Rate constants for the reaction of singlet oxygen with diazocompounds

Rate constants for the reaction of singlet oxygen with a series of diazocompounds and diazoketones have been measured. Diazoketones were found to possess lower reactivity than diazocompounds.

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- . , .

     

Infrared spectra of nitric oxide adsorbed on photoreduced V/SiO2 catalyst

Studies of the IR spectra of surface species produced via NO adsorption on selectively photoreduced V/SiO₂ catalysts indicate that at low coverages NO is adsorbed on V³⁺ ions to form strongly bonded mononitrosyl species V³⁺...... NO. With increasing NO coverage, V³⁺ is oxidized to V⁴⁺, which is accompanied by the appearance of gaseous N₂O and weak adsorption of NO on V⁴⁺.

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- , NO V/SiO₂ . , V³⁺ NO V³⁺... NO. V³⁺ V⁴⁺, N₂O NO V⁴⁺.

     

On the initial treatment of kinetic data

The kinetic methods usually employed to determine reaction orders involve some sort of mathematical approximation and provide values approximate and very often discrepant. Three methods are reported to determine accurate reaction orders without introducing approximations.

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, , , , . .

     

Investigations on the ternary system Ag-P-S and thermal behaviour of the compounds

Parts of the ternary system Ag-P-S were investigated by DTA- and X-ray measurements. The quasibinary section of Ag₂S-P₄ S₁₀ is described. The thermal behaviour and X-ray diffraction patterns of Ag₇PS₆, Ag₃PS₄, Ag₇P₃S₁₁, Ag₄P₂S₇ and Ag₂P₂S₆ were studied. DTA-diagrams and X-ray powder data are given.

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Zusammenfassung Mittels DIA- und Röntgendiffraktionsmessungen wurden Teile des Dreikomponentensystemes Ag-p-s untersucht. Es wird der quasibinäre Schnitt von Ag₂S-P₄ S₁₀ beschrieben. Weiterhin wurden das thermische Verhalten und die Röntgenbeugungsbilder von Ag₇PS₆, Ag₃PS₄, Ag₇P₃S₁₁, Ag₄P₂S₇ und Ag₂P₂S₆ untersucht. DTA-Diagramme und Röntgen-Pulverdaten werden gegeben.

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Ag-P-S. Ag₂S-P₄S_IO. $ Ag₇PS₆, Ag₃Ps₄, Ag₇P₃S_II, Ag₄P₂S₇ Ag₂P₂S₆. .

     

Multiple reaction scheme modelling

Analyses of the kinetics of the effective reactions, resulting from linear combinations of a wide range ofn ^th order single reactions in a multiple set with variously chosen energies of activation and pre-exponential factors, generated under simulated non-isothermal conditions, have been carried out. The global kinetics parameters of the several mode's were obtained by subjecting extent and rate of reaction data, generated at a number of different linear heating rates, to Arrhenius, Kissinger and Friedman isoconversional analyses. Multiple sets, comprising from five to fifty individual members, with order varying from 0.25 to 5 have been considered. The effects of model design on the overall reaction kinetics parameters are discussed. Criteria applicable to experimental thermoanalytical data for recognition of multiple reactions are presented.

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Zusammenfassung Es wurde eine Analyse der Kinetik von Effektivreaktionen durchgeführt, die sich unter Annahme simulierter nicht-isothermischer Bedingungen mit einem Multipel von unterschiedlich gewählten Aktivierungsenergien und präexponentiellen Faktoren aus der Linearkombination von Einzelreaktionen mit einem breiten Bereich der Reaktionsordnungn ergaben. Die globalen kinetischen Parameter der einzelnen Modelle wurden unter Anwendung der isokonversiven Friedman-, der Arrhenius- und Kissingeranalysen aus Größe und Quotient der Reaktionsdaten ermittelt, die für eine Anzahl verschiedener Aufheizgeschwindigkeiten generiert wurden. Multiple mit fünf bis fünfzig Elementen mit Werten zwischen 0,25 und 5 wurden betrachtet. Es wird die Abhängigkeit der kinetischen Reaktionsbruttoparameter von der Gestaltung des Modelles besprochen. Es werden Kriterien gegeben, die an experimentellen thermoanalytischen Daten zur Erkennung von Mehrfachreaktionen angewendet werden können.

