摘要:

AbstractClassical and dynamic light scattering, electric birefringence, kinetic, surface tension, conductivity and rheological measurements were carried out on so called viscoelastic detergent solutions of Cetylpyridiniumsalicylate (CPySal). The results indicate that spherical micelles are formed in these solutions above the critical micelle concentration (cmc) = 1.5 · 10−4M. From the cmc on the concentration of the micelles increases linearly with the total detergent concentration up to a second critical concentration (cmc11= 4.5 · 10−4M). Upon further increase of the total concentration, the concentration of the micelles remains constant and the globular micelles grow to rodlike micelles. The length of the rods increases linearly with the total concentration. The residence time of a detergent molecule in the rod is longer than in the globular micelle. The surface charge density of the rods is smaller than for the spherical micelles. In unstirred solutions the rods are randomly oriented but their center of masses are ordered. As a consequence the rods can rotate freely as long as their main axis is shorter than the mean distance between the aggregates but their translational diffusion is hindered by the existence of lattice like ordering. Shearing of the solution leads to large areas of a new metastable nematic type phase in which the rods are oriented with respect to each other. These oriented domains are the source for the apparent elasticity of the solutions. When the shearing of the solution is stopped, the elasticity decays with rather long time constants that can amount to several minutes. — The complete equilibration of the solution after the system was perturbed by dilution or a change in temperature takes up to severa

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850402

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractThe appearance of induction periods when oxidizing p‐phenylene diamines may be due to different reasons. In acidified aqueous solution distinct induction periods are observed for the formation of semiquinonediimine as well as quinonediimine with nearly all oxidizing agents employed. In this case primary oxidation is very slow because of the low concentration of oxidizable unprotonated p‐phenylenediamine. After the formation of some semiquinonediimine which is unprotonated, however, its subsequent oxidation accelerates the reaction in an autocatalytic way. Under different conditions of reaction either formation of quinonediimine or semiquinonediimine is retarded. Certain foreign substances give rise to a significant shortening or prolongation of the induction period, although the actual oxidation reaction is not noticeably. The different mechanisms are discussed and the reaction rates for the autocatalytic reaction are presented for some redox syst

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850403

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractWith1H NMR‐spectroscopy the complex formation of Co(II)‐ions with the crown ether 15‐crown‐5 was studied in methanol, dimethylformamide, and mixtures thereof. — Evidence is presented for a fluctuating structure of coordinated crown ether which behaves in our case as a four dentate ligand. At 298 K the solvent exchange rates of the remnant solvate molecules are reduced by coordinated crown ether in comparison to the pure solvent complexes. The activation parameters present information about the solvent exchange

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850404

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractAn electrode process is directly contributing to the impedance only in the case of its flux and its generalized force being connected with a charge transport and a voltage resp. (“electric process”). E. g. conduction and transfer reactions cause resistances, charging processes in the simplest case cause capacitances. Complications by gradients (e. g. of conductivity) within the dielectric are discussed. — A contribution to the impedance by another process appears provided that such a concentration is altered by it, the rate of an “electric process” depends on, too. Especially this is the case with common reactants. The kind of coupling is effecting a dependence of the contribution to the impedance on data of both processes. — The elements of impedance are determined by parameters independent of frequency, the meaning of which is discussed. In case of elements depending only on one parameter, it is a resistance, a capacity, a Warburg‐parameter, or an inductivity. Additional parameters have the meaning of rate or time constants or a geometrical meaning. From all parameters kinetic data of the electrode processes occurring are available. Therefore, the task of evaluation of impedance spectra may be understood as estimation of the values of the

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850405

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractUsing conductivity and pressure jump relaxation measurements the complex formation of BeSO4has been studied in mixtures of water and hexamethylphosphoric triamide (HMPT). The rate of substitution of a solvent molecule in the inner solvation sheath of the beryllium ion by a sulphate ion depends on the composition of the solvate species Be(HMPT)i(H2O)4‐iand on the type of solvent molecule being replaced by the sulphate ion. Above a mole fractionxHMPT≥ 0.2 six relaxation processes have been observed. From the conductivity and the kinetic measurements the existence of a Be(SO4)22−complex was inferred in the mixed solvents. Measurements of the densities, dielectric constants and viscosities of the solvent mixtures are rep

