bluuebunny/crossref_metadata_2025 huggingface dataset:
On the solvent Effect on the Proton Spin‐Lattice Relaxation Time of Pyridine in Different solvents
Authors: Chatterjee N. , Czubryt J. J. , Bock E. , Tomchuk E. , Hutton H. M. , Kydon D. W.
Published: March 2014

The solvent effect on the proton spin‐lattice relaxation time of the pyridine molecule in the following solvents was determined at 25°C: pyridine‐d5, benzene‐d6, Cyclohexane‐d12, acetone‐d6, chloroform‐d, carbon disulfide, and carbon tetrachloride. It was found that the experimental results were in good agreement with the predictions of Hill's theory of molecular reorientation in pure liquids and binary liquid mixtures.
Das “Angular‐Overlap”‐Modell für niedersymmetrische Koordinationsverbindungen III. Optische Eigenschaften von Hydroxokomplexen des dreiwertigen Chroms
Authors: Schläfer Hans‐Ludwig , Martin Monika , Schmidtke Hans‐Herbert
Published: March 2014

Eine Reihe von Absorptions‐ und Reflexionsspektren von ein‐ und zweikernigen Hydroxokomplexen des dreiwertigen Chroms wurden aufgenommen. Die Bandenaufspaltungen, welche von niedersymmetrischen Ligandenfeldkomponenten herrühren, werden mit Hilfe üblicher theoretischer Verfahren (Ligandenfeldtheorie und “Angular Overlap“‐Modell) gedeutet. Das besondere spektroskopische Verhalten von Hydroxidliganden erklärt sich zwanglos durch das “Angular Overlap“‐Modell auf Grund starker π‐Bindungseffekte. Wenn der zweite spinerlaubte Übergang stärker aufgespalten ist als der erste, ergibt sich aus dem Modell die für Hydroxo‐Komplexe korrekte Reihenfolge der Quartett‐Terme: 4B1 ⩽ 4E < 4B2 ⩽ 4E < 4A2. Die Ligandenfeldtheorie liefert dieses Resultat nur, wenn für die niedersymmetrischen Ligandenfeldparameter Wertebereiche angenommen werden, die physikalisch kaum begründet werden können (nämlich für negative k = Ds/Dt‐Werte).
Röntgenstrukturuntersuchung der flüssigen absoluten Schwefelsäure. 1. Mitteilung: Theoretische Grundlagen, Separation der beobachteten Streuintensität in den intra‐ und intermolekularen Anteil, Bestimmung der Molekülstruktur
Authors: Weidner Jörg U. , Geisenfelder Horst , Zimmermann Herbert
Published: March 2014

Die Intensitätsverteilung der Röntgenstreustrahlung von flüssiger 100%iger Schwefelsäure wurde bei 20°C mit einem Zählrohr‐Goniometer gemessen und auf Absorption, Polarisation und Compton‐Streuung korrigiert. Für die Absorptionskorrektur bei Proben mit rechteckigem Querschnitt wird eine Beziehung abgeleitet, die es gestattet, verschiedene Schwächungskoeffizienten für kohärente und inkohärente Streustrahlung zu berücksichtigen. Aus der experimentellen korrigierten Intensität wurden die reduzierte Intensität und die radiale Elektronendichteverteilung ermittelt.

Es wird ein Verfahren beschrieben, mit dem die totale reduzierte Intensität bzw. radiale Elektronendichteverteilung unter Verwendung eines groben Molekülmodells in den intra‐ und intermolekularen Anteil zerlegt werden kann. Das Verfahren setzt weder die Kenntnis der exakten Molekülstruktur noch diejenige der Nahordnung der Moleküle in der Flüssigkeit voraus. Eine Erweiterung des Verfahrens gestattet es, systematische Fehler näherungsweise zu eliminieren.

Aus der intramolekularen reduzierten Intensität wurde mit einem iterativen Optimierungsverfahren die Struktur des Moleküls in flüssiger Phase berechnet. Die Ausgleichsrechnung nach der Methode der kleinsten Quadrate ergibt zwei Molekülmodelle, die gut mit den experimentellen Ergebnissen zu vereinbaren sind. Im Modell I hat die SO4‐Gruppe des Schwefelsäuremoleküls die Punktsymmetrie C2, im Modell II die Symmetric C2v.

Die S – O‐Abstände betragen bei beiden Modellen innerhalb der Fehlergrenzen übereinstimmend S – OH: 1,55 Å, S – O: 1,42 Å. Sie entsprechen denjenigen in kristalliner Schwefelsäure. Die Winkel O‐S‐O stimmen beim Modell II innerhalb der Fehlergrenzen mit dem Tetraederwinkel überein. Beim Modell I sind die Werte aufgespalten, jedoch nicht so stark wie in kristalliner Schwefelsäure. Die gefundenen mittleren Schwingungsamplituden für die S – O‐und O–O‐Atompaare sind vergleichbar denjenigen, die für das SO4−‐‐Ion spektroskopisch ermittelt wurden. Die Frage, welchem der beiden Molekülmodelle größere physikalische Relevanz zukommt, läßt sich allein aufgrund der Röntgenstrukturuntersuchung nicht eindeutig entscheiden.
Zur Frage der Assoziation von Tri‐p‐biphenylyl‐methyl Eine ESR‐spektroskopische Untersuchung zum Selwood‐Effekt
Authors: Ohmes Ernst , Kothe Gerd , Naujok Annemarie , Zimmermann Herbert
Published: March 2014

Es wird ein Verfahren beschrieben, das es gestattet, die Konzentration von Radikallösungen ESR‐spektroskopisch durch Vergleich mit einem DPPH‐Standard zu bestimmen. Die Signale von Probe und Standard werden mit einem ESR‐Spektrometer mit Feldmodulation gemessen und automatisch auf Lochkarten registriert. Anschließend werden sie mit einem Computerprogramm zweimal integriert und auf das Signal eines sekundären Rubin‐Standards normiert, der fest im Resonator eingebaut ist. Aus den normierten, integralen Absorptionen von Probe und primärem Standard läßt sich die Radikalkonzentration der untersuchten Substanz ermitteln. Zur Bestimmung der Fehlergrenzen des Verfahrens wurde die Konzentrations‐ und Temperaturabhängigkeit der Radikalkonzentration cR von DPPH‐Proben innerhalb weiter Grenzen untersucht. Die Standardabweichung war kleiner als ± 10%.

