bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrostatic Processing of Mineral Salt Mixtures: The Selectively‐stimulated Contact Charging of Kieserite (MgSO4 · H2O). An Interpretation
Authors: Ernst Lajos 
Published: March 2014

AbstractIn the electrostatic processing of crude potash salt, a mixture of mainly KCl, NaCl and MgSO4 · H2O, the single salt particles gain an electric charge component‐selectively on contact with each other. This enables the components to be separated in an electric field. The component‐selective stimulation of contact charging can be achieved using a technology developed over many years, where small amounts of certain monocarboxylic acids are added to the salt mixture, while the relative humidity of the ambient air is maintained at some definite value. – Recently a model has been proposed to elucidate the mechanism of stimulated contact charging. It has been applied in the case of NaCl. H2O molecules bonded in surface‐cation‐vacancies of the crystal have an important role in this model, which will be extended in the present work to the case of the stimulated contact charging of kieserite. This enables the interpretation of empirical diagrams characterising the electrostatic salt separation to be made for the first time. Conversely, this may be regarded as a convincing verification of the model itself.
Kinetics of the Corrosion of Iron in Aqueous Electrolytes at Temperatures up to 300°C
Authors: Heusler K. E. , Kusian B. , McPhail D. 
Published: March 2014

AbstractThe corrosion behaviour of iron was investigated in aqueous borate buffer solutions with and without additions of sodium chloride and in quaternary salt brine at temperatures between 150°C and 300°C. A magnetite film grows according to the parabolic rate law. The parabolic rate constant is independent of the pH‐value, increases with the electrode potential and with the chloride concentration, and attains a maximum at about 250°C. The parabolic rate constants are compared to literature data and theoretical calculations. – After some time the corrosion rate drops to a steady state value, if the chloride concentration is not too high and the electrode potential not too positive. The steady state corrosion rate increases with the temperature according to an activation enthalpy of 41 kJ/mol and remains less than 10 μA/cm2 up to 300°C. Above some critical electrode potential becoming more negative with the concentration of chloride, a local corrosion is observed producing flat pits covered by thick oxide layers. At the very high chloride concentration of the quaternary salt brine the whole surface becomes activated and corrosion proceeds rather uniform.
Reduction of Ag+ in Aqueous Polyanion Solution: Some Properties and Reactions of Long‐Lived Oligomeric Silver Clusters and Metallic Silver Particles
Authors: Henglein Arnim , Linnert Thomas , Mulvaney Paul 
Published: March 2014

AbstractRadiolytic reduction of AgClO4 solutions containing a polyanion leads to the formation of long‐lived oligomeric silver clusters which are stabilized on the polymer chains. Under suitable conditions, the accompanying formation of colloidal silver consisting of metallic particles is strongly suppressed and cluster concentrations of several 10−4 M can be produced. In the presence of polyacrylate, the clusters are particularly long‐lived; they have absorption bands at 300 nm, 340 nm, and 370 nm. The bands of the latter two clusters are red‐shifted as compared to the bands of the unstabilized clusters or clusters stabilized by polyphosphate. The Ag24+ cluster, which is formed in the initial stages of Ag+ reduction, absorbs at 275 and 480 nm in the presence of polyacrylate. – The various clusters react at different rates with electron acceptors, such as oxygen, carbon tetrachloride and nitromethane. The clusters also react with complexing agents, such as ammonia, cyanide and hydrogen sulfide anions, to form larger particles of silver and/or larger complexed clusters. The great reactivity of the clusters towards nucleophilic reagents is explained by the high coordinative unsaturation of the silver atoms in the clusters. This also explains the stabilization of the clusters by the anion groups of the polymers used. – These reactivity studies were also complemented by investigating the reactions of larger silver particles, which already have metallic properties, with complexing agents. The oxidative corrosion of such particles is strongly accelerated by the complexing agents. A mechanism for the catalysis of the oxidative corrosion is presented, in which the principle steps are the complexation of silver atoms on the surface with simultaneous electron transfer into the metal interior (“pre‐complexation” or “pre‐oxidation” of surface atoms) followed by pick‐up of the electrons by oxygen.
Electrostatic Interactions of Bodies Bearing Thin Double‐Layers I. General Formulation
Authors: Adamczyk Z. , Belouschek P. , Lorenz D. 
Published: March 2014

AbstractThe modified Poisson‐Boltzmann (PB) equation was formulated for a system of flat dissimilar double‐layers by considering the excluded volume effect. Limiting solutions of the modified PB equation derived for an isolated plate, and for two‐plate system at large and small separations and arbitrary electrolyte composition were discussed. Results obtained for the parallel‐plate geometry were generalized to regularly shaped bodies (either convex or concave around their contact point) bearing thin double‐layers by applying the surface integration procedure analogous to the Derjaguin summation method. The excluded volume effect proved to be important for the dimensionless parameter β larger than 10−2 leading to a considerable increase of the potential difference across double‐layers and to a slight increase of the interaction force between bodies at large separations. At small separations, however, the force remains finite due to the excluded volume effect (in the constant charge model) in contrast to previous results predicting that the force should tend to infinity in this limit. It was also predicted that the presence of trace amount of polyvalente ions (e.g., Al3+ ion) decreased considerably the force between bodies immersed in a 1–1 electrolyte.
Dilute Random Distribution of Small Chiral Ellipsoids in a Chiral Fluid: Optical Properties
Authors: Lakhtakia Akhlesh 
Published: March 2014

AbstractAn integral equation method has been used to derive the polarizabilities of a small chiral ellipsoid immersed in a chiral fluid. These polarizabilities are then used to obtain the effective electromagnetic/optical properties of a dilute random suspension consisting of randomly‐oriented, ellipsoidal, chiral particles in a chiral fluid. The optical rotation and the circular dichroism of the suspension are obtained.
Solvent Induced Intramolecular Electron Exchange Kinetics in 1,3‐Isodisubstituted Aromatic Radical Anions II. Activation Parameters
Authors: Grampp G. , Shohoji M. C. B. L. , Herold B. J. , Steenken S. 
Published: March 2014

AbstractFrom the alternant line broadening effect in the ESR‐spectra of the radical anions of 1,3‐dinitrobenzene and benzene‐1,3‐dicarbaldehyde in various protic and aprotic solvents the rates of intramolecular electron exchange were determined in the temperature range 260–340 K. Using Marcus theory and the Rips‐Jortner approach for the uniform adiabatic limit of electron transfer it is shown that the amount of transferred charge ze0 decreases with increasing temperature. This result is explained on the basis of the effect of temperature on the specific asymmetric solvation of the anions. For the 1,3‐dinitrobenzene radical anion in protic solvents the charge transfer number z changes slightly from 0.96 to 0.90 within 250–340 K and in aprotic solvents from 0.55 to 0.32 within 280–340 K. For benzene‐1,3‐dicarbaldehyde radical anion in protic solvents z changes from 0.40 to 0.29 within 260–320 K. From the measured activation parameters for the intramolecular electron exchange the values for the inner sphere reorganization energies λi were estimated, using values for the outer sphere reorganization λ0 as obtained by applying an ellipsoidal cavity model to the measured solvent dependence of the rates. For the 1,3‐dinitrobenzene radical anion λ0 increases with the degree of solvent association (from 18.4 to 106.4 kJ/mol), whereas λi varies much less (82.4–116.0 kJ/mol) for all protic and aprotic solvents investigated. From the difference in λ0 for protic and aprotic solvents, the value for the energy of solvation of the anions by hydrogen bonding is obtained as ≈ 10 kJ/mol.
Determination of Binary Diffusion Coefficients in Liquid Nonelectrolyte Mixtures using the Taylor Dispersion Technique
Authors: Thiel Peter , Paschke Albrecht , Winkelmann Jochen 
Published: March 2014

AbstractThe concentration dependence of mutual diffusion coefficients in four binary systems N,N‐dimethylformamide‐toluene, dimethylsulfoxide‐toluene, sulfolane—toluene and n‐heptane—toluene is determined at 298.15 K using the Taylor dispersion method. To detect the dispersion of the injected sample a flow‐through differential refractometer is applied. The refractometer output signals are recorded at constant time intervalls and a five parameter working equation is fitted to the concentration profile of the sample by a nonlinear least‐square procedure. Diffusion coefficients at infinite dilution were obtained and five empirical correlations for estimating diffusivities at infinite dilution are tested against our results.
Electrochemistry of Colloidal Silver Particles in Aqueous Solution: Deposition of Lead and Indium and Accompanying Optical Effects
Authors: Henglein A. , Mulvaney P. , Holzwarth A. , Sosebee T. E. , Fojtik A. 
Published: March 2014

AbstractColloidal silver particles (ca. 8 nm in diameter) act as microelectrodes in aqueous solution. They are charged via electron transfer from free radicals which are generated radiolytically. The stored electrons reduce adsorbed Pb2+ and In3+ ions. — The first monolayer of lead atoms deposited on the silver particles does not absorb at 215 nm where metallic lead has an absorption band. The Pb atoms cause the 380 nm surface plasmon band of the silver particles to be shifted to shorter wavelengths. This is explained in terms of electron donation from chemisorbed Pb atoms to the silver carrier. The Pb atoms of a submonolayer (which are formed by “under‐potential” deposition) do not react with methyl viologen, MV2+, whereas the lead atoms deposited in subsequent layers (“Nernst potential” deposition) are readily oxidized by MV2+. The absorption spectrum of colloidal lead in water is also discussed (εmax = 3.2 · 104 M−1 cm−1 at 215 nm). — Reduction of In3+ on the silver particles also leads to a blue‐shift of the plasmon band. It is attributed to electron transfer from deposited In atoms. However, as In metal deposition proceeds, In+ is produced by the conproportionation of the indium metal with In3+. When almost all the In3+ ions have been reduced, indium metal is further deposited by In+ reduction. Silver particles carrying a tight indium shell absorb at 225 nm with ε = 3.8 · 104 M−1 cm−1. This ε‐value is somewhat lower than the calculated one, and attributed to a reduction in mean free path for conduction electrons in small In colloids.
Determination of the Rate Constants for the Gas Phase Reactions of NO3 with H, OH and HO2 Radicals at 298 K
Authors: Becker E. , Rahman M. M. , Schindler R. N. 
Published: March 2014

AbstractThe reactions of NO3 with H (1), OH (2) and HO2 (3) radicals have been investigated at 298 K using a discharge flow system equipped with mass spectrometric and fluorescence detectors. The rate constants k(1) and k(2) were determined by numerical modeling of experimental [OH] profiles from reactions (1) and (2). In the reaction of NO3 with HO2 (3) the growth and decay of [OH] as well as the decay of [HO2] were measured. Comparison of these two profiles provided evidence for two different reaction paths (3a) and (3b), for which the rate constants were determined by numerical modeling. Experiments carried out in a wide range of reactant concentrations yielded in units of cm3 molecule−1 s−1 k(1) = (0.94 ± 0.2) · 10−10, k(2) = (1.22 ±0.35) · 10−11, k(3a) = (2.5 ± 0.7) · 10−12, and k(3b) = (1.9 ± 0.8) · 10−12. The results are compared with literature data.
Determination of Rate Constants for the Reactions of the CH2SH Radical with O2, O3, and NO2 at 298 K
Authors: Rahman M. M. , Becker E. , Wille U. , Schindler R. N. 
Published: March 2014

AbstractCH2SH radicals were produced by the reaction of F atoms with an excess of CH3SH and detected mass spectrometrically at m/e 47 using an electron energy of 9.5 eV. Rate constants for the reactions of CH2SH with the oxidants O2 (k1), O3 (k2) and NO2 (k3) at 298 K were determined by measuring the decay of the radical in the presence of excess oxidants. The following results were obtained: magnified imageThe rate constant for the reaction (4) F + CH3SH → products was determined to be k1 = (2.4 ± 0.4)·10−10 cm3 molecule−1 s−1. The branching into the channels (4a) F + CH3SH → CH2SH + HF and (4b) F + CH3SH → CH3S + HF was investigated by using CD3SH, and k4a/k4 = 0.6 ± 0.1 was obtained.
Collisional Deactivation of O2(1Σg+) by Small Polyatomic Molecules
Authors: Schmidt Reinhard 
Published: March 2014

AbstractLiterature data on the collisional deactivation of O2(1Σg+) by small polyatomic molecules in the gas phase are interpreted by a deactivation model which has proven to describe successfully the experimental findings for the collisional deactivation of O2(1Δg) in the liquid phase. Deactivation occurs by electronic to vibrational energy transfer from the excited O2 molecule to peripheral bonds X—Y of the quenching molecule. Using data on Franck‐Condon factors and transition energies for the possible coupled transitions O2(1Σg+, ν = 0 → 1Δg, ν = m) and X—Y (ν' = 0 → ν' = n) experimental rate constants kXYΣ of O2(1Σg+) quenching by X—Y can quite well be reproduced by calculated ones. The only parameter of the model which has to be changed is related with the electronic factor f of the corresponding O2 transition. As ratio of electronic factors of the 1Δg → 1Σg+ singlet‐triplet and 1Σg+ → 1Δg singlet‐singlet transitions fST/fSS = 6 · 10−5 is obtained. Independent measurements of radiative lifetimes of these transitions in an Ar‐matrix yield fST/fSS = 9 · 10−5 confirming our results. Thus for the first time collisional deactivation of O2(1Δg) and O2(1Σg+) by small polyatomic molecules is explained consistently.
An Abnormal Electrocapillary Response Stated by the Drop Time Method in Alkaline Solutions of Hemoglobin
Authors: Kuik Marian , Krassowski Kazimierz 
Published: March 2014

AbstractIn a narrow range of ammonia concentration of the buffer, solutions containing hemoglobin showed an increase instead of a decrease of drop time. The effect is greater in the presence of cobalt(II) ions. In both cases it disappears at higher ammonia concentration. The effect is a complex phenomenon, involving movement of the mercury drop surface, aggregation of hemoglobin, formation of Co(II)‐hemoglobin complexes, and adsorption of hemoglobin, its complexes and aggregates. A scheme explaining the origination of the anomaly is given. The significance of this effect for the determination of electrocapillary curves by the drop‐time method and in precise polarography is pointed out.
Oxirane Formation in the Reaction of NO3 Radicals with Alkenes
Authors: Wille U. , Rahman M. M. , Schindler R. N. 
Published: March 2014

AbstractMass spectra of products formed in the reaction between NO3 and cis‐2‐butene, isobutene, 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene at 298 K and p = 3–10 mbar were obtained, using a fast flow system with molecular beam sampling. The spectra indicate formation of an oxirane in each reaction. Within experimental error the oxirane yields in the reaction of cis‐2‐butene and of 2,3‐dimethyl‐2‐butene were identical (90 ± 10)%. The rate of oxirane formation was found to obey the rate equation for the reaction:NO3 + alkene → oxirane + NO2. (1).Good agreement was obtained for the rate constants of reaction (1) determined from the rate of oxirane formation and those determined in earlier works from the consumption of reactants.
Surface plasmon resonance as a technique to study adsorption to aluminum oxide surfaces
Authors: Miller C. E. , Meyer W. H. , Knoll W. , Wegner G. 
Published: March 2014

AbstractThe adaptation of the Surface Plasmon Resonance (SPR) method to the study of aluminum oxide surface interactions with organic and polymeric molecules is achieved through the preparation of a thin‐layer of Al2O3 on the silver layer in which the plasmon is generated. Extensive analyses of this system indicate that it is not ideal, but adequate for SPR surface studies. The use of this system for specific Al2O3 surface analyses, including equilibrium and kinetic adsorption analyses, is demonstrated.
1H‐NMR studies on thermochromism Ni(ii) complexes with N,N‐diethylethylenediamine
Authors: Ghosh Ashutosh , Nakamura The Late Daiyu , Ikeda Ryuichi 
Published: March 2014

AbstractThe temperature dependence of the second moment (M2) of 1H NMR absorptions was measured in solid thermochromic bis(N,N‐diethylethylenediamine)Ni(II) complexes. Perchlorate and tetrafluoroborate having a thermochromic phase transition at Ttr = 383 and 367 K, respectively, showed a discontinuous M2 change at Ttr indicating that a marked change of the chelate‐ring motions takes place at the transition. A small M2 value of ca. 8 G2 observed above the respective Ttr could be explained by the excitation of the chelate‐ring puckering together with a large‐amplitude librations of the whole complex ions. A gradual M2 decrease upon heating from 100 to 400 K was observed in bromide and iodide exhibiting continuous thermochromism. These M2 changes and the reported visible electron absorption maxima showed a quite analogous temperature dependence. This suggests that some kind of chelate‐ring motion such as the puckering also takes place in the continuous thermochromism complexes.
Tailoring magnetic interactions of organic solids: Modification of triphenylverdazyl
Authors: Dormann E. , Winter H. , Dyakonow W. , Gotschy B. , Lang A. , Naarmann H. , Walker N. 
Published: March 2014

