bluuebunny/crossref_metadata_2025 huggingface dataset:
Vapour Pressures of Molten Alkali Chloride–Aluminium Chloride Mixtures
Authors: Linga Hogne , Motzfeldt Ketil , Øye Harald A.
Published: March 2014

Vapour pressures have been measured for molten mixtures in the systems MCl–AlCl3 where M = Li, Na, or K, in the composition range 0 to 50 mol.‐% AlCl3. Based on earlier work it is assumed that the main species in the vapour are MAlCl4(g) and AlCl3(g), with minor contributions from Al2Cl6(g) and MCl(g). The liquids are considered as binary mixtures MCl–MAlCl4 with unsymmetrical positive deviations from ideality. By means of this model, the measured vapour pressures are interpreted in terms of partial pressures of each of the vapour species; thermodynamic data are derived for the molten mixtures, and calculated phase diagrams on the MCl side are presented for the three systems.
Fluid Mixtures at High Pressures Fluid Phase Equilibria in the Systems Fluorobenzene + Water, 1,4‐Difluorobenzene + Water, and 1,2,3,4‐Tetrahydronaphthalene + Decahydronaphthalene(trans) + Water up to 360 MPa
Authors: Jockers R. , Schneider G. M.
Published: March 2014

As part of an extended research program concerning the phase behaviour and thermodynamics of fluid mixtures at high pressures the gas‐gas equilibria of the binary systems fluorobenzene + water and 1,4‐difluorobenzene + water as well as the liquid‐liquid equilibria in the ternary system 1,2,3,4‐tetrahydronaphthalene + decahydronaphthalene(trans) + water were measured in an optical high temperature high pressure cell in the temperature range from 280 to 420°C and at pressures up to 360 MPa. At high pressures all these systems show upper solution temperatures that rise with increasing pressure. – Additionally the critical phase behaviour of nearly all binary water systems investigated up to now is reviewed. The parameters that influence the phase separation in these systems are shortly discussed, and it is shown that the shapes and the relative positions of the steeply ascending branches of the criticalp(T) curves mainly depend on the size as well as on the π‐electrons of the molecules of the non‐aqueous component.
Electrochromic Changes of Light Absorption by the Electric Field of the Electrolytic Double Layer
Authors: Plieth W. J. , Gruschinske P. , Hensel H.‐J.
Published: March 2014

The optical properties of molecules adsorbed on a metal/electrolyte interface depend on the electric field across the double layer. The changes with the electrode potential can be measured by modulation reflection spectroscopy. This provides a method for measuring specifically optical properties of the adsorption layer.
Basicity of Diaza‐Aromatic Compounds, II
Authors: Bluhm Th. , Bluhm A. , Behjati B. , Knop J. V.
Published: March 2014

The pK values and the thermodynamic data for diazaphenanthrenes with both nitrogen atoms in one benzene ring were determined from the pH‐ and temperature‐dependence of the electron excitation spectra. – The basicity gradations of diazaphenanthrenes are discussed in connection with the known pK values of other diazaaromatic and monoaza‐aromatic compounds. It is found that the effect of a second nitrogen atom in lowering the basicity appears to be due not to an inductive but to an electrostatic field effect. – The theoretically expected linear relationship exists between the calculated total energy differences of the di‐ and the mono‐protonated diazaphenanthrenes on the one hand and the corresponding pK values on the other.
Bestimmung der Dissoziationsenergien des Iminoradikals aus Daten der Prädissoziation seines (c1 Π)‐Zustandes
Authors: Zetzsch C.
Published: March 2014

Die Kombination von spektroskopischen Beobachtungen des (c1 Π)‐Zustandes von NH und ND ermöglicht die Konstruktion einer Grenzkurve für die Prädissoziation dieses Zustandes. Bei Interpretation der Beobachtungen als Prädissoziation durch Rotation ergibt sich für den Grundzustand (X3Σ−) von NH die untere Grenze der Dissoziationsenergie D0 > 3,45 eV.
Spectroscopic Study of Electronic Energy Transfer from N2(A) and CO(a) to NO in a Beam Experiment
Authors: Ottinger Ch. , Simonis J. , Setser D. W.
Published: March 2014

