bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass and Charge Transfer across the Organic/Aqueous Phase‐Boundary in Electrolysis Processes using Two‐Phase‐Emulsion Mixed Electrolytes
Authors: Feess Hans , Wendt Hartmut 
Published: July 2012

AbstractFour different process‐techniques are distinguished of how to conduct the electrochemical conversion of sparsely water‐soluble substrates in aqueous solutions in the form of two‐phase emulsions. Based on detailed experimental investigations these techniques are discussed with respect to (a) the underlying principles of mass and charge transfer across the organic/aqueous phase boundary (b) their technical implications and their applications.
Molecular Liquids
Authors: Kohler Friedrich 
Published: July 2012

AbstractThe essential aspects of a microscopic description of atomic liquids are reviewed, with emphasis on geometric features of the hard sphere model assembly. Before dealing with some microscopic modifications caused by the non‐spherical symmetry of polyatomic molecules, the deviations of molecular liquids from the law of corresponding states are discussed. Then the influences of electric moments are considered in some detail, especially the interference between effects of dipole moments, quadrupole moments and anisotropic molecular shape. Finally, recent perturbation theories for molecules with anisotropic molecular shape are discussed which use hard non‐spherical bodies as reference system.
Einfache Modelle für kalorische Eigenschaften der Flüssigkeiten
Authors: Luck Werner A. P. 
Published: July 2012

AbstractAn efficient hole‐model of unpolar liquids is described. Deviations of the theorem of corresponding states are corrected by one factor, which is caused by the type of package. The possibility of distance independant pair‐potentials of the hole‐model is explained by the summation of Lennard‐Jones‐potentials. The temperature independant position of the first maximum of radial distribution curves is interpreted.—H‐bonded liquids are described by an orientation defect model, which gives the caloric properties quantitatively.
Molecular Theory of Liquids and Liquid Mixtures
Authors: Rowlinson J. S. 
Published: July 2012

AbstractThis paper reviews the present position of statistical or molecular theory of simple liquids and their mixtures, with particular emphasis on the quantitative success of perturbation theories. It is shown that the limits to our present understanding are provided not so much by imperfections in the statistical mechanics as by our ignorance of the precise form and strength of the intermolecular potentials for all molecules except the noble gases and their mixtures.
A Statistical Mechanical Equation of State and the Applicability to Fluid Phases
Authors: Peters C. J. , Lichtenthaler R. N. 
Published: July 2012

AbstractIn this paper the practical applicability of the statistical mechanical virial equation of state will be discussed. Therefore a new method to utilize the advantages of perturbation theory as well as the integral equation method is proposed. Also a suitable numerical technique is introduced to fit experimental pVT‐data to the virial equation of state.
Die Flüssigkeit an ihren Grenzflächen
Authors: Fischer J. 
Published: July 2012

AbstractThe liquid‐gas and the liquid‐solid interface are investigated for a model fluid with Lennard‐Jones interaction starting from the Born‐Green‐Yvon equation. For the liquid‐gas interface the coexisting densities, the surface tension, the density profile and the surface thickness are obtained and compared with results of computer simulations and experimental results on Argon. For the case of the liquid‐solid interface the structure of the liquid close to the wall is shown for different densities and temperatures.
Molecular Structure of Expanded Liquid Selenium up to 1400 °C
Authors: Edeling M. , Freyland W. 
Published: July 2012

AbstractThe static structure factor, S (Q), and the pair correlation function, g (R), of liquid selenium have been investigated by neutron diffraction in the temperature range from 600°C to 1400°C at pressures up to 300 bar. Within this temperature range the intramolecular bond length increases slightly from 2.37 Å to 2.38 Å and the coordination number of nearest neighbors decreases from 2.0 to 1.8. From these findings and especially from the detailed analysis of the shape of the first peak of g (R) we conclude that the structural data give no indication for the existence of a significant concentration (≥ 1019 cm−3) of threefold coordinated sites (branched chain molecules) in liquid selenium at elevated temperatures. For the intermolecular distance distribution in the range 2.8 ≤ R ≤ 4.4 Å a continuous decrease up to a minimum around 1200°C is observed. This indicates a denser packing of small linear chain molecules with increasing temperature.
Self‐Diffusion and Reorientational Motion in an Aqueous LiI Solution. A Molecular Dynamics Study
Authors: Szász Gy. I. , Heinzinger K. , Riede W. O. 
Published: July 2012