Die Methode wurde dazu verwendet, die Konzentrations‐ und Temperaturabhängigkeit des Radikalgehalts γ von Proben aus Tri‐p‐biphenylylmethyl (TBM) in Toluol bzw. Benzol zu bestimmen. Die Darstellung der Radikallösungen erfolgte in einer abgeschmolzenen Apparatur unter Stickstoff durch Umsetzung von Tri‐p‐biphenylyl‐methyl‐chlorid mit Silberpulver. Die Einwaagekonzentration des Radikals c0 wurde aus der Menge des eingesetzten Chlorids und seinem Enthalogenierungsgrad ermittelt.

Der Radikalgehalt der Probe γ = cR/c0 ist – in übereinstimmung mit älteren Messungen auf der magnetischen Waage – innerhalb der Fehlergrenzen temperaturunabhängig. Daraus folgt, daß TBM in Lösung nicht assoziiert ist und als monomeres Radikal vorliegt.

Der Radikalgehalt aller ESR‐spektroskopisch untersuchten Proben war γ < 1. Das Radikaldefizit kann nicht auf Assoziation, Lösungsmitteleinschlüsse in der Probe oder auf anomalen Diamagnetismus des Radikals (Selwood‐Effekt) zurückgeführt werden. Der Selwood‐Effekt ist auszuschließen, da ESR‐spektroskopisch nur die paramagnetische Suszeptibilität erfaßt wird. Wir nehmen an, daß Sekundärreaktionen für das Radikaldefizit verantwortlich sind.
Study of Dye Sensitization Effects at the ZnO Anode by Noise and Pulsed Light Measurements
Authors: Gomes W. P. , Cardon F.
Published: March 2014

The sensitization of the anodic current at the ZnO single crystal/electrolyte interface by optically excited xanthene dyes was studied by means of noise and pulsed light measurements. A discussion is given of the possible reaction mechanisms involved in the anodic oxidation of the sensitizing dye molecules. From the experiments, quantitative conclusions are drawn concerning the time constants associated with the different reaction steps.
The Effect of Illumination on the Anodic Dissolution of Cadmium Sulphide in the Presence of a Redox System
Authors: Sitabkhan F.
Published: March 2014

An electrochemical cell —

Indium|CdS monocrystal|Electrolyte|Pt

was used to study the transfer of electrons and ions through the interface CdS/electrolyte using the current‐voltage relationship in the dark and under illumination with 480 nm light. During illumination with light of wavelength less than 510 nm electron‐hole pairs will be generated. The electrons from the sulphide ion and/or electrolyte ions adsorbed on CdS, can recombine with the holes and the remaining electrons from this recombination enter the conduction band as free charge carriers. The presence of quinhydrone prevents the neutralization of sulphide ions in the surface and the anodic dissolution of CdS under illumination is reduced.
Stabilisierung des Additionskomplexes bei der Reaktion O + C2H4
Authors: Eusuf M. , Wagner H. Gg.
Published: March 2014

Bei der Reaktion von Sauerstoffatomen mit Äthylen entsteht mit steigendem Druck zunehmend mehr Azetaldehyd. Äthylen‐Oxid konnte bis zu einem Druck von 80 atm nicht nachgewiesen werden. Die Druckabhängigkeit der Azetaldehydausbeute läβt sich mit einer „Lebensdauer”︁ des Additionskomplexes C2H4O* von ≥ 0,5 . 10‐10 sec deuten. Es wird angenommen, daβ die Stabilisierung über elektronisch angeregtes Azetaldehyd erfolgt.
Experimental Investigation of the Effect of Pressure on the Viscosity of Water in the Temperature Range 10–150°C
Authors: Kestin J. , Khalifa H. E. , Sookiazian H. , Wakeham W. A.
Published: March 2014

The paper describes the design and operation of an instrument for the measurement of the viscosity of liquids in the temperature range 10–150°C and the pressure range 0,1–30 MPa. Measurements of the viscosity of liquid water under these conditions are reported. The instrument is of the oscillating‐disk type and its design has been carried out with due regard to the theory of its operation and other, physical, constraints so as to optimize the precision of the viscosity measurements for water and aqueous solutions of inorganic salts. In addition, the experimental measurements of the logarithmic decrement and period of the disk oscillations have been reduced to the electronic measurement of time so that the experimentally realizable precision is made commensurate with the theoretical expectation. — The physical limitations imposed by size, measurement capability and corrosion resistance have precluded the possibility of absolute measurements of viscosity with the present instrument. Nevertheless, the availability of accurate values for the viscosity of water in the temperature range 0–100°C at a pressure of 0.1 MPa and in the range 100–150°C at its saturation vapor pressure, has allowed an accurate determination of the edge correction factor for the oscillating‐disk assembly to be made. In turn, precise determinations of the viscosity of liquid water over the entire temperature range 10–150°C and pressure range 0,1–30 MPa relative to this calibration have been performed. It is estimated that the precision of the present measurements is one of ±0.2%, which is consistent with their reproducibility, and that the accuracy of the final reported viscosities is ±0.3% up to 40°C deteriorating to ±0.5% at 150°C. — The experimental data are compared with the correlation promulgated by the Eighth International Conference on the Properties of Steam. The standard deviation is one of only ±0.3%, which is within the error band of the international correlation. Owing to the high precision of the present experimental results, they are to be preferred. — A correlation of the present experimental data is provided which reproduces the tabulated viscosities to within their estimated uncertainty. The correlation has been developed in the form η = η (P, T) wherein pressure and temperature are the independent variables. The choice is preferable to a correlation in terms of density and temperature from the viewpoint of practical application.
Calculation of the Structure of Laminar Flat Flames I: Flame Velocity of Freely Propagating Ozone Decomposition Flames
Authors: Warnatz J.
Published: March 2014

