium calibration was linear up to 500 g ml^–1 (r²=0.999) and 21 g ml^–1 uranium could tolerate up to a 1000-fold excess of cadmium (wt/wt). Both procedures could tolerate 10 g ml^–1 levels of metal ions, such as chromium, copper, manganese, molybdenum and vanadium.     

Fällungsanalyse im Mikrogrammbereich: Eine neue Methode

Zusammenfassung Eine neue Methode zur Durchführung gravimetrischer Bestimmungen im Mikrogrammbereich wurde beschrieben; diese beruht im wesentlichen darauf, daß der Niederschlag nicht mehr zusammen mit dem Filter, sondern nach Überführen mit einem geeigneten Lösungsmittel in einem separaten Wägegefäß gewogen wird.Die dazu nötigen Geräte und deren Herstellung wurden beschrieben. Nach dieser Methode wurden folgende Bestimmungen mit zufriedenstellender Richtigkeit durchgeführt: 2,5–25g Al, 5–50g Cu und 5–50g Zn mit Oxin, 2,5–25g Fe(III) und 2,5–25g Ti(IV) mit N-Benzoyl-phenylhydroxylamin, 5–50g Ni und 5–50g Cu mit Salicylaldoxim, 2,5–50g Co(II) und 2,5–50g Fe(III) mit -Nitroso--naphthol sowie 5–50g Chlorid als Silberchlorid.

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Precipitation analysis in the microgram-scale: A new method

Summary A new method for gravimetric determinations in the microgram-scale is described. This method is based on the fact that the precipitate is not weighed together with the filter but is transferred to a separate weighingvessel using a suitable solvent. The necessary simple devices and their use are described. The following determinations were carried out with satisfying accuracy: 2,5–25g Al, 5–50g Cu and 5–50g Zn with Oxine, 2,5–25g Fe and 2,5–25g Ti withN-benzoylphenylhydroxylamine, 5–50g Ni and 5–50g Cu with salicylaldoxime, 2,52–50g Co and 2,5–50g Fe with -nitroso--naphthol and 5–50g chloride as silver chloride.

     

Conformational study of chiral heterocyclic enamino ketones

An assumption regarding the existence of a homoconjugation effect involving enaminoketo and phenyl groups as a result of the drawing together in space of their orbitals was made on the basis of circular dichroism (CD) data and an examination of the preferred conformations of two-ring enamino ketones with -phenylethyl and -benzylethyl substituents. A study of enamino ketones with a chiral alkyl substituent attached to the nitrogen atom made it possible to confirm this assumption.Communication XLIX from the series Stereochemical Studies. See [1] for communication XLVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1230–1233, September, 1978.     

Radiation-induced reactions of cholesterol in an aqueous medium

⁶⁰Co -ray radiolysis of cholesterol /3-hydroxy-5-cholestene/ /I/ in the two-phase system /water-ethyl acetate/ and in the presence of air has been studied using TLC and GC methods. The following products were observed in the irradiated mixture: 3, 7-dihydroxy-5-cholestene /II/, G O. 36, 3-hydroxy-7-keto-5-cholestene /III/, G 1.48, 3-hydroxy-7-keto-5-cholestane /IV/, G 0.22, 3,5,6-trihydroxy-5-cholestane /V/, G 0.83, 5,6-epoxy-3-hydroxy-5-cholestane /VIa/, G 0.26, 5,6-epoxy-3-hydroxy-5-cholestane /VIb/, G 0.24, and 2, 3-dihydroxy-5-cholestene /VII/, G 0.22. The dose dependence of the formation of these products shows that the cholesterol derivatives substituted in the position 7 /II–IV/ are formed from a common precursor — the radical Ia. On the other hand, the products of the 5–C=C double bond reactions /V and VI/ are formed independently. Also the product VII is formed independently. A reaction scheme that is in agreement with these results is proposed.     

Influence of nucleating agents on crystallization of polypropylene

The effect of talc as an artificial nucleating agent in different concentrations on the crystallization of polypropylene (PP) has been studied. It is considered that the induction time should be taken into account in the Avrami evaluation of isothermal crystallization. From a study of nucleated PP samples prepared in different ways, it has been proved that the nucleating effect of talc slightly decreases with increasing time spent by the sample in the state of the polymer melt. It has been shown that crystallization of non-nucleated polypropylene strongly depends on the material of the sample pan. It has been established that dilatometry cannot be used to study the isothermal crystallization of nucleated polypropylene, since microcracks appear in the sample, partly compensating the volume decrease due to the crystallization process.

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Zusammenfassung Die Wirkung von in unterschiedlichen Konzentrationen als künstliches Keimbildungsmittel angewandtem Talk auf die Kristallisation von Polypropylen wurde untersucht. Bei der Auswertung der isothermen Kristallisation nach Avrami ist die Induktionszeit in Betracht zu ziehen. Bei der Untersuchung von auf verschiedene Weise hergestellten Polypropylenproben wurde festgestellt, dass die keimbildende Wirkung von Talk desto geringer ist, je länger sich die polymere Probe im geschmolzenen Zustand befand. Es wird gezeigt, dass die Kristallisation von keimbilden den Mitteln nicht ausgesetztem Polypropylen stark vom Material des Probengefässes abhängt. Es wurde festgestellt, dass die Dilatometrie nicht zur Untersuchung der isothermen Kristallisatior von mit keimbildenden Mitteln versetztem Polypropylen geeignet ist, da in der Probe Mikrokrack Produkte auftreten, die die durch den Kristallisationsprozess verursachte Abnahme des Volumens teilweise kompensieren.

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. , . , . . , , , .

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This work was presented in part at the 7th International Conference on Thermal Analysis, August 22–28, 1982, Kingston, Ontario.

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The authors are indebted to Messrs M. Pati and J. Volk for the preparation of the samples, and to Dr. A. Solti for her help during the dilatometric measurements.