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, n- , . , , . , 5 50 , 0,25 5. . , .

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The continuing support of this work by the management of Merck and Co. is gratefully acknowledged.     

Determination of various deformation processes in impact-modified PMMA at strain rates up to 105%/min

The deformation processes in impact-modified PMMA, which deforms homogeneously, were determined by means of the stress/strain experiment (, ) with simultaneous lateral strain measurement (_lat) in a wide range of strain rates () up to 10⁵%/min (impact stress). The elastic, plastic cavitation and plastic shear processes were determined as a function of strain. Therefore we calculated the elastic strain ( _el), the elastic volume expansion ( _{vol el}), the cavitation strain ( _cav), which is identical with the plastic volume expansion ( _{vol pl}), the shear strain ( _sh) and the energy densities (W_el, W_cav, W_sh) related to these three processes.For strains of 3 % onward it was found that plastic shear processes and plastic cavitation processes are responsible for a partial loss of elastically stored energy. Both plastic processes turn out to be mostly anelastic deformations, their amount depending strongly on the strain rate. The contributions of the processes to the total deformation of the unmodified PMMA in its strain range are similar to those of the impact-modified PMMA, and the high impact strength is caused by a shift of the catastrophic rupture to very high strains.     

A bifunctional stopcock-winch device in cells for infrared investigations of solids

A simple glass device is described acting as stopcock and winch at the same time. The device is especially suitable for the dislocation of solid sample holders in IR cells.

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, . .

     

Effect of quantization of molecular rotations on the rate of capture in the ion-linear dipole system

The version of transition state theory that accounts for quantization of the rotational energy of a dipole gives ion-dipole capture rate constants in good agreement with the statistical adiabatic channel model and, in the region , gives results more accurate than those obtained by numerical trajectory calculations.

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, , - . , .

     

A differential scanning calorimetric study of some phenol derivatives

Differential scanning calorimetry has been applied to derive the fusion enthalpies and entropies of series of mono and dimethylphenols, mono and dichlorophenols, and mono and dinitrophenols.

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Zusammenfassung DSC wurde verwendet zur Ermittlung der Schmelzenthalpie und Entropie der Reihen von Mono- und Dimethylphenolen, Mono- und Dichlorphenolen, Mono- und Dinitrophenolen.

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- , - , - .

     

A Thermal study of the precipitates formed in ammonia neutralization of acidic solutions of dissolved phlogopite

The precipitates containing mainly iron, aluminium and magnesium hydroxides, obtained from phlogopite dissolved in nitric acid by means of the neutralization procedure with ammonia, have been investigated by thermal analysis (TG, DTG and DTA). According to the present study, which is part of a larger investigation into the chemical utilization of Finnish mica minerals, the formation of solid solutions between iron and aluminium hydroxides in silt increases with an increasing neutralization temperature. Nitrogen exists mainly in the form of nitrate in silts, and magnesium forms mixed hydroxides with aluminium, which causes a separation between the iron hydroxide and magnesium aluminium hydroxide phases.

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Zusammenfassung Die von in Salpetersäure gelöstem Phlogopit durch Neutralisierung mit Ammoniak erhaltenen, hauptsächlich Eisen-, Aluminium- und Magnesiumhydroxid enthaltenden Niederschläge wurden thermoanalytisch (TG, DTG und DTA) untersucht. In der vorliegenden Arbeit, die Teil einer grossangelegten Untersuchung zur chemischen Nutzung finnischer Glimmermineralien ist, wird gezeigt, dass die Bildung fester Lösungen von Eisen- und Aluminiumhydroxiden in Schluff mit zunehmender Neutralisationstemperatur ansteigt. Stickstoff kommt in Schluff hauptsächlich in Form von Nitraten vor, und Magnesium bildet Mischhydroxide mit Aluminium, was eine Trennung der Eisenhydroxidphase von der Magnesium-Aluminium-Hydroxidphase bewirkt.

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, , , . . , , . , , , , .

     

Isolation,purification, and characterization of cyclomaltodecaose (ε-CD)

-Cyclodextrin (-CD) is a cyclic oligosaccharide, composed of ten -1,4-linked D-glucoses reported by Frenchet al. in 1965¹⁾, but has not been studied because of the difficulty in the preparation and purification of large-ring CDs composed of more than nine -1,4-linked D-glucose units. This report describes the purification and characterization of -CD. Furthermore, the crystal and molecular structure of -CD hydrate -CD 19H₂O) was elucidated by X-ray analysis.     