Nitric oxide molecules were excited into the A 2Σ+ state by near‐resonant excitation‐transfer collisions with metastable N2(A3Eu+) and CO(a3 Π) molecules in a beam‐gas experiment. The latter species were produced by near‐resonant charge transfer of N+2 and CO+ with NO. The rotational and vibrational excitation of NO(A), as deduced from the NO(A → X) emission spectra, are discussed. The cross sections for excitation of NO(A) by N2(A) and CO(a) drop by about two orders of magnitude between 1 and 200 eVLab. The excitation transfer reactions between N2(A) or CO(a) with NO to give NO(B2 Π), although also near‐resonant, do not occur appreciably in this energy range.
Grundlagen der Kinetik mineralbildender Prozesse
Authors: Schmalzried H.
Published: March 2014

The most complex physico‐chemical process “mineral formation in multicomponent system” is discussed in the sense of limiting cases. The following elementary processes are briefly treated: nucleation and formation of new phases, matter transport in one phase multicomponent system, heterogeneous reaction in multicomponent system. In many cases zero, one and two dimensional crystalline defects play an important role for the morphological and kinetical development of minerals. The role of point defect thermodynamics for the transport coefficient and transport theory of crystalline multicomponent systems is pointed out in some detail.
Mineral Reactions as Indicator of Non‐Ideal Mixing Properties of Supercritical Gas Mixtures
Authors: Ziegenbein Dieter
Published: March 2014

The investigation of suitable mineral equilibria (e.g. decarbonation reactions) allows to deduce the mixing properties of supercritical gas mixtures. The data obtained are best ascertained in an intermediate range of fluid composition and where ideal mixing occurs. The mixing properties of CO2 in CO2 – H2O mixtures are deduced from the equilibrium conditions of the reaction CaCO3 + SiO2 = CaSiO3 + CO2 at 4 kbar and 870 – 1070 K. The “close‐to‐Nature” high pressure experiments yield considerable larger positive deviation from ideal mixing than results deduced from P‐V‐T measurements or thermodynamic calculations.
Die Bedeutung des intermediär oxidierten Schwefels für die Genese hydrothermaler Sulfat‐Sulfid‐Lagerstätten
Authors: Oberste‐Padtberg Rüdiger
Published: March 2014

What one observes in hydrothermal ore deposits and their wall rock are sulfates (baryte, anhydrite, alunite) and sulfides (pyrite, galena etc.). The nature of the ore forming solution has to be extrapolated. Many authors maintain that sulfur occurs in solution in the extreme oxidation states S6+ and S2− only. However, theoretical considerations and experiments show that intermediate oxidized sulfur species (IOSS) are more frequent than generally assumed. Under hydrothermal conditions (p, T, po2) sulfate will be reduced stepwise; IOSS are dominant. Oxidation, reduction and disproportionation lead to the formation of sulfides and/or sulfates. Sulfate‐acceptors resp. sulfide‐acceptors keep the disproportionation going. IOSS provide a new model to explain the transport of metals and sulfur in the same hydothermal solution and the simultaneous crystallization of sulfates and sulfides. A further advantage of this model is the fact that heavy metals and earth alkali metals are more soluble by orders of magnitude as IOSS than as sulfate and sulfide.
Kinetische Kohlenstoff‐Isotopenfraktionierung im CO2 – H2O‐System des Laacher Sees
Authors: Puchelt Harald
Published: March 2014

Unexpected shifts of 13C concentrations observed with carbondioxide emerging from the water close to the eastern shore of Lake Laach could be explained by kinetic C isotopefractionation. This was caused by preferential 12C incorporation into HCO3‐ions as long as no saturation of CO2 was reached and time was not sufficient for establishing isotopic equilibrium. – Laboratory experiments with tank carbon‐dioxide bubbling through triple distilled water in columns up to 4 m high provided fractionations as large as 7.2‰. 13Carbon was found to be enriched in the passing carbondioxide. The effect decreased with time (i.e. with increasing saturation). – The fractionation becomes larger the higher the water column is. It depends also on the size of the carbondioxide bubbles and the water temperature. – These shifts of isotope ratios which occur frequently in nature invalidate fast conclusions regarding the origin of carbondioxide. Careful investigations of the degree of saturation and time available for equilibration are required before genetic conclusions from C isotope ratios are allowed.
Die Fraktionierung der stabilen Isotope des Kohlenstoffs und des Sauerstoffs bei der Bildung von Calcit an der Erdoberfläche
Authors: Usdowski E. , Hoefs J. , Menschel G.
Published: March 2014

