Showing papers in "Zeitschrift für Physikalische Chemie in 1982"
940 citations
TL;DR: In this paper, an experimental situation is briefly described and an estimate is made of the best values at 298.15 K and atmospheric pressure, which is used to judge the results of work on the temperature and pressure dependence of D.
Abstract: Results on tracer and self-diffusion coefficients D of the various isotopic species of water as reported in the literature vary widely. The experimental situation is briefly described and an estimate is made of the best values at 298.15 K and atmospheric pressure. The conclusions are used to judge the results of work on the temperature and pressure dependence of D. A brief account on isotopic effects on tracer and self diffusion in water is given.
161 citations
TL;DR: The specific reactions of these intermediates have been studied for systems with pyrene as the primarily excited acceptor and various aromatic and aliphatic amines as electron donors by measuring exciplex decay times and by evaluating time-resolved extinction measurements carried out with and without an external magnetic field of 500Gauß as mentioned in this paper.
Abstract: Photoinduced electron transfer in polar solvents generates exciplexes and radical pairs. The specific reactions of these intermediates have been studied for systems with pyrene as the primarily excited acceptor and various aromatic and aliphatic amines as electron donors by measuring exciplex decay times and by evaluating time-resolved extinction measurements carried out with and without an external magnetic field of 500Gauß. The time-independent rate
126 citations
72 citations
60 citations
TL;DR: In this paper, experimentelle Ergebnisse für the beiden Selbstdiffusionskoeffizienten and den einen gegenseitigen Diffusionskoesffizienen für die vier binären wäßrigen Mischungen with Methanol, Ethanol, Acetonitril' and Dimethylformamid bei 25°C mitgeteilt.
Abstract: Es werden experimentelle Ergebnisse für die beiden Selbstdiffusionskoeffizienten und den einen gegenseitigen Diffusionskoeffizienten für die vier binären wäßrigen Mischungen mit Methanol, Ethanol, Acetonitril' und Dimethylformamid bei 25°C mitgeteilt. Die benutzte Methode war teilweise die NMR-Spin-Echo-Technik und teilweise das Diaphragmaverfahren, verbunden mit Tracer-Aktivitäts-, Dichteoder Brechungsindexmessungen. Aus den Diffusionsdaten wurde dann für jedes System ein Satz von Geschwindigkeitskorrelationskoeffizienten hergeleitet. Der herausragende Effekt, der sich für die Wasser— Wasser-Korrelationskoeffizienten ergab, war deren positives Vorzeichen in drei Fällen; dies deutet auf Wasser—WasserAssoziation hin. Es ergaben sich geringfügige gleichfalls positive Effekte für Geschwindigkeitskorrelationen zwischen den gelösten Teilchen.
44 citations
TL;DR: In this paper, the dispersion of the second virial coefficients B(T) was determined in the case of neopentane at four different temperatures between 283 and 363 K. Berthelot's equation gave the best overall-fit of reasonable experimental ß(r)-values of NEOPENTANE in the extended range 283 < 7" < 550.
Abstract: Scanning-wavelength interferometry is proposed as a method for precise investigations of the (complex) index of refraction of gases in dependence on wavelength A, temperature and pressure p. At — 293 the (real) index of refraction of the gases He, Ne, Ar, H2, N2, 02 and CH4 has been investigated in dependence on (0 < < 1.4 bar) and (400 nm < < 700 nm) in order to determine the dispersion of the mean molecular polarizabilities a(i). In the case of neopentane C(CH3)4 corresponding measurements are accomplished at four different temperatures between 283 and 363 K. In addition to the hitherto unknown dispersion of ( ) second virial coefficients B(T) are determined. Berthelot's equation gave the best overall-fit of reasonable experimental ß(r)-values of neopentane in the extended range 283 < 7" < 550 . For this gas the influence of temperature on a(A) and the influence of gas Sorption on B(T)measurements are discussed.
37 citations
TL;DR: In this article, the authors investigated the chemical diffusivity in cobaltous oxide at 1000 C by means of electric conductivity in conjunction with the classical relaxation method within an oxygen partial pressure range from 1.0 atm to 0.001 atm.
