bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zur infrarotspektroskopischen Bestimmung von Adsorptionswärmen
Authors: Ramstetter A. , Baerns M. 
Published: March 2014

AbstractHeats of adsorption of gaseous methylcyclopentane, maleic anhydride, buten‐1, butadiene and furane on V2O5/P2O5 impregnated alumina were determined by infrared spectroscopy from the temperature dependence of the intensity of selected infrared bands and from the frequency shift of hydroxyl groups of the adsorbent. The measured heats of adsorption are in good agreement with values obtained by a gaschromatographic method. The determination of heats of adsorption from the temperature dependence of intensities of selected infrared bands is also applicable when different surface complexes are simultaneously formed.
The Ratio of Interlamellarly Fixed Water to Bulk Water Used as Quality Criterion in O/W Creams
Authors: Junginger H. 
Published: March 2014

AbstractO/W creams with crystalline gel structures are supposed to be four phase systems. Their dominant structural elements are the hydrophilic and lipophilic gel phases. The hydrophilic gel phases have — depending on the hydrophilic character of their polar groups — a very strong swelling capacity. Further, a dynamic equilibrium is maintained between the water interlamellarly inserted into the hydrophilic gel phase and the bulk water phase. The latter is mainly fixed mechanically by the hydrophilic gel phase. — The lipophilic gel phase, however, which immobilize the dispersed phase, have no or only an extremely weak swelling capacity. By means of thermogravimetry (TG) a quantitative differentiation between water interlamellarly fixed in the hydrophilic gel phase and bulk water is possible. — It is concluded that the ratio of interlamellarly fixed water and bulk water is an important criterion for the properties of O/W creams and that TG can be suitably applied not only as in process control during product manufacturing but also as a useful tool in the development of O/W creams with a controlled water release. During physical ageing of O/W creams the ratio of interlamellarly fixed water and bulk water is shifted towards the bulk water phase.
Messungen der dielektrischen Relaxation in Aerosol‐OT/H2O/Cyclohexan‐Lösungen
Authors: Henze R. , Schreiber U. 
Published: March 2014

AbstractThe complex relative dielectric permittivity of Aerosol‐OT(AOT)/water/cyclohexane solutions has been measured within the frequency range 5 kHz‐ 10 GHz. The investigated solutions were of oil‐rich type with variing AOT‐ and water content. A marked dielectric relaxation has been found. The dielectric increment as well as the conductivity steeply increase with the water content, while the relaxation time decreases. The results are consistent with a theoretical model of a heterogeneous dielectric consisting of ellipsoidal shaped, conductive inclusions in a nonpolar, low conductive solvent.
Mizellare und mesomorphe Strukturen in wäßrigen Polyglykoletherlösungen 2. Mitteilung [1]
Authors: Heusch R. 
Published: March 2014

AbstractThe phase diagram of the reaction product of p‐tert‐octyl‐phenol with 7–8 mole ethylene oxide (®Triton X‐l 14) and water and of mixtures of oleic acid amide heptaglycol ether with water show that mesomorphous structures are existent down to the range of the CMC. — In the miscibility gaps of the phase diagrams, lamellar structures occur in the surfactant‐rich phases, of which photographs taken with the polarizing and electron microscope are shown. These lamellae can store considerable quantities of foreign substances. They can, for example, store hydrophobic proteins while the hydrophilic proteins remain behind in the aqueous phase. In this way, it is possible to easily separate hydrophobic proteins form hydrophilic ones. — It is shown that a miscibility gap is formed in polyglycol ether/water systems through a dehydration of water‐soluble hydrate structures, which are stable in the solution below the miscibility gap. Split miscibility gaps are formed through a stepwise dehydration of the water‐rich hydrate structures.
Flow Birefringence Measurements on Viscoelastic Surfactant Solutions
Authors: Löbl M. , Thurn H. , Hoffmann H. 
Published: March 2014

AbstractRheological and flow birefringence measurements both in the oscillating and in the constant shear rate mode were carried out on mixtures of aqueous solutions of Tetradecylpyridiniumsalicylate and Tetradecyltrimethylammoniumsalicylate. In these mixtures the flow behavior varies from purely viscous to strong elastic. Experimental evidence for the theoretically predicted validity of the linear stress optical law in viscoelastic detergent solutions containing rodlike particles is given. Furthermore it is found, that the stationary and dynamic viscoelastic behavior of the systems under consideration can be described by a single relaxation time according to the Maxwell model. A comparison with data from micellar kinetics shows, that the macroscopic flow behavior of these solutions is determined and controlled by the chemical relaxation time of the micellar structures. This chemical relaxation time varies about two orders of magnitude in the mixtures while the shear modulus G0, which is determined by the number density of the rod‐like micelles, remains approximately constant.
Physikalisch‐chemische Grundlagen der Phosphat‐Substitution in Waschmitteln
Authors: Schwuger M. J. 
Published: March 2014

AbstractWith the beginning of the 60's world‐wide investigations on phosphate substitution in detergents were conducted. The reason for these studies was the eutrophication of seas by phosphates. The solution of this problem was seriously influenced by ecological, toxicological, application and performance properties as well as by economic aspects. — All demonds for a suitable phosphate substitute were met by the water‐insoluble, finely dispersed, ion‐exchanger zeolite A. In the meantime zeolite A is introduced into detergents in many countries. In 1983, in the Federal Republic of Germany a completely phosphate‐free, zeolite A‐containing detergent was introduced in the market. — This study is concerned to the physicochemical backgrounds of this substitution with special emphasis to effects of zeolite A. Under certain circumstances zeolite A‐containing detergents are safer than conventional phosphate products.
Potential Dependence and Time Evolution of the Double Layer Structure and Topography of Silver Electrodes Part II: Roughened Silver Films
Authors: Waser Rainer , Weil Konrad G. , Wiese Harm 
Published: March 2014

AbstractSilver films were electrochemically roughened by oxidation/reduction cycles in different solutions. — Aging of these films in contact with electrolyte solution was monitored for various potentials by means of double layer capacitance measurements. No specifically adsorbable species were present during the aging process. The surface flattening taking place is strongly dependent of the initial microstructure developed during the roughening cycle. — The influence of traces of dissolved oxygen as the main “impurity” was studied in detail. The capacitance/potential curves indicate a pH dependent adsorption/desorption of the superoxide ion O2−. The effect of this process on the mechanism of the O2‐reduction is discussed.
Hyperfiltration of Acetonitrile/Water Mixtures Through Ion Exchange Membranes: Influence of Selective Solvation of Counterions on Selectivity
Authors: Philippsen Elke , Woermann D. 
Published: March 2014

AbstractIt is shown that the transport properties of ion exchange membranes in hyperfiltration experiments with acetonitrile/water mixtures are determined by the selectivity of solvation of the counterions by the components of the mixture.
Oxide Solid Solutions and its Internal Reduction Reactions
Authors: Schmalzried H. 
Published: March 2014

AbstractIn analogy to the internal oxidation of oxide solid solutions, the internal reduction of oxide solid solutions is investigated. The kinetics of internal reactions are formally analyzed, and it is shown experimentally that these reactions in the reduction mode do occur as predicted. In the case of internal reduction of transition metal oxide solid solutions of the type (A, B) O, often fast diffusion paths determine the evolution of the reaction morphology.
Mechanistic Studies with Mass Spectroscopic Cyclic Voltammetry: Anodic Oxidation of Hydroxylamine on Pt
Authors: Karabinas P. , Wolter O. , Heitbaum J. 
Published: March 2014

AbstractThe anodic oxidation of NH2OH on Pt in neutral and acid solutions was studied using CV, RRDE and Mass Spectroscopic Cyclic Voltammetry. Thus, the i/ϕ‐curves obtained could be correlated to the rates of formation of the gaseous products N2, N2Ot NO and NO2. Three anodic waves were distinguished, each representing 2e‐processes as concluded from the products NOH, NO2− and NO3− belonging to the respective wave. NO is a side product formed by anodic oxidation of NOH within the raising part of the second wave. A detailed mechanism is proposed on the basis of these findings.
Sonolysis of Chloroform
Authors: Henglein A. , Fischer Ch.‐H. 
Published: March 2014