A method is described which allows to include complete multicomponent formulation of diffusion and heat conduction in the solution of the time‐dependent conservation equations of a laminar flat flame. Calculations with simplified transport models are presented for comparison. — For the ozone decomposition flame this method is used for the determination of the flame velocity of freely propagating flames as a function of the initial ozone oxygen ratio. There is agreement with experimental values. Discrepancies between calculated results given in the literature and those of experiments are explained.
Bestimmung der Standardbildungsenthalpien von ClNO3, Cl2O und ClO2
Authors: Alqasmi R. , Knauth H.‐D. , Rohlack D.
Published: March 2014

Thermochemische, bei 298 K durchgeführte Messungen an den Gasreaktionen

und

liefern übereinstimmende Werte für die Standardbildungsenthalpie von ClNO3: ΔBH0298,15/kJ mol−1 = 26,4 ± 0,8. Über die Messungen an den Gasreaktionen

und

wurden die Standardbildungsenthalpien von Cl2O und ClO2 ermittelt: \documentclass{article}\pagestyle{empty}\begin{document}$ \Delta ^{\rm B} H_{298,15\left({{\rm Cl}_{\rm 2} {\rm O}} \right)}^0 {\rm /kJ}\,{\rm mol}^{ - 1} = 81,4 \pm 1,7,\Delta ^{\rm B} H_{298,15\left({{\rm ClO}_{\rm 2} } \right)}^0 {\rm /kJ mol}^{ - 1} = 93,3 \pm 2,1. $\end{document}
Der Einfluß der Lage der Fermi‐Energie auf das Mischungsverhalten von Palladium/Aluminium‐Legierungen
Authors: Schaller H. J.
Published: March 2014

Durch Messungen der elektromotorischen Kraft an galvanischen Zellen, die einen CaF2‐Elektrolyten enthielten, wurde die Aktivität von Aluminium in Pd/Al‐Legierungen zwischen 700 und 800°C bestimmt. Die Ergebnisse konnten durch ein unabhängiges Verfahren, das der Reduktion von Al2O3mittels eines H2– H2O‐Gemisches in Gegenwart von Palladium bei 1000°C, ergänzt und bestätigt werden. – Die Aluminium‐Aktivitäten weisen stark negative Abweichungen von der Raoultschen Geraden auf; so beträgt die relative partielle freie Exzeßenthalpie des in unendlicher Verdünnung gelösten Aluminiums −260 kJ/mol bei 700°C. – Zwischen den thermodynamischen und den elektronischen Eigenschaften zahlreicher Palladium‐Legierungen besteht eine enge Korrelation. Für die unendlich verdünnte Lösung in Palladium ist die relative partielle freie Exzeßenthalpie durch die Lage des Fermi‐Niveaus und die Wertigkeit der zulegierten Komponente bestimmt. Dies verdeutlicht den dominierenden Einfluß der Ladungsverschiebung auf die Mischungseigenschaften beim Zulegieren von Elektronendonatoren zum Palladium
The Adsorption of Hydrogen on Carbon Monoxide Covered Nickel Films. Part I: Isotherms, Change in Resistivity and in Work Function
Authors: Papp H.
Published: March 2014

The adsorption of H2 on CO‐covered Ni films was investigated in the temperature range of 77 to 273 K by means of measuring the change in resistivity, the change in work function, isotherms and isosteric heats of adsorption. – At 77 K molecular H2 is only physically adsorbed on a CO covered Ni film with a minor increase in resistivity. H2, atomised by a hot tungsten filament, is readily adsorbed on a CO layer at 77 K, the accompanying change in work function is −1.45 eV. – Molecular H2 is adsorbed on a CO‐covered Ni film in the temperature range of 180 to 273 K with a decrease in resistivity and a temperature dependent decrease in work function. The maximum change in work function is −80 mV at 185 K and 5 · 10−2 Pa. The initial isosteric heat of adsorption of H2 is 36 ± 2 kJ/mol, which decreases slowly with increasing coverage.
Enthalpy of Mixing of Chlorobenzene, 1,2‐Dichlorobenzene, and 1,3‐Dichlorobenzene with Some n‐Alkanes
Authors: Wilhelm Emmerich , Inglese A. , Grolier J.‐P. E. , Kehiaian H. V.
Published: March 2014

A dynamic microcalorimeter of the Picker design has been used to measure enthalpies of mixing of nine binary mixtures composed of chlorobenzene, of o‐dichlorobenzene, and of m‐dichlorobenzene, with each of the three alkanes, n‐heptane, n‐nonane and n‐tetradecane. Experiments were performed in the discontinuous mode at 298.15 K and atmospheric pressure, covering the whole concentration range. For 7 ⩽ n ⩽ 14 (n denotes the number of C‐atoms of a n‐alkane), the maximum excess enthalpy HEmax increases with increasing n for the chlorobenzene series, whereas for both the o‐ and m‐dichlorobenzene series a small decrease is observed. In all three cases this dependence on n is approximately linear:
Cl35/Cl37 Isotope Effects in the Fragmentations of Metastable Perchlorinated Alkane‐ and Silane‐Ions
Authors: Potzinger P. , Basu S.
Published: March 2014

Metastable transitions in the substances CCl4, CCl4, C2Cl6, SiCl4, and Si2Cl6 have been measured by the MIKE method. For the most intense transitions isotope effects as well as relative translational energies of the products have been determined. In all cases a normal isotope effect was observed. The kinetic isotope effects range from 1.9 in case of a simple Cl elimination from SiCl+4 to values close to 1 in complex molecular elimination processes. For fragmentations into products consisting of non radical species a large kinetic energy release was observed presumably due to an energy barrier in the potential energy surface.
Trends and Systematics in Mineral Thermodynamics
Authors: Navrotsky Alexandra
Published: March 2014

The stability of complex oxide and silicate phases can be understood in terms of equally important contributions of energy and entropy effects. The change in coordination number at high pressure in silicates has a profound effect on thermodynamic properties. Properties of spinel solid solutions can be systematized using a refined cation distribution model, while those of solid solutions involving no cation redistribution can be correlated with the volume mismatch of the end‐members for a wide variety of structures and compositions. Ordering and exsolution in complex solid solutions is an important feature.
Bifurkationen bei Stoßwellenereignissen
Authors: Jakubith Manuel
Published: March 2014