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850406

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractWhen carbon monoxide is adsorbed on iron films at temperaturesT≥ 373 K carbon dioxide and carbon are formed. The Boudouard equilibrium is, however, not established at the chosen reaction conditions. In the presence of hydrogen the carbon monoxide adsorption leads to the formation of methane, carbon dioxide, and water. There is no correlation between the formation of water and of methane. The methane formation increases with both the increase in the total pressure and the increase in the partial pressure ratiopH2:pco. The ratio of the partial pressures of CO, H2, CO2, and H2Opoint to the establishment of the water gas equilibrium at medium temperature

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850407

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractThe interaction of carbon monoxide and hydrogen with metal films of Fe, Co, Ni, and FeCo‐alloy has been investigated by means of thermal desorption mass spectrometry. ‐ Since no exchange was observed between different CO‐isotopes adsorbed, desorption of CO can be treated as a first order reaction. At low coverages, the activation energies of desorption have been measured as 83,133,116, and 67 kJ/mol for Fe, Co, Ni, and FeCo‐alloy respectively. ‐ Hydrogen is adsorbed dissociatively. At low coverages the activation energies of desorption have been found to be 65, 110, 82, and 60 kJ/mol resp. ‐ The rate constants for desorption of both, CO and H2, strongly increase with increasing coverage. At saturation coverage, a dynamic equilibrium between the gas phase and the adsorbed molecules is established. ‐ CO inhibits the adsorption of H2and displaces preadsorbed H2in part. No reaction products have been observed following the coadsorption or the consecutive adsorption of CO and H2. ‐ The kinetics of the systems can be described by a system of coupled differential equations. The according solutions show that the pressure should exceed 0.1 Torr in order to observe CH‐reaction products, provided that the rate determining step of hydrocarbon formation is the hydrogenation of

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850408

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractMultiplicity of the steady state is to be expected if thermodynamics permits the existence of a metal as well as that of an oxide on the surface of a catalyst in contact with the reactants; oscillations in the kinetic regime may result if neither of these two phases is kinetically stable.

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850409

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractAn ultrahigh vacuum cryostat consisting of a stainless steel body flanged to an analyzer cell for spectroscopy and laser‐induced processes in the entire spectral region between ca. 50 and 0.2 μm at base pressures in the low 10−10mbar range and sample temperatures between 10 and 600 K is described for the first time. ‐ Under helium bath operation, (4 ± 1) K was measured on the sample holder and (10 ± 2) K in the sample without using thermal contact materials. The metal to metal joint between helium reservoir (stainless steel) and sample holder (OFHC copper) according to the conflat flange method proved to be tight for many baking cycles. The integral leak rate of the whole ultrahigh vacuum apparatus as well as the optical transmission are reported. The windows developed do not show irradiation effects at peak intensities of 10 MW · cm−2per CO2laser pulse. The cryostat is equipped with a quadrupole mass spectrometer and evaporation sources for salts and metals. The analyzer cells are compatible with the sample chamber dimensions of most commercial spectrometers. ‐ Examples of applications are presented in the fields of low temperature gassolid interaction, cryospectroscopy of stable and new metastable adsorbates, selective and efficient evaporation and desorption induced by l

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850410

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractThe nuclear magnetic relaxation titrations is applied to study the oxidation of malonic acid with BrO3⊖in the presence of Mn3⊕/Mn2⊕as catalyst. The maximum amplitude of the free induction decay in a 180°‐τ‐90°1H‐NMR pulse experiment is used as a measure for the spin‐lattice relaxation rate 1/T1. Thereby, the oscillating nature of the reaction can be followed up conveniently. It is shown that the reduction Mn3⊕→ Mn2⊕in this reaction is of first order with respect to the

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850411

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY