bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relating Cation Solvation in Solvent Mixtures with Solvent Exchange Rates — A 1H‐NMR Study on Co(II)‐Ions
Authors: Dickert F. L. , Hellmann S. W. 
Published: July 2012

AbstractSpecific and statistical solvation of Co(II)‐ions in mixtures of methanol with dimethylformamide respectively hexamethylphosphoric triamide was found by 1H‐NMR‐spectroscopy. Relations are given, which correlate these possible solvation models with the kinetics of solvent exchange. On this basis, specific outersphere solvation of the methanol rich Co(II)‐solvate‐complexes by dimethylformamide can be deduced. For mixtures of hexamethylphosphoric triamide with methanol, the statistical solvation behaviour is additionally favoured by a strong solvent‐solvent interaction.
Optical Spectra of Matrix‐Isolated Aluminium
Authors: Abe H. , Kolb D. M. 
Published: July 2012

AbstractA reinvestigation of matrix‐isolated aluminium shows that the optical spectra of previously published work on Al contained prominent bands originating from Al2O. We report for the first time the absorption and emission yield spectra of Al atoms in noble gas matrices which are free of aluminium suboxide contamination. A study of the concentration dependence allowed a decision as to which bands in the spectral range from 450 nm to 200 nm belong to Al, Al2 and Al2O. From the vibronic fine structure of an absorption band at 3 eV for Al2, ωe = 238 ± 5 cm−1 is found for the dimer in Ar, Kr and Xe. For Al atoms in Kr two rather stable trapping sites are observed.
Measurements of Solubilities of Solid CO2 in C2H4, C3H6, i‐C4H8, n‐C5H12 and of n‐C5H12 in C3H6
Authors: Teller Matthias , Knapp Helmut 
Published: July 2012

AbstractLiquidus curves for five binary mixtures were determined in a low temperature equilibrium apparatus. It can be assumed that the solid phase consists of the pure solute. The experimental results were correlated and binary coefficients for a simple gE model were calculated as a function of temperature.
Röntgenographische und dilatometrische Untersuchungen zur Fehlordnung im Strontiumchlorid
Authors: Daniel G. , Nölting J. 
Published: July 2012

AbstractSrCl2 cristallizes in the fluorite structure and shows, like all materials with this structure, anomal properties with regard to thermodynamic as well as to transport phenomena. In a temperature region starting about 200 K below the melting point (1146 K) a pronounced maximum of Cp is found, which is to be identified with a Schottky anomaly. Most significant are the increasing values of ionic conductivity with rising temperature. They mostly exceed those of a typical ionic melt. The degree of the “molten” anion lattice and the distinct places of the defect ions are not clarified until now. The temperature of transition at the maximum of the expansion coefficient value at T = 1000 K has been determined by dilatometric measurements. The existence of predominant Frenkel‐disorder has been demonstrated by comparing X‐ray and dilatometric measurements. The ratio of ionic radii relative to the configuration in the fluorite structure has been determined from lattice parameter and the crystal structure.The enthalpy of formation of Frenkel disorder has been calculated from dilatometric measurements to ΔHf = (248 ± 8) kJ mol.
The Effect of Added Salts on the Proton Exchange Rate of Water as Studied by17O NMR
Authors: Hertz H. G. , Versmold H. , Yoon C. 
Published: July 2012

AbstractLine shapes of the17O n.m.r. of the solvent water have been measured in solutions containing small amounts of HCl or NaOH and various inorganic and organic salts. Proton life times τ in the water molecule have been derived from these spectra. The life time in the neutral electrolyte solutions, the maximum life time, the rate constants for the proton exchange catalized by H+and OH−ions, and the pH value at which the maximum r occurs are reported. Correlations with the well‐known structure forming and structure breaking properties of ions are discussed. The results are also compared with the electrical extraconductivity observed in these solutions.
Investigation of Hydrogen Atom Addition to Vinyl Monomers by Time Resolved ESR Spectroscopy
Authors: Beckert D. , Mehler K. 
Published: July 2012

AbstractBy means of time resolved ESR spectroscopy in the microsecond time scale the H atom addition to different vinyl monomers was investigated. The H atoms produced by pulse radiolysis of aqueous solutions show a strong recombination CIDEP effect which also allows the recombination rate constant of H atoms to be determined. By analysis of ESR time profiles with the modified Bloch equations the relaxation times T1, T2, the polarization factors and the chemical rate constants with scavengers were obtained. Besides the H atom addition rate constants to different vinyl monomers the structure of the monomer radical was determined for acrylic acid.
The Thermal Conductivity of Argon, Nitrogen and Carbon Monoxide in the Temperature Range 300 — 430 K at Pressures up to 10 MPa
Authors: Haran K. N. , Maitland G. C. , Mustafa M. , Wakeham W. A. 
Published: July 2012