AbstractIt is concluded from a molecular dynamics simulation of a 2.2 molal aqueous LiI solution that in all three subsystems – bulk water, hydration water of Li+ and I− – the self‐diffusion is decreased and the rotational correlation time is increased compared with pure water. This result is a consequence of the existence of a second hydration shell of Li+. The usefulness of molecular dynamics simulations for the interpretation of macroscopic properties of aqueous electrolyte solutions on a molecular level is demonstrated.
Brillouin Light Scattering and Structural Relaxations in Ionic Solutions
Authors: Breitschwerdt K. G. , Polke E. 
Published: July 2012

AbstractThe hypersonic velocity and the hypersonic absorption have been measured in aqueous solutions of alkali halides in the temperature range between ‐170 and +20°C by Brillouin light scattering techniques. Both the dispersion of the hypersonic velocity and the frequency dependence of the reduced hypersonic absorption indicate the existence of structural relaxations in the frequency range 3–24 GHz. At temperatures down to −40°C the structural relaxation may be described by a simple rate process of Debye‐type. Below temperatures of about −40°C the ionic solutions exhibit viscoelastic behavior.
Light Scattering Studies of Pentanediols in Liquid and Supercooled Liquid State
Authors: Fytas G. , Dorfmüller Th. 
Published: July 2012

AbstractThe depolarized Rayleigh spectra of 1,5‐, 2,4‐, and 2 me‐2,4‐pentanediol have been measured in the temperature range of −40°C to +80°C using Fabry‐Perot interferometry. Additionally we report measurements of the correlation spectra of 2,4‐pentanediol in bulk and in solution and of neat 2 me‐2,4‐pentanediol in the temperature range of −75°C to −30°C using photon correlation spectroscopy. From the temperature and concentration dependence of the relaxing scattering intensities informations about the structure of these liquids have been obtained. The relaxation times of 1,5‐ and 2 me‐2,4‐pentanediol follow the change of the macroscopic viscosity with the temperature, in accordance to the Stokes‐Einstein‐Debye equation. This is not the case in 2,4‐pentanediol where we have to distinguish between a local and a macroscopic viscosity.
Inhomogene Schwingungsbandenverbreiterung aufgrund lokaler Konzentrationsschwankungen im flüssigen System Methyljodid‐Chloroform
Authors: Döge G. , Bien T. , Poßel M. 
Published: July 2012

AbstractSome molecular vibrations bands of methyl iodide and chloroforme show drastic broadenings in mutual liquid mixtures at mean concentrations. This effect has been attributed to the existence of different microscopic environments of the vibrating molecules. Possibilities to get informations about structure of the liquid mixtures and molecular dynamics by studying this effect are discussed.
Equilibrium and Susceptibility Behaviour of the Pd/H2 System in the Critical and Supercritical Region
Authors: Wicke E. , Blaurock J. 
Published: July 2012

AbstractInvestigations of the palladium/hydrogen system about the critical point of demixing revealed surprising results in thermodynamic behaviour – i.e. ordering of the dissolved hydrogen – and in electronic effects, i.e. magnetic susceptibilities: Although the equilibrium hydrogen pressure increases with temperature smoothly and without irregularity from the two‐phase region through the critical point into the homogeneous supercritical phase – at constant (critical) concentration – the lnp – 1/T line exhibits a sharp curvature (“kink”) at the critical point.—The occurrence of the kink is shown to be a consequence of the unsymmetrical shape of the coexistence curve. This shape is related to a decrease in entropy that grows on quickly with rise of hydrogen concentration (third power), indicating a strong ordering tendency even in the supercritical phase. The Bragg‐Williams approximation, mostly applied in connection with mean‐field theory, is therefore not adequate, actually, to this system.—The supercritical phase enables investigation of electronic properties along broad ranges of continuously varying concentrations. Measurements of the magnetic susceptibility of PdHn in this range with 0 < n < 0.55 in comparison with Pd1‐xAgx alloys revealed higher values for PdHn at equal valence electron concentration (n = x). In this aspect the rigid‐band model, obviously, does not correlate the two systems.
An Attempt to Detect Higher Ion‐Ion Correlations (Microheterogeneity) in Aqueous Solutions of Rb and Cs Halides
Authors: Hertz H. G. , Mazitov R. 
Published: July 2012