Calcite is not precipitated immediately from a supersaturated calcium bicarbonate solution because the initial activity of CO32− is small. Therefore, the solution degasses at first CO2 until at a critical value of ΔG of about – 1 kcal/mol calcite begins to nucleate. The fractionation of carbon isotopes between the dissolved carbonate and the atmosphere occurs under isotopic equilibrium. The precipitating calcite, however, exhibits substantial isotopic disequilibrium. The composition of the precipitated and the dissolved carbonate are virtually identical though they should differ by a Δ13C‐value of about 2‰. Isotopic disequilibrium is also indicated by the oxygen isotopes: 18O‐temperatures do not agree with the observed temperatures of calcite formation.
Quasi‐One‐Dimensional Behaviour of Hydrogen in H0.35MoO3 and H0.33WO3 as Revealed by Proton NMR
Authors: Ritter Cl. , Müller‐Warmuth W. , Spiess H. W. , Schöllhorn R.
Published: March 2014

The 1H NMR has been studied in the hydrogen bronzes H0.35MoO3 and H0.33WO3 prepared by galvanostatic cathodic reduction. Both systems reveal an extreme anisotropy of the hydrogen mobility due to quasi‐one‐dimensional behaviour. – In H0.35MoO3 the temperature dependent 1H wideline data give strong evidence that hydrogen is clustered in quasi‐one‐dimensional channels. Analysis of the temperature dependence of the second moment M2, the transverse relaxation time T2, and the spin‐lattice relaxation time T1 yields essentially the same valueEA = 30 kJ/mol for the activation energy of the translational motion of hydrogen within the channels. In H0.33WO3 evidence for the quasi‐one‐dimensional behaviour is provided by the frequency dependence of T1 and the marked non‐exponential recovery of the nuclear magnetization in the vicinity of the T1 minimum. The activation energy for the translational motion is EA = 3.6 kJ/mol only, indicating high mobility of hydrogen in this bronze.
Luminescence and Optical Absorption of Pure and Transition‐Metal‐Doped Al2TiO5 with a View to Solar Energy Applications
Authors: Lam R. U. E.'T. , Blasse G.
Published: March 2014

The luminescence properties and the diffuse reflection spectra of pure Al2TiO5, and Al2TiO5 – Me (Me = V, Cr, Mn, Fe, Co, Ni, Rh) are reported. Our measurements indicate that Al2TiO5 shows an optical absorption edge at 4.1 eV. This large bandgap makes the material unsuitable for solar energy applications. Al2TiO5 can be coloured by transition‐metal ions due to the occurrence of Men+ → Ti4+ charge‐transfer transitions.
The Influence of Illumination on the Flat Band Potential of the Contact TiO2/CH3CN(+ H2O)
Authors: Schumacher R. , Teschner D. M. , Heinzel A. B.
Published: March 2014

Results are reported on the flat band potential Vfb of the contact TiO2/CH3CN. The informations were taken from capacitance/voltage and photocurrent/voltage measurements. As electrolyte either pre‐dried CH3CN or various mixtures of dried CH3CN with H2O were used. It was found that both the addition of H2O and illumination with band gap light affect Vfb considerably. – It could be shown that Vfb‐values determined from photocurrent/potential measurements differ up to 2 V from values evaluated from capacitance/potential measurements taken on unilluminated electrodes. However, Vfb‐values obtained from capacitance measurements on pre‐illuminated electrodes agree well with data from photocurrent measurements. The results are discussed in terms of alterations of the inner Helmholtz plane. Finally, consequences of the observed Vfb shifts on the charge transfer process are outlined.
Zur infrarotspektroskopischen Bestimmung von Adsorptionswärmen
Authors: Ramstetter A. , Baerns M.
Published: March 2014

Heats 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

O/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

The 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

The 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

Rheological 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

With 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

Silver 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

It 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

In 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

The 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

Chloroform 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

Small 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

A 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

The 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

This 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

The 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

The 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

Recent 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

Double 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

Electrolyte 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

The 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

Hydrogen 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

The 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

Stopped‐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

The 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.
The Formation of Carbenium Ions and Naked Anions by the Protonation of Phthalophenone with a Super Acid
Authors: Brandner G. , Dickert F. L. , Lehmann E.
Published: March 2014

Two molecules of a strong acid such as CF3SO3H are necessary to cleave the lactone ring of phthalophenone. NMR and conductivity measurements reveal that the carboxylate group has to be protonated for this purpose followed by its solvation with an additional molecule of acid. But CF3SO3‐ which is simultaneously formed behaves as a naked anion in the solvent dichloromethane. CNDO‐Calculations indicate a strong interaction between the charged central carbon atom and the ‐COOH group in which is accompanied by an unusually large twisting of the phenyl rings.
Test of a Symmetry Reduced Extended RISM (XRISM) Equation Against Diffraction Experiments on Liquid Benzene and Hexafluorobenzene and Evaluation of Optimized Potentials
Authors: Bartsch E. , Bertagnolli H.
Published: March 2014

Symmetry reduced extended RISM (XRISM) calculations have been performed on the polar molecular liquids benzene and hexafluorobenzene. By comparing XRISM results and Monte Carlo simulation data for benzene, good agreement between both methods could be shown applying different closures. Testing XRISM theory against X‐ray and neutron diffraction experiments, it could be demonstrated that the method is suited to extract optimized Lennard‐Jones (12,6) potentials. Although a good overall agreement with experimental data could be achieved, the remaining differences suggest that it is necessary to use more complicated potentials in order to obtain a full description of the structural details provided by the experiments. — A variation of the partial charges can be tentatively interpreted in terms of electrostatic interactions playing a decisive role in the determination of the short‐range structure in the studied polar molecular liquids.
Solid‐Solute Phase Equilibria in Aqueous Solution. I. Solubility Constant and Free Enthalpy of Formation of Huntite
Authors: Königsberger E. , Gamsjäger H.
Published: March 2014

Solid binary carbonate phases often dissolve congruently in aqueous media, even when they are not stable under the prevailing conditions. From the thermodynamic point of view these dissolution reactions lead to a metastable equilibrium with fixed composition, when neither diffusion in the solid state nor recrystallization from the solution occurs. The solubility of natural huntite. CaMg3(CO3)4, was studied potentiometrically at 50°C and I = 3.0 mol kg−1 (Na)ClO4. Since it dissolved congruently the solubility constant log *Kpso = log{[Ca2+]0.25 [Mg2+]0.75 p[H+]−2} = 10.36 ± 0.03 was used to calculate its standard free enthalpy ΔfG0298 (Ca0.25Mg0.75CO3) = −1045.0 ± 2.4 kJ mol−1; thus huntite is considerably less stable than the corresponding mechanic mixtures of calcite or dolomite and magnesite respectively. Stable and metastable equilibria in carbonate systems can be graphically presented by phase diagrams with In *Kpso and mole fractions as variables, where *Kpso is the total solubility constant defined by *Kpso = ([Ca2+] + [Mg2+]) p [H+]−2.
Charge Carrier Generation and Transport in Polyvinylcarbazole: A Model System for Polymeric Photoconductors
Authors: Kaul H. , Haarer D.
Published: March 2014

The problem of electron‐hole separation in polyvinylcarbazole (PVK) is discussed, based on new “time of flight” data, covering a time range from 10 nanoseconds to about 10 minutes. The experimental data are analyzed with the aid of the Onsager‐theory of electron‐hole recombination and yield an Onsager radius r0 of 18 ± 2 Å. Due to the high sensivity of the method it is possible to reproduce the low field regime of the Onsager recombination scheme. There are still sizeable deviations between the theoretical and the experimental quantum yields in the mid field regime. These differences do not enter into the determination of the r,‐value to a great extent because ro shows a weak logarithmic dependence on the extrapolated low and high field values of the charge carrier yields. The discrepancies between theory and experiment are believed to be caused by inhomogeneous electrical fields due to localized space charges in the zone of charge generation; they may in future provide information about the magnitude of “internal fields”.
NQR Spectroscopy and Structure of Photochromic 2,3,4,4‐Tetrachloro‐1‐oxo‐1,4‐dihydronaphthaline and 2,4,4‐Trichloro‐1,4‐dihydronaphth[1,8‐cd]isothiazole‐1,1‐dioxide
Authors: Brummer Stefanie , Weiss Alarich
Published: March 2014