AbstractMeasurements of the thermal conductivity of argon, nitrogen and carbon monoxide have been carried out over the temperature range 300 – 430 K and at pressures up to 10 MPa in a transient hot‐wire apparatus. The measurements on argon confirm that the accuracy of the experimental results is one of ± 0.3%. Substantial differences have been found between the thermal conductivity of nitrogen and carbon monoxide in the limit of zero density. This observation can only be satisfactorily explained by the existence of large differences between the diffusion coefficients for internal energy for the two gases. In turn these results indicate that this functional of the intermolecular pair potential may be particularly sensitive to its non‐spherical part. – At elevated densities the temperature independence of the excess thermal conductivity as a function of density is confirmed to a high degree of precision.
Morphologie und Phasenunterschiede bei V2O5 und TiO2 in Mischoxidkatalysatoren — Ursachen und gegenseitige Beeinflussung
Authors: Backhaus K. O. , Haase R. , Illgen U. , Jancke K. , Richter‐Mendau J. , Scheve J. , Schulz I. , Vetter J. 
Published: July 2012

AbstractCoated catalysts, consisting of a compact ceramic core and a shelly coat prepared by mixing TiO2 with vanadium oxalate are investigated After thermal decomposition of the oxalate crystalline phases of vanadium oxide were observed on the anatase surface area. The thermal transformation of anatase into rutile is determined by these phases as proved by X‐ray analysis. A model describes the formation of V6O13 and the transformation of anatase into rutile by structural fits.
Anisotropy of Rotational Diffusion in Liquid α,ω‐Dichloroalkanes
Authors: Peplińska B. , Pąjak Z. 
Published: July 2012

AbstractFrom the analysis of 1H and 13C spin‐lattice relaxation times and self‐diffusion coefficients measured for α,ω‐dichloropentane, ‐hexane and ‐octane, the rotational diffusion coefficients of the prolate ellipsoid type molecules treated as rigid symmetrical tops are derived. The effect of slow internal motions on the predominant dipolar relaxation is shown to be negligible as compared to the overall reorientation. The evidenced anisotropy is very pronounced — reorientation about the major symmetry axis is over ten times faster than about the perpendicular axes. Some hydrodynamic models, tested by the experimentally determined intramolecular contributions to the proton spin‐lattice relaxation rates, appear to be insufficient for the adequate description of the motional behaviour.
High Temperature Thermodynamics of Solutions of Hydrogen and Deuterium in Palladium and its Alloys
Authors: Kleppa O. J. 
Published: July 2012

AbstractThe solutions of hydrogen in palladium and its alloys are classical examples of interstitial metallic solutions. Although these alloys have been studied for a very long time, a good deal of new information has become available in recent years, partly as a result of the application of the combined calorimetric‐equilibrium approach. This experimental method, which was developed in our laboratory about 10 years ago, allows essentially simultaneous determinations of the Gibbs energies, the enthalpies and the entropies of solution. This approach has been particularly useful in throwing new light on the temperature dependence of the thermodynamic properties, and also on their dependence on the alloying constituents. Special interest is attached to the new information on the partial entropies of hydrogen, which points strongly toward a temperature dependent, non‐random distribution of the hydrogen atoms among the available interstitial sites.
Application of Thermodynamic Models in Phase Diagram Assessment
Authors: Hillert Mats 
Published: July 2012

AbstractBy the use of examples which mainly concern the configurational entropy of alloy systems an attempt is made to illustrate the application of physical and mathematical models to the assessment of alloy systems. It is emphasized that methods, which are often regarded as independent of models, depend very strongly on some hidden choice of a model. It is shown that different physical models can give the same mathematical model. For further developments it may be essential to test what physical model gives the most realistic description of the situation in the real system. It is also shown that different mathematical models can represent the data very well even when the properties of the system are very specific.
Calculation and Representation of Phase Equilibria in Multicomponent Systems
Authors: Henig E.‐Th. , Kattner U. , Petzow G. 
Published: July 2012