AbstractA set of inequalities is given as a formal definition of what we understand to be microheterogeneity. At the same time some known theoretical and experimental facts are mentioned representing already verifications of the criteria given. Experimental results for the87Rb,133Cs, and81Br nuclear magnetic relaxation rates in the respective aqueous halide solutions as a function of concentration and temperature are reported. These data are partly interpreted in terms of higher ion‐ion correlations, and partly a reduction of the first hydration number of the cations yields the explanation. The association parameterAis used to detect a feeble degree of water‐water association in the RbX and CsX solutions, X = Cl, Br, I. We conclude that we have evidence for microheterogeneity.
Photoelectrochemical Cells with Polycrystalline Cadmium Sulfide as Photoanodes
Authors: Neumann‐Spallart M. , Kalyanasundaram K. 
Published: July 2012

AbstractA simple procedure for the fabrication of fairly efficient polycrystalline CdS electrodes from CdS powders is described (by coating a thin film of a paste formed with an aqueous solution of a surfactant and ZnCl2 on a Ti substrate and sintering at 670°C in Ar). Light conversion efficiencies of these thin film (‐20 μm) electrodes have been tested in two regenerative solar cells (with Fe(CN)63‐/4‐ and polysulfide redox systems) and ζsolar and ζ490nm have been found to be 0.37% and 4.4%, respectively for the former. The onset of the photoresponse was λ 520 nm with maximum efficiency at λ = 490 nm (2.53 eV). Photoelectrochemical cells of the type CdS/reductant//water/Pt for the visible light induced H2 generation from water have also been assembled and were found to produce H2 with a quantum yield of 5–16%.
Temperature Dependence of the Reaction OH + OH → H2O + O
Authors: Wagner Günter , Zellner Reinhard 
Published: July 2012

AbstractRate constants for the disproportionation reaction (1) OH + OH → H2O + O in the range 250–580 K have been measured by flash photolyzing H2O/N2 mixtures and monitoring the decay of OH using quantitative UV resonance spectrometry. The result k1 = (3.2 · 0.8) 10−12 exp (‐242/T) cm3/molecule · s, does not correlate with existing high temperature data and confirms previously suggested non‐Arrhenius behaviour for this reaction. On the basis of all available data the temperature variation of k1 over the range 250–2000 K is best represented by the empirical expression k1(T) = exp (‐27.73 + 1.49 · 10−3T) cm3/molecule · s. The extent of the Arrhenius graph curvature can be reconciled by a “close‐collision” model incorporating the energy variation of accessible product states.
Molecular Motion of Cations and Phase Transitions in Tetramethylammonium Hexachloroplatinate (IV), ‐tellurate (IV), and ‐stannate (IV) as Studied by CW and Pulsed 1H NMR and DTA Measurements
Authors: Prabhumirashi Laxman S. , Ikeda Ryuichi , Nakamura Daiyu 
Published: July 2012

AbstractThe temperature dependences of the 1H spin‐lattice relaxation time T1, at 20 MHz and of the second moment of 1H NMR absorptions were studied in tetramethylammonium hexachloroplatinate (IV), ‐tellurate (IV), and ‐stannate (IV), which are referred below as (tetMA)2PtCl6, (tetMA)2TeCl6, and (tetMA)2SnCl6, respectively. From the measurements of DTA and pulsed 1H NMR carried out below room temperature, four phases were found in (tetMA)2PtCl6 while two phases in both of the remaining complexes. The 1H NMR studies revealed that, with decreasing temperature, the most part of the rotational or reorientational freedom of tetMA cations freezes at almost the same temperature, but a small fraction of the motional freedom still remains even at lower temperatures. From the analysis of the shallow T1 minimum clearly observed for (tetMA)2TeCl6, this motion activated in this complex and also in (tetMA)2PtCl6 is unambiguously attributed to a small‐angle reorientation of four methyl groups in the cation around their staggered conformation. The mechanism of the phase transitions detected in these complexes is discussed in relation to the motion of tetMA cations.
DNMR‐kinetische Untersuchungen der Beweglichkeit von 1,4‐diacyl‐substituierten 1,4‐Dihydropyrazinen
Authors: Kollmannsberger Georg , Gottlieb Raphael , Pfleiderer Wolfgang 
Published: July 2012

