Coordination of Heterovalent Iron Atoms in SrCo1 – yFeyO3 – zSolid Solutions

Mössbauer spectroscopy was used to study hyperfine interactions on ⁵⁷Fe nuclei of SrCo_{1 – y} Fe _y O_{3 – z} solid solutions (0.2 y 0.8). The ⁵⁷Fe spectra measured in the paramagnetic temperature range look like a superposition of two quadrupole doublets whose parameters correspond to high-spin Fe⁴⁺cations ( = 0.1 mm/s; = 0.4 mm/s) in the anion surrounding with coordination number 5 (tetragonal pyramid) and to Fe³⁺cations ( = 0.3 mm/s; = 0.4 mm/s) in the distorted octahedral environment. The relative number and pattern of distribution of heterovalent cations (Co⁴⁺, Co³⁺, Fe⁴⁺, and Fe³⁺) in the B-sublattice of perovskites were determined. The values of the electronic exchange constants in the solid solutions obtained through Mössbauer spectroscopy were compared with those obtained from thermodynamic calculations. The oxygen penetration in perovskites was found to depend on their composition and structure.     

1A1⇔5T2 Spin Transition in Heterometallic Solid Phases FexNi1-x(Htrz)3(NO3)2 · H2O (Htrz = 1,2,4‐Triazole)

Solid phases Fe_xNi_1-x(Htrz)₃(NO₃)₂ · H₂O (0.4 x 0.8$) and Ni(Htrz)₃(NO₃)₂ · H₂O were synthesized and studied. The phases were studied by means of magnetochemistry, powder Xray difraction analysis, and electronic and IR spectroscopy. The heterometallic phases are described by the stoichiographic method of differentiating dissolution (DD). The values of x were determined by two methods — atomic absorption and DD. Magnetochemical data showed that the solid phases exhibit a hightemperature ¹A₁ ⁵T₂ 0.5 x 0.8 and disappears at x = 0.4. The spin transition is accompanied by thermochromism (color changed from pink to white at 0.6 x 1 and from pink to light lilac at x = 0.5). A decrease in x leads to a decrease in the temperature of the forward (under heating T_c ) and reverse (under cooling T_c ) transitions, a decrease in hysteresis value ( T_c), and a smearing of the spin transition.     

Phase Equilibria in the System CuO-Fe2O3-Sb2O4-O2

Results of X-ray phase analysis were used to construct the phase diagram of the system CuO-Fe₂O₃-Sb₂O₄-O₂ at 1000°C in air. Two Cu_2x Fe_4-3x Sb _x O₆ solid solutions (0 x 0.154 and 0.923 x 1) of, respectively, hematite and bixbyite structure were identified.     

Die Anwendung Thermoanalytischer Methoden zur Charakterisierung Faserbildender Organischer Hochpolymerer

Zusammenfassung An Hand von Literaturbeispielen und eigenen Arbeiten wird eine Übersicht über Anwendungsmöglichkeiten der Thermogravimetrie (TG) auf dem Gebiete der faserbildenden organischen Hochpolymeren gegeben. Die Untersuchung der relativen Thermostabilität, deren Veränderung durch Modifizierung der Polymeren oder den Zusatz von Stabilisatoren und die Ableitung kinetischer Daten werden besonders herausgestellt. Die Vorteile der Differentialthermogravimetrie sowie die Notwendigkeit isothermer thermogravimetrischer Untersuchungen zur Charakterisierung des thermischen Langzeitverhaltens werden erläutert. Abschließend werden allgemeine Einschränkungen und Empfehlungen für die Anwendung der TG, z. B. die Kombination mit anderen Charakterisierungsmethoden, genannt.

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A review on the application of thermogravimetry (TG) in the field of fiber-forming organic high polymers is given by examples from the literature and from the work of the author. The investigation of the relative thermostability, their changes by modification of the polymers or by addition of stabilizers and the calculation of kinetic values are particularly stressed. The advantage of derivative thermogravimetry and the necessity for isothermal thermogravimetric investigation to characterize the longtime behaviour of polymers are explained. Finally, general limitations of, and recommendations for, the application of TG, e.g. the combination with other methods of investigation, are mentioned.

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Résumé On donne une vue d'ensemble sur les possibilités d'application de la thermogravimétrie (TG) dans le domaine des hauts polymères organiques fibriformes, en se servant d'exemples pris dans la littérature et de travaux personnels. On dégage les données relatives à la stabilité thermique et aux changements qui s'y rapportent si l'on modifie le polymère ou si on le traite par des stabilisateurs; on présente également le calcul des paramètres cinétiques. On montre les avantages de la thermogravimétrie différentielle ainsi que la nécessité d'effectuer des essais thermogravimétriques isothermes pour caractériser le comportement thermique de longue durée. Enfin, on mentionne les limites et les avantages dans l'emploi de la TG, par exemple, l'emploi combiné avec d'autres méthodes de caractérisation.

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() . , , , . , . () .

     

Partial oxidation of methane on Cr2O3/Al2O3

The oxidation of methane on supported chromia was studied at temperatures varying between 423 and 743 K and CH₄/O₂ ratios between 1 and 9 in a differential reactor. The main reaction products observed were carbon monoxide and formaldehyde. The rates of reaction obey a power law expression.

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, 423 743 CH₄/O₂ 1 9, . . .

     

Effect of the dielectric constant on the reactivity of alkyl and polychloroalkyl radicals in addition and substitution reactions

Generalized data for the effect of reaction medium on the elementary steps of radical homo-and cotelomerization of olefins with carbon tetrachloride are generalized.

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.

     

Distribution of components in the rare earth ammonia synthesis catalysts and effect of additives

The distribution of components in the HG-1 ammonia catalyst promoted by rare earth oxide (successfully developed by the authors) was analyzed by electron microprobe photography. The results enable us to explain the effect of additives upon the activity as well as the remarkably high lifetime of catalyst.

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HG-1, ( ) , . , .

     

Isomerization of unsaturated compounds on Pd/Al2O3 in the presence of additives

Studies of the effect of zinc chloride and aluminium additives on the activity of a Pd/Al₂O₃ catalyst (5 wt.%Pd) in the isomerization of heptene-1, allylbenzene,p-allylphenol and 4-allyl-2-methoxyphenol (eugenol) indicate that the rate and selectivity of isomerization depend on the sequence of addition of salts and reagent to the catalytic system. The simultaneous addition of ZnCl₂ or AlCl₃ with olefin, produces a 2–3 fold increase in the isomer yield compared to ethanol.

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Pd/Al₂O₃- (5 .% Pd) -1, , -, 4--2- (). , . ZnCl₂ AlCl₃ 2–3 .

     

Dissociation equilibrium between uncharged and charged local anesthetic lidocaine in a surface-adsorbed film

The dissociation equilibrium between uncharged local anesthetic lidocaine (LC) and charged local anesthetic LC (LCH⁺) in a surface-adsorbed film was investigated by measuring the surface tension and pH of aqueous solutions of a mixture of hydrochloric acid and LC. The surface tension values decreased slightly with increasing total molality m_t at 0X₂0.5, where X₂ is the mole fraction of LC in the mixture, while they decreased rapidly with increasing m_t at 0.5<X₂1. It was shown from the pH measurements that almost all LC molecules were changed into LCH⁺ ions by protonation at 0X₂0.5 and both forms coexisted only at 0.5<X₂1. The quantities of the respective LC and LCH⁺ transferred from the aqueous solution to the adsorbed film, i.e., their surface densities, were calculated by applying the thermodynamic equations derived to the surface tension and pH data. A greater quantity of LC than LCH⁺ existed in the adsorbed film at the coexisting composition. The partitioning behavior of LC and LCH⁺ in the adsorbed film was characterized by three composition regions: (1) slight partitioning of low surface-active LCH⁺ in the region at 0X₂0.5, (2) preferential partitioning of LC at 0.5<X₂<around 0.7, and (3) negative partitioning of LCH⁺ at around 0.7X₂1. The present results clearly indicate that uncharged local anesthetics transfer into hydrophobic environments such as cell membranes more than charged ones.     

Hydrophile-lipophile balance of alkyl ethoxylated surfactants as a function of intermolecular energies

Summary The semiempirical MNDO method has been used in order to examine the variation of the molecular properties of hydrocarbons C_nH_2n+2 (with 1n19) and ethylene oxide chains CH₃(CH₂CH₂O)_mCH₃ (with 1m19) as a function of their molecular length. Least-square fits of those properties have been calculated, along with two mathematical relations between the hydrophile-lipophile balance of alkyl-phenol ethoxylated surfactants and (1) the ratio of molecular lengths between their lipophilic and hydrophilic branches; (2) the intermolecular energies between the molecules of surfactant, water and hexane.     

Kinetics of ion exchange sorption of phosphate

The kinetics of phosphate sorption on Amberlite IRA-400 has been studied as a function of temperature, nature of counterions, at two different concentrations. The film and particle diffusion coefficients and the activation parameters of the process are calculated.

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IRA-400 , . .

     

Contribution to the kinetics of the process of dissolution

Some characteristics of the kinetic equation of dissolution are discussed, bearing in mind that in the course of the process, along with the concentration of the solution, the surface of the soluble substance is also changed. The opportunity for the appication of an exponential kinetic equation is pointed out. Methods are proposed for calculating the solubility and also for using the integral forms of the exponential equation. The meaning of the coefficient of proportionality is explained.

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, , ◹ . . , . .

     

Diacetylenic Derivatives of Fe2(CO)6(μ-EE′): Spectroscopic Investigations of Fe2(CO)6{μ-EC(H) = C(C≡ CMe)E′} (E = E′, E ≠ E′; E, E′ = S, Se, Te)

The diacetylenic adducts, Fe₂(CO)₆{-EC(H) = C(C CMe)E} (E = E, E E; E, E = S, Se, Te) (1–8) have been obtained from the room temperature stirring of Fe₂(CO)₆(-EE) with HC CC CMe in methanol solvent containing sodium acetate. Compounds 1–8 have been characterized by IR and multinuclear NMR (¹H, ¹³C, ⁷⁷Se, and ^l25Te) spectroscopy. Trends in the chemical shifts of ⁷⁷Se and ¹²⁵Te NMR spectra of Fe₂(CO)₆{-EC(H) = C(C CMe)E} with a variation of EE are discussed.     

Coupling of thermometric titrimetry and constant-current coulometry: Study and applications

Two systems involving the coupling of thermometric and coulometry are presented. In the first assembly, the two electrodes were in the same compartment. Bromocoulometry was used to test the possibilities of this coupling in the sequential titration of a vitamin C+ aspirin mixture about (10^–4 M) and the determination of enthalpy changes. In a second coupling system, the anodic and cathodic compartments were separated by a sintered-glass disc of porosity 3. The conditions for obtaining an electrochemical cell which is also a good calorimeter are discussed. Examples of applications are given, such as analytical measurements, the study of an electrochemically catalysed reaction and of the thermal effects of electrode reactions.

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Zusammenfassung Zwei Systeme werden beschrieben, die eine Kombination von thermometrischer Titrimetrie und Coulometrie darstellen. Bei der ersten Vorrichtung sind die Elektroden im gleichen Raum Untergebracht. Die Bromocoulometric wurde zur Testung der durch diese Kombination für die aufeinanderfolgende Titration von Vitamin C/Aspirin Gemischen (ungefähr 10^–4 M) und für die Bestimmung der Enthalpieänderungen gebotenen Möglichkeiten angewandt. In einem zweiten kombinierten System waren Anoden- und Kathodenraum durch ein Sinterglasfilter der Porosität 3 voneinander getrennt. Es werden die Bedingungen diskutiert, die notwendig sind, um eine elektrochemische Zelle zu erhalten, die zugleich auch ein gutes Kalorimeter ist. Anwendungsbeispiele sind angegeben, wie analytische Messungen und elektrochemische Untersuchungen katalysierter Reaktionen oder thermischer Effekte von Elektrodenreaktionen.

