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  • Inorganic Chemistry  (6,777)
  • Industrial Chemistry
  • 1985-1989  (3,587)
  • 1950-1954  (2,931)
  • 1915-1919  (1,735)
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  • 1
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Liquid-liquid direct-contact heat transfer in a spray column was studied numerically for a low hold-up. The solutions of the conservation equations of mass, momentum and energy for both phases agree well with earlier experimental results, if one assumes a rigid liquid-liquid interface. Heat transfer inside is dominated by transient conduction and natural convection. It was found that the Nusselt number for free convection depends essentially only on the Rayleigh number.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 374-378 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Wall shear rate vectors in a bubble column and an airlift-loop reactor were measured using the limiting-current electrodiffusion technique. In connection with a new circular three-segment probe, the magnitudes and directions of shear rates were determined. The results for the bubble column are in good agreement with hot film-anemometry measurements in the same column. Moreover, the spiral flow structure, postulated in the shear-zone model of Franz, has been confirmed. In addition, the measuring technique was used to determine the flow structure in an airlift-loop reactor employed for the cultivation of animal cells. The region above the gas distributor of this fermenter has been identified as critical for mechanical damage to the cells.
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  • 3
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fermentation under modified gravity could be of interest in application to (a) increasing productivity of growth and growth linked production with microorganisms at high cell densities and (b) increasing the productivity of highly viscous pseudoplastic polysaccharide fermentation. In both cases, higher oxygen transfer rates in centrifugal fields result in higher productivities since these fermentations are usually oxygen limited. A further aspect of fermentation under increased gravity is the reduction of foam since foam coalescence time decreases with acceleration number. On the other hand, under microgravity, shear reduction would allow growth and production even for very shear sensitive organisms. In order to carry out fermentations under modified gravity, a special type of fermenter-the centrifugal field bioreactor CFBR-has been developed at the Institute of Chemical Engineering (Head: Prof. Mersmann) of the Technical University of Munich. For the first time, exoprotein biosynthesis of lipase with S. carnosus has been carried out under sterile and controlled conditions in this novel bioreactor, in presence of increased mass forces.
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  • 4
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental technique and evaluation method is described for the determination of local heat transfer coefficients in tubes or other ducts. By means of a rotary mixing valve, cold and warm fluid flows are mixed in order to generate an arbitrarily shaped but periodically oscillating inlet temperature profile at the test tube. The propagation of the fundamental harmonic oscillation from the fluid to the outer surface of the tube wall is calculated analytically. Comparison of fluid and wall oscillations yields the heat transfer coefficient to be measured. The inaccurate measurement of fluid bulk temperature in the centre of the cross-section is compensated by an additional correction. Experiments were carried out with turbulent water flow through a copper tube. Measured heat transfer coefficients were compared to values calculated using Hausen's equation and good agreement was obtained.
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  • 5
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 395-399 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mean droplet diameter of the dispersed phase in pulsed plate extraction columns was measured for binary and ternary systems. A change in the droplet size in the presence of solute, dependent on such factors as the direction of mass transfer, droplet size in the binary system, radio of diffusion coefficients, viscosity of the continuous phase, interfacial tension and driving force for extraction was observed. Two new empirical correlations of mean droplet sizes in mass transfer conditions are proposed. These correlations have been successfully applied to other extraction columns.
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  • 6
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 406-413 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During molecular distillation in a falling film apparatus, temperature and concentration of the more volatile components undergo a marked decrease in axial and radial directions, due to the distillation in vacuo. The gradients produce changes in the rate of surface evaporation and separation efficiency along the flow path. A theoretical study of this problem is presented for binary mixtures. The respective differential equations for heat and mass transfer in the liquid film are solved numerically. As the results demonstrate, the aspect ratio of an apparatus should be large when a high separation is required and small when a high distillation rate is more important.
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  • 7
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Flow phenomena, local heat and mass transfer and pressure drop of corrugated passages in process equipment are examined. Based on a method for measuring local heat and mass transfer, developed in previous investigations, a procedure has been formulated for the determination of local heat and mass transfer in corrugated passages. Using the analogy between heat and mass transfer, this technique allows the determination of heat transfer distributions in any structures with high local resolution. The corresponding pressure drop is presented together with the local and integral heat and mass transfer of different structures. It is shown that differences in heat and mass transfer as well as in pressure drop are due to different flow phenomena which also characterize mixing behaviour.
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  • 8
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Crystallizer design has to take into account the physical and chemical properties of the solution and solids as well as the geometry, type and operating conditions of the crystallizer. The most important property of a crystallizing system is its solubility. High solubility leads to low relative supersaturation and large mean crystal size, and vice versa. High solubility systems can be sensitive to abrasion and attrition. For low solubility systems, mixing is crucial.
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  • 9
    Electronic Resource
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 419-426 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper considers the dynamic performance of instruments in control systems. Errors connected with transient measurements are discussed. It is shown that it is not always proper to assign common statistical properties to these dynamic errors. Emphasis is placed on temperature sensors. Common industrial thermometers are described and factors affecting their response discussed. An a-priori dynamic performance prediction procedure is presented. This permits preinstallation estimation of response characteristics of sensors used in industrial processes. Sensors in service also require performance assessment since they can deteriorate with use. In-situ testing is useful for this purpose and a recently develolped procedure is described.
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  • 10
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modelling of the kinetics of a 20-N hydrazine thruster is carried out by considering two different heterogeneous reaction channels for hydrazine decomposition to the intermediate ammonia. The parameters of the reactor model are estimated by making use of temperature profiles at the wall of the decomposition chamber. Simulated ageing of the catalyst revealed an increase of the rate of deactivation with increasing total firing time.
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  • 11
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The principle of ultrasonic spectrometry is based on the measurement of the ultrasonic extinction caused by the presence of particles. From measurements at different frequencies and with the knowledge of the ultrasonic extinction cross section of the particles, a system of linear equations can be established and solved to obtain the particle size distribution and particle concentration. With an experimental apparatus covering the frequency range from 1.7 MHz to 81 MHz, particles ranging from 20 to 1000 μm in diameter may be analyzed. The measurements can be carried out with particle concentrations as high as 10% by volume.
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  • 12
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The “nozzle scrubber” is a wet scrubber in which the scrubbing water is dispersed in dust laden gas stream by means of one or more pneumatic nozzle. This scrubber is distinguished by an excellent collection efficiency for submicron dust at an unusually low energy and water consumption. So far, the physical effects affecting the separation cannot be explained by a well-defined theory. Therefore, it is sensible to investigate the collection efficiency with regard to the mechanisms of inertial impaction, turbulent diffusion and coalescence induced by turbulence. The experimental equipment is of a very simple design. A light scattering device was used to measure the particle distributions. In addition, electron micrographs were analyzed to obtain information about the submicron particles. The influence of operating parameters on grade efficiency has been demonstrated by their systematic variation. The contribution of turbulent diffusion to the collection efficiency has been confirmed; nevertheless, grade efficiencies were also measured when inertial impaction prevailed.
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  • 13
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study describes the gas and liquid distributions in a column with structured packings. The column is 0.5 m in diameter. It is equipped with a total of 1289 detectors in the top and bottom cross-sections. These detectors provide a detailed picture of the gas and liquid flows through elements of only 25 × 25 mm2. The maldistribution in the gas bulk flow is negligible. Only the observed wall can contribute to malperformance. The gas flows in parallel to sheet orientation, thus introducing a radial transport. Together with the change in the orientation of subsequent packing elements, this results in good gas mixing. It was observed that the liquid wall flow rate decreases when the gas velocity exceeds 1.7 m/s. Up to the loading point, the maldistribution of the liquid is constant. Above this point, the equality of the distribution deteriorates rapidly, due to the occurrence of large-scale liquid segregation.
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  • 14
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 235-244 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Film theory under consideration of one-sided diffusion is a satisfactory basis for the calculation of vapour condensation from a flowing turbulent mixture with non-condensable gases. At atmospheric pressure and low condensate flow rates, coefficient equations for smooth tubes are used as a rule. At higher pressures and thus, at higher temperatures and gas densities, there are additional parameters. For instance, non-ideal behaviour of the gas phase or the surface roughness affects the condensation process. These parameters were examined in a test plant under variation of pressure, steam concentration and temperature in a vapour/air mixture. At pressures of up to 21 bar, the Reynolds number of the gaseous phase reaches a maximum value of 128 000 and of 720 for the condensed phase. After description of the test facility, the experimental results are explained and discussed. It is shown that the experimental results are not in a good agreement with the common calculating methods. Taking into account the non-ideal behaviour of the steam/air mixture and the roughness of condensate surface by using a friction factor ξr, all the results could be calculated with an accuracy of ± 20%. This was achived with a modification of the coefficient equation of Gnielinski [1] and by using the equation of Andreussi [2] for the friction factor of a cocurrent annular flow. With respect to one-sided diffusion, the film theory is still applicable. The described method for the determination of local transfer coefficients includes the common calculating method. It represents an extension of the general validity of the film theory.
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  • 15
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 245-248 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mass transfer data are presented for absorption of oxygen in a centrifugal film apparatus. The apparatus was designed to exclude the formation of foam by gas dispersion in liquid. Cells and micro-organisms are not subjected to high shear stress. Therefore, this equipment can be applied in fermentation processes. In the present work, experimental data and correlations were obtained on splitting of the liquid film and oxygen absorption into the film through a spiral ridge formed on the conical surface. The performance of the apparatus is found to be equivalent to those of other types of absorbers.
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  • 16
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 249-254 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Thermally stabilized combustion has a number of unique characteristics which permit the generation of steam or other forms of process energy from the heat of combustion of a gaseous or clean liquid fuel in remarkably compact, integrated apparatus while truly minimizing the concentrations of NOx, CO and unburnt fuel in the effluent. These characteristics, which have been identified by a long-range program of research, are described and the advantages and limitations of this process are discussed.
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  • 17
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 18
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989), S. 20-26 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For design and simulation of chemical process furnaces in accordance with present-day standards, the temperature distributions in the firebox and in the reactors must be generated simultaneously. This calls for coupling of the simulations of the firebox and of the reactor. For the calculation of heat transfer in the firebox, a generalized furnace simulations program, based on the zone method, is applied. Monte Carlo simulation techniques are used to determine the view factors. The location of the burners is explicitly accounted for. Absorption and emission of radiation by the flue gas are calculated by considering band contributions for carbon dioxide and water. For the simulation of the steam reforming reactors, a one-dimensional heterogeneous model, which accounts for the presence of intraparticle partial pressure gradients, is used. The simulated temperature distribution in the furnace is in excellent agreement with industrial results, as is the simulated product distribution.
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  • 19
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    Chemical Engineering & Technology - CET 12 (1989), S. 333-339 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The most important investigations on liquid weeping and entrainment in plate columns with downcomers are reveiwed. The formulae for calculating column plate efficiency under conditions of liquid weeping and entrainment have been derived on the basis of mass balance equations. The presented model is a generalization of the models of AIChE and Colburn. Sample results are shown graphically. The effect of liquid entrainment on tray efficiency predicted by the model is in agreement with experimental data of FRI.
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  • 20
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The knowledge of the heat transfer coefficient on the inner side of a heated vessel wall is of the utmost importance for the design of agitated vessels. In the case of large Reynolds numbers, the heat transfer is mainly determined by these numbers whereas, with small Reynolds numbers, the heat transfer is better described by considering the Grashof number. Investigations of heat transfer in agitated narrow vessels have shown that the height/diameter ratio exerts virtually no influence on the heat transfer when multi-impeller stirrers are used. The heat transfer to stirred suspensions can be described by relationships valid for liquids if the characteristic data of the liquid are replaced by those of the suspension and when the solids volume concentration is also taken into account. This relationship allows the heat transfer coefficient to be calculated for given solids volume concentrations of up to 60%.
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  • 21
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to achieve optimal energy-saving, load-dependent operation of rectification columns, development and implementation of model-based control concepts are necessary. This paper reports on the design and step-by-step testing of a state observer for the estimation of two state variables which cannot be measured directly, namely the vapour rate and the location of mass transfer zone (temperature front) in the stripping section of a production column. The procedure is described, and the relevant simulation and operation results are presented and discussed. Initial experience, gained when the concept was put into practical operation, is reported.