AbstractThe AA'BB'‐part of the proton NMR spectra of the 1,4‐diacyl‐1,4‐dihydropyrazines 1‐4 reveals a strong temperature dependence resulting from the restricted rotation of both acyl groups around the C – N bonds. A dynamic model is postulated for the interconversion of the cis‐ and transforms which are in equilibrium. Activation enthalpies and activation entropies have been determined from the comparison of theoretical and experimental spectra. The results are discussed by use of HMO‐calculations.
Formation of an Inversion Layer in n‐Type MoSe2 Electrodes: Observation in the Presence of Highly Oxidizing Redox Systems
Authors: Jaeger C. D. , Gerischer H. , Kautek W. 
Published: July 2012

AbstractThe creation of an inverted surface region at an n‐type MoSe2 electrode is demonstrated by two different experimental techniques. In one technique the ac conductivity of a thin electrolyte layer in contact with a MoSe2 single crystal was determined where the surface of the MoSe2 behaves like a parallel shunt resistor. Injection of minority carriers by oxidized thianthrene induced a substantial increase in the surface conductivity of the MoSe2. In the second technique, the impedance of the MoSe2 electrode was determined over the frequency range of 100 to 50000 Hz. A plot of the impedance in the complex plane showed that the low frequency limit of the ohmic impedance component dramatically decreases in contact with oxidized thianthrene. This can also be interpreted as an indication for the formation of an inversion layer.
Temperature Dependence of Excess Thermodynamic Properties of Binary Mixtures of Organic Compounds
Authors: Koenen Hans‐Eckhardt , Gaube Johann 
Published: July 2012

AbstractFor calculations on distillation processes it is necessary to know the vapor‐liquid‐equilibrium (VLE) data at the desired temperature range. Very often data are available only for different temperature ranges. Therefore it is necessary to convert the VLE data from one temperature range to another.—The excess functions of the various types of mixtures have very different temperature dependence. Therefore we classified the mixtures according to the temperature dependence of the excess Gibbs energy and the excess enthalpy. The thermodynamic properties of the mixtures of organic compounds exhibit remarkable regularities.—In the case of non‐associated mixtures the excess Gibbs energy and the excess entropy are directly proportional to the excess enthalpy. Here simple expressions for describing the temperature dependence of the excess functions could be obtainedmagnified imageThe temperature dependence of the excess functions of the associated mixtures can be described by the Chemical Theory of Solutions.—The analysis of the available thermodynamic data shows that our classification serves a two‐fold purpose. First it is very useful for estimating the temperature dependence of excess functions. Second it shows how an analysis of the GE vs. HE(T) curves may enhance the general understanding of interactions in mixtures.
Small Angle Neutron Scattering Measurements on Ionic Detergent Solutions with Rodlike Micelles
Authors: Kalus J. , Hoffmann H. , Reizlein K. , Ulbricht W. , Ibel K. 
Published: July 2012

AbstractSmall angle neutron scattering (SANS) measurements have been carried out on aqueous solutions of Cetylpyridinium‐Salicylate (CPySal). The data show the existence of rodlike micelles with the length L and the radius R. The radius R of 21.5 A is independent of the detergent concentration while the L‐values increase with increasing concentration. For 10 mM solutions the micelles show considerable nearest neighbour order.
Soret Coefficients and Transported Entropies of Nonisothermal Liquid Alkali Nitrate + Silver Nitrate Mixtures
Authors: Fuchs W. , Richter J. 
Published: July 2012

AbstractIn a thermocell containing two silver electrodes the stationary state of thermal diffusion in the systems of molten KNO3 + AgNO3, RbNO3 + AgNO3, and CsNO3 + AgNO3 is measured at 513 K, 533 K, and 563 K as a function of the composition of the mixture. These measurements provide the thermoelectric power ε∞ (of the steady state) which depend linearly on temperature at a given composition. Thus it is possible to combine the ε∞‐values, extrapolated to higher temperatures, with the published ε∞‐values (thermoelectric power of the initial state) at 633 K and to compute the transport quantities of non‐isothermal melts in the temperature range from 493 K to 633 K. The transported entropies of the two ion constituents, a linear combination of the heats of transport of the same constituents, and the Soret coefficients of the three liquid systems mentioned are discussed, in connection with the same quantities for the systems LiNO3 + AgNO3 and NaNO3 + AgNO3, evaluated in a previous paper, thus leading to a complete investigation of the alkali nitrate systems.
Molecular Dynamics of Liquid Argon: Collision Times and Durations
Authors: Samios J. , Samios D. , Mersch W. , Dorfmüller Th. 
Published: July 2012