Abstract: Chemical diffusivity in cobaltous oxide at 1000 C, has been investigated by means of electric conductivity in conjunction with the classical relaxation method within an oxygen partial pressure range from 1.0 atm to 0.001 atm. The experimental procedure is extensively described. The results are interpreted in accordance with a previous mathematical error analysis on the relaxation method. Z)Co0 varies from about 5 to 9 10~7cm2/s in going to the highest oxygen pressure. The measured absolute values for 0Co0, between different runs and within any sample, are highly reproducible. The enhancement factor [1 + z] currently encountered with that type of experiment, is here equal to two.
25 citations
TL;DR: In this article, the absorption of light by nitrate ions is characterized by a strong band at 200 nm (e = 9.9103cm~1 M~') and a weak one at 300 nm (s = 7.4cm-1 M
Abstract: The absorption of light by nitrate ions is characterized by a strong band at 200 nm (e = 9.9103cm~1 M~') and a weak one at 300 nm (s = 7.4cm-1 M~'). The spectral shifts of the nitrate bands due to the addition of high concentrations of perchloric acid have been measured. Using the Forster cycle [1] the acidities of the two excited nitric acids have been determined to be stronger than that of the nitric acid in the ground state [pK(HN03) =
20 citations
20 citations
TL;DR: In this article, the magnetic relaxation times of various groups of acetic acid in mixtures with CC14 and C6D12 were measured by measuring the magnetic relaxations of the various protons in these mixtures.
Abstract: The systems CH3COOH-CCL, and CH3COOH-C6D12 were studied by measuring the magnetic relaxation times 7\\ of the various protons in these mixtures. From these data, intermolecular relaxation rates arising from interactions among the protons of OHand CH3groups were determined. By means of the association parameter A association between various groups of acetic acid in mixtures with CC14 andC6D12 has been investigated. Closest distances of approach between various protons ofacetic acid and configurations ofmaximum probability are reported for the pure liquid and the mixtures. For pure acetic acid a comparison with X-ray and neutron scattering results is given.
TL;DR: In this article, the results indicate that the adsorption rate of NO on jarosite is low and that the effective surface area is to be increased by increasing the inter-lamellar spacing.
Abstract: Potassium-, sodium-, rubidium-, ammoniumand hydronium jarosites have been synthesized to investigate the adsorption activity for mainly NO and S02 as typical atmospheric pollutants. The static measurements of the equilibrium adsorption were done at 303 K by the gravimetric method, and the selective adsorbability of NO from a simulated flue gas at 373 K by the flow-gasmethod. The results indicate that jarosites in general are promising as adsorbents for NO in particular. It has to be recognized, however, that the adsorption rate ofNO on jarosite is low and that the effective surface area is to be increased. The rate ofadsorption ofNO on jarosite derivatives appears to be influenced by the inter-lamellar spacing. The adsorbability of S02 on jarosites is not distinctive among other adsorbents. The properties ofjarosite have been discussed in the light of its crystallographic structure and the state of agglomeration.
TL;DR: In this article, the total vapour pressure measurements performed at 313-15 K by a static method were reported for binary mixtures of acetone with five aliphatic hydrocarbons (hexane, heptane, octane, nonane, decane) and five aromatic hydrains (benzene, toluwe, ethyl benzene, o-xylene, pxylene).
Abstract: Results of the total vapour pressure measurements performed at 313-15 K by a static method are reported for binary mixtures of acetone with five aliphatic hydrocarbons (hexane, heptane, octane, nonane, decane) and five aromatic hydrocarbons (benzene, toluwe, ethylbenzene, o-xylene, p-xylene). From the pressure isotherms the following quantities have been calculated by Barker's method: constants of the Redlich-Kister ^-approximation polynomials, activity coefficients, vapour compositions and some auxiliary functions concerning the least squares approximation and vapour phase nonideaKty.
TL;DR: In this paper, the anodic oxidation of hydrazine, methylhydrazine and 1,1-dimethylhydrazines at carbon fibre electrodes in acetonitrile is studied by means of cyclic voltammetry.
Abstract: The anodic oxidation of hydrazine, methylhydrazine and 1,1-dimethylhydrazine at carbon fibre electrodes in acetonitrile is studied by means of cyclic voltammetry. The above compounds are oxidized to the corresponding diimides following irreversible, diffusion controled reactions. Comparing the experimental with the theoretical peak currents we come to the conclusion that only j of the molecules undergoes oxidation, while the remaining! actas acceptors of the protons released during the corresponding reactions. The fibres are oxidized in air at high temperatures thus forming acidic groups on their surface. These groups inhibit the oxidation of hydrazine, while in the meantime the reduction of azobenzene in acetonitrile solutions is facilitated. For the latter a characteristic pre-wave is observed, reaching a maximum value for a given depolarizer concentration. The increase of the pre-wave with heating time constitutes a measure for the carbon oxidation.