Dynamic deformation of solid materials by shock‐waves is described qualitatively in terms of bifurcation theory. The onset of shock‐wave metamorphoses like formation of planar elements, diaplectic glasses and high‐pressure phases is therefore caused by branching of lattice atoms and the bifurcation of physical states respectively. An evidence is given by the discussion of photoelectron spectra of recovered shock treated enstatite.
Partielle molare Größen binärer Grandit‐Mischkristalle
Authors: Wassermann A. , Fehr K. T. , Huckenholz H. G.
Published: March 2014

Properties of partial molar volumes, activities, activity coefficients, mixing free energies, and excess free energies of grossular (Ca3Al2Si3O12) in solid solution with andradite (Ca3Fe2+3Si3O12) and of grossular in solid solution with uvarovite (Ca3Cr2Si3O12) are derived from phase equilibria data. All specific properties show a non‐ideal behaviour. Positive deviations from ideality is demonstrated for excess free energy data within the grossular rich portion of the grossular – andradite and grossular – uvarovite solid solution as well. These results are in accordance with experimental results and petrographic observations.
Point Defects in Oxide Solid Solutions (IV). Correlated Diffusion of Cations and Vacancies in (Co, Mg)O‐Mixed Crystals
Authors: Schnehage M. , Dieckmann R. , Schmalzried H.
Published: March 2014

Magnesium tracer diffusion coefficients have been determined experimentally for the oxide solid solution (CoxMg1 ‐x)1 ‐ δO as a function of temperature and compositionx.2612Mg was used as the stable tracer isotope and analysed by mass spectrometry. Combination of these data with previously obtained data on Co‐tracer diffusion allowed to explain quantitatively the pronounced correlation effects during cation diffusion and to calculate the individual jump frequencies of the cations. Finally, chemical diffusion coefficients of the vacancies are derived and compared with data from relaxation experiments.
Raman Scattering: Fast Axial Rotation of Methylhalides and Acetonitrile in the Liquid State
Authors: Gompf J. , Versmold H. , Langer H.
Published: March 2014

The temperature dependence of the degenerate methyl stretching Raman profiles of CH3CN, CH3I, CD3I, CH3Cl, and CH3F and, further, for CH3CN the pressure dependence are investigated. The Raman bands are analysed in terms of the small angle diffusion and the J‐diffusion model both with and without Coriolis interaction. The comparison with the small angle diffusion model is carried out in the frequency domain. For the analysis in terms of the J‐diffusion model, first experimental orientational correlation functions are calculated. Then, by following theoretical arguments, the overall correlation function is decomposed into two partial correlation functions g(2)1(t) and g(2)2(t). There is limited agreement with previous magnetic relaxation studies on the fast axial spinning motion. In particular, it is found that the partial correlation function g(2)2(t) shows little temperature and pressure dependence, which cannot satisfactorily be accounted for by the existing models.
Pulse Radiolysis Investigation of Diene Radical Cations
Authors: Mehnert R. , Brede O. , Cserép Gy.
Published: March 2014

Monomer and dimer radical cations of isoprene, eis‐ and trans‐1,3‐pentadiene, 1,3‐cyclohexadiene, 1,4‐cyclohexadiene, and 1,5‐cyclooctadiene were observed in n‐butyl chloride solution after electron pulse irradiation. The optical absorption spectra of diene monomer radical cations obtained by pulse radiolysis compare well with spectra measured in γ‐irradiated matrices [1, 2]. Diene monomer radical cations are formed by charge transfer from n‐butyl chloride radical cations

with rate constants between 5 and 10 · 109 dm3 mol−1 s−1. From the decay of the corresponding diene monomer cation absorption rate constants of the dimerization reaction

were determined. The diene dimer radical cation bands were identified by their kinetic behaviour in a wide temperature range. Spectroscopical assignments of the absorption bands are discussed.
External Heavy Atom Effects of Counterions on Excited Aromatic Molecules in Aqueous Micellar Solutions of Cetyltrimethylammonium Salts
Authors: Wolff Thomas
Published: March 2014

Fluorescence (ϕf) and triplet quantum yields (ϕt) of anthracene, 9‐methylanthracene, 9,10‐dimethylanthracene, fluorene, indeno[2,1‐a‐]indene, and N‐methyldiphenylamine were measured by means of fluorimetry, conventional flash photolysis, and laser flash photolysis. Ethanol and aqueous micellar solutions of cetyltrimethylammonium chloride (CTAC) and of cetyltrimethylammonium bromide (CTAB) were used as solvents. ϕf values decreased while ϕt values increased when the solvent was changed from CTAC to CTAB. It could be shown that ϕf + ϕt is constant under all conditions investigated. Therefore, the results have to be explained by an external heavy atom effect of bromide counterions.
Hydrogen Absorption in Cubic Ti3Sb
Authors: Rao K. V. S. Rama , Mrowietz M. , Weiss Alarich
Published: March 2014

The absorption isotherms of hydrogen in the cubic intermetallic phase Ti3Sb were measured in the range 400 ≤ 77°C ≤ 800; 0.001 ≤ pH2/bar ≤ 0.925. The relative partial molar enthalpy of hydrogen solution at infinite dilution was found to be ΔH0H/J(K mol)−1 = −55.0 ± 1.5. The relative partial molar excess entropy of the solution at infinite dilution has been calculated to be ΔSE,0H/J(K mol)−1 = −63 ± 1, assuming the number of available interstitial sites per metal atom to be 0.75. The results are compared with data on other similar titanium alloys.
Electrical and Magnetic Properties of Molten Tlx(AgTlSe2)1 ‐ x Alloys
Authors: Uemura Osamu , Segawa Makoto , Satow Tsuneo
Published: March 2014

