摘要:

AbstractA new model for the desorption kinetics of single substances and of mixtures is developed. The heterogeneity of the adsorbing surface is included in the model. A comparison with experimental data shows, that the new equation can predict the mixture behavior even for a system with strong deviations from ideality.

ISSN:0005-9021    

DOI:10.1002/bbpc.198800001

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

年代:1988

数据来源: WILEY

摘要:

AbstractA new model for adsorption equilibria on heterogeneous surfaces is developed. First an analytical equation for single‐component adsorption is derived. Then the model is extended to mixtures. The comparison with experimental data shows that single‐component data can be described and extrapolated in a wide pressure and temperature range. The mixture data of a strongly real adsorpt system can be predicted with good accuracy only from single‐component sorptive data and the vapor‐liquid equilibrium of the considered system. A simplified model with mixture parameters gives good extrapolation to other tempe

ISSN:0005-9021    

DOI:10.1002/bbpc.198800002

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

年代:1988

数据来源: WILEY

摘要:

AbstractElectro‐optic and rheological measurements were carried out on PTFE‐fibrilles. The crystalline fibrilles had an axial ratio of about 100 and a thickness of 200 Å. The dispersions were stabilized by ionic Perfluorosurfactants and could be kept for months without precipitation. — The rotational diffusion constant of the fibrilles was determined as a function of the volume fraction. Both electric birefringence and rheological measurements gave identical results for the orientation times. In the dilute and semidilute concentration range the rotational diffusion constant was the same and did not change at the overlap concentration. The shear modulus was found to increase in the semidilute concentration with the square of the volume fraction of the PTFE fibrilles. — Electric birefringence measurements with AC‐pulses showed a remarkable result. The stationary birefringence changed sign as a function of the frequency. It is concluded that this phenomenon is related to the adsorption/desorption equilibrium of the surfactant ions on the PTFE fibrilles. The equilibrium is shifted by the electric field. These conclusions could be confirmed by light scattering measurements in

ISSN:0005-9021    

DOI:10.1002/bbpc.198800003

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe Poisson‐Boltzmann equation in the cylindrical cell model is solved numerically for charged polyelectrolyte solutions containing mono‐ or di‐valent counterions and mono‐valent coions. The results, which describe the ion distribution around the polyion, are compared with those derived from the Poisson‐Boltzmann equation for salt‐free solutions in the limit of infinite dilution and with the Manning counterion condensation theory. This approach generalizes the results of Le Bret and Zimm for the dependence of the condensation radius on the polyion concentration to polyelectrolyte solutions containing added salt and shows how counterion condensation occurs even at finite concentration. The general conclusion drawn not only supports further evidences that the Manning condensation theory can be deduced from the Poisson‐Boltzmann equation but also suggests that counterion binding changes progressively from a free to condensed phase, as the polyion charge density parame

ISSN:0005-9021    

DOI:10.1002/bbpc.198800004

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe theory of Donnan‐equilibria is extended to systems in which chemical equilibria are involved. Equal temperatures of the outer phases, as well as ideal solutions are assumed. The membranes shall be impermeable for at least one ionic species. Comparison of the theory with experimental data at precipitation membranes shows a conspicuous dependence of the permeabilities on the pH‐values of the fluid phases. A hypothetical model to explain this effect is discus

ISSN:0005-9021    

DOI:10.1002/bbpc.198800005

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

年代:1988

数据来源: WILEY

摘要:

AbstractThermodynamic data of the antimony oxides were determined by solution calorimetry in molten NaOH/KOH (483 K), drop and differential scanning calorimetry and solid state electrochemistry. The formation of Sb2O4from Sb2O3and Sb2O5is an exothermic process (ΔRH(483 K.) = — 25 ± 4 kJ/mol). The molar heat capacity data of the antimony oxides are discussed in comparison with the differentCPfunctions of the literature. The Gibbs free energies of formation at 873 K of Sb2O3(—472 ± 5 kJ/mol) and Sb2O4( — 570 ± 10 kJ/mol) are consistent with calculated values from data com

ISSN:0005-9021    

DOI:10.1002/bbpc.198800006

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe functional dependence of current density and overpotential for an electrochemical process taking place at the interface between a “blocking” electrode and a solid electrolyte and whose rate determining step is the tangential diffusion over the interface was evaluated. — The conditions of applicability to such systems of the classical electrochemical kinetics were criticized. — In particular, it was put into evidence that, even in the case of a linear trend between the logarithm of the current density and overpotential, the extrapolation of the straight line portion to zero overpotential in some cases does not allow the determination of the value of the exchange current

ISSN:0005-9021    

DOI:10.1002/bbpc.198800007

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

年代:1988

数据来源: WILEY

摘要:

AbstractLarge surface area photoelectrochemical cells exhibit low fill factors mainly due to mass transport polarizations in the electrolyte. To avoid that problem transparent (and conductive) materials must be used either as substrate to the photoelectrode or as a counter electrode. — It is shown here that cobalt(II), can reduce the overpotential at the interface between the transparent electrode and polysulfide electrolyte, without loss in transmittivity, rendering those materials good counter electrode. Surface analyses reveal that the metal ions form some kind of a sulfide superstructure with typical grain size of few tens of angstroms. The binding to the oxide layer is briefly discusse

ISSN:0005-9021    

DOI:10.1002/bbpc.198800008

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of pressure was studied on the dimerization reactions of six di‐ and tri‐substituted nitrosobenzenes in carbon tetrachloride at 25°C. The obtained configurational volume changes for the prototype one bond formation reactions are in the range of —17 to —21 cm3mol−1at 6.13 MPa. The volume changes were interpreted in terms of the perturbation theory of liquid; they were dominated by the volume change in the reference system composed of hard spheres. Small differences between the observed and theoretical reference volume changes were ascribed to the perturbation due to electrostatic interactions between the solute and solvent; the perturbation volume changes were estimated by the Kirkwood theory of dipolar

ISSN:0005-9021    

DOI:10.1002/bbpc.198800009

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of pressure on the rate and equilibrium constants for the dimerization reaction of 2,4,6‐trimethylnitrosobenzene in acetonitrile was studied up to 196 MPa at 25°C in order to examine whether the dynamical effect on the reaction process in solution can be neglected as assumed in the transition state theory. All the rate constants relevant to the dimerization were determined by the pressure relaxation method. The configurational reaction volume for the dimerization and the activation volume for the dissociation were —17.4 ± 0.7 and + 5.1 ± 0.3 cm3mol1at 98 MPa, respectively. The experimental results were in reasonable agreement with the theoretical ones that were calculated for the model system composed of hard spheres according to the liquid theory and the transition state theory. The dynamical effect on the activation volume was not detected in the present reaction

ISSN:0005-9021    

DOI:10.1002/bbpc.198800010

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

年代:1988

数据来源: WILEY