AbstractThe synthesis of the free radicals 1‐(4'‐bromophenyl)‐3,5‐diphenyl‐verdazyl (Br‐TPV), 1‐(4'‐isopropyl‐phenyl)‐3,5‐diphenyl‐verdazyl (IP‐TPV), 1,3,5,6‐tetraphenyl‐verdazyl (Ph‐TPV), 6‐(1′‐naphthyl)‐1,3,5‐tri‐phenyl‐verdazyl (1N‐TPV), 6‐(2′‐naphthyl)‐1,3,5‐triphenyl‐verdazyl (2N‐TPV), 6‐(4′‐bromophenyl)‐1,3,5‐triphenyl‐verdazyl (BrPh‐TPV) and 1,3,5,6,6‐pentaphenyl‐verdazyl (PhPh‐TPV) is described. Their magnetic properties (static magnetic susceptibility, ESR) are reported for crystalline samples. They are compared with those of 1,3,5‐triphenyl‐verdazyl (TPV) which behaves as a quasi‐onedimensional antiferromagnet in the crystalline form. Exchange interaction is increased by a factor larger than 3 compared with TPV by the introduction of the additional ring in Ph‐TPV. For Ph‐TPV and PhPh‐TPV also the crystal structure was derived by X‐ray analysis. These results are discussed with special emphasis on their meaning for the tailoring of magnetic interactions in organic solids.
Effect of high pressure on the infrared spectra of solid nitro‐ and nitrito‐cobalt(iii) ammine complexes
Authors: Boldyreva E. V. , Burleva L. P. , Burgina E. B. , Baltachinov V. P. , Ahsbahs H. , Uchtmann H. , Doulepov V. E. 
Published: March 2014

AbstractIR‐absorption spectra of Co(III) ammine complexes [Co(NH3)5NO2]XY and [Co(NH3)5ONO]XY (XY = Cl2, Br2, I2, (NO3)2, Cl · NO3) were studied at static pressures up to 20 kbar in a diamond anvil cell. The measured pressure induced shifts of valence (symmetric and asymmetric) and deformational frequencies of the NO2‐group were compared with a normal coordinate analysis of [Co(NH3)5NO2]2+ and [Co(NH3)5ONO]2+ models to determine the influence of kinematic factors on IR‐vibrational frequencies. The experimentally observed frequency shifts induced by pressure were interpreted on the basis of theoretical simulation of the spectra. The blue shift of both δ(NO2) and νas(ONO) vibrational frequencies in the complexes with nitro (via nitrogen) coordination can be explained by a decrease in N‐O bond lengths. The blue shift of νs(ONO) and the red shift of νas(ONO) frequencies in the solid complexes with nitrito (via oxygen) coordination can be explained by a decrease of the O‐N‐O bond angle with increasing pressure. For comparison, the pressure induced shifts of νs(ONO) and νas(ONO) for two Cr(III)‐ammine complexes [Cr(NH3)5ONO]XY (XY = Cl2, (NO3)2) were also measured. Whereas the pressure dependence of νs is similar to the corresponding Co‐compounds, νas is only slightly pressure dependent.
Thermodynamics of liquid cesium‐cesium hydride mixtures at high pressures and temperatures
Authors: Szafranski A. W. , Keller E. , Franck E. U. 
Published: March 2014

AbstractThe hydrogen pressure in equilibrium with liquid phases of the system cesium‐cesium hydride has been measured between 575 and 750°C at pressures between 30 and 600 bar. The results support the discussion of metal‐nonmetal transition in this system. Apparatus and procedure have been described earlier. An autoclave was used with an outer and an inner compartment with equilibrated hydrogen pressures. A critical solution point was found at 665°C, 157 bar and a mole fraction x(CsH) = 0.68. Below this temperature two liquid phases coexist. Nine isotherms of hydrogen pressure in dependence of cesium‐cesium hydride composition have been determined at sub‐ and supercritical temperatures. The melting temperature of pure cesium hydride has been redetermined to 522°C at nearly 30 bar. A monotectic point exists at 519°C. The width of the two phase region in terms of mole fraction difference, Δx, as a function of subcritical temperature gives a “classical” critical exponent β = 0.5. A careful calculation suggests a “bulge” of the two phase equilibrium boundary curve near x(CsH) = 0.85; this is the region of prominent metal‐nonmetal transition. Activity coefficients and excess functions of Gibbs energy, enthalpy and entropy are presented.
High pressure vapour‐liquid equilibria in binary mixtures of carbon dioxide and benzaldehyde, bromobenzene, chlorobenzene, 1,2‐dichlorobenzene and 2‐chloro‐1‐methylbenzene at temperatures between 313 and 393 k and pressures up to 22 MPa
Authors: Walther D. , Maurer G. 
Published: March 2014

AbstractThe high‐pressure vapour‐liquid equilibrium in binary mixtures of carbon dioxide and five aromatic compounds (benzaldehyde, bromobenzene, chlorobenzene, 1,2‐dichlorobenzene and 2‐chloro‐1‐methyl‐benzene) has been investigated by a flow technique at temperatures between 313 and 393 K at pressures up to about 22 MPa. For none of these mixtures – with the exception of CO2 + benzaldehyde – experimental results have been reported before. The experimental arrangement is described. The results of the measurements are reported, discussed and correlated by a recently developed generalized Bender equation of state.