The electrical conductivity, the magnetic susceptibility, and the thermoelectric power of liquid Tl‐AgTlSe2 alloys have been obtained, respectively, as a function of temperature and composition from near the liquidus temperature up to about 900°C. In the region of low Tl concentration, the temperature dependences of these electronic properties follow an Arrhenius‐type activation process where the carriers excite thermally into the extended states. In the Tl rich region, above 66.7 mol‐% Tl, the temperature dependence of the conductivity becomes extremely small at high temperature, suggesting that the metallic contribution is important in this range. The electrical conductivity shows a deep minimum around 66.7 mol‐% Tl, the value of which was measured as 4.0 Ω−1 cm−1 at 400°C. Corresponding to this behaviour, a steep diamagnetic maximum was observed in the susceptibility vs. composition curve. Furthermore, the thermoelectric power changes its sign around this composition from positive in the AgTlSe2 excess side to negative in the Tl excess side. The maximum positive value of the thermoelectric power in the vicinity of 66.7 mol‐% Tl was roughly 290 μV · deg−1 at 600°C. The asymmetric form of isotherms for these quantities around 66.7 mol‐% Tl resembles that in the related liquid Tl – Se alloys which have been examined in detail with respect to their electronic behaviour indicating that the metal‐semiconductor transition occurs at the composition corresponding to AgTl3Se2 (66.7 mol‐% Tl) in the liquid system Tl‐AgTlSe2.
Conductivity and Debye Length in Aerosol‐OT Hexane/Liquid Paraffin Solutions
Authors: van Mil P. J. J. M. , Crommelin D. J. A. , Wiersema P. H.
Published: March 2014

A new equation was derived for the calculation of the Debye length from conductance measurements in non‐polar media, taking into account the existence of triple ions. Measurements were carried out for the system dioctyl sodium sulfosuccinate (Na‐AOT) in hexane and liquid paraffin. With the equation the Debye length can also be calculated for viscous solvents (liquid paraffin) even when the concentration of Na‐AOT is too small for the conductivity to be measured.
Einfluß von Dispersion und Vorgeschichte dispersen Nickels auf dessen katalytische Eigenschaften bei der Hydrierung von Benzol, CO2 und CO
Authors: Kirch R. , Kotter M. , Riekert L.
Published: March 2014

Disperse Nickel was prepared by impregnating alumina supports of different pore‐morphologies with solutions of Ni(NO3)2 or Ni(HCOO)2, drying, and reducing with H2 either these compounds or NiO generated therefrom. The surface‐area of disperse metallic nickel in the resulting catalysts was obtained through chemisorption of hydrogen; rates of hydrogenation of benzene at 325 K and of CO2 and CO at 500 K were observed and normalized by the extent of nickel‐surface in the porous solids. — The kinetics of reduction of Ni2+‐compounds is controlled by nucleation of the metallic phase, leading to preferential formation of larger crystallites of the metal at lower temperatures. Hydrogenation of benzene is structure insensitive, whereas hydrogenation of CO2 and CO appear to be structure sensitive.
Enhancement of the Ionic Conductivity in Solid‐Solid‐Dispersions by Surface Induced Defects
Authors: Maier Joachim
Published: March 2014

The finding that dispersions of insulators such as alumina or silica in ionic conductors may exhibit considerably enhanced ionic conductivities compared to the pure material, has become a promising topic for optimizing the electric properties in solid state research. Up to now the basic mechanism for this effect is unknown, the more so since two phase mixtures of two ionic conductors have been found to show a similar enhancement. In this work space charge regions are considered as being responsible for the effect. In the case of insulators as second phases possible surface interactions are taken into account resulting in drawing mobile ions out of the boundary layers and thus increasing the vacancy concentration or in pushing mobile ions into interstitial positions. In the case of two ionic conductors with the same mobile ion, the contact equilibria demand a double effect. The concentration distributions are discussed and lead to a quantitative expression for the space charge contribution in such dispersions. These calculations are in excellent accord with conductivity data of silver chloride (+ alumina, silica) as regards temperature, concentration and particle size. Experiments from the literature are also brought into the discussion. The influence of the surface activities of alumina is tested by modifying the surface chemically. Thermodynamic data for the surface interaction are given. The maximum effect to be expected by conductivity enhancements via surface induced defects and optimization conditions are discussed.
Laser Study of the Triplet State of 4‐Nitrostilbenes in Solution; Estimation of the Equilibrium Constant (3t* ⇄ 3p*) and the Rate Constant for Intersystem Crossing (3p* → 1p). XIII1
Authors: Görner Helmut , Schulte‐Frohlinde Dietrich
Published: March 2014

Decay of the lowest triplet state of 4‐nitro‐, 4,4′‐dinitro‐, and 4‐nitro‐4′‐methoxystilbene (NS, DNS, and NMS, respectively) was studied by nanosecond laser photolysis in solution at room temperature. The triplet decays predominantly via intersystem crossing at the twisted configuration followed by internal rotation into the cis or trans ground states. Rate constants for triplet decay were determined in various solvents as a function of the concentration of ferrocene, azulene, and oxygen. Quenching by azulene and ferrocene leads only to trans isomers whereas quenching by oxygen does not markedly shift the photostationary state are room temperature. The results support the assumption of an equilibrium between the planar trans configuration (3t*) and 3p* and allows the estimation of kp and the triplet equilibrium constant K5 = k5/k−5 = [3p*]/[3t*]. K5 shows a trend to decrease with increasing solvent polarity. For NS this corresponds to a shift of the 3t* ⇄ 3p* equilibrium from — 75% of the 3p* configuration in n‐pentane to ˜25% in methanol. This shift is explained by the greater stabilization of the planar 3t* configuration by polar solvents in comparison to that of the less polar twisted 3p* configuration. The solvent dependent change in kp is less pronounced, giving average values of 3.0 · 107 and 1.7 · 107 s−1 for NS and NMS, respectively.
Phase Transition Behavior and Permeation Properties of Cationic and Anionic Artificial Lipids with Two Alkyl Chains
Authors: Kumano Atsushi , Kajiyama Tisato , Takayanagi Motowo , Kunitake Toyoki , Okahata Yoshio
Published: March 2014

