Kinetic-morphological peculiarities of solid-state isomerization of complexes

The thermal solid-state isomerizations of Copy₂Cl₂ (py=pyridine), Nien₂(NO₂)₂ and Nien₂(NCS)₂ (en=ethylenediamine) were studied by thermal analysis, thermomicroscopy, X-ray diffraction and IR-spectroscopy. It was shown that the reactions proceed by nuclear formation and growth. The kinetic-morphological peculiarities of the processes suggest that the process-determining stage is a phase stage, i. e. structural transformation. The topography and kinetics of processes are therefore determined by the crystal structures of the initial material and the reaction product, and by the contact conditions at the interface. The stress relaxation processes affect the morphology of the products and the kinetics of the transformation.

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Zusammenfassung Thermische Isomerisierungsreaktionen in fester Phase wurden durch thermische Analyse, Thermomikroskopie, Röntgenbeugung und IR-Spektroskopie an CoPy₂Cl₂ (Py=Pyridin), Nien₂(NO₂)₂ und Nien₂(NCS)₂ (en=Ethylendiamin) untersucht. Es wird gezeigt, dass die Reaktionen durch Keimbildung und Wachstum ablaufen. Die kinetischen und morphologischen Charakteristika der Prozesse weisen darauf hin, dass der geschwindigkeitsbestimmende Schritt ein Phasenschritt, d. h. eine Strukturumwandlung ist. Deshalb sind Topographie und Kinetik der Vorgänge durch die Kristallstrukturen des Ausgangsstoffe und des Reaktionsprodukts und durch die Kontaktbedingungen an der Grenfläche bestimmt. Die Spannungsrelaxationsprozesse beeinflussen die Morphologie der Produkte und die Umwandlungskinetik.

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, , ₂l₂, Nien₂(NO₂)₂ Nien₂(NCS)₂, en= , = . , . - , . , . .

     

Application of thermal analysis to the investigation of catalysts

A short review of the possibilities of application of thermal analysis to the investigation of catalysts is given: analysis of catalysts, investigation of the processes during the preparation of catalysts, desactivation of catalysts, and interaction of reactants or catalytic poisons with the catalysts. Several examples are mentioned.

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Zusammenfassung Eine kurze Übersicht über die Möglichkeiten des Einsatzes der Thermoanalyse zur Prüfung von Katalysatoren wird gegeben: Analyse der Katalysatoren, Prüfung der Vorgänge während der Herstellung von Katalysatoren, Inaktivierung von Katalysatoren, Wechselwirkungen zwischen Reagenzien oder Katalysatorengiften und den Katalysatoren. Eine Anzahl von Beispielen wird erwähnt.

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Résumé On piésente une rapide vue d'ensemble sur les possibilités d'application de l'analyse thermique à l'étude des catalyseurs: l'analyse des catalyseurs, l'étude des processus ayant lieu lors de la préparation des catalyseurs, la désactivation des catalyseurs, l'interaction de réactifs ou de poisons sur les catalyseurs. Plusieurs exemples sont mentionnés.

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. , , —, —, — , . , — . .

     

Einfluß der Anionensolvatation auf die Komplexbildung in Donorlösungsmitteln

Zusammenfassung Der Einfluß der Anionensolvatation auf die Komplexbildung in Donorlösungsmitteln wird folgendermaßen beschrieben: Der thermodynamische Solvatationseffekt hängt vom Verhältnis der freien Solvatationsenthalpien zur freien Enthalpie des Gesamtvorganges der Komplexbildung ab; d. h., je geringer die Akzeptorstärke des Akzeptors, um so mehr wird durch die Solvatation die Donorstärke eines Anions im Vergleich zu derjenigen des Neutraldonors erniedrigt. Der spezifische Solvatationseffekt bringt das spezifische Solvatisierungsvermögen eines Lösungsmittels gegenüber einem Anion (bei gegebenem Akzeptor) zum Ausdruck. Protonenhaltige Lösungsmittel, z. B. Wasser, Methanol, Essigsäure, Ameisensäure, Formamid, haben eine hohe Tendenz zur Wasserstoffbrückenwechselwirkung; sie solvatisieren Halogenid- und Pseudohalogenidionen wesentlich stärker als aprotische Donorlösungsmittel. Die Donorstärke eines anionischen Liganden wird in einem solchen Lösungsmittel entsprechend erniedrigt. Zum Vergleich der Stabilität eines Komplexes in verschiedenen Lösungsmitteln können ihre Donizitäten allein nicht herangezogen werden. Die solvatisierenden Eigenschaften von Donorlösungsmitteln nehmen ab: H₂O>ROHDMSOES>ANTMSNMDMF>DMA>HMPT.