AbstractThe general features of thermodynamic calculation of phase equilibria are reviewed. This includes analytical description of the thermodynamic functions by approximations or models, determination of the resulting adjustable coefficients from experimental data, calculation of phase equilibria based on the Gibbs free energy functions of individual phases and graphical representation of the results. Special emphasis is given to different types of two‐dimensional representations only containing partial information about the multidimensional higher order systems.
Enthalpy Measurements on Refractory Metals and Alloys by Levitation Calorimetry
Authors: Frohberg Martin G. , Betz Cerhard 
Published: July 2012

AbstractMeasurements of enthalpy by levitation drop‐calorimetry. Principle of measurement. Experimental data of Nb, Mo, Ta in solid and liquid state. Determination of enthalpies of mixing by levitation technique. Temperature measurement. Investigation of Fe–Cu and Nb–Si‐alloys.
Enthalpies of Formation of Ag — Si, Au — Si and Ag — Au — Si Liquid Alloys at 1423 K
Authors: Hassam S. , Gaune‐Escard M. , Bros J. P. 
Published: July 2012

AbstractThe enthalpies of formation of silver‐silicon, gold‐silicon and silver‐gold‐silicon were determined at 1423 K over a large concentration range; a very high temperature calorimeter was used for these investigations. Our ternary experimental results were represented correctly with a modified Kohler's relation.
Calorimetric Investigations of Liquid Alkaline Earth Metal Alloys
Authors: Sommer F. , Lee J. J. , Predel B. 
Published: July 2012

AbstractThe concentration dependences of the enthalpy of mixing of liquid copper‐magnesium and calcium‐copper alloys have been determined, applying direct mixing calorimetry, in the temperature range between 1120 and 1225 K. The enthalpies of mixing are discussed in connection with known thermodynamic quantities and the asymmetrical concentration course obtained can be described by an association model. Systematic comparison is carried out between the experimentally obtained enthalpies of mixing – together with other recent experimental data – and those obtained according to the Miedema model. The concentration dependence used in the model is not able to describe the results of alloy melts with strong compound formation tendency. The enthalpy of mixing can be calculated in nearly 40% of the systems investigated with less than 30% error and in 64% with an error less than 2.5 kJ mol−1.
Prediction of Formation Enthalpies of the Compounds MgHg(s) and CaHg(s)
Authors: Hilpert K. 
Published: July 2012

AbstractThe formation enthalpies per mole of an atom of the compounds MgHg(s) and CaHg(s) are determined as − 28.2 ± 0.8 and − 56.8 ± 4.6 kJ mol−1 respectively, by studying the vaporization of compounds of the Mg – Hg and Ca – Hg systems with a new Knudsen cell‐mass spectrometer system. Values of − 30 [MgHg(s)] and − 59 kJ mol−1 [CaHg(s)] are predicted with the volume contraction model, as well as − 34.6 [MgHg(s)] and − 1.6 kJ mol−1 [CaHg(s)] with the Pauling model of ionic bond using the electronegativities of Gordy and Thomas. The enthalpies of formation are discussed and compared with those of intermetallic compounds with predominantly ionic bond. The enthalpies of formation per mole of an atom of the compounds BaHg(s) and SrHg(s) are predicted as − 61.6 and − 77.9 kJ mol−1, by applying the Pauling model of ionic bond with the electronegativities of Gordy and Thomas.
The Palladium‐Silver‐Hydrogen System: A Quasi‐Chemical Approach
Authors: De Avillez R. R. 
Published: July 2012

AbstractThe quasi‐chemical model extended to include both first and second neighbor interactions between interstitial and substitutional matrix atoms [7] was applied to the Pd – Ag – H system and found to provide a satisfactory fitting for the available experimental data over the temperature range from 350 to 850 K. The calculated interaction coefficients suggest that hydrogen solution in Pd – Ag alloys will tend to be short‐range ordered, the hydrogen atoms occupying preferentially the interstitial sites surrounded by first neighbor palladium atoms and second neighbor silver atoms.
Nuclear Quadrupolar Spin Relaxation and Association in Binary Liquid Metallic Alloys
Authors: Elwenspoek M. , Brinkmann R. , Maxim P. , Paulick C. , Quitmann D. 
Published: July 2012