AbstractChloroform is decomposed by irradiation with ultrasonic waves to yield a large number of products. The major products are various unsaturated compounds. Decomposition occurs only in the presence of a monoatomic‐ or diatomic gas. Free radicals and carbenes are postulated as intermediates of sonolysis which can only be scavenged by volatile additives such as O2 or c‐hexene. In the presence of 10% c‐hexene, the rate of sonolysis of chloroform is increased and various additional products are formed. Pure c‐hexene is decomposed at a much lower rate than chloroform. The sonolysis of chloroform proceeds at a rate comparable to that of water.
Small Angle Neutron Scattering Measurement on a Micellar Solution of Dodecylammonium‐Trifluoro‐Acetate
Authors: Hoffmann H. , Kalus J. 
Published: March 2014

AbstractSmall angle neutron scattering experiments (SANS) were carried out at 25°C with solutions of dodecylammonium‐trifluoroacetate (DATFA, C12H25NH3CF3CO2) in pure D2O. The concentration of the DATFA solutions was varied between 10 and 160 mM. The isotropic solution borders on a liquid crystalline phase of the lamellar type which begins at around 200 mM. The scattering intensity as a function of the scattering angles could be fitted on the basis of spherical or ellipsoidal vesicles with an appreciable variance in the diameter or axes respectively. Between 40 and 80 mM a major change of the shape of the micelles was established.
Absolute Rate Coefficients in IR‐Photochemistry: Simple Estimates of the Rate Constant from Molecular Parameters
Authors: Lupo Donald W. , Quack Martin 
Published: March 2014

AbstractA simple analytical expression for the steady state IR‐photochemical rate coefficient k(st) is presented, which has been obtained by semiempirical extension of statistical limiting cases and fitting to results of exact statistical model calculations. The analytical expression predicts k(st) values in good agreement with exact model results. The effect of specific unimolecular dissociation rates on k(st) is discussed.
Cationic motions and phase transitions in solid [(CH3)4N]2MX4 (M = Pd, X = Cl, Br; M = Pt, X = Br) complexes as studied by 1H NMR, differential thermal analysis, and X‐ray powder diffraction techniques
Authors: Sato Setsuko , Ikeda Ryuichi , Nakamura Daiyu 
Published: March 2014

AbstractThe temperature dependences of 1H spin‐lattice relaxation time, T1, differential thermal analysis, DTA, and X‐ray powder diffraction at and above room temperature were observed for tetramethylammonium tetrachloropalladate(II), tetrabromopalladate(II), and tetrabromoplatinate(II). At room temperature, the three complexes form isomorphous tetragonal crystals. Unusual solid‐solid phase transitions which were sensitive to moisture were found for the two tetrabromo complexes above room temperature. X‐ray powder patterns taken at various temperatures above room temperature for both complexes disclosed that the crystal structure determined for the samples once heated above transition temperatures was different from the above one determined at room temperature prior to the heating treatment. For the tetrachloro complex, 1H T1 curve observed is similar to the normal BPP curve except for a shoulder appearing on the hot side. Each tetrabromo complex yielded three different kinds of stable phases, i.e., the room, intermediate, and high temperature phases and additionally the supercooled metastable states of the latter two phases. The existence of two crystallographically nonequivalent cations is suggested for both bromo complexes in each intermediate metastable state. From the analysis of 1H T1 data obtained, motional parameters were determined for the cation in the crystals.
The thermal conductivity of liquid methane
Authors: Mardolcar U. V. , Nieto Castro C. A. De 
Published: March 2014

AbstractThis paper presents new measurements of the thermal conductivity of liquid methane at 110, 125, 155 and 180 K and pressures up to 10 MPa obtained with a transient hot wire equipment. The instrument is capable of measuring the thermal conductivity of fluids with an accuracy of ± 0.5% in all the thermodynamic states far from the critical region. — A reliable scheme for the interpolation and extrapolation of the thermal conductivity of liquid methane is presented. Values for the thermal conductivity of liquid methane along the saturation line were obtained, with an estimated accuracy better than 1%.
Der Einfluß der Nahordnungsstruktur auf die chemischen Verschiebungen der Aromatenprotonen in flüssigen Mischungen von Acetonitril mit 5 aromatischen Lösungsmitteln
Authors: Boyadjiev Borislav 
Published: March 2014