TL;DR: In this paper, the photochemical and photophysical behavior of 9-styrylphenanthrene and its pyridyl analogues, the 9-phenanthryl, n-pyridisyl-ethylenes (n = 2, 3, 4), were studied in fi-hexane and acetonitrile-water.
Abstract: The photochemical and photophysical behaviour of 9-styrylphenanthrene and its pyridyl analogues, the 9-phenanthryl, n-pyridyl-ethylenes (n = 2, 3, 4), were studied in fi-hexane and acetonitrile-water. Fluorescence spectra, quantum yields and lifetimes and trans-» eis photoisomerization quantum yields were determined for the trans isomers. The cis~» trans photoisomerization and dehydrophotocyclization quantum yields were measured for the eis isomers. The photocyclization products were isolated and characterized. The results obtained give a general picture of the competition among the various deactivating processes in these compounds. Mechanistic information is obtained also by comparison with what was found for other stilbenelike molecules.
TL;DR: In this article, the activation energies for viscous flow have been calculated with the help of the Feakins, Freemantle and Lawrence equation, and the S-coefficients for all the amino acids at the three pH's follow the sequence ß(iH2o) > ß (mNaOH) > ^<ü.hci) over tne above temperature range.
Abstract: — 40 °C in the concentration range 0.005 to 0.1 molai, and the B-coefficients have been calculated using the equation / 0 = 1 + Be. The corresponding activation energies for viscous flow have been calculated with the help of the Feakins, Freemantle and Lawrence equation. The S-coefficients for all the amino acids at the three pH's follow the sequence ß(i„H2o) > ß(mNaOH) > ^<ü.hci)over tne above temperature range. The gradual decrement of ß-coefficients from water to HCl has been discussed in terms of decreasing electric field of the ions concerned. From the temperature coefficient of it has been inferred that the simultaneous influence of polar and non polar parts is responsible for the extra structure enhancement by the y-amino acids in aqueous solution.
TL;DR: In this article, it was shown that linear response theory when applied to binary diffusion in liquids in the limting case x − * 0 contains the validity of the principle of linear momentum conservation.
Abstract: It is shown that the formalism of linear response theory when applied to binary diffusion in liquids in the limting case x¡ -* 0 contains the validity of the principle of linear momentum conservation. A somewhat more detailed microscopic interpretation is given. Next the treatment is extended to the entire composition range 0 < x¡ < 1 introducing the most simple composition dependence and satisfying the requirement of microscopic reversibility. This leads to the definition of standard velocity correlation coefficients for ideal mixtures. Some well known thermodynamic relations are compared with the results derived from momentum conservation.
TL;DR: The band structure of unoxidized bis(glyoximato)nickel(II) has been studied by means of the crystal orbital (CO) formalism that has been implemented into a semi-empirical INDO model as mentioned in this paper.
Abstract: The band structure of unoxidized bis(glyoximato)nickel(II) has been studied by means of the crystal orbital (CO) formalism that has been implemented into a semiempirical INDO model. The unoxidized polymer crystallizes in a so called M-L-M conformation where the shortest intercell distances are found between the 3d center (M) of one cell and ligand (L) atoms in the neighbouring unit cells. Several ligand bands are predicted on top of the Ni 3 d bands. The low crystal symmetry leads to a pronounced /r-dependence in the character of the Ni 3 Estates ( , , functions). The results are compared with previous INDO CO data derived for Ni stacks with direct metal-metal interactions (M-M conformation).
TL;DR: In this article, the activity of the electrons has been calculated from the corresponding values of the concentration, thus leading to an expression for the dependence of ae from the equilibrium partial pressure p 0l of oxygen in Pb02.
Abstract: · 1020cm\"3 has been measured. With the aid of Fermi-Dirac-statistics the activity a, of the electrons has been calculated from the corresponding values of the concentration, thus leading to an expression for the dependence of ae from the equilibrium partial pressure p0l of oxygen in Pb02. This dependence may approximately be written in the form at~p¿'is. These results are in agreement with a disorder model of lead dioxide, where hydrogen ions on interstitial lattice sites together with quasi-free electrons are considered to be the dominating disorder centres.