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, . . — 10^–4 M . — N^o3. , . , , .

     

Analyse thermique differentielle et cinetique de reaction

Résumé Dans cette seconde partie, en désignant par la vitesse de chauffe supposée constante et(t) un paramètre dépendant du tempst, caractérisant le degré d'évolution de la transformation considérée, on établit les équations des courbes de température différentielleT== f [, (t)] dans le cas des transformations de phase (fusion, solidification) des transformations allotropiques et dans le cas des réactions de dismutation sans variation de masse. On montre également comment les relations obtenues sont modifiées lorsque l'on considère les réactions avec ou sans variation de masse, inverses de celles déjà étudiées. Enfin, on établit théoriquement les propriétés de la dérivée d/dt T, propriétés dont une est mise à profit dans certaines études de cinétique hétérogène faites à partir des courbes d'analyse thermique différentielle.

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Equations are given for describing the differential temperature curves of phase transformation (fusion and solidification) and allotropic transformations, as well as of dismutation reactions proceeding without any change in weight. It is shown how the obtained relationships are modified according to whether the reaction proceeds with or without weight change. Finally, the properties of the derivative d/dt gDT are established theoretically that can be used to advantage in the investigation of heterogeneous kinetics on the basis of DTA curves.

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Zusammenfassung Die Gleichung der differentialthermoanalytischen KurveT == f[, (t)] für den Fall von Phasenumwandlungen (Schmelzen, Erstarren), von allotropen Umsetzungen und von ohne Gewichtsänderung verlaufenden Umwandlungsreaktionen wurden theoretisch abgeleitet, wobei die konstante Aufheizungsgeschwindigkeit,(t) ein zeitabhängiger, den Verlaufsgrad der Reaktion kennzeichnender Parameter ist. Es wurde gezeigt, wie sich die erhaltenen Beziehungen ändern, wenn die Reaktionen mit oder ohne Gewichtsänderung in entgegengesetzter Richtung verlaufen. Gewisse Eigenschaften der Derivierten d/dtT wurden theoretisch untersucht. Eine von ihnen läßt sich bei der Untersuchung der Kinetik von heterogenen Reaktionen durch die Differentialthermoanalyse verwenden.

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II , (, ) , T=f[,(t)], ,(t) — , , . , . d/dt T; .

     

Proanthocyanidins of Polygonum coriarium. I

Six proanthocyanidins have been isolated from the roots ofPolygonium coriarium. The structures of three oligomeric proanthocyanidins have been established: taranin, consisting of [epigallocatechin gallate]-(48)-[epigallocatechin gallate]-(48)-[epigallocatechin-(48)-epigallocatechin₂-(48)-epigallocatechin; taranoside A - [epigallocatechin gallate]-7-0-[-(16)--D-Glcp]₃-(48)-[epigallocatechin-(48)-epigallocatechin]₂-(48)-gallocatechin; and taranoside B - [epigallocatechin gallate]-7-O-[-(16)--D-Glcp]₄-(48)-[epigallocatechin-(48)-epigallocatechin]₂-(48)-epigallocatechin-(48)-[epigallocatechin gallate).Institute of the Chemistry of Plant Substances, Uzbekistan Republic Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 59–67, January–February, 1992     

Photoakustikspektroskopische Untersuchungen an Filtergl?sern

Zusammenfassung Verschiedene Filtergläser wurden mit Hilfe der Photoakustikspektroskopie im Bereich 300800 nm untersucht. Die Ergebnisse zeigten, daß die PAS wertvolle spektroskopische Informationen liefern kann, die die Transmissionsmessungen ergänzen können. Absorptionsmaxima, die durch Transmissionsmessung nicht erfaßbar sind (T10^–5), können bestimmt und den farbgebenden Kationen zugeordnet werden.