AbstractWe present experimental data for the nuclear quadrupolar spin relaxation rate Rq in liquid InxSb1–x, HgxK1–x and In50Hg50. The results for the concentration and temperature dependence of Rq can be qualitatively interpreted with the framework of association in these systems (quasi ternary solution model). We conclude that the relaxation is mostly due to the decay of associates in HgIn and to rotational diffusion of associates in Hg – K. In In – Sb, the corresponding correlation times seem to be equal so that both relaxation processes may contribute to the relaxation. The analysis of microscopic experiments using the concept of association may prove useful for a better understanding of the nature of the associates.
Free Energy Criteria for Glass Forming Alloys
Authors: Saunders N. , Miodownik A. P. 
Published: July 2012

AbstractThe thermodynamic characterisation of a number of glass forming systems (Au – Si, Pd – Si, Ni – Ti, Ti – Be, Zr – Be and Hf – Be) has been reviewed, and the free energy curves calculated for the glass forming temperature as well as for the temperature of maximum rate of crystallisation, in order to check how far the data which models the equilibrium diagrams provides suitable guidance for metallic glass formation. It is shown that the glass forming range is accurately predicted from the region where the liquid phase is more stable than other competing single phases, thus confirming the importance of the T0 concept. The systems considered offer a variety of behaviour which emphasises the importance of metastable compound formation as well as the inhibition of some equilibrium compounds. The present treatment is compared with other approaches to the problem.
Electron Transfer Reaction Between Ferrocene and Tris (1,10‐Phenanthroline) Cobalt (HI) in Micellar Systems
Authors: Cavasino F. Paolo , Sbriziolo Carmelo , Pelizzetti Ezio 
Published: July 2012

AbstractThe kinetics of the electron transfer reaction between ferrocene and tris (1, 10‐phenanthroline) Cobalt (III) have been studied by the stopped‐flow method at 20.0°C and ionic strength 0.02 mol dm−3 in the presence of anionic (SDS), cationic (CTAB) and non‐ionic (Triton X‐100) micelles. Cationic and non‐ionic micelles inhibit the oxidation reaction according to a model in which the ferrocene is partitioned between the aqueous and micellar pseudo‐phases, the reaction proceeding primarily in the aqueous phase. On the contrary anionic micelles catalyze the reaction which occurs in the micellar phase. The estimated binding constants of ferrocene to the different micelles are quite similar.
A Fluorescence Microscopic Study Concerning the Phase Diagram of Phospholipids
Authors: Lösche M. , Sackmann E. , Möhwald H. 
Published: July 2012

AbstractThe phase diagram of phospholipid monolayers is investigated using fluorescence microscopic and thermodynamic techniques. The images recorded using low light level camera tubes show patterns of inhomogeneities in the condensed as well as in the expanded states. These are ascribed to different dye solubilities and different molecular densities, respectively, in coexisting phases. – For pressures above that corresponding to a sharp break in surface pressure versus area isotherms at least two phases coexist. The monolayer is macroscopically fluid with an almost constant diffusion coefficient throughout the so‐called liquid expanded, liquid condensed and the intermediate phase. For dipalmitoylphosphatidylcholine (DPPC) at molecular areas as small as 55 Å2/molecule a drastic decrease in diffusion by about two orders of magnitude is observed. The gas/liquid transition is observed from a formation of characteristic, symmetrical lipid domains on the water surface.
The Solubility of Electrolytes in Homogeneous Mixtures of Water‐Miscible Organic Solvent (MOS)
Authors: Alfassi Zeev B. , Weiss J. 
Published: July 2012

AbstractThe solubility of several electrolytes in homogeneous mixtures of water‐miscible organic solvent (acetone, methanol, tetrahydrofuran, dioxane and acetonitrile) was found to obey the equation S = Sw exp (‐ λf) where Sw and S are the solubilities in water and the mixture respectively, and f is the volume fraction (or mole fraction) of the organic solvent. This dependence can be explained assuming the additivity of the standard state chemical potential of the electrolyte in the mixture, i.e. μ = f · μ + (1 ‐ f) μ0.
Ultraschalluntersuchungen in flüssigen und plastischen Phasen
Authors: Kreutzenbeck H. J. , Ledwig R. , Würflinger A. 
Published: July 2012

AbstractDifferent devices have been developed for ultrasonic measurements at atmospheric and elevated pressures up to 1 kbar. The velocities of sound for liquid toluene, 2,3‐dimethylbutane, cyclohexane, and camphene have been determined. In the case of 2,3‐dimethylbutane also preliminary absorption measurements at elevated pressures have been performed, according to which the activation volume for the hindered internal rotation is negligible. Furthermore some plastic phases have been studied. The velocities of sound (longitudinal mode) of cyclohexane and camphene increase considerably on freezing in contradiction to the findings of others. Additional measurements of the transverse modes allow a rough estimation of the elastic stiffness constants.
Der pKa‐Wert von Redox‐Indikatoren auf Graphitelektroden
Authors: Huck H. 
Published: July 2012