Membrane structure and crystal‐liquid crystal phase transition behaviors were investigated for the water system of totally artificial lipids with cationic or anionic head group and two alkyl chains. These artificial lipids formed multilamellar liposomes composed of a bimolecular layer. The phase transition temperature from gel to liquid crystalline lamellae decreased steadily to a limiting temperature with an increase in water concentration up to the lipid fraction of 0.80 — 0.85. This kind of phase diagram means that the artificial lipids have characteristics of both thermotropic and lyotropic mesomorphisms. For the cationic artificial lipid, the thickness of the bimolecular lamella in a gel state was shorter than a bimolecular length calculated on the assumption of planar zigzag conformation of the alkyl chains. This suggests that the hydrocarbon chains in a gel state are packed with the chain axes inclined at a certain angle to the lamellar surface. The diffusive permeability of the polymer/artificial lipid composite membranes to water or ions exhibits a distinct jump in the vicinity of the crystal‐liquid crystal phase transition temperature.
NMR Studies on Hydrogen Chemisorption and Water Formation on Platinum Black Catalysts
Authors: Reinecke N. , Haul R.
Published: March 2014

Fourier Transform NMR spectroscopy has been used to study the reduction of oxygen covered Pt‐black and the chemisorption of hydrogen. The 1H Knight shift is dependent on hydrogen surface coverage and Pt particle size. T1, and T2 relaxation times were measured for adsorbed H2O and H as a function of temperature. The results are discussed with respect to the surface stoichiometry and the mechanism of the catalytic water reaction, isosteric heats of hydrogen chemisorption, estimation of metal surface areas of Pt catalysts and surface mobility of adsorbed H2O and H.
Cation Exchange on Oxide Surfaces as Influenced by Surface Hydration Phenomena. I. Alkali Metal Ions on Silica
Authors: Peschel G. , Ludwig P.
Published: March 2014

The exchange of Li+, Na+, K+, Rb+, and Cs+ with protons of surface silanol groups of a silica sol was determined by a titration method. For very small concentrations ion exchange steeply increases up to a plateau located at about 0.14 mol kg−1 ranging from about 10−4 up to 3 · 10−1 M. Whereas Na shows only a slight increase of exchange, Li+ and K+ display no detectable reaction with the silica surface in this concentration range. For higher concentrations ion exchange increases in a more normal manner. The low degree of ion exchange is interpreted by formation of a hydration sheath around the alkali cations adsorbed on the silica surface.
Depth Profiling of Hydrogen Isotopes in Metals by Elastic Recoil Detection and Nuclear Reaction Techniques under In‐Situ Conditions
Authors: Albers P. W. , Sicking G. H. , Earwaker L. G. , England J. B. A.
Published: March 2014

The application of the ERD‐technique with 2.8 MeV and 25 MeV α‐particles respectively and of the specific nuclear reaction D(d,p)T for the determination of hydrogen isotopes in metals is described in detail. — The methods were applied to hydrided and/or deuterated elements (Ti, Zr, Pd), alloys (Pd0.92Y0.08, Fecralloy, steels), intermetallic compounds (TiMn‐ and ZrMn‐Laves phases) and a Ti/Cu‐target containing all the three hydrogen isotopes. — Images are obtained about the hydrogen depth distribution in near surface regions of the materials (roughly 400 nm in case of 2.8 MeV ERD, 200 um in case of 25 MeV ERD, and 500 nm in case of D(d,p)T). By aid of standardization the hydrogen content of a number of samples was determined. Information was obtained about the presence of impurities in the specimens. Prominent results of the investigations are:

Laves‐phase systems (Ti0.4Mn0.6, Zr0.33Mn0.67) are activated for hydrogen absorption by segregation processes, whereby overlayers of Ti(Zr)‐hydride are formed. These overlayers are separated from the bulk‐hydride by a hydrogen depletion zone.

Cold‐rolled specimens (Pd, Pd0.92Y0.08) trap hydrogen in near surface states.

Surface oxidation of Fecralloy leads to an effective barrier for hydrogen‐uptake, due to the formation of Al‐oxide overlayers.
Paramagnetic probe for molecular interactions: II. 7Li NMR study of lithium cation solvation by a nitroxide radical
Authors: Kolodziejski Waclaw
Published: March 2014

LiClO4‐organic solvent‐nitroxide radical systems were studied using 2,2,6,6‐tetramethylpiperidine nitroxide radical (TMPN). The Li+‐TMPN interaction was observed by means of the 7Li NMR contact shift and the paramagnetic broadening of the 7Li NMR signal. The effects were found to be solvent dependent and were interpreted with donor and acceptor numbers of solvents. The quantitative analysis of the data was done and the formation constants, the life times and the 7Li hyperfine splitting constants of the Li+‐TMPN complexes were determined. The 7Li NMR results and the former EPR results were compared.
Small‐angle neutron scattering‐measurements on a surfactant system consisting of cationic and anionic surfactant molecules
Authors: Hoffmann H. , Kalus J. , Scbwandner B.
Published: March 2014

Results of small‐angle neutron scattering (SANS) experiments are reported on the mixed cationic anionic surfactant system Tetradecyl‐pyridinium‐heptylsulfonate (C14PyC7SO3). In the concentration range between 10 mM and 160 mM, the scattering curves show a correlation peak. The scattering vector at the correlation peaks shifts with the volume fraction of the surfactant with a power low having an exponent 0.43. The data can be explained on the basis of rodlike micelles which become shorter with increasing concentrations. For the two highest concentrations 320 and 640 mM the correlation peak disappeared. This change in the scattering curves is attributed to a change in the aggregation behaviour of the system. It is found that at these concentrations the short chain anionic surfactant bind in a one to one ratio with the anionic surfactant and the micelles are practically uncharged, while in the rodlike concentration range the dissociation degree is higher. In the concentration range of the rodlike micelles the correlation peak becomes weaker with increasing concentration.
Experimental and theoretical study of the apparent molar volumes of 1‐alcohols in linear hydrocarbons
Authors: Costas M. , Alonso M. Caceres , Heintz A.
Published: March 2014