AbstractThe mean collision time 〈τC〉 and the mean durations of collision 〈τD〉 in liquid argon were calculated by a molecular dynamics computer simulation. The calculations were performed from the triple point temperature of T = 83.81 K to T = 150 K. The collision rates Z were obtained under isothermal, isochoric and isobaric conditions and the corresponding derivativesmagnified imageas well as the isokinetic coefficientmagnified imagehave been calculated for our model and for liquid cell models. The use of the coefficients thus introduced for the calculation of frequency factors in solution kinetics is discussed. A comparison with collision induced spectra shows that the calculated values of 〈τC〉 and 〈τD〉 are in agreement with experimental data in liquid argon.
Calculated Koopmans' Defects for Transition Metal Compounds in the Framework of an Effective Semiempirical Hamiltonian: Bis(π‐pentadienyl)dinickel
Authors: Böhm Michael C. 
Published: July 2012

AbstractA variable semiempirical Hamiltonian of the INDO type is employed in order to investigate the magnitude of reorganization effects (Koopmans' defects) in the photoelectron (PE) spectrum of bis(π‐pentadienyl)dinickel (1). The dependence of the calculated reorganization energies as function of the resonance integral βμνAB and as function of the two‐center electron‐electron interaction integral γμνAB is studied in detail. βμνAB has the property of an inverse coupling constant enlarging calculated Koopmans' defects with reduced βμνAB values. For γμνAB an exponential formula with a variable range parameter has been used; reorganization effects are of stronger importance in the case of short‐range forces with large γμνAB gradients. In the long‐range limit a significant reduction of the calculated reorganization energies is observed. The theoretically determined Koopmans' defects are calculated via a renormalized approximation for the self‐energy part in the perturbational framework of the one‐particle Green's function formalism.
Osmoseeffekte beim Stofftransport durch flüssige Membranen
Authors: Draxler J. , Marr R. 
Published: July 2012

AbstractThe water transport through the membrane of a stable w/o/w‐emulsion has been investigated. It has been found that the surfactant SPAN 80, which is added to the emulsion as a stabilizing agent, is a good carrier for water molecules. The water transport from the outer water phase through the organic membrane phase into the inner water phase causes swelling of the emulsion and therefore several properties of the emulsion are changed. An admixture of various carriers to the membrane phase showed that nitrogen containing agents have less influence on the water transport than oxygen containing agents. Organic phosphoric or carboxylic acids enhance the water transport whereas emulsions containing anion exchangers (like ALIQUAT 336) show an almost ideal behaviour: the water transport by SPAN 80‐molecules is prevented without affecting the properties of the carrier.
Clustering of Liquid Molecules on Solid Surfaces
Authors: Lagaly G. , Witter R. 
Published: July 2012

AbstractThe strong self‐association of DMSO, FA, DMFA, H2O controls their adsorption by swelling systems, for instance, by vermiculite, a mica‐type layer silicate. Using this type of porous adsorbents the influence of the interlayer charges has to be reduced by replacing the interlayer cations by alkylammonium ions. In equilibrium with the liquids (DMSO, FA, DMFA, H2O, EtOH) the silicate layers are prized apart until distinct cavities for the sorption of the liquids are created. Their volumes are independent on the chain length of the alkylammonium ions.—The mutual influence between the clustered liquid molecules and the alkyl chain arrangements determines the interlayer structure. Therefore, substitution of alkylammonium ions by trimethyl alkylammonium ions not only changes the type of the liquid clusters but also the alkyl chain arrangement. Dimethyl dialkylammonium ions impede the formation of liquid clusters because of the strong van‐der‐Waals interactions between the chains, and only allow incorporating isolated guest molecules.—The surface excess isotherms describing competitive adsorption of DMSO and H2O show substantially linear sections. The DMSO/H2O ratio in the adsorbed phase is constant through most of the mole‐fraction range of DMSO in solution (mole fractions DMSO from x1 = 0.15 to 0.95). DMSO is preferentially adsorbed, the ratio DMSO/H2O being 4–5.