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The influence of anion-solvation on complex formation in donor solvents

The said influence is described as follows: the thermodynamic solvation effect depends on the ratio of the free enthalpy of solvation to the free enthalpy of the complex forming reaction. It is increased by decreasing acceptor strength of the acceptor. The specific solvation effect is due to the specific solvating power of a solvent towards an anion (with given acceptor). Protonic solvents are known to have higher tendencies for hydrogen bridge interactions. They are stronger solvating agents for halide and pseudohalide ions than aprotic donor solvents. The donor properties of a donor anion is decreased in such solvents and the donicity alone is no longer a useful guide to estimate the relative stabilities of a complex in such media. The solvating properties of donor solvents decrease in the following order: H₂O>ROHDMSOES>ANTMSNMDMF>DMA>HMPT.

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Herrn Professor Dr.Richard Kieffer zum 65. Geburtstag gewidmet.     

Oxidative stability of lubricants for dry circuit sliding contacts

The thin film oxidation resistance of isoparaffin and two polyol esters synthetic lubricants was studied by high pressure differential scanning calorimetry. The oxidation induction time of each lubricant was measured by isothermally heating the sample in an oxygen environment. Arrhenius plots were constructed to predict the service life of the lubricant at low temperatures. The results indicate that polyol esters exhibit better oxidative stability than isoparaffins.

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Zusammenfassung Mittels Hochdruck-Differential-Scanning-Kalorimetrie wurde die Dünnschicht-Oxydationswiderstandsfestigkeit von Isoparaffin- und zwei synthetischen Polyolesterschmiermitteln untersucht. Die Oxydationsinduktionszeit jedes Schmiermittels wurde durch isothermes Erhitzen der Probe in Sauerstoff gemessen. Zur Vorhersage der Lebensdauer der Schmiermittel bei niedrigen Temperaturen wurden die entsprechenden Arrhenius-Diagramme erstellt. Die Ergebnisse zeigen, dass Polyolester über eine bessere oxydative Stabilität verfügen als Isoparaffine.

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, . . . , , .

     

Catalysts for metathesis of olefins obtained through [Mo3O4(C2O4)3 (H2O)3]2? coordinated to γ-Al2O3

New highly active catalysts for the metathesis of olefins have been obtained through the interaction of [Mo₃O₄ (C₂O₄)₃ (H₂O)₃]^2– anion with Al₂O₃ surface and further activation in H₂ or CO atmosphere.

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[Mo₃O₄ (C₂O₄)₃ (H₂O)₃]^2– Al₂O₃ H₂ CO .

     

The Radiation Resistance of Films Obtained by Plasma Deposition of Polypropylene Electric-Discharge and Thermal Degradation Products

By means of the ESR technique, it was shown that paramagnetic species with polyconjugated carbon–carbon bonds are stabilized in the films produced in a plasma from polypropylene (PP) electric-discharge and thermal degradation products. A high radiation resistance of the film material was revealed, which was manifested as a 160-fold lower radiation-chemical yield of radicals relative to that from parent polypropylene (G _R 0.4 for precursor PP and G _R 0.0025 for the plasma-deposited film). The obtained films were insoluble in common organic solvents and resistant to acid and alkali solutions. The film density was 1.4 g/cm³.     