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Investigation of filter glasses by photo-acoustic spectroscopy

Summary Various filter glasses were investigated in the range of 300800 nm by photo-acoustic spectroscopy. The results showed that PAS is able to deliver valuable spectroscopic information supplementary to transmission measurements. Absorption maxima which are not detectable by transmission measurements (T10^–5) can be determined and attributed to the dyeing cations.

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Die Arbeit wurde durch Mittel der Deutschen Forschungsgemeinschaft und des Verbandes der Chemischen Industrie — Fonds der Chemie — sowie der Fa. Henkel KGaA unterstützt, wofür wir an dieser Stelle herzlich danken. Den Glaswerken Schott in Mainz danken wir für die Überlassung der untersuchten Filtergläser.     

Lithium phosphate catalyst, III. New supported catalyst

Some new non-stoichiometric Li₃PO₄ supported on -Al₂O₃, -Al₂O₃, TiO₂ and SiO₂ are described as catalysts. The catalysts are used in the isomerization of propene oxide. The catalyst supported on SiO₂ is more active and selective to allyl alcohol than the catalysts described in the literature till now.

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, Li₃PO₄, -Al₂O₃, -Al₂O₃, TiO₂ SiO₂, . . , , SiO₂.

     

Enthalpic study of structural relaxation and crystallization in some metallic glasses

Structural relaxation and crystallization have been studied in the metallic glasses Fe₃₉Ni₃₆Cr₅P₁₄B₆, Fe₈₁B₁₉, Fe₇₆Co₄B₂₀ and Fe₇₅V₄B₂₁ by DSC.Different coefficients of calibration of the DSC cell were determined for the two phenomena.The enthalpy of relaxation increases with increasing quenching rate for Fe₃₉Ni₃₆Cr₅P₁₄B₆ and with increasing number of alloy components for Fe-B-based glasses. In the latter systems. relaxation is never completed before the start of crystallization.The enthalpy of crystallization does not depend on the quenching rate for Fe₃₉Ni₃₆Cr₅P₁₄B₆, and does not change during annealing within the relaxation field before crystallization.

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Zusammenfassung Strukturelle Relaxation und Kristallisation der metallischen Gläser Fe₃₉Ni₃₆Cr₅P₁₄B₆, Fe₈₁B₁₉, Fe₇₆Co₄B₂₀ und Fe₇₅V₄B₂₁ wurden mittels DSC untersucht. Verschiedene Koeffizienten zur Kalibrierung der DSC-Zelle wurden für die zwei Phänomene bestimmt. Die Entalpie der Relaxation steigt mit zunehmender Abkühlungsgeschwindigkeit im Falle von Fe₃₉Ni₃₆Cr₅P₁₄B₆ und mit zunehmender Zahl der Legierungskomponenten im Falle der Fe-B-Gläser an. In den letztgenannten Systemen ist die Relaxation niemals vor Beginn der Kristallisation beendet. Die Entalpie der Kristallisation ist im Falle von Fe₃₉Ni₃₆Cr₅P₁₄B₆ unabhängig von der Abkühlungsgeschwindigkeit und ändert sich auch nicht beim Tempern im Relaxationsgebiet vor der Kristallisation.

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Fe₃₉Ni₃₆Cr₅P₁₄B₆, Fe₈₁B₁₉, Fe₇₆Co₄B₂₀ Fe₇₅V₄B₂₁. . Fe₃₉Ni₃₆Cr₅P₁₄B₆ , Fe-B — . . Fe₃₉Ni₃₆Cr₅P₁₄B₆ .