摘要:

AbstractTwo oxidation paths of paraphenylenediamines (R) forming quinone diimines (T+) are discussed: either two subsequent 1‐electron steps with parallel dismutation of the radical intermediate (S+) or one 2‐electron step with subsequent symproportionation, forming the radical. By means of a stopped flow apparatus with 5 mixing chambers which allows premixing of selected reactants and pH‐jumps it is shown that the (irreversible) oxidation with iodine follows the second mechanism. Iodine is unable to react with the semiquinone diimine. Only unprotonated R and free I2are the reacting species. The rate constants of 14 p‐phenylenediamines are between 1 · 106and 2 · 109l · mol−1s−1at 25 °C. The site of attack of iodine is the NR2‐group. Possible intermediates are discussed. The protonation constants of R and the extinction coefficients of the examined compounds at two characteristic wave

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830902

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe paper describes a new experimental set‐up for neutron scattering experiments on fluid systems at high temperatures and pressures. This technique has been applied for the investigation of the static structure factorS(Q) of expanded fluid rubidium up to 1970 K and 150 bar. The first results obtained up to these conditions show a strong decrease of the intensity of the first peak inS(Q) and a pronounced increase of the scattering at small angles with reducing densities. Within experimental errors no shift in the position of the first peak is found above 900 K. These observations together with the corresponding behaviour of the Fourier transform ofS(Q) indicate, that with expansion the distance of nearest neighbours changes only a little, whereas the number of nearest neighbours decreases by about a factor of two, if the density is reduced from 1.2 g cm−3at 900 K to 0.6 g cm−3at 1970 K. It is the first time that such a change in the microscopic structure has been studied experimentally for a fluid metal over a wide range of temperatures and densities. The correlation between the increase inS(O) and the change in the mean interatomic interaction is briefly disc

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830903

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe valence x‐ray photoelectron spectra of GeS, GeSe, and GeTe are investigated theoretically by means of solid state clusters using the scattered wave method. For GeTe relativistic and non‐relativistic energy band structures are calculated in terms of the KKR method. It is found that the characteristic features of the photoelectron spectra for the germanium chalcogenides under investigation can be interpreted sufficiently well on the basis of the cluster calculations. For GeTe, however, relativistic corrections to the cluster one‐electron energies seem to be indispen

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830904

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe rate of oxygen transfer between CO and CO2has been measured on Au, Pt, and Au Pt supported on SiO2at 250 °C, constant partial pressure of CO of 42 Torr, and 0.25

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830905

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

年代:1979

数据来源: WILEY

摘要:

AbstractThermal polymerization of PTS has been measured under hydrostatic pressure up to 6 k bar as a function of temperature. It is found that the induction time for autocatalytic reaction acceleration decreases much faster with pressure than predicted by Baughman's theory. The rate constant used to describe the first order reaction regime increases with pressure according to exp(p/p0) withp0= 1.68 ± 0.05 kbar. Both effects are shown to arise from the components of hydrostatic force field acting perpendicular to the polymer chain direction and facilitating bond formation between neighboring monomer molecules. — Measurement of the lattice contraction alongb‐direction as a function of conversion at 1 bar indicates agreement with Baughman's theory which is based on the change of the elastic strain energy inb‐direction. It is concluded that this theory describes thermal polymerization of PTS at constant pressure but cannot account for reaction acceleration by lateral compression of the lattice. An explanation for the independence of the activation energy on conversion and pressure is sug

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830906

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

年代:1979

数据来源: WILEY

摘要:

AbstractDielectric measurements in the frequency domain were performed at lipid bilayer membranes, with low concentrations (<5 · 10−9M) of dipicrylamine in the aqueous solution. A bridge circuit allowed to superimpose d. c. voltage and a. c. excitation voltage at the membrane. The output‐signal of the bridge corresponded to the charge at the membrane. Besides an a. c. component at the fundamental frequency of excitation it contained higher harmonics due to the non‐linear charge‐voltage relation. ‐ A theory is given describing second harmonic generation as a function of frequency. The model is equivalent to a two‐state dipole model. The first non‐zero terms in an approximation for small a. c. voltage are reported. Experimental results are in accordance w

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830907

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

年代:1979

数据来源: WILEY

摘要:

AbstractSpecific conductances of Et4NPF6, Pr4NPF6, Bu4NPF6, LiPF6, KPF6, LiClO4, and KSCN in propylene carbonate were studied at high concentrations in the temperature range from +25°C to ‐45°C. Data are fitted by a least‐squares method to a four‐parametric empirical equation, yielding the maximum specific conductance κmaxand the corresponding concentration μ. Within the frame‐work of a hydro‐dynamic model the Stokes‐radii of the ions and the solvent viscosity are found to be the most important conductance‐determining parameters, affecting both κmaxand μ Ionic association in solutions with propylene carbonate as the solvent is not of significant importance. Kinetic treatment of conductance yields temperature‐dependent activation energies, but at any one temperature equal for all sal

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830908

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

年代:1979

数据来源: WILEY

摘要:

AbstractLiquid mixtures of propionic acid + triethylamine showed very negative enthalpies of mixing which could not be determined directly in a flow microcalorimeter of Picker type. Therefore difference heats were measured by mixing various mixtures thereby covering the whole range of concentration propionic acid/triethylamine. Excess enthalpies of mixing were calculated from these data by a mathematical procedure recently suggested in the literature. This method allows the time‐saving use of a Picker calorimeter of high precision for investigating also systems exhibiting excess enthalpies of mixing in the range of several thousand Joule per mole. The minimum of the excess enthalpy of ‐ 3150J mol−1was found at a mole fraction of propionic acid of 0.75 indicating the formation of an (1:3)‐aggregate. A second smaller minimum seen at a mole fraction ∼0.63 may result from a (1:2)‐aggregate indicated before only by a non‐thermodynamic method. The structure of the liquid mixtures

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830909

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

年代:1979

数据来源: WILEY

摘要:

AbstractGas‐liquid chromatography is used to measure the solubilities of eight solvents (benzene, toluene, nitroethane, dioxane, n‐heptane. cyclo‐hexane, isopropanol, and 1,2‐dichloroethane) in (vinylchloride/vinyl acetate) copolymers containing 0, 3, 10, 17, and 100 weight percent vinylacetate. Measurements were made at 125 and 140 °C. The solubilities are only weakly dependent on polymer com

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830910

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

年代:1979

数据来源: WILEY

摘要:

AbstractDer Zerfall von Äthan (0,54 ppm in Argon) in CH3‐Radikale erfolgt bei TemperaturenT>1700 K undp≈︁ 1,5 bar hinter Stoßwellen derart schnell, daß CH3als quasi‐Ausgangssubstanz angesehen werden kann. Durch direkte Messung des zeitlichen Verlaufes der H‐Atomkonzentration in der Reaktionszone hinter Stoßwellen konnte im Temperaturbereich 2150 ≤T≤ 2850 K die Geschwindigkeitskonstante der Radikalreaktionbestimmt werden. Die Gesamtdichte, bei der die Versuche ausgeführt wurde

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830911

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

年代:1979

数据来源: WILEY