Reactivity of the CCl3CH2CH2. radical in processes of homo-and cotelomerization of olefins with carbon tetrachloride

From the kinetic studies of CCl₃CH₂CH₂Br addition to 1-hexene, the rate constant of addition of the CCl₃CH₂CH ₂ ^. ( _e ¹ R) radical to 1-hexene [1g _e ¹ k_h=(5.2±0.1)–(13 000±800)/RT] has been determined. From the cotelomerization data, rate constants of the interaction of _e ¹ R-radical with ethylene [1g _e ¹ k_e=(6.1±0.2)–(21 400±1 200)/RT] and carbon tetrachloride [1g _e ¹ k_t=(7.5±0.2)–(37 000±1 200)/RT] have been calculated.

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CCl₃CH₂CH₂Br 1-. CCl₃CH₂CH ₂ ^. - _e ¹ R^.)- 1- (1g ¹ K=(5,2±0,1)–(13 000±800)/RT), 1- , ¹ R- (1g ¹ K=(6,1±0,2)–(21 400±1200/RT) CCl₄ (1g ¹ K=(7,5±0,2–(37 000±1 200)/RT).

     

Electrical and Optical Diagnostics of Dielectric Barrier Discharges (DBD) in He and N2 for Polymer Treatment

Synchronous, real-time optical and electrical diagnostics have been carried out on dielectric barrier discharges in flowing gases (air, He, N₂) at atmospheric pressure. A true Atmospheric Pressure Glow Discharge (APGD) is observed in N₂ when O₂ and H₂ concentrations are below 500 ppm and 2500 ppm,respectively, and the APGD regime can be beneficially modified by suitably chosen dielectric coatings. X-ray photoelectron spectroscopy (XPS) analyses of some APGD-treated polymer surfaces are presented.     

Synthesis and Photochromic Properties of 2-(3-Nitro-2-pyridylmethyl)benzazoles

2-(3-Nitro-2-pyridylmethyl)benzazoles were synthesized, and their photochromic properties were studied by flash photolysis. Introduction of a nitropyridyl instead of the nitrophenyl moiety into the 2-methyl group insignificantly increases the basicity of the methylene group. Nitropyridyl-substituted benzazoles give rise to three detectable photoinduced forms: the corresponding anion at pH > 10, azamerocyanine at pH 4 , and monomethinecyanine at pH 1. Irradiation of solutions of weakly basic benzoxazole and benzothiazole derivatives at pH 4 results in formation of neutral chelate structures in which the hydrogen atom is linked simultaneously to two nitrogen atoms: one in the pyridine ring, and the second, in the azole ring.     

Investigations of hard elastic polypropylene with respect to the coil-strand-transition model

Hard elastic polypropylene was investigated by x-ray scattering using synchrotron radiation and by performing stress strain measurements in different liquids. It was found that the long period increases with elongation up to 1.3–1.4. Beyond this extension a change in the deformation behavior takes place. In the range from 1.1 to 1.3–1.4 the deformation measurements in the different liquids are in good agreement with the coil-strand-transition model. The proposed linear relationship between the deformation work and the elongation could be confirmed. The same holds for the surface energy. Moreover, the calculated ratio between the surface energy and the deformation work agrees with the measurements.     

Oxidation stability of polymeric materials dynamic DSC/DTA method

The dynamic DSC/DTA method was observed to give better selectivity and reproducibility than the isothermal method when estimating relative oxidation stability of plastics materials. The dynamic DSC/DTA method is in this survey exposed to a round robin test. Results of various instruments and test stations are compared, and their compatibility is unexpectedly good. Subsequently the dynamic DSC/DTA method was chosen as the quality control method and will be published as Finnish standard SFS 3449.

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Zusammenfassung Bei der Bestimmung der relativen Oxydationsbeständigkeit plastischer Materialien wurden mit der dynamischen DSC/DTA-Methode eine bessere Selektivität und Reproduzierbarkeit als mit der isothermen Variante beobachtet. Die dynamische Methode wurde in verschiedenen Laboratorien getestet. Die mit verschiedenartigen Geräten in verschiedenen Laboratorien erhaltenen Testergebnisse stimmen überraschend gut überein. Die dynamische DSC/DTA-Methode wurde deshalb als Qualitätskontrollmethode gewählt und wird als finnische Norm SFS 3449 herausgegeben.

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, / , . . , . , . / SFS 3449.