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  • 22
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    Chemical Engineering & Technology - CET 12 (1989), S. 345-350 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous crystallization of potassium carbonate was investigated in a mixed suspension mixed product removal (MSMPR) crystallizer with 7.0 1 working volume. Highly polydispersed product was obtained, with x50 varying between 320 and 670 μm. Crystal growth rates can be described by the model of Abegg, Stevens and Larson (ASL) (size dependent crystal growth rate). Values of G0 = 8.6 × 10-9 to 3.6 × 10-8 m/s and B0/ϕ = 2.7 × 108 to 4.2 × 109 1/m3s were obtained for mT = 45 to 92 kg/m3 and ε = 0.45 ± 0.05 W/kg. Nucleation kinetics at 27 °C can be described by the equation: B0/ϕ = kBϕsε0.73G02.5. Since G0 ∝ σ, convection and/or diffusion rather than surface integration are the crystal growth controlling mechanisms.
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  • 23
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    Chemical Engineering & Technology - CET 12 (1989), S. 356-357 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 24
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    Chemical Engineering & Technology - CET 12 (1989), S. 54-63 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a chemical reactor is depressurized or pressure in a vessel, filled with saturated liquid, has to be decreased, generally both vapour and liquid flow out through the relief valve. Since chemical reactors are usually operated with toxic and explosive fluids, the discharged liquid which vaporizes on the ground around the vessel may reach dangerous concentrations, causing explosions or accidents with the poisonous gas. During a research project, some fundamentals were developed for the design of separation systems which separate liquid from vapour and store it in a receiver. The requirement for a separation efficiency of a least 80% is related to the condition that the separated liquid should flow back into the reactor still during the pressure relief phase. For safety reasons, both separation and re-storage are to be carried out without the supply of external energy. Theoretical and experimental investigations of pressure distribution within the piping to the relief valve and in an integrated separator show that re-storage of the separated liquid in the vessel can be achieved under certain flow conditions. Therefore, the separator must be integrated in the pipe at a certain height above the vessel, so that the hydrostatic pressure of the separated liquid, corresponding to the difference in height, is sufficient to lead it back through another pipe against the internal pressure of the vessel. First, several separators were tested with air-water mixtures. A swirl separator and a reversing separator have been developed to such an extent that they appear suitable for the set task. Experimental results with air-water mixtures and refrigerant R12 upon pressure relief show separation efficiencies of between 90 and 100% at low pressure drops within the whole operating range. As an alternative to separation outside the vessel, a rotary separator was also developed which is fixed to the outlet opening in the vessel. A centrifugal field is produced by the separator rotor and the heavier liquid is largely separated from the vapour so that only drops in the range 〈 100 μm flow together with the vapour towards the central standpipe. The outflowing vapour leaves the separator via 4 tangentially arranged nozzles, under critical conditions. The vapour flow momentum drives the separator rotor. The arrangement was developed and tested during various series of experiments, under conditions or pressure relief with refrigerant R12. So far, separation efficiencies between 60 and 95% have been achieved at stirring speeds of up to 2500 min-1.
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  • 25
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    Chemical Engineering & Technology - CET 12 (1989), S. 89-96 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Depressurization of a pressure vessel, containing a liquid or a gas is limited by the maximum possible mass flux. This flux occurs at a certain drop in pressure. The ratio of ambient pressure to that inside the vessel must be less than a certain critical value. The critical pressure ratio depends on the thermodynamic state of the fluid inside the vessel and on the geometry of the outlet cross-section. The outlet can be a pipeline, a safety valve or a rupture disk. The results of known theoretical and experimental work are presented. In previous experiments, saturated liquids, two-phase flows or pure vapours were examined. In order to predict the critical pressure ratio, certain assumptions are necessary. These are derived for three well-defined cross-sections of the vessel outlet.
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  • 26
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    Chemical Engineering & Technology - CET 12 (1989), S. 103-109 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the past decade, the sintering of model supported metal catalysts, i.e. catalysts consisting of metal deposited on very thin and flat oxide films, has been intensively investigated by transmission electron microscopy. In the current paper, a mathematical model, based on an atomic migration mechanism, for the sintering of these catalysts is presented. The predictions of the model, based on Monte Carlo simulations, are in very good agreement with the experimental observations, i.e. phenomena such as ‘apparent’ particle migration, splitting and neck formation between particles are predicated by the model.
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  • 27
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    Chemical Engineering & Technology - CET 12 (1989), S. 109-112 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anaerobic fermentation of molasses distillery slops to biogas was carried out with the aid of an adapted and selected anaerobic mixed culture. Two different types of fermenters were used, namely an agitated pretreatment fermenter and a column fermenter with glass rings as carriers for micro-organisms. The production of biogas in both fermenters amounted to between 0.6 and 0.8 dm3/g COD. The aerobic pretreatment of distillery slops by T. fermentans, yeast during a 4 to 6 h period allows a high reduction of COD in the subsequent anaerobic phase of the process. After treatment of the distillery slops by T. fermentans, it was possible to convert between 85 and 93% of the organic matter to methane. Conversion was about 93% with loading rate of 25g COD/litre day.
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  • 28
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    Chemical Engineering & Technology - CET 12 (1989), S. 155-161 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The conversion of methanol over zeolite H-T was investigated in a fixed bed reactor. H-T was prepared from Na-T by ion exchange with HCl and NH4Cl solutions. The HCl solution caused appreciable dealumination. High yields of ethene were obtained with NH4Cl exchangeed zeolites Na-T with 45% decationization, high proprne yields with low HCl or NH4Cl Exchanged catalysts. Low methanol partial pressures and short residence times favoured the formation of lower olefins. Lowest coking rates were observed at a reaction temperature of 693 K. The catalytic activity decrased slowly with the number of reaction/regeneration cycles. The distribution of procucts 〉 C2 could be described by the most probable distribution of Schulz and Flory.
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  • 29
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    Chemical Engineering & Technology - CET 12 (1989), S. 170-175 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents a method mathematical modelling of cocurrent multitubular fixed-bed reactors. The method is adapted to the most widespread type of industrial reactor design, i.e. the system fitted with disk-and-doughnut baffles. The proposed model makes it possible to estimate the influence of non-uniformity of the heat carrier flow on the reactor characteristics, taking into account the coolant streams by-passing via the tube-to-baffle clearances. Based on the model, the effect of the operating parameters as well as of some more important geometrical parameters of the reactor on an exemplary highly exothermic process of partial benzene oxidation to maleic anhydride is discussed.
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  • 30
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    Chemical Engineering & Technology - CET 12 (1989), S. 188-195 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Collection efficiency and pressure loss of a venturi scrubber can usually be determined from the calculation models of Barth and Calvert. However, this only leads to reasonable results if the droplets are uniformly distributed throughout each cross-section of the washing zone. In this work, a two-zone models is developed which allows the calculation of the venturi scrubber at operating conditions with a non-uniform droplet distribution. The scrubber geometry is also taken into account. A venturi scrubber was developed on the basis of this new model. Its energy consumption is significantly lower than the well-Known optimum characteristic of Wicke and Holzer. For ideal operating conditions, a new optimum characteristic is given which should be the aim of future optimizations.
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  • 31
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steady-state concentrations of the transferred reactant in the bulk phase and the non-flowing diffusion boundary layer of an isothermal, isobaric two-phase reactor with an irreversible first-order reaction and constant composition of one phase.
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  • 32
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    Chemical Engineering & Technology - CET 12 (1989), S. 200-204 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model of floc destruction resulting form mass forces in a centrifugal field is postulated and its validity examined. This model is to be regarded as a supplement to the existing shear-loading disagglomeration models. In order to verify this additional floc disintegration mechanism, appropriate investigations were carried out with flocculated suspensions of silica and Hamburg dock sludge. As a result, in addition to floc disintegration by shear forces within a turbulent flow and in the centrifuge inlet, the existence of another mechanism was demonstrated. This consists in the floc destruction in a centrifugal field where particles in excess of a certain size, or specifically heavier components, are preferentially torn out of the floc. This floc disintegration by mass forces can lead to a classification effect in centrifuges which also subject the flocs to instant high centrifugal forces.
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  • 33
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    Chemical Engineering & Technology - CET 12 (1989), S. 205-212 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A circular loop reactor was built for application to a heterogeneous liquid-liquid reaction. In order to investigate the dispersion behaviour of droplets in the reactor, basic experiments were performed using a number of liquid-liquid dispersions. Droplets discharged form the impeller region were found to grow due to coalescence in the circulation region. Mean droplet diameter decreased exponentially with elapsing time. An expression correlating the steady-state mean droplet diameter with the operating conditions was derived. Moreover, the transition time required for the droplet diameter to reach the equilibrium value was determined and correlated with the operating conditions.
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  • 34
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    Chemical Engineering & Technology - CET 12 (1989), S. 213-217 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Important aspects of K1a measurement in agitated aerated vessels are briefly characterized from the standpoint of reliability of the measured data. An analysis of the shortcomings of dynamic methods for measuring the K1a is given. A new modification of the dynamic method is proposed, which excludes these inadequacies through a special experimental arrangement. This was verified by comparing the data with those obtained by an independent steady-state method. The new method can serve as a standard of reference, suitable for testing newly developed methods for K1a measurement. The initial response method was tested in this way in non-coalescent liquids, and shown to lead to errors of the order of hundreds of percent. K1a values obtained with the initial response method were found to depend strongly on the probe's location in the vessel.
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  • 35
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Secondary nucleation in industrial crystallizers depends on both supersaturation and mechanical stress by stirring. Most models which consider mechanical stress assume that nucleation is proprotional to the energy transferred to the crystals during collisions. This is not based on any physical relationship and, in addition, the models do not satisfactorily reproduce the experimental results. Own model, based on the theory of Hertz/Huber, which accounts for the stress of the crystals caused by impact, gave better results. This well-known and proven theory allows the calculation of the volume abraded during collisions between crystals and stirrer or walls. Introducing a nucleate efficienncy, the effect of mechanical stress on the rate of secondary nucleation, due to stirring intensity and crystallizer size, can be determined.
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  • 36
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    Chemical Engineering & Technology - CET 12 (1989), S. 147-154 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The sintering effect of highly dispersed metals is the reason for the following phenomena: thermal deactivation, particle size effect, separable or non-separable kinetics and the isokinetic relationship ( = compensation effect). A comparison of these phenomena reveals a contradiction which can be reconciled by a new particle size effect. This effect is characterized in the following way: The dependence of specific activity on particle size is always connected with a variation of the activation energy, caused by the particle size distribution. Therefore, this effect is referred to as the partical size and distribution effect, P.S.D.E. This new concept describes all the observed phenomena of the conventional partical size effect. Moreover, it is consistent with similar effects such as non-separable kinetics and the isokinetic relationship. In consequence, the method of isothermal measurement of specific activity is inadequate.
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  • 37
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    Chemical Engineering & Technology - CET 12 (1989), S. 255-261 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Carman-Kozeny equation is applicable in the viscous flow regime but, as the powder becomes finer, this equation fails. The controlling factor is the ratio of the hydraulic diameter to the mean free path of gas molecules (rH/λ) and, as this approaches unity, “slip flow” occurs. This effect increases with (a) increasing fineness, i.e. rH reduced, (b) decreasing porosity, i.e. rH reduced, and (c) decreasing pressure, i.e. λ increased. In order to account for the enhanced flow arising as a result of this failure, a second term is introduced into the equation and this includes an unknown “constant” (δK0/K), the coefficient of slip. It was considered probable that this so-called constant was a function of (rH/λ), and an attempt was made to investigate this relationship.
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  • 38
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    Chemical Engineering & Technology - CET 12 (1989), S. 269-273 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 39
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    Chemical Engineering & Technology - CET 12 (1989), S. 262-269 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Studies of flow characteristics and residence time distribution, (RTD), have been undertaken in a range of geometrically similar, laboratory nozzle-type reactors. High-speed cine-photography was employed to record the complex phenomena of liquid mixing in the reactor and also to record on film the colour of an injected tracer solution leaving in the effluent. A novel atomic absorption spectrophotometric (AAS) technique was applied to transform the results of the latter film into response curves. This technique provide detailed quantitative data on the residence time distributions (RTD) for different feed rates. A multiparameter model, comprising a network of CSTR's and plug flows, was developed to simulate the experimental response data. Good agreement was obtained between model predictions and experimental results. The experimental technique and theoretical approach are recommended for analyzing the flow patterns and mixing mechanisms in such reactors.