AbstractThe proton chemical shifts of benzene, thiophene, pyridine, pyridazine and pyrimidine were measured at 298 K as a function of concentration in acetonitrile. The susceptibility values that are needed to correct the chemical shifts were evaluated according to a nmr method. The local structure of the mixtures were interpreted by using the model of hard convex bodies, assuming the predominance intermolecular repulsive forces at high densities. So it was possible to calculate the contact values of the pairdistribution function. The derivatives of these contact values were compared with the derivatives of the chemical shifts as a function of concentration. — This allows to identify different local structurs around the protons of the aromatic molecule.
The effects of pH and adsorbed hydrolysed metal ions on the photodissolution of colloidal cadmium sulphide
Authors: Hayes Robert , Freeman Pamela A. , Mulvaney Paul , Grieser Franz , Healy Thomas W. , Furlong D. Neil 
Published: March 2014

AbstractThe quantum yields for the photodissolution of colloidal CdS in Ludox stabilized aerated solutions, have been measured as a function of pH. It has been found that the quantum yield decreases with increasing pH. Electrophoresis measurements indicate that this decrease is due to the formation of Cd2+ hydrolysis products on the surface of the colloid as the pH is increased. Support for this conclusion is obtained from experiments in which hydrolysed Co11, Ni11 and Zn11 species were deliberately deposited onto CdS colloids. The reactions involved in the photocorrosion of CdS are discussed in light of the present results and with respect to mechanims proposed in the literature.
Recent developments in double layer theory
Authors: Carnie Steven L. 
Published: March 2014

AbstractRecent developments in the theory of the double layer are discussed with special emphasis on results for the Primitive Model double layer obtained since 1984 and computer simulations of the behaviour of water near surfaces. Recent results for the HNC/HNC theory of the Primitive Model double layer are compared with two new approaches, which allow ion‐ion correlations to change in response to a varying surface charge. Both new approaches appear very promising, and herald the imminent completion of this phase of double layer research. Computer simulation studies of point‐charge models of water near simple, non‐polar surfaces are then reviewed. The paper finishes with a look at the limited simulation results for water near polar surfaces and aqueous electrolyte at a non‐polar surface, studies which presage a new stage of double layer theory — the simulation of the metal/aqueous electrolyte interface.
Electrical double layer forces in thin interlayers between macroscopic bodies of different materials when being immersed in electrolyte solutions
Authors: Peschel Gerhard , Keldenkh Jorg 
Published: March 2014

AbstractDouble layer forces arising in thin liquid interlayers between two solid plates are determined by using a special device by which a spherically formed plate is pressed against a planar one when both plates are immersed in an electrolyte solution to be tested. The plates are manufactured from fused silica and rutile, respectively. The faces of the plate couples are provided with a high‐grade politure with a remaining roughness not exceeding the order of 1 nm. For one plate couple made of fused silica the faces are covered by a thin layer of chromium. As the fluid test medium aqueous and ethanolic solution of NH4CI and NH4Br, respectively were used. Emphasis was laid on determining the decay lengths of the double layer forces and comparing them with the values derived from theory.
Optically generated space charge layer in insulators: Electrolyte electroreflectance at the BiI3/electrolyte interface
Authors: Hüsser O. E. , von Känel H. 
Published: March 2014

AbstractElectrolyte electroreflectance (EER) is a powerful technique for studying important properties of the semiconductor/electrolyte interface such as the flatband potential and the density and distribution of surface states. EER is, however, usually restricted to semiconductors and metals, the required electrical field strength being present in the space charge and Helmholtz layer, respectively. We report now about EER measurements on high resistivity BiI3 electrodes where the space charge — and therefore the resulting electrical field — is generated optically, i.e. by background irradiation. At the same time, the latter leads to a huge enhancement of the photoresponse.
The participation of surface decomposition intermediates in charge transfer processes at dark p‐type GaP/electrolyte interfaces
Authors: Yun Lu Shou , Vanmaekelbergh D. , Gomes W. P. , Cardon F. 
Published: March 2014

AbstractThe competition between the anodic decomposition of the dark p‐GaP electrode in aqueous electrolytes and the stabilization of this electrode by ferrous ions was studied by rotating ring‐disk experiments. The same competition mechanism was found to operate as that, formerly deduced for the illuminated n‐GaP/Fe2+ electrode. This mechanism also explains the observed decrease of the anodic current density with increasing Fe2+ concentration at given electrode potential. Quantitative differences in reactivity between dark p‐type and illuminated n‐type GaP are interpreted on the basis of the difference in band edge position under circumstances of anodic current flow, as deduced from capacitance results. The change in surface charge with varying electrode potential, observed by capacitance measurements, is discussed.
Effect of terraces and steps in the electrocatalysis for formic acid oxidation on platinum
Authors: Motoo Satoshi , Furuya Nagakazu 
Published: March 2014