The 35Cl NQR spectra of the photochromic compounds 2,3,4,4‐tetrachloro‐1‐oxo‐1,4‐dihydronaphthaline. β‐TKN, and 2,4,4‐trichloro‐1,4‐dihydronaphth[1,8‐cd]isothiazole‐1,1‐dioxide, TCNS, were studied from 77 K to the decomposition temperature. The crystal structure of TCNS was determined, space group C‐P21/m, Z = 2, a = 818.3(2) pm, b = 828.0(2) pm, c = 905.4(2) pm, β = 107.552(2)°, σcalc = 1.752 Mg · m−3. No phase transition is observed for the two title compounds in the temperature range of the 35Cl NQR spectroscopy. The 35Cl NQR spectra are discussed in connection with the crystal structures. — For a few other compounds related to the photochromic ones, 2,2,3,4‐tetrachloro‐1‐oxo‐1,2‐dihydronaphthaline (α‐TKN), 2,3,4,4,5,6‐hexachloro‐cyclohexadiene‐(2,5)‐one‐(1) (HCP), 2,2,3,4,4‐pentachloro‐1‐oxo‐1,2,3,4‐tetrahydronaphthaline, and 2,3,4‐trichloro‐1‐naphthol, results of NQR spectroscopy are given, too.
In Situ Observation of a Phase Transformation in α‐(BEDT‐TTF)2I3 using a Contactless Technique
Authors: Späth K. , Gross F. , Heidmann C. P. , Andres K.
Published: March 2014

We describe a novel apparatus for contactless measurement of the conductivity of small platelet‐shaped charge transfer crystals from above room temperature down to helium temperatures. This technique is employed to study the temperature dependence of the conductivity in the quasi two‐dimensional organic conductor α‐(BEDT‐TTF)2I3 both in its pristine form and after annealing at 360 K. The low temperature behaviour is found to change from insulating (metal‐to‐insulator transition at 135 K) to metallic.
Single Crystals from Optically Active Diacetylenes and Polydiacetylenes
Authors: Kröhnke C.
Published: March 2014

Diacetylene monomers with chiral side groups have been synthetized. The monomer crystals polymerize upon irradiation or thermal annealing. The thermal polymerization was studied and the potential use of the resulting polymer crystals as optical devices was discussed. A characterization of the monomers and one polymer in solution with regard to specific rotation was obtained.
Intrinsic Fluctuations in Macromolecular Self‐Replicating Systems
Authors: Fernandez Ariel
Published: March 2014

The relevance of stochastic effects at very low template concentration for Qß‐catalized‐template‐instructed RNA replication is established. The fluctuations in rates and in elongation intermediate concentrations are determined making use of a center manifold stochastic reduction of the fast‐relaxing kinetic degrees of freedom. The strength of these far‐from‐equilibrium fluctuations is scaled with the small rate‐control characteristic parameters of the system. The fluctuations in the concentration of the chain‐elongation intermediate complexes are enhanced as the template chain becomes shorter, thus, a deterministic description does not hold for RNA chains of the order of 50 nucleotides. Some results on the de‐novo synthesis of RNA are reinterpreted in the light of these experimental findings. The far‐from‐equilibrium fluctuations determine the scattering of lag‐times corresponding to the macroscopically‐detectable amplification of the template. The results show very good agreement with the experimental evidence.
Advanced NMR methods for liquids and solids: Two‐dimensional spectroscopy
Authors: Ernst R. R.
Published: March 2014