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  • 40
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A superposition of simple physical equations allows a satisfactory, comprehensive fluid dynamic description of jet-loop reactors in multiphase operation up to a dispersed phase hold-up of 15%. In the case of higher concentrations, there are further interactions which are not yet included in the model description. Apart from the drag coefficient of the single-phase jet loop, information on the particle swarm behaviour, i.e. on the slip velocity of the dispersed phase is required. Explicit formulation of the influence of the relevant geometrical parameters permits a reliable scale-up without additional adaptation parameters.
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  • 41
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    Chemical Engineering & Technology - CET 12 (1989), S. 280-288 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A cubic equation of state is modified in such a way that prediction of PVT data from 40 model compounds, typical of coal oil, becomes possible with an absolute mean deviation of less than 2% for saturated liquid volumes and vapour pressures 〉 1 bar. Additional correlations for binary interaction parameters are obtained by an optimization procedure using vapour-liquid euilibrium (VLE) data from known heavy hydrocarbon liquid/light gas systems. When the modified equation is applied to coal-derived liquids, only specific gravity and boiling analysis data of the coal liquids are required, primarily in order to determine the equation-of-state parameters. The proposed equation is shown to allow a good prediction of VLE data for systems consisting of wide-boiling-range coal oils and light gases. Experimental values were obtained at elevated temperatures and pressures with a circulation flow apparatus.
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  • 42
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Heat transfer and fluid mechanical data were computed for laminar channel flows containing strong longitudinal vortex pairs. The strong vortices are generated by thin delta wings and delta winglet pairs of low aspect ratios and large angles of attack. These wings are attached to the channel walls. The data show that longitudinal vortices cause high local peaks in heat transfer and marked increases in the overall channel heat transfer. These increases occur over a wide region of channel wall, compared to the vortex generating wing area. The results are of special interest for compact heat exchangers. The heat transfer enhancement allows a considerable reduction in the heat transfer area which, in turn, reduces the manufacturing and operating costs.
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  • 43
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Grade efficiencies must be measured in order to characterize particle collection in cyclones. For real, irregularly shaped partcles, the grade efficiencies depend on the shape and orientation of the particles and the flow around them. Therefore, the collection characteristics of cyclones should be defined in relation to spherical particles. Deviations occurring on the use of real, irregularly shaped dusts can then be attributed to a material influence. A fast and accurate measuring technique to determine the collection characteristic for spherical particles is described, followed by the presentation of results of extensive investigations on small model cyclones. A similarity relationship is presented. The validity of this relationship was confirmed by investigations with similar, larger cyclones.
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  • 44
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    Chemical Engineering & Technology - CET 12 (1989), S. 33-37 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The absorption of nitric oxide (NO) in phosphoric acid esters and polyethylene glycol ethers which contain cupric halides has been investigated. Due to high solubility of cupric halides and high equilibrium constants of formed nitrosyl complexes, the effective solubility of nitric oxide can be enhanced to about 100-fold its solubility in the salt-free organic liquid which itself amounts to only about 5-fold the NO-solubility in water. Calculations taking into account flue gas conditions indicate that the required gas-liquid ratio in industrial absorption processes will lie in the normal range of flue gas scrubbing processes, namely in the region of 400:1 to 1000:1 in volume. Thus, such a reversible absorption process could a viable alternative to SCR-processes in flue gas denitrification.
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  • 45
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    Chemical Engineering & Technology - CET 12 (1989), S. 96-102 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of alkali treatment, nitrogen supplement and hydraulic retention time on methane production rate from semi-continuous anaerobic digestion of 5% wheat straw-water mixtures were investigated. The experiments were carried out in laboratory scale fermenters, fed with 1 1 of basic, alkali treated and nitrogen supplemented 5% wheat straw-water mixtures, respectively, and maintained at 55 °C. Digestion experiments were performed for hydraulic retention times of 8, 10 and 15 days. The amount and composition of produced gas were measured until steady state was attained in each run. The steady-state methane production rates were found to increase with hydraulic retention time and with the type of slurry in the following order; basic, nitrogen supplemented and alkali treated slurry. Data obtained from the experiments were employed to determine the kinetics of methane production from anaerobic digestion of wheat straw, for the assessment of pretreatment effects on process kinetics. The predicted methane production rates were found to be in a reasonably good agreement with the measurements.
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  • 46
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    Chemical Engineering & Technology - CET 12 (1989), S. 71-87 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In the course of polymerization in homogeneous systems, the viscosity of the reaction mass increases by several orders of magnitude. The viscosity increase is affected by reaction conditions, concentration and properties of the formed polymer. Empirical correlations for homogeneous and heterogeneous polymerizations are given. Viscosity significantly affects the polymerization kinetics as well as heat, mass and momentum balances of the polymerization reactor. The influence of viscosity and its increase on conductive heat transfer, stirrer power input and cooling capacity, molecular diffusion and mass transfer coefficients, mixing time and residence time distribution in homogeneous and heterogeneous polymerizations in stirred tank and tubular reactors is reviewed.
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  • 47
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    Chemical Engineering & Technology - CET 12 (1989), S. 113-130 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Starting from the review of current industrial designs, the present paper analyzes thermal interaction between reactants and coolant in multitubular fixed-bed reactors. The interaction can be described quantitatively in terms of parameters characterizing transport processes both on the tube side and in the intertubular space. The study provides a detailed discussion of existing methods and correlations used for the evaluation of these parameters. The methods presented here can be considered as a basis for the development of a more comprehensive approach to the modeling and design of multitubular catalytic reactors.
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  • 48
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The prediction of leak areas in pressure vessels is an important objective in the safety analysis of chemical plants. Using suitable design rules, a leak-before-break behaviour can be achieved. This contribution outlines a procedure for the leak-before-break design of nozzle attachments and the determination of the size of the corresponding opening area. In addition, K1-factors and leak areas for a number of nozzle geometries have been calculated and plotted.
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  • 49
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    Chemical Engineering & Technology - CET 12 (1989), S. 218-225 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Most chemical engineers presently accept that the mass transfer rate in desorption from the solid to the gas phase or from the liquid to the gas phase is accelerated with increasing temperature in the liquid or the solid phase, or increasing partial pressure of inert gas in the gas phase, and/or decreasing total system pressure in the gas phase. Nevertheless, many reports about such mass transfer are still based on the former concept, which completely contradicts the actual phenomena mentioned above. Here, we discuss the contradiction and suggest a way of resolving it in terms of diffusion theory.
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  • 50
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    Chemical Engineering & Technology - CET 12 (1989), S. 226-233 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The explosion behaviour of CH4/air mixtures inside a closed 0.065 m3 spherical and a 1 m3 cylindrical vessel was investigated to determine the effect of turbulence on the structure and propagation rate of transient turbulent flames for different initial turbulence levels generated by 4 ventilators installed inside the equipment. Laser-Doppler and hot wire anemometry were used to measure the turbulent motion. It was found that fairly uniform turbulence could be achieved in the central zones of the vessels and that the RMS-values of flow velocity were proportional to the ventilator speed. The evaluation of burning velocity from the pressure/time records showed that, starting from an initial burning velocity which depends on the initial turbulence level, the flame accelerates as a result of pressure, temperature and turbulence effects. Maximum burning velocity coincides with the inflexion point of the pressure/time curve, and is followed by a rapid deceleration of the flame front. A linear relationship between burning velocity and measured RMS-velocity is recognized in the observed range of RMS-values.
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  • 51
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Distillation has been, up to now, the standard method for separating fluid mixtures in the process industry and the consensus is that it will remain so for years to come. The only disadvantage of distillation is its high energy requirement. In the following, it will be demonstrated on the example of an ideal ternary mixture, how the energy requirement of distillation process can be reduced. Very effective are some modifications of single columns, optimization of column sequences and direct or indirect column coupling. It will be shown that, just by column coupling, the energy requirement can be reduced to a third.
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  • 52
    ISSN: 0930-7516
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of turbulence on local heat and mass transfer is systematically analyzed. Essential prerequisite is the availability of measurement methods, based on convective mass transfer, which allow the visualization of heat and mass transfer distributions. The results show that, even at low turbulence intensities, the flow and transport phenomena are decisively influenced by the specific design of turbulence grids and the orientation of the grid wires with respect to the stagnation line. Thereby, two different flow mechanisms occur which may interact. The anisotropy of grid turbulence leads to the “wire-gap effect” depending on the actual position of the grid wires in relation to the stagnation line. The other mechanism is based on the wavy wake velocity distribution behind screens and grid which, in conjunction with the centrifugal instability of stagnation flows, may lead to longitudinal vortices. The results indicate why turbulence has not been sufficiently considered in the available (semi-) empirical correlations. Information needed for an accurate prediction of heat and mass transfer in turbulence flows is discussed.
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  • 53
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An independent preliminary mechanistic prediction method for leakage rates through small slit-shaped through-wall cracks, based on coupled pressure drop and (critical) mass flux calculation is presented. The predictions are verified against initially subcooled liquid refrigerants and water data collected during experiments in real and model cracks in a wide range of parameters. The achieved accuracy of prediction is already comparable to that of the experimental results. Further model modifications are put forward.
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  • 54
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    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To improve the rate of convergence of random search optimization procedures, the incorporation of a gradient-oriented one-dimensional search is investigated. With this modification to the random search procedure based on uniform sampling and region contraction [1], convergence to within 0.01% of the global optimum was obtained substantially faster for typical chemical engineering problems. It was also found that the reliability of obtaining the global optimum was improved.
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  • 55
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    Chemical Engineering & Technology - CET 12 (1989), S. 318-323 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A special stress measuring device for determining the normal and shear stresses acting on silo walls was developed and tested. The load cell can be used for measuring simultaneously the normal stress as well as the intensity and direction of the shear stress.
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  • 56
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The chlorination of an alumina with BET surface area of 100 m2/g has been studied in situ by transmission IR measurements at about 670 K. The chlorinating gases consisting of Cl2 and CO were employed individually and in equimolar proportion. The IR results do not reveal the presence of a phosgene surface species which could support the only mechanism proposed so far to explain the chlorination. A detailed alternative reaction mechanism is suggested for the high temperature chlorination reaction, taking into account the IR results, together with the known electron donor-acceptor properties of the activated alumina and the reaction gases: Cl2 molecules accept electrons from oxide ions with a lower coordination number on the alumina surface, leading to the formation of Cl-and Oad. While Cl- yields AlCl3, Oad reacts further with CO producing CO2.
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  • 57
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The vapour phase hydrogenation of 1,3-cyclo-octadiene (COD) over Pd on alumina has been studied in the gas phase, using a recycle reactor. The dependences of COD hydrogenation rates and those of the consecutive cyclo-octene (COE) hydrogenation on the reaction conditions are well described by a model which takes into account mass transfer in the porous layer of palladium. The kinetics of the COE hydrogenation is of a Langmuir-Hinshelwood type. The hydrogenation of COD is of first order with respect to hydrogen. The reaction order with respect to COD is -0.15. If the catalyst surface is completely covered by COD, the hydrogenation of COE is totally suppressed. This indicates a much stronger adsorption of COD than of COE. Hydrogenation of COE can only occur in the innermost part of the pores when the transport of COD by diffusion is insufficient to supply the entire active surface of the catalyst. This happens if the ratio PH2/PCOD exceeds 2/ϕ2 with ϕ being the Thiele's modulus. This relationship permits a simple evaluation of the effective diffusion coefficient in the porous Pd-layer.
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  • 58
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    Chemical Engineering & Technology - CET 12 (1989), S. 63-70 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is shown in this report that, under certain conditions, cleaning of exhaust air by absorption presents an interesting alternative to the existing methods. In particular, this process can be used with advantage for small quantities of exhaust air, high and strongly fluctuating solvent concentrations and solvent mixtures such as those occurring in batch operation. A washing agent was employed which had not been previously used for this purpose. Its properties, which were investigated in the laboratory, were confirmed during a 15-months' trial period in a semi-industrial plant. The process and plant were optimized for practical use. Through its option of solvent recovery from exhaust air, this physical absorption process contributes to environmental control.