AbstractHydrogen and oxygen adsorption was examined on 14 stepped surfaces having [100] zone axis and on 17 stepped surfaces having zone axis of [110]. The electrocatalytic activity for formic acid oxidation was also studied. It was found that there are 6 groups of hydrogen peaks and corresponding oxygen peaks which are typical for the low index planes (111), (100), (110), and for (533) and (311). The electrocatalytic activity changes with terrace width, the maximum of which is on the (111) terrace and on (210).
Catastrophe situation for potential‐assisted electron transfer in relation to temperature‐dependence of tafel slopes
Authors: Conway B. E. , Wilkinson D. P. , Tessier D. F. 
Published: March 2014

AbstractThe conventional representation of Tafel slopes, b, for activation‐controlled electrode processes as b = RT/βF with β a constant having the significance of a barrier symmetry factor or Brønsted type coefficient, is rarely followed with respect to the observed dependence of b on T. Rather, b is represented more generally in the form b = RT/(βH + TβS) F where βH and Tβs are formally enthalpic and entropic components of the overall β that determines the effect of changing electrode potentials (V) on the electrochemical Gibbs energy of activation and hence on the rate. — Special attention is directed to a “catastrophe” situation that arises in some experimentally observed behaviour where b is virtually independent of T, i.e. when TβS ≫ βH, so that apparently the normal effect of V on the electron exit energy that determines the potential‐dependence of the activation energy, is obscured. — Discussion of this situation, and presentation of recent new results for proton transfer at Hg, indicates that there are important effects of V “external” to the metal on both the entropy and enthalpy of activation, in addition to the effect of V on the electron Fermi level, relative to vacuum. Compensation effects between variations of the enthalpy and entropy of activation are related to this “external” effect of V.
Extremely Sensitive Optical Detection System for Stopped‐flow Measurements of Reactions with Very High Rate Constants or Small Absorbance Changes
Authors: Goez Martin 
Published: March 2014

AbstractStopped‐flow experiments are usually performed with optical detection. In case of low absorptivities or low concentrations of the measured substances a very high sensitivity is necessary. A special optical detection system with this feature is described. By a differential configuration of the detectors and the use of high light intensities fluctuations of the light source and detector shot noise were greatly reduced in their effects. The detection system is capable of performing extremely sensitive kinetic measurements from 290 to 620 nm within the time‐scale of stopped‐flow experiments. Kinetic traces with a full scale absorbance down to 5 · 10−4 were recorded. In this extreme case, the signal to noise ratio was still as good as 25:1. With typical values for absorptivities, optical path length, and dead time, even diffusion controlled electron transfer reactions could thus be observed in a stopped‐flow apparatus.
The One‐Dimensional Band Structure of (Tetrazaporphyrinato)iron(II)
Authors: Böhm Michael C. , Ramírez Rafael , Olés Andrzej M. 
Published: March 2014

AbstractThe one‐dimensional (1 D) band structure of (tetrazaporphyrinato)Fe(II) (Fe(tp)) has been investigated in the framework of a semiempirical Hartree‐Fock (HF) self‐consistent‐field (SCF) crystal orbital (CO) approach. The calculated ground state of this 1D solid is of spatial B1g symmetry. This configuration in the 3d6 material is determined by two half‐filled bands of the insulating Mott‐Hubbard‐type where all CO microstates in the first Brillouin zone are singly occupied. Both Mott‐Hubbard dispersions are strongly metal‐centered, i.e. 3dz2 and 3dxy. The width of the σ‐type (3dz2) band amounts to ca. 0.21 eV while a nearly dispersionless band is predicted for the δ interaction (3dxy). These two half‐filled 3d bands lie below the Fermi energy, while the highest occupied states are of ligand π character. The band structure properties of the Mott‐Hubbard insulator have been determined by means of a grand canonical (GC) averaging procedure which corresponds to an approximate spin‐restricted mean‐field description. The HF SCF energy of the “spin‐paired” 3d6 configuration is predicted to have a higher energy. Therefore, an “aufbau” principle is not valid in the ground state of this 1D material. The implications of this ground state on the magnetic properties of Fe(tp) are also discussed.