The potential of nuclear magnetic resonance for the determination of the molecular structure of matter is reviewed. In particular, two‐dimensional spectroscopy has emerged as a most powerful technique for structural problem solving and for the investigation of molecular dynamics.
Rechnergestützte Analyse komplexer NMR‐Spektren. Untersuchungen zur spektralen Darstellung und Vergleichsfunktion
Authors: Schäfer A. , Ziessow D.
Published: March 2014

NMR Spectra of more than three strongly coupled spins need to be analyzed with the aid of iterative computer programs. Computation times and convergence depend on the employed measure V of similarity between experimental and theoretical data. The latter are calculated with suitably chosen values for the parameter vector p of the spin system so that V(p) constitutes an error function. Various functions are classified in terms of the representation of spectra and their properties are discussed along particular cross‐sections in the parameter space. This includes the dependence on the normalization of the theoretical spectrum (largest peak vs. integral) and kind of unsigned errors (squared vs. absolute value). Computation times and convergence behaviour show that broadened spectra and integral functions may well be used to represent the full spectrum, while triangular line shapes may be of advantage when transition frequencies and intensities are available only.
Nuclear quadrupole interactions in solids: A survey
Authors: Smith J. A. S.
Published: March 2014

Nuclear quadrupole interactions have been measured in solids for nearly forty years; with recent improvements in techniques and sensitivity, they are finding much application in the study of electronic structure and molecular motion. The most complete information on the quadrupole coupling tensor comes from investigations of single crystals as in recent 35Cl quadrupole resonance studies in low magnetic fields of 1,2‐dichloro‐3‐nitrobenzene and (CH3)3C.CO2SbCl4 and in high magnetic fields of 17O magnetic resonance in benzophenone. High‐field studies of quadrupole splitting in the nuclear magnetic resonance spectra of powders are becoming increasingly used, particularly 27Al interactions in minerals and zeolites and 2H splittings and their relation to structure and motion in polymers. The sensitivity of radiofrequency techniques can be considerably increased by the use of double resonance methods, illustrated by recent work on 17O quadrupole interactions in O — H…O hydrogen bonds, 7Li of defects in lithium metal, and 14N in the detection of disorder in p‐nitrobenzoic acid crystals. Nuclear methods have an important part to play because of their remarkable sensitivity; the use of Mössbauer spectroscopy in the study of Fe(0) clusters and perturbed angular distribution techniques to measure 19F quadrupole interactions by means of an excited nuclear state of spin 5/2 provide interesting examples. Finally, recent theoretical and experimental work has been attempting to resolve the important question of the extent of charge transfer in ionic solids, illustrated by recent 57mFe studies of α‐Fe2O3 and 7Li, 14N in the superionic conductor Li3N.
79,81Br and 127I NQR studies of hydrobromides and hydriodides of amino acids and dipeptides
Authors: Kehrer Armin , Fleck Silvia , Weiss Alarich
Published: March 2014

By 79,81Br and 127I NQR the hydrobromides of 1‐asparagine, 1‐asparatic acid, glycyl‐1‐alanine, and glycylglycine and the hydriodides of 1‐asparagine, 1‐glutamic acid, and glycylglycine were studied in the temperature range of 77 ≤ T/K ≤ 420 (or decomposition point). — A reversible phase transition is observed for glycyl‐1‐alanine hydrobromide at 203 ± 1 K. 79,81Br NQR frequencies are strongly influenced by N⊕—H…Br⊖ and O—H…Br⊖ hydrogen bonds. The 79Br frequencies can be grouped into two bands, one at 12.4 < v/MHz < 18.5, the other at 24.8 < v/MHz < 26.4. The compounds of the high frequency group are characterized by N⊕—H…Br⊖ and O—H…Br⊖ hydrogen bonds, whereas the bond scheme of the low frequency compounds is determined by N⊕—H…Br⊖ bonds only. This grouping of amino acid and dipeptide hydrobromides according to frequency band and hydrogen bond scheme can be applied to the hydriodides, too. The ones with a O—H…I⊖ hydrogen bond have nuclear quadrupole coupling constants of N⊕ > 120 MHz, the other compounds with N⊕—H…I⊖ hydrogen bonds only show nuclear quadrupole coupling constants of 70 < e2QzzQh−1/MHz < 120.