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  • 59
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Combustion rate of flat graphite plates in oxidizing flows with velocities of up to 80 m/s and stagnation temperatures between 1600 and 2500 K were investigated. The flow field and its local properties were recorded in addition to surface temperature of the solid sample and change in surface structure. The experiments, in which the surface temperature of graphite was adjusted and carefully controlled by radiation shields, indicated that, under these experimental conditions, between 15 and 20 wt-% of carbon was lost as particles of up to 100 μm which burnt rapidly in the boundary layer region. Subtraction of erosion rates from the recorded global combustion rates yield the heterogeneous chemical reaction rates, which are approximated by an Arrhenius type function for the mathematical modelling. Since steep temperature and concentration gradients occur in the boundary layer, the local values of the multicomponent transport coefficients were evaluated in order to design a more realistic computational procedure which, in addition, also includes radiative heat transfer. Computational checks revealed that, in the past, the assumption of mean constant values for the transport coefficients has led to errors of up to 100% in the evaluation of the chemical reaction and global combustion rates.
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  • 60
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    Chemical Engineering & Technology - CET 12 (1989), S. 358-364 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The energy consumption of ammonia plants based on steam reforming of naphtha or natural gas can be reduced by shifting the reforming load from the primary to the secondary reformer. It is shown that lowering of the primary reformer operating temperature 20 °C results in 2% increase of unconverted methane content in the outlet stream. The increased methane content can be processed in the secondary reformer if the process air inlet temperature is increased to 400 °C. The lower operating temperature reduces the energy consumption of the primary reformer by about 6% (and the overall consumption by about 2%) and also prolongs the service life of reformer tubes.
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    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 12 (1989) 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 62
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    Chemical Engineering & Technology - CET 12 (1989), S. 1-11 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of micromixing limits on a process of crystallization in an MSMPR crystallizer is studied with respect to power law growth and nucleation kinetics. Three limiting cases corresponding to maximum mixedness and complete segregation in an MSMPR crystallizer and plug flow configuration were analyzed for processes in which supersaturation is generated by conventional techniques. The sensitivity of these three limiting cases to the supersaturation generation term in each mode of operation was investigated using several numerical examples. The study demonstrates the effects of mixing on the overall crystallizer performance and, in particular, the enormous micromixing influence at high supersaturation generation rates. The difference in the product CSD arise from the variations of supersaturation profiles experienced by the elementary volumes throughout their sojourn. Characterization of mixing in a real crystallizer at some intermediate levels is emphasized with the aid of relevant industrial examples.
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  • 63
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    Chemical Engineering & Technology - CET 12 (1989), S. 15-19 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Effective interfacial area a and volumetric liquid-side mass transfer coefficient kLa of an RTL contactor were obtained at different stirring speeds by absorption of oxygen from air into 0.8 kmol/m3 sodium sulphite solution, in the presence of Co++ ions. The values of a and kLa ranged from 80 to 150 m2/m3 and 0.0003 to 0.00053 s-1, respectively, when stirrer speed was increased from 8 to 40 rpm. When kL alone was evaluated, it was found to be practically constant, irrespective of stirring speed.
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  • 64
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This contribution reports on the theory underlying a uniform representation of heat transfer to submerged surfaces in fixed bed reactors and of gas convective part of heat transfer in fluidized beds with coarse-grained bulk solids and/or at elevated pressure. Based on an analysis of the pressure drop behaviour of fixed bed percolation at different gas pressures and with different bulk solids, a new dimensionless pressure drop parameter was developed. Fixed bed heat transfer data are very well correlated by this new dimensionless number. As soon as fluid throughput is in excess of minimum fluidization velocity, the pressure drop parameter transforms into the well-known Archimedes number. These two dimensionless numbers are connected by the condition of equilibrium for pressure drop and mass of practices in a fluidized bed. This equilibrium is fulfilled as soon as fluidization commences. Up to now, the Archimedes number has been generally accepted as the significant parameter, determining the gas convective part of heat transfer in fluidized beds; however, without any physical interpretation of this parameter. Introduction of the pressure drop number, which is consistent with the Archimedes number, reduces the heat transfer behaviour to pressure drop characteristics. The usefulness of this concept is proven by the comparison of experimental results and prediction.
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  • 65
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    Zeitschrift für anorganische Chemie 572 (1989), S. 89-94 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: About New Oxochromates: SrCr10O15 and BaCr10O15 Containing Divalent Chromium: MCr22+Cr83+O15High temperature reaction using reducing atmosphere lead to the new compounds (I) SrCr10O15 and (II) BaCr10O15. Single crystal X-ray investigations show orthorhombic symmetry: space group D2h18-Ccmb; I: a = 10.059; b = 11.406; c = 9.224 Å; II: a = 10.126; b = 11.491; c = 9.392 Å; Z = 4. Cr2+/Cr3+ are octahedral coordinated by O2-. Inside a CrO6-octahedral network are cavities comparable with those of some polyacids filled by Sr2+ or Ba2+ ions.
    Notes: Mit Hochtemperaturreaktionen in reduzierender Atmosphäre gelang die Darstellung der gemischtvalenten Oxochromate(I) SrCr10O15 und (II) BaCr10O15. Diese kristallisieren orthorhombisch, Raumgruppe D2h18-Ccmb mit (I): a = 10,059; b = 11,406; c = 9,224 Å und II: a = 10,126; b = 11,491; c = 9,392 Å; Z = 4. Cr2+/Cr3+ bilden mit O2- ein Oktaedergerüst, je 12 Oktaeder bauen wie bei Polysäuren für Sr2+ bzw. Ba2+ einen großvolumigen Hohlraum auf.
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  • 66
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    Zeitschrift für anorganische Chemie 572 (1989), S. 109-114 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: BaNi2In4Sc4O15 with BaV10O15-Structure, but Ordered Metal DistributionSingle crystal X-ray investigations of BaNi2In4Sc4O15 [space group D2h18-Cmca, a = 12.146; b = 10.880; c = 9.834 Å; Z = 4] show a statistical distribution of Ni2+ and Sc3+ of one of the possible point positions. The other oxygen octahedra are occupied by In3+ and Sc3+. This is the difference to compounds of the formula BaM10O15 (M = V, Cr, Ni/Cr) with total statistical metal distribution.
    Notes: Einkristalluntersuchungen an BaNi2In4Sc4O15 [Raumgruppe D2h18-Cmca. a = 12,146; b = 10,880; c = 9,834 Å; Z = 4] zeigen, daß Ni2+ nur mit Sc3+ eine der oktaedrisch koordinierten Metallpunktlagen statistisch besetzt. Alle anderen Polyeder sind frei von Ni2+, womit diese Verbindung sich von den Oxiden BaM10O15 (M = V, Cr, Ni/Cr) mit total statistischer Metallverteilung unterscheidet.
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  • 67
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    Zeitschrift für anorganische Chemie 572 (1989), S. 102-108 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A Contribution on the Crystal Chemistry of Oxotantalates. V. Ordered and Disordered Metal Distributions in MnZn2Ta2O8 and Mn0.33Zn0.67Ta2O6The compounds (I) MnZn2Ta2O8 and (II) Mn0.33Zn0.67Ta2O6 were prepared by solid state reactions. Single crystal X-ray investigations show (I): a = 19.286; b = 5.922; c = 5.228 Å; β = 90.3°; Z = 4; space group C2h6-C2/c; (II): a = 4.730; b = 17.154; c = 5.093 Å; Z = 4; space group D2h14-Pbcn. I belongs to the Zn3Nb2O8-type with ordered Mn2+, Zn2+ distribution. II crystalizes like tri-α-PbO2 (for example ZnTa2O6) but in respect to the metal distribution it belongs to the disordered α-PbO2-type.
    Notes: Mit Hilfe von Festkörperreaktionen wurden (I) MnZn2Ta2O8 und (II) Mn0,33Zn0,67Ta2O6 einkristallin dargestellt. [(I): a = 19,286; b = 5,922; c = 5,228 Å; β = 90,3°; Z = 4; Raumgruppe C2h6-C2/c; (II): a = 4,730; b = 17,154; c = 5,093 Å; Z = 4; Raumgruppe D2h14-Pbcn] I gehört zum Zn3Nb2O8-Typ mit geordneter Mn2+,Zn2+-Verteilung. Die Verwandtschaft zum Columbit wird aufgezeigt. II kristallisiert wie tri-α-PbO2 (z. B. ZnTa2O6), allerdings mit einer ungeordneten Metallverteilung, womit sie kristallchemisch zur α-PbO2-Struktur gehört.
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  • 68
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    Zeitschrift für anorganische Chemie 572 (1989), S. 126-134 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Chalcogenolates. 192. S-Bis(trimethylsilyl)amino Esters of Dithiocarbamic Acids. 1. Synthesis and PropertiesThe title compounds RR′N—CS—S—N[Si(CH3)3]2, where R = R′ = CH3, C2H5, CH(CH3)2, CH2—C6H5, and with R = CH3 and R′ = C6H5 have been prepared by three procedures: by splitting the S—S bond of disulfanes [RR′N—CS—]2S2 with Na[N(Si(CH3)3)2] and with [(CH3)3Si]2N—MgBr as well as by reaction of Na[S2C—NRR′] with BrN[Si(CH3)3]2. The yields are compared.Physical and chemical properties are described, mass spectra are given.
    Notes: Die Titelverbindungen RR′N—CS—S—N[Si(CH3)3]2 mit R = R′ = CH3, C2H5, CH(CH3)2 und CH2—C6H5 sowie mit R = CH3 und R′ = C6H5 wurden nach drei Verfahren hergestellt: durch Spaltung der S—S-Bindung von Disulfanen [RR′N—CS—]2S2 mit Na[N(Si(CH3)3)2] und mit [(CH3)3Si]2N—MgBr sowie durch Reaktion von Na[S2C—NRR′] mit BrN[Si(CH3)3]2. Die Ausbeuten werden verglichen.Physikalische und chemische Eigenschaften sowie Massenspektren werden mitgeteilt.
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  • 69
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    Zeitschrift für anorganische Chemie 573 (1989), S. 12-18 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Oxoindate Ba4In2O7Ba4In2O7 was prepared for the first time by solid state reaction and investigated by X-ray methods. (Space group D4h17-14/mmm, a = 4.175; c = 29.483 Å; Z = 2). It shows a close crystal chemical relationship to Ba3In2O6 and La2SrCu2O6. One of the oxygen point positions is occupied only by a half. This fact alleviates the understanding of the layer structure of Ba4In2O7. The compound is compared with Sr4Tl2O7 and a further discussion in respect to Ba5In2O8 shows the probable identity of Ba5In2O8 with Ba4In2O7.
    Notes: Ba4In2O7 wurde erstmals dargestellt und an Einkristallen mit Röntgenbeugungsmethoden untersucht. (Raumgruppe D4h17-14/mmm, a = 4,175; c = 29,483 Å; Z = 2). Es liegt eine enge kristallchemische Verwandtschaft zu Ba3In2O6 und z. B. La2SrCu2O6 vor. Eine der Sauerstoffpunktlagen ist nur zur Hälfte besetzt; das macht den Schichtstrukturaufbau verständlich. Ba4In2O7 wird mit Sr4Tl2O7 verglichen. Eine Diskussion zeigt, daß Ba5In2O8 vermutlich mit Ba4In2O7 identisch ist.
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  • 70
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    Zeitschrift für anorganische Chemie 573 (1989), S. 19-23 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: About an Oxotantalate with Partly Ordered Corundum-Structure: Mn0.6Mg3.4Ta2O9In the system of mixed crystals of the composition Mn4-xMgxTa2O9 single crystals with x = 3.4 were examined by X-ray methods (space group D43d-P3c1; a = 5.2141; c = 14.178 Å; Z = 2). The point positions of the divalent metals are occupied in an ordered manner. Order and disorder are discussed in respect to Mn2Zn2Nb2O9, Mn3ZnNb2O9, and oxotantalates (MM′)4Ta2O9 [M, M′ = Zn, Ni, Mg].
    Notes: Im System Mn4-xMgxTa2O6 wurden Einkristalle für x = 3,4 mit Röntgenbeugung untersucht (Raumgruppe D43d-P3c1, a = 5,2141; c = 14,178 Å, Z = 2). Mn2+ und Mg2+ besetzen die entsprechenden Metallpunktlagen partiell geordnet. Der Grad der Ordnung wird im Vergleich zu Mn2Zn2Nb2O9, Mn3ZnNb2O9 und den Oxotantalaten (MM′)4Ta2O9 [M, M′ = Zn, Ni, Mg] diskutiert.
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  • 71
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    Zeitschrift für anorganische Chemie 573 (1989), S. 63-74 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ligand Exchange on Halogenonitrosyl-technetate(II) Compounds. An EPR StudyHalide ligand exchange reactions on the 4t52g low-spin halogenonitrosyltechnetate(II) complexes (n-Bu4N)2[Tc(NO)Cl5], (n-Bu4N)[Tc(NO)Br4], and (n-Bu4N)[Tc(NO)I4] have been analyzed by EPR. The EPR parameters go, aTco, ‖ and A‖Tc measured for the different mixed-ligand complexes of the type [Tc(NO)X4-pYpZ]2- (X, Y-Cl, Br, I; Z - axially coordinated solvent molecule or halide) are shown to be clearly correlated to the composition of the coordination sphere and can be used to characterize the mixed-ligand complexes unambiguously.
    Notes: Es wird über EPR-Untersuchungen zum Halogen-Ligandenaustausch an den 4t52g-„low-spin“-Halogenonitrosyltechnetat(II)-Komplexen (n-Bu4N)2[Tc(NO)Cl5], (n-Bu4N)[Tc(NO)Br4] und (n-Bu4N)[Tc(NO)I4] berichtet. Die Spektrenparameter go, aTco,g‖ und A‖Tc der verschiedenen beobachteten Gemischtligandkomplexe des Typs [Tc(NO)X4-pYpZ]2- (X, Y-Cl, Br, I; Z - axial koordiniertes Solventmolekül bzw. Halogenid) zeigen eine definierte Abhängigkeit von der Zusammensetzung der Koordinationssphäre und erweisen sich für die eindeutige Charakterisierung von Gemischt-Ligandenkomplexen als geeignet.
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    Zeitschrift für anorganische Chemie 573 (1989), S. 75-88 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Chalcogenolates. 193. S-Bis(trimethylsilyl)amino Esters of Dithiocarbamic Acids. 2. Spectroscopic CharacterizationElectron absorption, infrared, and nuclear magnetic resonance spectra (1H, 13C, 29Si, 15N) of the title compounds RR′N—CS—S—N[Si(CH3)3]2 with R = R′ = CH3, C2H5, CH(CH3)2, CH2—C6H5 as well as with R = CH3 and R′ = C6H5 are communicated and discussed.Coupling constants have been determined (data see „Inhaltsübersicht“).For the compound with R = R′ = CH3 the free activation energy of the rotation barrier around the N—CS bond is ΔG* = 58 kJ/mol at -2°C (coalescence temperature).
    Notes: Elektronenabsorptions-, Infrarot- und Kernresonanzspektren (1H, 13C, 29Si, 15N) der Titelverbindungen RR′N—CS—S—N[Si(CH3)3]2 mit R = R′ = CH3, C2H5, CH(CH3)2, CH2—C6H5 sowie mit R = CH3 und R′ = C6H5 werden mitgeteilt und diskutiert.Folgende Kopplungskonstanten wurden ermittelt (R = R′ = CH3):\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} ^{\rm 1} {\rm J}\left({{}^{\rm 1}{\rm H} - {}^{12}{\rm C}} \right) = 119{\rm Hz},{}^2{\rm J}({}^1{\rm H} - {}^{29}{\rm Si} = 6,5{\rm Hz}, \\ ^{\rm 1} {\rm J}\left({{}^{{\rm 13}}{\rm C} - {}^{12}{\rm Si}} \right) = 57,7{\rm Hz},{}^2{\rm J}({}^{13}{\rm C} - {}^{15}{\rm N} = 1,97{\rm Hz}, \\ ^{\rm 1} {\rm J}\left({{}^{{\rm 29}}{\rm Si} - {}^{15}{\rm N}} \right) = 8,97{\rm Hz},{}^3{\rm J}({}^{15}{\rm N} - {}^1{\rm H)} \approx 0,5{\rm Hz}{\rm .} \\ \end{array} $$\end{document}Für die Verbindung mit R = R′ = CH3 beträgt die freie Aktivierungsenergie der Rotationsbarriere um die N—CS-Bindung ΔG* = 58 kJ/mol bei der Koaleszenztemperatur (-2°C).
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  • 73
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    Zeitschrift für anorganische Chemie 573 (1989), S. 107-118 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: „LaTa5O14“, a Derivative of the Tetragonal Tungsten Bronzes. Preparation and Structure„LaTa5O14“ single crystals were synthesized for the first time by heating mixtures La2O3/Ta2O5 (1:5) at temperatures of T = 1 685°C in air. „LaTa5O14“ crystallizes in the orthorhombic space group Cmmm with a = 16.977(1) Å, b = 17.594(1) Å and c = 3.8480(4) Å. The structure was refined to give R = 6.36% and Rw = 3.27%. The Ta atoms are partly surrounded by O octahedrally, partly pentagonal-bipyramidal. The unit cell is built up by layers of composition [Ta22O62]14- connected along the [001] direction with holes filled up totally or partly with La. The relationship to the tetragonal tungsten bronzes will be discussed.
    Notes: Im System La2O3/Ta2O5 gelang erstmals die Darstellung von gelben „LaTa5O14“-Einkristallen durch Tempern der Gemenge La2O3/Ta2O5 (1:5) bei T = 1 685°C an Luft. „LaTa5O14“ kristallisiert orthorhombisch in der Raumgruppe Cmmm mit den Gitterkonstanten a = 16,977(1) Å, b = 17,594(1) Å und c = 3,8480(4) Å. Die Struktur wurde bis R = 6,36% bzw. Rw = 3,27% verfeinert. Ta(1), Ta(3) und Ta(4) sind oktaedrisch, Ta(2) ist pentagonal-bipyramidal von O umgeben. Schichten aus diesen Polyedern sind über O-Teilchen entlang [001] miteinander eckenverknüpft. Vom Ta-O-Netzwerk der Zusammensetzung [Ta22O62]14- gebildete Lücken sind ganz oder teilweise mit La-Teilchen gefüllt; die Verbindung besitzt deshalb nur annähernd die Zusammensetzung LaTa5O14. Eine Verwandtschaft zu den tetragonalen Wolframbronzen ist erkennbar.
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    Zeitschrift für anorganische Chemie 573 (1989), S. 119-127 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: High Resolution Electron Microscopy Investigation of La3TaO5(OH)Cl3 and Pr3TaO4Cl6 - A Comparison with Calculated ImagesThe phases La3TaO5(OH)Cl3 and Pr3TaO4Cl6 prepared by chemical transport have been investigated by high resolution electron microscopy. The micrographs taken agree well with simulated images. In spite of the close relationship of both structures the simulated images are not as similar as expected. The unoccupied channels at the corners of the cell can be seen distinctly. According to the resolution of our electron microscope La3TaO5(OH)Cl3 lattice constants of which are too small does not show any further detail, whereas the sites of the heavy atoms of Pr3TaO4Cl6 can be recognized at a suitable value of defocus.
    Notes: Kristalline Proben von La3TaO5(OH)Cl3 und der neuen Verbindung Pr3TaO4Cl6 konnten durch eine chemische Transportreaktion erhalten werden. Bei elektronenmikroskopischen Untersuchungen in Hochauflösung zeigten die Aufnahmen eine gute Übereinstimmung mit Bildern, die mit einem Kontrastprogramm simuliert worden waren. Wie eine Gegenüberstellung von zwei simulierten Defokusserien ergab, ist die enge strukturelle Verwandtschaft der beiden Oxidchloride hier nicht unmittelbar wiederzufinden. Man erkennt bei beiden Verbindungen die an den Eckpunkten der Zelle gelegenen unbesetzten Kanäle, die sich deutlich vom übrigen Kontrastmuster abheben. Bei La3TaO5(OH)Cl3, der Verbindung mit den kürzeren Gitterkonstanten, reichte das Auflösungsvermögen unseres Mikroskops für weitere Details im Innern der Elementarzelle nicht aus, während bei Pr3TaO4Cl6 die Schweratomlagen bei geeigneten Defokusbedingungen noch zu erkennen sind.
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  • 75
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    Zeitschrift für anorganische Chemie 573 (1989), S. 133-142 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Oxotellurates(VI) of the Alkali Metals. Existence and Constitution of Li6TeO6For the first time Li6TeO6 is prepared as transparent, colourless single crystals, and the structure has been determined [four-circle diffractometer data, Siemens AED2, MoKα, 371 out of 371 IO(hkl), R = RW = 0.7%, R3, a = 791.99(6) pm, c = 696.44(7) pm, Z = 3].The structure refinement shows that Li6TeO6 is a variant of the NaCl-Typ. Nevertheless there is a relationship with α-Li6UO6 [2]. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, the latter derived from Mean Effective Fictive Ionic Radii, MEFIR, are calculated and discussed.
    Notes: Erstmals wurden klar durchscheinende, farblose Einkristalle von Li6TeO6 dargestellt und strukturell untersucht. [Vierkreisdiffraktometerdaten, Siemens AED2, MoKα-Strahlung, 371 von 371 IO(hkl), R = RW = 0,7%, R3, a = 791,99(6) pm, c = 696,44(7) pm, Z = 3].Die Strukturbestimmung zeigt, daß Li6TeO6 eine Variante des NaCl-Typs ist. Dennoch besteht Verwandtschaft mit α-Li6UO6 [2]. Der Madelunganteil der Gitterenergie, MAPLE, sowie Effektive Koordinationszahlen, ECoN, diese über Mittlere Effektive Ionenradien, MEFIR, werden berechnet und diskutiert.
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    Zeitschrift für anorganische Chemie 573 (1989), S. 157-169 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Two New Variants of the NaCl Type of Structure: On Li4MoO5 and Li4WO5For the first time in form of colourless, transparent single crystals of Li4MoO5 [annealed mixtures of Li2O and MoO3, Li:Mo = 4.2:1, Ni-cylinder, 950°C, 28 d] as well as Li4WO5 [annealed mixtures of Li2O and WO3, Li:W = 4.4:1, Au-tube, 950°C, 28 d, slowly cooling] have been prepared. Single crystal data show isotypic oxides of the Li4TeO5-type, a deformed variant of the NaCl-type of structure [Li4MoO5: 1379 IO(hkl), four-circle-diffraktometer Philips PW 1100, ω--2Θ scan, AgKα, R = 8.7% and RW = 8.3%, space group P1 with a = 511.9(1), b = 772.7(2), c = 506.4(1) pm, α = 101.70(1)°, β = 101.48(1)°, γ = 108.58(2)°, Z = 2 and Li4WO5: 1027 IO(hkl), Philips PW 1100, ω-2Θ scan, MoKα, R = 4.0% und RW = 3.7%, space group P1 with a = 510.94(5), b = 771.59(7), c = 506.09(4) pm, α = 101.804(8)°, β = 101.78(1)°, γ = 108.770(9)°, Z = 2]. The structural relations are deduced from Schlegel Diagrams. The Madelung Part of Lattice Energie, MAPLE, and Effective Coordination Numbers, ECON, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.
    Notes: Erstmals wurde in Form farbloser, transparenter Einkristalle Li4MoO5 [aus Gemengen von Li2O und MoO3. Li:Mo = 4,2:1, Ni-Bömbchen, 950°C, 28 d] sowie Li4WO5 [aus Gemengen von Li2O und WO3, Li:W = 4,4:1, Au-Rohr, 900°C, 30 d] dargestellt. Nach Einkristalldaten liegt bei den isotypen Oxiden vom Li4TeO5-Typ eine Ordnungsvariante des NaCl-Typs [Li4MoO5: 1379 IO(hkl), Vierkreisdiffraktometer Philips PW 1100, ω-2Θ scan, AgKα, R = 8,7% und RW = 8,3%, Raumgruppe P1 mit a = 511,9(1), b = 772,7(2), c = 506,4(1) pm, α = 101,70(1)°, β = 101,48(1)°, γ = 108,58(2)°, Z = 2 bzw. Li4WO5: 1027 IO(hkl), Philips PW 1100, ω-2Θ scan, MoKα, R = 4,0% und RW = 3,7%, Raumgruppe P1 mit a = 510,94(5), b = 771,59(7), c = 506,09(4) pm, α = 101,804(8)°, β = 101,78(1)°, γ = 108,770(9)°, Z = 2] vor.Die strukturellen Zusammenhänge werden aus den Schlegel-Diagrammen abgeleitet. Der Madelunganteil der Gitterenergie, MAPLE, sowie Effektive Koordinationszahlen, ECON, diese über Mittlere Fiktive Ionenradien, MEFIR, berechnet, werden mitgeteilt und diskutiert.