Cyclohexene skeletal isomerization activity of sepiolites modified with B3+ or Al3+ ions

The effect of sepiolite modification by B³⁺ and Al³⁺ ions on catalytic performance were investigated in cyclohexene skeletal isomerization (CSI) reaction. Catalytic activity to 1- and 3-methylcyclopentenes (1- and 3-MCP) fit the Bassett-Habgood kinetic model for first order processes. These ions induced strong acidity in the sepiolite and the best results (greater activity and selectivity to 1-MCP) were found when the sepiolite was exchanged with an BF₃/methanol solution which contained 3 wt.% of the B³⁺ ion.

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B³⁺ Al³⁺ . 1- 3- - . . - 1-- , BF₃/, 3 . % B³⁺.

     

Interaction of PM12?nVnO40?(3+n) (M=Mo, W) heteropoly complexes with nitrogen oxide

In aqueous solution, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) hetero-polyanions provide a much faster oxidation of NO than mononuclear VO ₂ ⁺ ions, yielding HNO₂, NO ₃ ^– and reduced HPA.

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, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) , VO ₂ ⁺ , NO HNO₂ NO ₃ ^– .

     

Mössbauer study of the thermal decompositions of alkaline earth tris(oxalato)ferrates(III)

The thermal decompositions of alkaline earth tris(oxalato)ferrates(III) (Mg, Ca, Sr and Ba) have been studied by Mössbauer spectroscopy and other techniques. During the thermal decomposition, dehydration occurs first, followed by reduction to iron(II) species, and oxides and ferrites (MFe^IIIO₄) are then formed at higher temperature. In the case of strontium tris(oxalato)ferrate(III), strontium ferrite (SrFe^IVO₄) is formed at 700°.

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Zusammenfassung Die thermische Zersetzung von Tris(oxalato)ferraten(III) der Erdalkalimetalle (Mg, Ca, Sr, Ba) wurde durch Mössbauer-Spektroskopie und andere Techniken untersucht. Im Verlaufe der thermischen Zersetzung verläuft zunächst die Dehydratisierung, gefolgt von der Reduktion zu Eisen(II)-Species. Oxide und Ferrite (MFe^IIIO₄) werden danach bei höheren Temperaturen gebildet. Strontium-tris(oxalato)-ferrat(III) geht bei 700 °C in Strontiumferrit (SrFe^IVO₄) über.

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() () , , ë . , , MFe^IIIO₄. 700° SrFe^IVO₄.

     

Thermal behaviour of riboflavin

From the thermal decomposition curves of riboflavin at various heating rates in static air atmosphere, the stages of thermal decomposition of this compound were established. The following kinetic parameters were calculated for the first decomposition stage of this process: activation energy (E _a ), reaction order (n), preexponential factor (A) and reaction rate constant (k). A mechanism of the changes is proposed.

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Zusammenfassung Die Stadien der thermischen Zersetzung von Riboflavin wurden aus den Kurven der thermischen Zersetzung in Luftatmosphäre bei verschiedenen Aufheizgeschwindigkeiten ermittelt. Für den ersten Zersetzungsschritt dieses Prozesses werden die Werte für die Aktivierungsenergie (E _a ), die Reaktionsordnung (n), den präexponentiellen Faktor (A) und die Reaktionsgeschwindigkeitskonstante (k) berechnet. Für die Umwandlungen wird ein Mechanismus vorgeschlagen.

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, , . , (E _a ), (n), (A) (k). .

     

Catalytic conversion of dimethylsulfide to methylmercaptan

The effect of reaction conditions on the methylmercaptan formation from dimethylsulfide in H₂S catalyzed by -Al₂O₃ has been studied. The reaction is first order with respect to dimethylsulfide. It has been revealed that the maximum activity in this reaction is observed for the catalysts whose surface contains a large number of aprotonic acid centers and moderate-strength basic sites.

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-Al₂O₃. , . . , , .