Apparent molar volumes ϕv have been measured for twelve alcohol/alkane mixtures between XOH = 0. 001 and 0. 2 at 298. 15 K. The systems studied were: methanol + n‐C6 ethanol and 1‐butanol + n‐C1, 1‐hexanol + n‐Cn with n = 6, 10, 12 and 16, 1‐heptanol + n‐C10, 1‐decanol + n‐Cn with n = 6, 10 and 16 and 1‐dodecanol + n‐C10 ϕv shows a sharp increase for XOH < 0. 05; values found at infinite dilute are several cm3/mol larger than the pure alcohol molar volume. Experimental results are compared with predictions from the Extended Real Associated Solution (ERAS) model which takes into account associational and physical effects as well as a reaction volume Δv* for hydrogen bond formation. Without any adjusted parameter the ERAS model gives good predictions for ϕv and the excess partial molar volumes at infinite dilution ΔV∞OH. It is found that, in the concentration region studied, the associational contribution dominates ϕv; the rapid fall of ϕv, with increasing alcohol concentration is due to alcohol self‐association and a corresponding increase in molecular cohesion. At infinite dilution, the associational contribution to ΔV∞OH. is nearly constant for all alcohols and hence the observed changes in ΔV∞OH values are almost entirely due to changes on the physical term. Experimental ΔV∞OH increase for a given alcohol as the chain length of the alkane increases and decrease for a series of increasingly longer 1‐alcohols in a given alkane. These changes are reproduced by the theory and explained in terms of differences in free volume between the two components as well as the associational contribution to ΔV∞OH.
An efficient calculation procedure of predicting heat conductivities of complex gaseous mixtures
Authors: Heintz Andreas
Published: March 2014

A simplified expression for the heat conductivity of multicomponent gaseous mixtures λmix has been developed which allows to predict λmix with sufficient accuracy under conditions which occur in flame combustion processes. Several modifications of the rigorous kinetic theory have been made in order to reduce the computational effort of calculating λmix of molecular mixtures containing 50 or more components. Empirical functional of collision integrals based on the principle of corresponding states have been used rather than integrals which require the detailed knowledge of intermolecular forces. The translational contribution to λmix appearing in the Hirschfelder‐Eucken expression is essentially simplified by using an empirical expression originally developed by Mason and Saxena for monoatomic gaseous mixtures. Parameters such as collision numbers and diffusion coefficients of internal energy needed for the calculation of the internal contribution to λmix are reported for 27 gases relevant to combustion processes. The formula used for λmix of molecular mixtures has proved to describe λmix of 107 binary and 13 ternary mixtures with an average deviation of ±2. 9% and ±3. 4% respectively and is expected to predict λmix of multicomponent gaseous mixtures with similar accuracy.
Composition and thermochemistry of the equilibrium vapour of the systems NaI—FeI2 and NaI—PbI2
Authors: Hilpert K. , Gerads H. , Kobertz D. , Miller M.
Published: March 2014

The vaporization of NaI/FeI2 and NaI/PbI2 samples of equimolar composition was investigated in the temperature ranges between 574 to 683 K and 562 to 669 K, respectively, by using the mass spectrometric Knudsen effusion method. The gaseous species I. I2, Nal. (NaI)2 FeI2, (FeI2)2, FeI3, NaFel3, and Na2FeI4 (NaI—FeI2 system) as well as Nal, (Nal)2, PbI2, (PbI2)2, and NaPbI3 (NaI—PbI2 system) are present in the equilibrium vapours. The equilibrium partial pressures of these species were determined with the exception of I, I2, and Fel3. Enthalpies and entropies of dissociation resulted for the reactions magnified image as ΔdH2980 (Eq. (1)) = 184 ± 5 kJ mol−1, ΔdH2980 (Eq. (1)) = 043 ± 8 j mol−1K−1;ΔdH2980 (Eq. (2)) = 333 ± 9 kj mol−1, ΔdH2980 (Eq. (2)) = 274 ± 14 J mol−1 K−1; and ΔdH2980 (Eq. (3)) = 168 ± 5 J mol−1, ΔdH2980 (Eq. (3)) = 151 ± 9 j mol−1 K−1. Equilibrium constants for these reactions are additionally given. The pressures of NaFel3(g) and NaPb13(g) as well as their enthalpies of dissociation are discussed with respect to their significance for semi empirical rules.
Surface‐enhanced raman scattering from ethylenediaminetetraacetic acid
Authors: Lee K. A. Bunding , McLennan G. , Gordon J. G.
Published: March 2014

Surface‐enhanced Raman scattering (SERS) from ethylenediaminetetraacetic acid (EDTA, NaO2CCH2N(CH2CO2H)CH2CH2N‐(CH2CO2Na)CH2CO2H) on silver and copper electrodes is reported. There is no SERS spectrum observed for EDTA on copper electrodes. The SERS spectrum on silver is very dependent on electrolyte and laser power. In nitrate electrolyte, most of the bands typical of EDTA are observed in the SERS spectra with small wavenumber shifts and small relative intensity changes. In 0.1 mol/1 chloride electrolyte the SERS spectra show indication of decarboxylation and are nearly identical to SERS spectra of N,N,N′,N′‐tetramethylethylenediamine (TMEDA, (CH3)2NCH2CH2N(CH3)2). However, SERS spectra of TMEDA show evidence that TMEDA also reacts. SERS spectra of ethylenediamine‐N,N′‐diacetic acid show many similar bands to those found in the SERS spectra of TMEDA.
IR reflection and raman spectroscopies of the anodic oxide films on tungsten
Authors: Ohtsuka T. , Goto N. , Sato N. , Kunimatsu K.
Published: March 2014

In order to understand the mechanism of the electrochromic reaction of hydrated WO3, the oxide film formed on tungsten in sulphuric and perchloric acid solutions has been studied by in‐situ optical techniques. Ellipsometric measurements reveal that the optical property of the film changes from a transparent substance to a coloured substance at a potential of E = 0.50 V (vs. RHE). The IR reflection absorption Spectroscopy (IRRAS) shows that the anodic oxide film is strongly hydrated forming two types of OH bonds, one corresponding to the incorporated H2O and the other to the OH bonded with tungsten ion. The Raman Spectroscopy (RS) shows that the anodic oxide film is an amorphous form of hydrated tungsten oxide including a terminal W(VI) = O bond. The mechanism of electrochromic reaction is discussed on the basis of IR and Raman spectra which change as the potential shifts from the transparent state to the colouring state. The electrochromic process may start with a reaction between the terminal W = O and the incorporated H2O: W(VI) = O + H2O(film) + e → W(V) — OH + OH−(film) The OH−(film) formed reacts in the film with H+ injected from the acid aqueous solution.
The anodic formation of lead iodide. Evidence for the underpotential deposition of a reversible monolayer
Authors: Tan Ah Chin , Wright Graham A.
Published: March 2014