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  • 77
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    Zeitschrift für anorganische Chemie 573 (1989), S. 185-194 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of CF3SClF+MF6- (M = As, Sb) and Crystal Structure of CF3SCl2+SbF6-CF3SClF+MF6- (M = As, Sb) is prepared by oxidative fluorination of CF3SCl with XeF+MF6-. The new salt is characterized by IR, Raman and NMR spectra in comparison with CF3SF2+MF6- and CF3SCl2+MF6-. In SO2 solution CF3SClF+SbF6- symmetrizises into CF3SF2+SbF6- and crystalline CF3SCl2+SbF6- with the monoclinic space group P21/c with a = 773.5(14) pm, b = 954.8(15) pm, c = 1242.0(18) pm, β = 100.24(8)°, Z = 4.
    Notes: Die Darstellung von CF3SClF+MF6- (M = As, Sb) erfolgt durch oxidative Fluorierung von CF3SCl mit XeF+MF6-. Das Salz wird schwingungs- und NMR-spektroskopisch charakterisiert, orientierend an den bekannten Daten von CF3SF2+MF6- und CF3SCl2+MF6-. In einer SO2-Lösung symmetrisiert sich CF3SClF+SbF6- zu CF3SF2+SbF6- und einkristallinem CF3SCl2+SbF6- mit der monoklinen Raumgruppe P21/c, a = 773,5(14) pm, b = 954,8(15) pm, c = 1242,0(18) pm, β = 100,24(8)°, Z = 4.
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  • 78
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    Zeitschrift für anorganische Chemie 573 (1989), S. 199-207 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Properties of 1,2,3-Thiazaboroles, 3-Sulfoimido- and 3-Pseudohalido-1,2,3-dithiaborolesThe reactions of 3,4,5-trimethyl- and 4,5-diethyl-3-methyl-1,2,3-dithiaborole with di-t.-butylsulfurdiimide leads to the 1,2,3-thiazaboroles 2. 3-Bromo-1,2,3-dithiaboroles react with trimethylsilyl-N-sulfinylamine, -isocyanate, and -cyanide by formation of 3-sulfoimido- (3), 3-isocyanato- (4), and 3-cyano- (5) -1,2,3-dithiaboroles. 3-Isothiocyanato-1,2,3-dithiaboroles (6) are formed by addition of elemental sulfur to 5. 1H-, 11B-, 13C-, 14N-, 15N-NMR-, mass-, and IR spectra are reported and discussed.
    Notes: Die Reaktionen von 3,4,5-Trimethyl- und 4,5-Diethyl-3-methyl-1,2,3-dithiaborol mit Di-t.-butylschwefeldiimid führen zu den 1,2,3-Thiazaborolen 2. 3-Brom-1,2,3-dithiaborole reagieren mit Trimethylsilyl-N-sulfinylamin, -isocyanat und -cyanid unter Bildung von 3-Sulfoimido- (3), 3-Isocyanato- (4) und 3-Cyano- (5) -1,2,3-dithiaborolen. 3-Isothiocyanato-1,2,3-dithiaborole (6) werden gebildet bei Addition elementaren Schwefels an 5. 1H-, 11B-, 13C-, 14N-, 15N-NMR, Massen- und IR-Spektren werden mitgeteilt und diskutiert.
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  • 79
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Elektrochemische Synthese von neutralen Nickel(II)-Komplexen mit Schiffschen Basen: Kristallstruktur von Bis-{N-[2-(2-pyridyl) äthyl]-salicylideneiminato}nickel(II) TrihydratNickel(II)-Komplexe mit im Pyridin-Ring substituiertem N-2-(2-pyridyl)-äthyl-salicylideneiminat wurden durch Elektrolyse einer nicht wäßrigen Lösung des entsprechenden Liganden hergestellt; als Anode diente ein Ni-Draht. Die Struktur von Bis-{N-[2-(2-pyridyl)äthyl]-salicylideneiminato}nickel(II). Trihydrat wurde röntgenographisch bestimmt. Der Komplex kristallisiert triklin in der Raumgruppe P1 mit den Gitterkonstanten a = 13,055(4) Å, b = 13,097(6)Å, c = 16,189(5) Å, α = 102,92(3)°, β = 99,80(3)°, γ = 90,42(3)° und Z = 4. Eine Least-squares-Verfeinerung führte zu einem R-Wert von 0,047. Das Molekül ist nicht zentrosymmetrisch, da die zwei dreizähnigen Liganden eine meridionale Konfiguration um das oktaedrisch koordinierte Nickel(II) annehmen.
    Notes: Nickel(II) complexes with N-2-(2-pyridyl)ethyl-ring substituted salicylideneiminatos have been synthesized by an electrochemical procedure using a sacrificial anode in non-aqueous solution of the corresponding ligand. The structure of bis{N-[2-(2-pyridyl)]-salicylideneiminato}-nickel (II) trihydrate has been determined by X-ray diffraction. Crystals are triclinic, space group P1, with four formula units in a cell of dimensions a = 13.055(4) Å, b = 13.097(6) Å, c = 16.189(5) Å, and α = 102.92(3)°, β = 99.80(3)°, γ = 90.42(3)°. Full matrix least squares refinement on R converged with a conventional agreement factor of 0.047. The molecule is non-centrosymmetric with two terdentate ligands in a meridional configuration around octahedral nickel(II).
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  • 80
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    Zeitschrift für anorganische Chemie 573 (1989), S. 231-239 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Studies of the Heterogeneous Catalytical Ring Alkylation of Toluene with Methanol on Modified Zeolites ZSM-5Various ways for controlling the catalytic activity, the shape selectivity, and the deactivation behaviour of modified zeolites ZSM-5 has been shown by the example of the heterogeneous catalytical conversion of toluene with methanol. The preferred formation of the industrially interesting para-xylene is possible by use of ZSM-5-zeolites composed of large crystals, by dealumination of the external surface after hydrothermal treatment, by poisoning of external active centres after impregnation with inorganic salts as well as by isomorphic incorporation of boron for silicon and/or aluminium in the zeolite framework.
    Notes: Am Beispiel der heterogen-katalysierten Umsetzung von Toluen mit Methanol wurden verschiedene Wege zur Steuerung der katalytischen Aktivität, der Formselektivität und des Desaktivierungsverhaltens modifizierter H-ZSM-5-Zeolithe aufgezeigt. Eine Ausprägung der bei der Toluenmethylierung technisch interessanten para-Xylen-Selektivität gelingt durch den Einsatz von großkristallinen ZSM-5-Zeolithen, durch Dealuminieren der äußeren Oberfläche mittels hydrothermaler Behandlung, durch Vergiften äußerer aktiver Zentren mittels Tränkung anorganischer Salze sowie durch den isomorphen Einbau von Bor für Silicium und/oder Aluminium im Zeolithgerüst.
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  • 81
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 82
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    Zeitschrift für anorganische Chemie 573 (1989), S. 240-240 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 83
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    Zeitschrift für anorganische Chemie 575 (1989), S. 26-30 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ni5HfB2O10 with Ordered Metal DistributionNi5HfB2O10 was prepared for the first time and investigated by X-ray methods. It crystallizes with orthorhombic symmetry, space group D2h16 - Pnma, a = 9.328; b = 6.120; c = 12.334 Å; Z = 4. In opposition to the Ni5TiB2O10-type all metal point positions are strongly ordered. The authors are in doubt about the partly statistic metal distribution within Ni5M4+B2O10 (M4+ = Ti, Zr, Ge).
    Notes: Ni5HfB2O10 wurde erstmals dargestellt und an Einkristallen untersucht. Ni5HfB2O10 kristallisiert orthorhombisch, Raumgruppe D2h16 - Pnma, a = 9,328; b = 6,120; c = 12,334 Å, Z = 4. Im Gegensatz zum Ni5TiB2O10-Typ weist NiHfB2O10 eine total geordnete Metallverteilung auf. Die partiell statistische Verteilung von Ni2+ mit M4+ (M4+ = Ti, Zr, Ge) wird in Frage gestellt.
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  • 84
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    Zeitschrift für anorganische Chemie 575 (1989), S. 17-25 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 27Al NMR Studies on Alkali FluoroaluminatesThe 27Al NMR spectra of the alkali fluoroaluminates sensitively reflect the kind of condensation of the AlF6 octahedra. Whereas the chemical shift of the octahedral Al is shown to be rather independent on structural details, clear differences in the electric field gradients of isolated and condensed AlF6 octahedra were found. In contrast to the isolated octahedra which show only weak effects of quadrupole interaction, both for chains and layers of AlF6 octahedra axial EFG tensors result with quadrupolar coupling constants of between 10 and 13 MHz; for the threefold chains in CsAlF4 only a value of 7.5 MHz is obtained.
    Notes: Die 27Al-NMR-Spektren der Alkalifluoroaluminate spiegeln in empfindlicher Weise die Verknüpfung der AlF6-Oktaeder wider. Während sich die chemische Verschiebung für das oktaedrisch koordinierte Aluminium als nahezu unbeeinflußt von strukturellen Details erweist, ergeben sich deutliche Unterschiede in den elektrischen Feldgradienten (EFG) zwischen isolierten und verknüpften AlF6-Oktaedern. Im Gegensatz zu den isolierten Oktaedern, bei denen Quadrupolwechselwirkungseffekte nur eine untergeordnete Rolle spielen, ergeben sich sowohl für Ketten als auch schichtförmige Verknüpfung der AlF6-Oktaeder axiale EFG-Tensoren mit Quadrupolkopplungskonstanten zwischen 10 und 13 MHz, bei Verknüpfung als Dreierstrangkette im CsAlF4 lediglich ein Wert von 7,5 MHz.
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  • 85
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    Zeitschrift für anorganische Chemie 572 (1989), S. 95-101 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A Contribution about the Crystal Chemistry of Alkaline Earth Oxochromates(V): Sr3(CrO4)2 and Sr18Ca3Cr14O56The crystal structure of (I) Sr3Cr3(CrO4)2 was examined by X-ray single crystal technique. It belongs to the Ba3(PO4)2-type, space group 3d5-R3m, a = 5.562; c = 20.221 Å; Z = 3. The replacement of Sr2+ leads to a compound of the formula (II) Sr18Ca3Cr14O56, space group 3v6-R3c, a = 11.004; c = 39.256 Å; Z = 3. The Sr2+ and Ca2+ ions occupy the alkaline earth positions in an ordered manner. So the formulation Sr2.57Ca0.43(CrO4)2 should be avoided although it belongs to the β-Ca3(PO4)2 = Ca3(CrO4)2-type. The crystal chemistry of (I) and (II) is discussed.
    Notes: Die Kristallstruktur von (I) Sr3(CrO4)2 wurde an Einkristallen exakt untersucht. Sie gehört zum Ba3(PO4)2-Typ, Raumgruppe D3d5-R3m, a = 5,562; c = 20,221 Å; Z = 3. Der Ersatz von Sr2+ gegen Ca2+ führt zur Verbindung (II) Sr18Ca3Cr14O56, Raumgruppe C3v6-R3c, a = 11,004; c = 39,256 Å; Z = 3. Es wird gezeigt, daß Sr2+ und Ca2+ die Erdalkalimetall-Positionen im β-Ca3(PO4)2-Typ geordnet besetzen, womit die Schreibweise Sr2,57Ca0,43(CrO4)2 nicht verwendet werden sollte, obwohl dieser Stoff zum β-Ca3(PO4)2 = Ca3(CrO4)-Typ gehört. Die Kristallchemie von (I) und (II) wird diskutiert.
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  • 86
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    Zeitschrift für anorganische Chemie 572 (1989), S. 63-74 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Molecular and Crystal Structure of 1,4-Bis[tris(tetrahydrofuran)lithium]-octaphenyltetrasilane1,4-Dilithium-octaphenyltetrasilane prepared from octaphenyl-cyclo-tetrasilane and lithium in tetrahydrofuran (THF) [4], can be isolated from tetrahydrofuran/n-pentane as an adduct with six molecules of tetrahydrofuran per formula unit. The orange-red compound crystallizes in the triclinic space group P1 {a = 1159.6(3); b = 1268.4(2); c = 1367.8(3) pm; α = 92,23(2)° β = 113.79(2)° γ = 111.62(2)° at -5 ± 3°C; Z = 1}. An x-ray structure determination (Rw = 0.046) shows the existence of a centrosymmetric molecule with an extended planar Li—Si4—Li unit; either lithium atom is bound to silicon and to the oxygen atoms of three molecules of tetrahydrofuran. Characteristic bond lengths and angles are: Li—Si 271; Si—Si 241 and 243; Si—C 190 to 192 pm; Li—Si—Si 126°; Si—Si—Si 127°. 29Si and 7Li n.m.r. measurements at low temperatures indicate the presence of three different adducts.
    Notes: Das aus Octaphenyl-cyclo-tetrasilan und Lithium in Tetrahydrofuran (THF) dargestellte, orangerote 1,4-Dilithium-octaphenyltetrasilan [4] kristallisiert aus Tetrahydrofuran/n-Pentan als Addukt mit sechs Molekülen Tetrahydrofuran triklin in der Raumgruppe P1. Die Verbindung weist folgende, bei -5 ± 3°C bestimmte Parameter der Elementarzelle auf: a = 1159,6(3); b = 1268,4(2); c = 1367,8(3) pm; α = 92,23(2)°; β = 113,79(2)° γ = 111,62(2)°; Z = 1. Nach den Ergebnissen einer Röntgenstrukturanalyse (Rw = 0,046) liegt ein zentrosymmetrisches Molekül mit gestrecktem, planarem Li—Si4—Li-Gerüst vor; jedes Lithium ist an Silicium und die Sauerstoffatome aus drei Tetrahydrofuran-Molekülen gebunden. Charakteristische Bindungslängen und -winkel sind: Li—Si 271; Si—Si 241 und 243; Si—C 190 bis 192 pm; Li—Si—Si 126°; Si—Si—Si 127°. 29Si- und 7Li-Kernresonanz-Messungen bei tiefen Temperaturen ergeben in Lösung drei unterschiedliche Addukte.
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  • 87
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    Zeitschrift für anorganische Chemie 572 (1989), S. 75-88 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal Derivatives of Molecular Compounds. II. Preparation and Structure of β-Potassium SilanideAt -5°C potassium silanide crystallizes from 1,2-dimethoxyethane/n-pentane in a to date unknown low temperature modification {β-form: orthorhombic, Pnma, Z = 4; a = 880.0(2), b = 541.6(1), c = 682.3(1) pm at -110 ± 3°C}. An x-ray structure determination shows the compound to be built up from isolated potassium cations and pyramidal silanide anions without perceptible disorder. Seven counterions make up the coordination sphere of either particle (K⃛Si 356 to 386 pm), two anion-anion contacts (Si⃛Si 355 pm) are observed in addition. The packing of ions represents a defect variant of the barite type, but there are also relationships to the high temperature modification (α-form, rock salt type) and to cesium trihydrogengermanide (thallium iodide type).
    Notes: Kaliumsilanid kristallisiert bei -5°C aus 1,2-Dimethoxyethan/n-Pentan in einer bisher unbekannten Tieftemperatur-Modifikation {β-Form: orthorhombisch, Pnma, Z = 4; a = 880,0(2), b = 541,6(1), c = 682,3(1) pm bei -110 ± 3°C}. Nach den Ergebnissen der Röntgenstrukturanalyse (R = 0,032) baut sich die Verbindung ohne erkennbare Fehlordnung aus isolierten Kalium-Kationen und pyramidalen Silanid-Anionen auf. Zur Koordinationssphäre beider Teilchen gehören sieben Gegenionen (K⃛Si 356 bis 386 pm); beim Anion kommen zwei zusätzliche Kontakte zu gleichnamigen Nachbarn (Si⃛Si 355 pm) hinzu. Die Kristallstruktur stellt eine Defektvariante des Baryt-Typs dar, Verwandtschaft besteht aber auch zur Hochtemperatur-Modifikation (α-Form, Steinsalz-Typ) und zum Caesium-trihydrogengermanidWährend der Name Kaliumsilanid unseres Erachtens eindeutig ist, sollte die homologe Germanium-Verbindung zur Unterscheidung von den binären Phasen Caesium-trihydrogengermanid genannt werden. (Thalliumiodid-Typ).
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  • 88
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Organo Transition Metal Compounds. 54. Formation of Cyclic Chalcogenides of the Type [Cp2*Zr(μ-E)]2 at Thermolysis of Permethylzirconocene Divinyl in Presence of Sulfur, Selenum, and Tellurium4-membered cyclic chalcogenides of the type [Cp2*Zr(μ-E)]2are formed at thermolysis of Cp2*Zr(CH=CH2)2 in presence of sulfur, selenum and tellurium using an aliphatic hydrocarbon as a solvent. During the reactions acetylene and ethylene are liberated in equimolar amounts, which indicates the formation of a zirconocene acetylene ethylene complex as an intermediate.
    Notes: Die Thermolyse von Cp2*Zr(CH=CH2)2 in aliphatischen Kohlenwasserstoffen als Lösungsmittel führt in Gegenwart von Schwefel, Selen und Tellur zur Bildung viergliedriger cyclischer Chalkogenide des Typs [Cp2*Zr(μ-E)]2. Die Reaktionen verlaufen unter Freisetzung äquimolarer Mengen an Acetylen und Ethylen, was auf die intermediäre Bildung eines Zirconocenethylen-acetylen-Komplexes schließen läßt.
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  • 89
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    Zeitschrift für anorganische Chemie 573 (1989), S. 208-214 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation of Ceramic Powders. II. Mg2TiO4, MgTiO3, and MgTi2O5 Formed by Hydrolysis of 2-EthoxyethylatesSolutions of 2-ethoxyethylates of magnesium and titanium in 2-ethoxyethanol submitted to hydrolysis, evaporation and heating of the residue up to 450°C allow to prepare Mg2TiO4, MgTiO3, and MgTi2O5 in an amorphous state with smaller than 1% of volatile components. Highly dispersed powders showing an increased sintering activity are obtained as a result of recrystallization. Mg2TiO4 is formed as inverse spinel phase in a metastable state.
    Notes: Die 2-Ethoxyethylate von Magnesium und Titan bilden in 2-Ethoxyethanol stabile Lösungen, deren Hydrolyse nach dem Abdestillieren des Lösungsmittels und Erhitzen des Rückstandes bis auf 450°C die Herstellung von Mg2TiO4, MgTiO3 und MgTi2O5 im amorphen Zustand mit weniger als 1% flüchtigen Bestandteilen gestattet. Die Rekristallisation führt zu hochdispersen sinteraktiven Pulvern, im Fall von Mg2TiO4 zur Bildung der inversen Spinellphase unter metastabilen Bedingungen.
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  • 90
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    Zeitschrift für anorganische Chemie 573 (1989), S. 223-230 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Pollucit- und Leucit-verwandte Phasen: A2BX5O12 und ACX2O6 (A = K, Rb, Cs; B = Be, Mg, Fe, Co, Ni, Cu, Zn, Cd; C = B, Al, Ga, Fe, Cr; X = Si, Ge)Darstellung und kristallographische Daten von 29 neuen Phasen dieser Strukturfamilie werden angegeben. Ein Überblick über die gesamte Strukturfamilie, die bis jetzt 59 Phasen enthält, wird gegeben. Die Familie enthält wenigstens sieben Strukturvarianten, von denen zwei die Pollucit-, CsAlSi2O6, und Leucit-, KAlSi2O6, Struktur sind. Beziehungen zwischen der Kationengröße und dem Strukturtyp werden vorgestellt. Ungewöhnliche Variationen in den Größen der Einheitszelle als Funktion der Kationengröße werden diskutiert, und auf die mögliche Bedeutung für das „partially collapsed framework“-Konzept von Taylor und Henderson wird hingewiesen.
    Notes: Synthesis and crystallographic data on 29 new phases in this family are given. A survey of the crystal chemistry of the complete family, containing 59 phases to date, is presented. The family contains at least seven structural variations, two of which are the pollucite, CsAlSi2O6 and leucite, KAlSi2O6 structures. Correlations between cation size and structure type are presented. Unusual variations in unit cell dimensions as a function of cation size are discussed and the possible relevance of the „partially collapsed framework“ concept of Taylor and Henderson indicated.
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  • 91
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Drei Bromide des Lanthans: LaBr2, La2Br5 und LaBr3Farbloses LaBr3 wurde durch Umsetzung von La2O3 mit NH4Br bzw. in einkristalliner Form durch chemischen Transport mit AlBr3 erhalten. Schwarze Einkristalle von LaBr2 und La2Br5 wachsen aus der Schmelze, die man bei der metallothermischen Reduktion von LaBr3 mit Lithium erhält (verschweißte Tantalampulle, 850°C). Die Kristallstrukturen der drei Lanthanbromide wurden verfeinert: LaBr2. 2H2-Typ, hexagonal (P63/mmc); a = 409,88(4) pm; c = 1 390,0(1) pm; R = Rw = 0,092; La2Br5. Pr2I5-Typ, monoklin (P21/m); a = 789,09(6) pm; b = 424,89(4) pm; c = 1342,3(1) pm β = 91,60(1)º; R = 0,067; Rw = 0,055; LaBr3. UCl3-Typ, hexagonal (P63/m) a = 797,13(4) pm; c = 452,16(4) pm; R = 0,036; Rw = 0,032.
    Notes: Colourless LaBr3 was obtained via the ammonium-bromide route and in singlecrystalline form by chemical vapour-phase transport with aluminium tribromide. Black single crystals of LaBr2 and La2Br5 have been grown from the melts that are obtained by lithium reduction of lanthanum tribromide in sealed tantalum ampoules at 850°C. The crystal structures of the three bromides of lanthanum were refined: LaBr2. 2H2-MoS2 type, hexagonal (P63/mmc), a = 409.88(4) pm, c = 1390.0(1) pm, R = Rw = 0.092; La2Br5. Pr2I5 type, monoclinic (P21/m), a = 789.09(6) pm, b = 424.89(4) pm, c = 1342.3(1) pm, β = 91.60(1)º, R = 0.067, Rw = 0.055; LaBr3. UCl3 type, hexagonal (P63/m), a = 797.13(4) pm, c = 452.16(4) pm, R = 0.036, Rw = 0.032.
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  • 92
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 2-Heteroatom-1,3-diazoles and Quinoxaline as Bridging π Acceptor Ligands for Metal Fragments M(CO)5 (M = Cr, Mo, W). Synthesis, Electrochemistry, Absorption and Emission SpectroscopyMono- and binuclear complexes of M(CO)5 fragments (M = Cr, Mo, W) with the 2,1,3-benzochalcogenadiazoles (chalcogens: O, S, Se) were synthesized and studied by cyclic voltammetry and by UV/Vis absorption and emission spectroscopy. The complexes exhibit low-lying metal-to-ligand charge transfer (MLCT, d → π*) transitions as evident from long wavelength absorptions and are easily reduced to yield persistent anion radicals. The bis(pentacarbonyltungsten) complexes of the sulfur and selenium ligands show weak near infrared (〉750 nm) emission from rather short lived MLCT excited states. While quinoxaline and monocyclic 2,1,3-thiadiazole also form binuclear W(CO)5 complexes, the related 2-methyl-1,2,3-benzotriazole does not bind W(CO)5 fragments in the neutral state but only as the more basic anion radical as evident from ESR spectroscopy.
    Notes: Ein- und zweikernige Komplexe von M(CO)5-Fragmenten (M = Cr, Mo, W) mit den 2,1,3-Benzochalkogenadiazolen (Chalkogene: O, S, Se) wurden dargestellt und durch Cyclovoltammetrie sowie durch UV/Vis-Absorptions- und Emissions-Spektroskopie untersucht. Die Komplexe weisen aufgrund niedrig liegender Metall-Ligand-Charge-Transfer (MLCT, d → π*)-Übergänge langwellige Absorptionen auf und werden leicht zu beständigen Radikalanionen reduziert. Die Bis(pentacarbonylwolfram)-Komplexe der Schwefel- und Selen-Systeme zeigen schwache Emission im nahen Infrarot (〉750 nm) aus sehr kurzlebigen MLCT-angeregten Zuständen. Während Chinoxalin und monocyclisches 2,1,3-Thiadiazol ebenfalls noch Bis(pentacarbonylwolfram)-Komplexe liefern, koordiniert 2-Methyl-1,2,3-benzotriazol W(CO)5-Fragmente nicht im Neutral-Zustand sondern - wie ESR-Untersuchungen zeigen - erst als basisches Radikalanion.