AbstractThe redox potentials of adsorbed weak aromatic acids (a) and their conjugate bases (b) on graphite electrodes at different pH were measured by means of cyclic voltammetry to obtain the apparent pK'a,ad‐values. In addition the desorption velocities Kd (a) and kd (b) were measured by cyclic voltammetry, from which the pK‐values due to different adsorbabilities of (a) and (b) were calculated. – It is shown that the difference ΔpK'a,ad of the pKa‐values on the surface and in the bulk of the solution is mainly caused by a charge in the adsorbed acid or conjugate base, and in the case of ion pair and chelat complex formation with the counter ions of the buffer also by the local field of the counter ion. Ion pairs were found with the reduced molecules, which have no charge distribution by mesomerie. The electronic structure has only then a notable influence, if the adsorbed molecule has conjugated π‐electrons and if these are easily polarized in the electrical field of the electrode. The dissociation field effect was also taken into consideration.
Das Zünden und Verlöschen einer autothermen Reaktion in einer porösen Partikel in oxidierender Atmosphäre
Authors: Meinköhn D. 
Published: July 2012

AbstractAn investigation of the critical stationary states of an exothermic reaction is presented, by which the phenomena of ignition and extinction are described. The set of critical states is represented in form of a space curve, for which the projection into the parameter plane is discussed. Geometryindependent bounds are derived for the components of the transition point at which criticality disappears.
Periodische und statistische Eigenschaften kohärenter Kurzzeit‐Strukturen in Tankflammen
Authors: Brötz W. , Schönbucher A. , Banhardt V. , Schieß N. 
Published: July 2012

AbstractCoherent structures of pool flames are visualized by the synchronous holographic interferometry. – There are large coherent structures which have periodical properties and small coherent structures both with periodical and statistical properties. The periodical phenomena can be classified into three types of instabilities. The first type is a low‐frequency instability with frequencies of the order of 12 Hz (for a n‐hexan pool flame, d = 4.6 cm) and depends considerably on the pool diameter. The second and third types have frequencies in the order of 300 Hz and 500 Hz, which depend mainly on the fuel type. – The statistical properties of the small coherent structures indicate that the turbulent exchange coefficients for heat and matter have values six times larger than the exchange coefficients for the momentum. The turbulent Prandtl numbers, Schmidt numbers and Lewis numbers are functions of the distance from the fuel surface. These functions vary between the following limits:
Elementarreaktionen in der Oxidation von Alkenen
Authors: Hoyermann K. , Sievert R. 
Published: July 2012

AbstractThe reactions of OH radicals with the isomers of butene (1‐C4H8, cis‐2‐C4H8, trans‐2‐C4H8, iso‐C4H8) have been studied at low pressure using an isothermal flow reactor (295 – 298 K, p = 0.9 – 10 Torr) and a Laval‐nozzle reactor (p < 0.1 Torr). The hydroxyl radicals have been produced via the reactions H/D + NO2 or F + H2O/D2O, hydroxy butyl radicals via the reactions F + 1‐C4H9OH, 2‐C4H9OH, sec‐C4H9OH, tert‐C4H9OH. Samples were withdrawn continuously by a molecular beam sampling system and were analyzed mass spectrometrically, applying synchronous ion counting and chemical modulation techniques. – The reaction mechanism is found as

The stabilization of the adduct is the main reaction channel at room temperature and around 1 Torr, abstraction reactions are negligeable. – The reaction mechanisms were analyzed in terms of addition/redissociation/stabilization/isomerization/decomposition, using unimolecular rate theory. The results were applied for the prediction of product formation at conditions of technical combustion processes.
Modeling Studies of the Homogeneous Formation of Aromatic Compounds in the Thermal Decomposition of n‐Hexane
Authors: Ebert K. H. , Ederer H. J. , Stabel U. 
Published: July 2012

AbstractThe pyrolysis of n‐hexane – as well as the thermal decomposition of n‐hexane with addition of propene and 1 ‐butene – was studied at 819 K up to very high conversions. A reaction model, consisting of elementary reactions, was developed. With this model the experimental results including the formation of benzene and toluene can be described. Inhibition effects, the rates of formation of various products and the effects of products on the reacting system are discussed.