     

The electronic spectrum of acrylonitrile

The vapor absorption spectrum of acrylonitrile CH₂CHCN has been measured in the vacuum ultraviolet region. In addition, an all-valence-electron molecular orbital calculation has been used to calculate the electronic structure and spectrum of the molecule. On the basis of the MO calculation, as well as a vibrational analysis of the observed spectrum, several electronic transitions are assigned. The lowest energy absorption band (2107Å, = 150) is assigned as an n ^* transition. Absorption bands at 2030Å (=1600), 1725Å ( = 2100), and 1570Å ( = 1920) are assigned as 0–0 bands associated with transitions that are, respectively, ^*,^*, and ^* in character.

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Zusammenfassung Das UV-Absorptionsspektrum von dampfförmigen Acrylnitril wurde gemessen und eine CNDO/2-Rechnung für die Elektronenstruktur durchgeführt. Auf dieser Basis konnten unter Zuhilfenahme der Analyse der Schwingungsstruktur im beobachteten Spektrum mehrere Banden zugeordnet werden: die 2107-Å-Bande ( = 150) einem n^*-Übergang, die drei Banden bei 2030Å ( = 1600), 1725Å ( = 2100) und 1570 Å ( = 1920)0-0-Übergängen von ^*-, ^*- bzw. ^*-Banden.

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Résumé Mesure du spectre d'absorption en phase vapeur de l'acrilonitrile CH₂CHCN dans la région de l'ultraviolet. Par ailleurs, la structure électronique et le spectre de la molécule ont été calculés à l'aide d'une méthode des orbitales moléculaires semi-empirique pour tous les électrons de valence. Sur cette base, ainsi que sur une analyse vibrationnelle du spectre expérimental, on procède à l'attribution de plusieurs transitions électroniques. La bande d'absorption de plus basse énergie (2107 Å, = 150) est attribuée à une transition n ^*. Les bandes d'absorption à 2030Å ( = 1600), 1275Å ( = 2100) et 1570Å ( = 1920) sont considérées comme des bandes 0 - 0 associées à des transitions ^*, ^* et ^* respectivement.

     

IR study of 1-hexene isomerization on HZSM-5 zeolites

In the IR spectra of 1-hexene adsorbed on HZSM-5 zeolites with different Si/Al ratios, a new band at 1510 cm^–1 has been observed. The cis/trans-2-hexene and trans-2-hexene/1-hexene ratios were determined.

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1-, HZSM-5 Si/Al, 1510 cm^–1. /-2- -2-/1-.

     

Einige Anwendungen der thermometrischen Methode zur Analyse und Charakterisierung von feindispersen Kieselsäuren und Silikaten

Zusammenfassung Unter Anwendung der thermochemische Methode werden die Bestimmungen von SiO₂, Al₂O₃, Na₂O, SO₃ und Feuchte in feindispersen Kieselsäuren und Silikaten beschrieben. Besonders eingegangen wird auf die aufeinanderfolgende Bestimmung von SiO₂ und Al₂O₃ sowie der hierbei beobachteten Vorteile und Störungen. Über die Möglichkeit der Verwendung der kinetisch-katalytischen Analyse mit thermometrischer Indikation zur Bestimmung von Cu und Mn werden Ausführungen gemacht. Der zweite Teil des Vortrages befaßt sich mit der Benetzungs- und Immersionswärme von feindispersen Kieselsäuren und Angaben zur Bestimmung dieser auch unter betriebsanalytischen Bedingungen. Für verschiedene Kieselsäuretypen werden unterschiedliche Benetzungswärmen gefunden. Auf die Notwendigkeit der Weiterführung solcher Messungen wird verwiesen.

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The authors describe the determination of the SiO₂, Al₂O₃, Na₂O, SO₃ and moisture contents of finely dispersed silicic acids and silicates by means of thermochemical methods. Special interest is paid to the determination of SiO₂ and Al₂O₃ as well as to the advantages of the method and to disturbing factors. The possibility of using kinetic-catalytic analysis with thermometric end-point detection for Cu and Mn determination is discussed. In the second part of the paper the authors deal with the heat of wetting and heat of immersion of finely dispersed silicic acid, and give data for their determination under circumstances of industrial analysis too. Differences in the heats of wetting were found for the different types of silicic acid. These studies require further measurements to be made.

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, , , . , . . . . .

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Überarbeitete Fassung einer Vorlesung zum 3. Seminar über thermometrische Analyse, Marienbad, CSSR, 1983.