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  • 93
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 575 (1989), S. 154-164 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A New Perowskite with Deficiencies in the Oxygen Part: Ba4[Na2W2O11]For the first time colourless single crystals of Ba2NaWO5.5 were prepared by reaction of Na4WO5 [2] and „BaO2“ [Ba:Na:W = 4:4:1, Ni-cylinder, 725°C, 35 d]. Single crystal data [432 of 505 I0 (hkl), Four-circle-diffractometer Siemens AED2, MoKα, R = 6.1%, Rw = 5,6%] verify the space group P mmm with a = 579.16(8), b = 580.85(8), c = 859.4(1) pm, Z = 1.The structure is based upon the CaTiO3-type of structure. Ba2+ take the place of Ca2+ meanwhile Ti4+ is substituted alternately by W6+ and Na+. Complete occupation of all lattice positions would lead to a deficite of positive charge. This is compensate by deficiencies in the oxygen part of the lattice. Related to [Na(1)1Na(2)1W(1)1W(2)1O(1)4O(2)2O(3)2O(4)3] these deficiencies are statistically distributed on O(4).Structural relations are deduced by Schlegel-Diagrams. The Madelung Part of Lattice Energie, MAPLE, Effektive Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated and discussed.
    Notes: Erstmals wurden farblose Einkristalle von Ba4[Na2W2O11] durch Reaktion von Na4WO5 [2] mit „BaO2“ [Ba:Na:W = 4:4:1, Ni-Bömbchen, 725°C, 35 d] dargestellt. Einkristalldaten [432 von 505 I0 (hkl), Vierkreis-Diffraktometer Siemens AED2, MoKα, R = 6,1%, Rw = 5,6%] belegen die Raumgruppe P mmm mit a = 579,16(8), b = 580,85(8), c = 859,4(1) pm, Z = 1.Der Struktur hegt der Perowskit-Typ zugrunde, wobei Ca2+ durch Ba2+ und Ti4+ gesetzmäßig durch W6+ und Na+ ersetzt ist. Das bei vollständiger Besetzung aller Positionen resultierende Defizit positiver Ladung ist durch Lücken im Anionenteil kompensiert. Gemäß [Na(1)1Na(2)1W(1)1W(2)1O(1)4O(2)2O(3)2O(4)3] liegen diese nur bei O(4), statistisch verteilt, vor.Die strukturellen Zusammenhänge werden mit Hilfe von Schlegel-Diagrammen erklärt. Der Madelunganteil der Gitterenergie, MAPLE, sowie Effektive Koordinationszahlen, ECoN, diese über Mittlere Fiktive Ionenradien, MEFIR, berechnet, werden mitgeteilt und diskutiert.
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  • 94
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 575 (1989), S. 165-170 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The New Intercalation Compound TaS2 · 0.5 C4NH5. Preparation and Physical PropertiesThe new intercalation compound TaS2 · 0.5 C4NH5 is obtained by reaction of 2H-TaS2 with surplus pyrrol in a closed system at 473 K. The powder diffraction pattern can be indexed based on a hexagonal unit cell with lattice parameters a = 3.315(1) and c = 22.256(7) Å. The temperature induced deintercalation has been studied from 293 to 1073 K. From 677 to 725 K there is a plateau in the TG curve which is attributed to the staging compound TaS2 · 0.33 C4NH5. Up to 1073 K a total mass of 10% has been squeezed out.From 300 to 50 K there is a nearly linear decrease of the resistivity of TaS2 · 0.5 C4NH5 while below 40 K a pronounced ascent has been observed followed by a transition to superconductivity at T ≤ 7,5 K. The degree of polymerized pyrrol in the host structure has been studied using XPS and a N1s signal, 5 eV broad, was monitored which indicates the existence of several sites of differently bonded N atoms.
    Notes: Die neue Intercalationsverbindung TaS2 · 0,5 C4NH5 entsteht bei der direkten Reaktion von 2H-TaS2 mit überschüssigem Pyrrol in geschlossener Ampulle bei einer Temperatur von 473 K. Das Pulverdiagramm der Titelverbindung ist auf Basis einer hexagonalen Zelle indizierbar mit a = 3,315(1) und c = 22,256(7) Å. Die thermische Deintercalation wurde im Temperaturbereich von 293 bis 1073 K untersucht. Zwischen 677 und 725 K deutet ein Plateau im TG-Diagramm auf die Existenz einer Phase der Zusammensetzung TaS2 · 0,33 C4NH5. Bis 1073 K wurde ein Massenverlust von 10% registriert.Im Temperaturbereich von 300 bis 50 K nimmt der Widerstand von TaS2 · 0,5 C4NH5 nahezu linear ab, unterhalb von T = 40 K ist ein ausgeprägter Anstieg zu verzeichnen. Ab T ≤ 7,5 K treten Übergänge in den supraleitenden Zustand auf. Im ESCA Spektrum deutet ein 5 eV breites N1s Signal auf die Existenz von Stickstoffatomen in unterschiedlicher Umgebung.
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  • 95
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 575 (1989), S. 202-208 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaktionen von Zinn(II)-fluorid mit HalogenenDurch oxidative Addition von X2 (X = Cl, Br) an SnF2 in Acetonitril wurden die Verbindungen SnF2Cl2(MeCN)2 (monomer) und SnF2Br2(MeCN)2 (polymer oder oligomer) erhalten. Die korrigierten v CN-Valenzschwingungen geben eine Information über die Stärke der Sn-N-Bindung. Die Umsetzungen von SnF2 mit Br2 und I2 in Gegenwart von DMSO bzw. mit I2 in Gegenwart von Pyridin führen bevorzugt zur Disproportionierung gegenüber der Bildung Halogengemischter Verbindungen. Das zeigt, daß die Stabilität der Halogengemischten Verbindungen mit der Differenz der Halogene in ihrer Gruppe abnimmt. Bei der Umsetzung von SnF2 und I2 in Acetonitril entsteht SnF4(MeCN)2. Damit eröffnet sich ein einfacher Weg zum SnF4 und seinen Komplexen, z. B. mit MeCN, das unter milden Bedingungen abgespalten oder durch andere Liganden substituiert werden kann. Mit dieser Methode wurden die Komplexe SnF4L2 (L = DMF, DMSO, THF, Py) dargestellt. Die Struktur der Verbindungen wird auf Grund der IR- und 119Sn-Mößbauer-Spektren diskutiert. Im Fall von SnF4L2 werden die Mößbauer-Verschiebungen und die Sn-F-Daten mit denen der SnCl4L2-Verbindungen verglichen.
    Notes: By oxidative-addition of X2 (X = Cl, Br) to SnF2 in acetonitrile, monomeric SnF2Cl2(MeCN)2 and polymeric or oligomeric SnF2Br2(MeCN)2 are obtained. The corrected v CN IR frequencies provide a good indication of the Sn-N bond strength. The reactions of SnF2 with Br2 and I2 in the presence of DMSO, and with I2 in the presence of pyridine yield the disproportionation products rather than the mixed-halide compounds. That suggests that the stability of the mixedhalide compounds decreases when the difference between the halides increases. The reaction of SnF2 with I2 in acetonitrile gives rise to SnF4(MeCN)2, and provides a simple and inexpensive route to SnF4 and its complexes, as MeCN is lost under mild conditions or substituted by other ligands. In this way we have prepared SnF4L2 (L = DMF, DMSO, THF, Py). The structure of the compounds is discussed in terms of the IR and 119Sn Mössbauer spectra and, in the case of SnF4L2, the Mössbauer isomer shift and the IR v Sn-F compared to the corresponding SnCl4L2 compounds.
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  • 96
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 576 (1989) 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 97
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 575 (1989), S. 240-240 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 98
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 576 (1989), S. 7-9 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 99
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 575 (1989), S. 217-228 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Untersuchung der Gleichgewichte in den Aluminium (III)-Glycin- und -Alanin-SystemenDie Bildung verschiedener basischer und gemischt-basischer Komplexe des AlIII-Ions in Gegenwart von Glycin und L-Alanin wurde 0,5 mol dm-3 (Na)NO3-Medium bei 25°C mittels EMK untersucht. Die Konzentration von Aminosäure zu AlIII wurden von 1 : 1 bis 10 : 1 variiert. Die durch die Anwendung der Methode der kleinsten Quadrate erhaltenen Daten weisen in Abwesenheit der Aminosäuren auf die Bildung des Dimeren [Al2(OH)2]4+ und Monomeren [AlOH]2+ mit den Stabilitätskonstanten log β22 = -7,03 ± 0,03 bzw. log β11 = -5,65 ± 0,09. Bei pH-Werten höher als ∼4,0 wird die Bildung des Trimeren [Al3(OH)4]5+ (log β34 = -12,60 ± 0,08) deutlich. In Gegenwart der Aminosäuren wurde der Hinweis auf die Bildung von [Al2(OH)4]2+ (log β24 = -15,65 ± 0,09) gefunden. Neben der Bildung der reinen basischen Komplexe können die im Titel genannten Gleichgewichte unter der Annahme von [Al(OH)3Gly] (log β131 = -7,53 ± 0,04), [Al2(OH)2(Gly)2] (log β222 = 6,56 ± 0.09) und [Al(OH)3Ala] (log β131 = -7,70 ± 0,03), [Al2(OH)2(Ala)2] (log β222 = 7,23 ± 0,07) als Hauptreaktionsprodukte erklärt werden.
    Notes: The formation of various hydrolytic and mixed hydrolytic complexes of the aluminium(III) ion in the presence of glycine and L-alanine, has been studied in 0.5 mol dm-3 (Na)NO3 medium at 25deg;C, by emf method. The concentration ratios of amine acids to aluminium(III) were varied from 1 : 1 to 10 : 1. The least-squares treatment of the data obtained, in the absence of the amino acids, indicates the formation of the dimer, [Al2(OH)2]4+, and monomer, [AlOH]2+, with the stability constants log β22 = -7.03 ± 0.03 and log β11 = -5.65 ± 0.09, respectively. At pH values higher then ∼4.0 formation of the trimer [Al3(OH)4]5+ (log β34 = -12.60 ± 0.08) becomes significant. In the presence of amino acids the evidence has been found for the formation of [Al2(OH)4]2+ (log β24 = -15.65 ± 0.09). Besides the formation of the pure hydrolytic complexes, equilibria in the title systems can be explained by assuming the main reaction products to have the compositions [Al(OH)3Gly] (log β131 = -7.53 ± 0.04), [Al2(OH)2(Gly)2] (log β222 = 6.56 ± 0.09) and [Al(OH)3Ala] (log β131 = -7.70 ± 0.03), [Al2(OH)2Ala2] (log β222 = 7.23 ± 0.07).
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  • 100
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 576 (1989), S. 65-70 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Investigations on the Thermal Stability of Different ZSM-5 ZeolitesThe thermal stability of ZSM-5 zeolites with different crystalform, Na2O content, and different ratio SiO2/Al2O3 was measured by determination of the benzene adsorption capacity of the products after heating at 600-1200°C. The results reveal the influence of the crystal form and especially of the Na2O content on the thermal stability. The thermal stability of ZSM-5 zeolites with the same crystal form decreases with increasing Na2O content. A dependence on the ratio SiO2/Al2O3 in the ZSM-5 zeolites was not observed.
    Notes: Die thermische Stabilität von ZSM-5-Zeolithen mit unterschiedlicher Kristallform, unterschiedlichem Verhältnis SiO2/Al2O3 wurde durch Messung der Benzoladsorptionskapazität nach dem Erhitzen der Produkte auf 600 bis 1200°C bestimmt. Die Kristallform und der Na2O-Gehalt der ZSM-5-Zeolithe beeinflussen die thermische Beständigkeit. Bei gleicher Kristallform sinkt die Thermostabilität mit steigendem Na2O-Gehalt der Zeolithe. Eine Abhängigkeit der thermischen Beständigkeit vom Verhältnis SiO2/Al2O3 des Gitters wurde nicht beobachtet.
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