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Thanks are due to the Finnish Plastics Industries Federation and its member companies for the helpful interest in the course of this survey.     

Free Radicals in the Photolysis and Radiolysis of Polymers: IV. Radicals in γ- and UV-Irradiated Wood and Lignin

Free radicals formed in the radiolysis and photolysis of wood and lignin were studied using X-band and D-band EPR measurements. It was found that singlet spectra at g 2, which appeared upon the low-temperature (77 K) - and UV irradiation of wood and lignin, or singlets detected in a posteffect on heating the irradiated samples belong to radicals having conjugated carbon–carbon bonds. Formyl radicals in -irradiated wood and peroxide radicals in - and UV-irradiated wood were detected for the first time using EPR spectra. The radiation-chemical and quantum yields of radical formation reactions were determined. In wood at 77 K, G _R 3.2 1/100 eV and _R 2 × 10^–3.     

Separation and recovery of heavy metals from hydrometallurgical effluents by solvent extraction

Summary The possibility of separating and recovering heavy metals from hydrometallurgical effluents by successive solvent extractions has been investigated by two different procedures with liquid waste from the Espindesa Zinc process. The waste (pH value near to 1.5) includes significant amounts of Zn (1.35), Cu (0.12), Co (0.32) and Mn (0.6 g/l) in the presence of big concentrations of macro-constituents (sulphate, chloride, Na) and Fe [8.8 g/l, mostly as Fe(II) salts]. As extractants, Amberlite La-2 (a secondary ammine, as chlorohydrate) and DEHPA (di-2-ethylhexyl-phosphoric acid) at 25% volume in kerosene were selected. The first method includes two extraction stages with LA-2 for Zn and Cu separation (the last one with 60 g/l of chloride ions) and three stages with DEHPA at pH values near to 1.5, 2.0 and 3.5 for isolating Fe, Mn and Co. The second method separates firstly Fe (as ferric salts) with DEHPA. Afterwards, one stage with LA-2 isolates Zn and three stages with DEHPA at pH values near to 2.0, 3.0 and 3.5 lead to fractions rich in Mn, Cu and Co. Reextractions from organic layers with water or HCl at different concentrations lead to purer solutions of the isolated metals. With both methods, the liquid waste can be converted into a saline solution with lesser problems for disposal.     

Brightness Reversion of Mechanical Pulps. Part XVII: Diffuse Reflectance Study on Brightness Stabilization by Additives Under Various Atmospheres

Brightness reversion of softwood (SW) and hardwood (HW) bleached chemithermomechanical pulps (BCTMP) with a 300–400nm light source under argon, oxygen, and air were studied in the absence and presence of UV-screens using UV–Vis reflectance difference spectroscopy. The UV-Vis difference absorption spectra of control SW and HW BCTMP testsheets indicate that as the concentration of atmospheric oxygen is increased, the absorption at max 360nm increases and a blue shift occurs. In all of the cases studied, brightness reversion was observed to occur under an argon atmosphere. The addition of benzophenone and benzotriazole additives to BCTMP testsheets resulted in a significant decrease in formation of chromophores absorbed at 400nm and 360nm. The possible mechanisms contributing to these effects are discussed in terms of the photoformation of lignin chromophoric structures.     

Structure of the cardiac aglycone syriogenin

Summary The results of a study of the mass spectra of syriogenin and its D-analog confirm that this cardiac aglycone has the structure of 3,12,14-trihydroxy-5,14-card-20(22)-enolide.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 615–617, September–October, 1974.     

The advantage of anti-Compton counting in the measurement of low-level radioactivity by gamma-ray spectrometry

The inherent advantage of anti-Compton counting of low-level radioactivity is defined in terms of changes in the limits of decision, detection and determination. It appears that the advantage factor can be expressed in the experimentally observed reductions of peak area, compton continuum and natural background. For an array equipped with a sample changer, the advantage factor for interference by the compton continuum is 4, while that for interference by the natural background amounts to 3. By sacrificing the sample changer and closing its gap with NaI-plug, additional factors of 1.5 and 2 can be obtained for compton and natural background, respectively.     