The electrocrystallisation of Pbl2 has been studied using cyclic voltammetry at a rotating disk electrode of polycrystalline lead. A small anodic peak, corresponding to formation of a monolayer of PbI2, was observed. The anodic charge of 170 μC/cm2 was independent of pH, iodide concentration, potential sweep rate and electrode rotation rate. Reversal of the potential sweep gave a cathodic peak at the same potential and with the same charge and peak current; this is good evidence for the reversible formation of the monolayer, which was shown to obey the Langmuir isotherm. The monolayer appeared at an underpotential of −65 mV with respect to the reversible potential of crystalline PbI2, and this can be explained by the reduction of surface tension which occurs when the solid electrode is covered by a monolayer. At higher potentials a porous film of crystalline PbI2 was formed by a dissolution‐precipitation mechanism, with the monolayer acting as the precursor for lead(I1) iodo‐complexes.
The influence of anions on the structure of underpotentially deposited Cu on Au(111): A LEED, RHEED and AES study
Authors: Zei M. S. , Qiao G. , Lehmpfuhl G. , Kolb D. M.
Published: March 2014

The underpotential deposition of Cu onto Au(111) in different electrolytes has been investigated by LEED, RHEED and AES. Ordered layers of (√3 × √3) R30° and (2.2 × 2.2) type were found for Cu at medium coverages in sulfate and perchlorate solutions, respectively. The formation of different superstructures in different electrolytes is caused by the specific adsorption of the anions.
Charge transfer kinetics at semiconductor electrodes
Authors: Memming R.
Published: March 2014

In the present paper various factors influencing the kinetics of charge transfer processes at semiconductor electrodes are described. It is shown that the interfacial currents can be determined by the interfacial kinetics as well as by the transport of electrons and holes through the space charge layer. In the case of minority carriers created by light excitation the corresponding photocurrent‐potential dependence is frequently influenced by minority carrier trapping at the interface. In addition the influence of surface chemistry such as e.g. oxide formation is demonstrated for some photoelectrochemical reactions. Various models are presented and discussed in detail.
Behaviour of surface intermediate states in anodic O2 evolution electrocatalysis at Co3O4 on Ni and Ti substrates
Authors: Conway B. E. , Liu T. C.
Published: March 2014

Determination of the behaviour of the adsorbed species that are the kinetically‐involved intermediates in multi‐step Faradaic reactions of the electrocatalytic type has remained an undeveloped area of electrode kinetics, yet is important in the evaluation of electrocatalysis and reaction mechanisms of electrode processes as a function of current‐density (i) and electrode potential (V). — From values of the complementary derivatives dV/d log i, AV(t)/d log t and dV(t)/d log [—dV(t)/dt], obtained from potential‐relaxation measurements, the electrochemical behaviour and change of steady‐state coverage with potential of the intermediate states in the OER at Co3O4 is derived. The behaviour observed is related to changes of oxidation state of the bulk oxide and its surface region. — The observed potential‐relaxation and a.c. impedance behaviour is different at Co3O4 on Ni and Ti substrates. It is clearly shown that this effect arises from the additional component of impedance at the interface which is introduced by the presence of a thin underlying oxide film of TiO2 on the Ti, on which the Co3O4 film is formed. These observations have practical interest regarding preparation of composite electrocatalytic surface films on Ti substrates. Over most of the potential range studied, however, the mechanism and electrode kinetic characteristics of the OER are the same for the two metal substrates. — The O2 evolution kinetics and associated potential‐relaxation behaviour on open‐circuit, following current interruption, are determined by two pseudo‐capacitances: one arising from the potential‐dependent state of oxidation of metal ions in the oxide film and a second, coupled contribution from the potential‐dependence of coverage by OH/O intermediates on the oxide film.
Analysis and Thermochemistry of the Equilibrium Vapour of the Nal‐SnI2 and ScI3‐SnI2 Systems
Authors: Miller M , Hilpert K.
Published: March 2014

The NaI‐SnI2 and ScI3‐SnI2 systems were investigated under equilibrium conditions in the temperature ranges between 620 K to 840 K and 726 K to 873 K, respectively, by using a mass spectrometer coupled with a two compartment Knudsen cell. The gaseous species NaI, (NaI)2, SnI2, NaSnI3 (NaI‐SnI2 system) as well as ScI3, (ScI3)2, SnI2, ScSnI5 (ScI3‐SnI2 system) are present in the vapours. Their partial pressures were employed in a second‐law evaluation. The enthalpy and entropy changes of the dissociation reactions

NaSnI3(g) ⇌ NaI(g) + SnI2(g) (1)

and

ScSnI5(g) ⇌ ScI3(g) + SnI2(g) (2)

as well as of the reactions for the vapour transport of Na or Sc

NaI(s) + SnI2(g) ⇌ NaSnI3(g) (3)

and

ScI3(s) + SnI2(g) ⇌ ScSnI5(g) (4)

resulted as ΔdH0298 (Eq. (1)) = 166 ± 5 kJ mol−1, ΔdS0298 (Eq. (1)) = 144 ± 7 J mol−1 K−1; ΔdH0298 (Eq. (2)) = 172 ± 8 kJ mol−1, ΔdS0298 (Eq. (2)) = 181 ± 11 J mol−1 K−1; ΔrH0298 (Eq. (3)) = 25 ± 3 kJ mol−1, ΔrS0298 (Eq. 3)) = −1.3 ± 4 J mol−1 K−1; and ΔrH0298 (Eq. (4)) = 94 ± 6 kJ mol−1, ΔrS0298 (Eq. (4)) = 47 ± 7 J mol−1 K−1. The equilibrium constants for these reactions are also given. The data are discussed with respect to their significance for chemical vapour transport and for semi empirical rules used to predict the dissociation enthalpies of gaseous heterocomplexes.