Laser Sintering of SnO2 : Sb Sol-Gel Coatings

Sb doped sol-gel SnO2 single layers (thickness 100 nm) were prepared from alcoholic solution and deposited via a dip coating process on fused silica substrates. The coatings have been sintered at a typical rate of 10–15 cm2/s by CO2 laser irradiation. The laser spot was scanned in one direction at a speed of 15,000 cm/s and the sample was moved in a perpendicular one at a speed up to 250 mm/s. The temperature of the topmost 10 m layer was monitored by a fast pyrometer (s resolution). The following properties of the coatings have been determined: the electrical resistivity , the carrier density n, and mobility , the structure, the thickness, the mesoscopic and micromorphology and the density. The sintering by CO2 laser radiation is mainly a thermal driven process. At T 500°C it allows to obtain coatings with a smaller resistivity (6.8×10–3 cm) than those produced by conventional furnace firing (el2.9×10–2 cm). The results are discussed in terms of particle size and packing density.     

A constitutional diagram of the system TiC−HfC−“MoC”

The system TiC–HfC–MoC was investigated by means of melting point, differentiothermoanalytical, X-ray diffraction and metallographic techniques on hotpressed as well as melted alloy specimens. A constitutional diagram from 1500°C through the melting range was established.Investigation of the (Hf, Mo)C system (isopleth: HfC_0.98–MoC_1.0) showed a small miscibility gap within the cubic monocarbide solution () [Tc=1630°C, (HfC)_0.45(MoC)_0.55]. The miscibility gap interacts with the solvus curve with a monotectoid-like decomposition reaction at 1575°C, (HfC)_0.35(MoC)_0.65.At temperatures below 1630°C, phase equilibria within TiC–HfC–MoC are characterized by a large miscibility gap connecting the TiC–HfC and HfC–MoC boundary systems. Additions of MoC to TiC–HfC alloys decrease the critical temperature (1780°C); additions of TiC to HfC–MoC alloys raise the critical temperature (1630°C). No maximum type ternary critical point or saddle point was found to occur.Isothermal sections were prepared at 1500°C and 1650°C. At temperatures above 1960°C (-MoC+C-MoC) a complete solid solution (-B 1) is formed within TiC–HfC–MoC. The melting behaviour (liquidus projection of TiC–HfC–MoC) shows flat melting temperatures in the MoC corner but extremely heterogeneous melting near the TiC–HfC boundary.Isothermal sections have been calculated assuming regular solutions.With 5 Figures     

Application of anti-Compton counting in instrumental neutron activation analysis

The inherent advantage of anti-coincidence counting of low-level radioactivity is defined in terms of changes in the limits of decision, detection and determination. It appears that the advantage factor can be expressed in the experimentally observed reductions of peak area, compton continuum and natural background. For an array equipped with a sample changer the advantage factor for interference by the compton continuum is4, while that for interference by the natural background amounts to 3. By sacrificing the sample changer and closing its gap with a Nal-plug, additional factors of 1.5 and 2 can be obtained for compton and natural background respectively.     

Electroreduction of α-glucose on CNT/graphite electrode modified by Zn and Zn–Fe alloy

Electroreduction of -glucose to form sorbitol on Zn/CNTs and Zn alloy/CNTs electrodes has been investigated in this paper. Carbon nanotubes (CNTs) used in this paper are grown directly on graphite disks by chemical vapor deposition. Zn and Zn alloy are electrodeposited on the activated CNTs/graphite electrode by pulse galvanostatic method. The micrographs of Zn/CNTs and Zn alloy/CNTs electrodes are characterized by scanning electron microscopy. The results show that the current efficiency of -glucose reduction on CNTs electrodes is much better than that on flat Zn electrodes. The order of the current efficiency on different electrodes is as follows: Zn/CNT (0.58) Zn–Fe/CNT (0.57)>Zn–Ni/CNT (0.43) Zn/graphite (0.42)>Zn (0.40). It indicates that CNTs have good potential application in electrosynthesis. Additionally, effects of some operating parameters, such as pH, temperature and -glucose concentration, on the current efficiency of -glucose reduction are also discussed.