ISSN:0005-9021    

DOI:10.1002/bbpc.19900940502

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

年代:1990

数据来源: WILEY

摘要:

AbstractPartial enthalpies of mixing of pyridines in methanol, ethanol, 1‐butanol, water and cyclohexane were determined calorimetrically at 25°C. From these data their molar enthalpies of transfer, at infinite dilution, from the inert solvent to the H bonded solvents were calculated. They were compared with the enthalpies of H bond formation between the pyridines and the alcohols in CCl4and the enthalpies of the selfassociation bonds in the pure liquids. Although in the pure alcohols more than 95% of the molecules are at a given time involved in H bonds with an energy of about 25 kJmol−1which is markedly larger than the energy of the pyridine‐alcohol bonds in CCl4, the molar enthalpy of transfer of the pyridines from an inert solvent to an H bonded one remains exothermic. A quantitative treatment of the competition between the two types of H‐bonds is presented. It is based on the thermodynamics of mobile order that was recently developed. It leads to an equation that reasonably predicts the transfer enthalpies. According to this treatment the competition reduces the complexation constant by a factorK0AB/(K0ABK0AA),K0ABandK0AAbeing the stability constants of the H bonds in the absence of competition. In water the exothermic effect is enhanced because the second O ‐ H group of the molecule forms much weaker selfassociation H‐bonds than t

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940503

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe paper is devoted to the study of the applicability to binary mixtures of an extension of the van der Waals model for the description of the thermal conductivity of pure liquid alkanes. This study is based upon recently obtained accurate data for the binary mixtures methane + ethane and n‐heptane + 2,2,4‐trimethylpentane. — A reduced thermal conductivity for the mixtures is defined such that its density dependence is identical to that of the pure components. — Furthermore, a scheme is developed that enables the prediction of the thermal conductivity of the mixtures at any temperatureT≤ 0.7Tcany pressure, solely from data for the pure components, i.e. without resort to any experimentally adjusted parameters for the mixtures. Such scheme is able to reproduce the available thermal conductivity data for the above mentioned systems with an error of the order of ±2% at a 2σ level (σ being the standard deviation), which is commensurate with the combined uncertainty of the experimental results for the pure components and for

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940504

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe paper presents a simple analytic volume‐explicit equation of state (EOS) for fluids of hard bodies made up to fused hard spheres (FHS). Application of this EOS to both pure fluids and fluid mixtures (via Amagat's law) provides an accurate description of practically all existing computer simulation data. It is found that deviations from the assumption of ideal mixing are restricted essentially to low densities only; at higher densities small deviations are detected only for quite large volume ratio of molecules while the shape does not seem to play a significant rol

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940505

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe relative static dielectric constant ε of methyl cyanide was measured from 20 to 350°C, from 50 to 2250 bar and for the liquid along the saturation line to 270°C (Tc= 274.7°C). — Equipment and experimental procedure are described. At 20°C and pressures of 50 and 2000 bar ε changes from 37.7 to 42.9. At 100°C the change over the same pressure range is from 26.6 to 32.4 and at 300°C from 2.50 to 18.5. The accuracy of the data is ±0.4% up to 100°C and ±0.6% up to 300°C. Above 300°C and below 200 bar the data may be uncertain within ±1 or ±2%. Diagrams with ε‐values in dependence of density and temperature are given. The Kirkwood correlation factor below a density of 0.4 g cm−3is slightly above unity. At densities higher than 0.4 g cm−3ε declines at all temperatures to about 0.8 at 0.8 g cm−3. This may indicate a certain degree of dimeri

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940506

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe electrochemical properties of the interface between graphite sample and electrolyte solution will change during the anodic intercalation process. The physical quantities which indicate these electrochemical properties can be calculated from the results of the AC impedance measurements. An equivalent circuit is suggested for the calculation. The results of this method are in very good agreement with those from other methods, therefore it is very helpful for studying the kinetics of the anodic intercalation process into graphite in the electrolyte solution.

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940507

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

年代:1990

数据来源: WILEY

摘要:

AbstractInvestigations at laboratory fermenters have shown that the nitrification of ammonia salt solutions by bacteriae is obstructed by Ca2+‐ or Mg2+‐ions in the waste water. This phenomenon is discussed on the base of electrostatic theories of the effect of divalent cations on phospholipid membranes. — In addition, X‐ray diffraction has been used to find possible differences between the actions of CaCl2and CaSO4. The phase behaviour of CaCl2‐ and CaSO4‐containing samples was found to be the same. Lamellar and disperse phases are observed at same temperatures and same Ca2+concentrations. So there is no significant difference in the electrostatic charging effect to be expected. But the disperse phases show differences: The thickness of the bilayer is smaller for CaCl2than for CaSO4. The main part of this reduction is due to the hydrocarbon chain region. Those differences can be explained by an embedment of Cl‐ions into the membrane surface which does not take place with SO2−4because of

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940508

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe refractive index of several perfluorinated surfactant solutions was measured as a function of the concentration. The plot of the refractive index against the concentration for each surfactant shows a sharp break at the cmc. For several systems the slope of the refractive index changed even its sign. The extent of this change is much bigger for perfluorinated surfactants than the change that is shown by hydrocarbon surfactants. It is shown by density measurements that the difference of the refractive index increment above and below the cmc is due to the difference of the partial molar volumes of the surfactant molecules in the monomer and in the micellar state. It is thus possible to determine volume changes in surfactant systems by means of the measurement of the refractive index.

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940509

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe simulation of the 4f—4f electric and magnetic dipole transition probabilities of Eu3+ions in Na5Eu(MO4)4(M = Mo and W) was carried out according to the Judd‐Ofelt theory. The experimental data consist of 295D0,1→7FJMtransitions between crystal field sublevels. — The optimization of the six non‐zeroBλkgparameters allowed for the D2dsymmetry yielded the following sets for Na5Eu(MoO4)4and Na5Eu(WO4)4(in 10−10cm units).B232= ‐2.01 (‐1.94),B432= 0.66 (0.57),B452= 3.31 (3.07),B652= 8.47 (6.72),B672= 2.27 (2.63) andB676= 31.11 (30.93), respectively. These sets give reasonable simulation to the experimental transition probabilities. The conventional Judd‐Ofelt theory was, however, unable to simulate the intensity of the “hypersensitive”5D0→7F2transition. Most of the discrepancies are due to the uncertainty in experimental data although the influence of basis set truncation (only 671 |LJM>levels out of the total of 3003 were included in the basis set of wave functions) and the approximate symmetry (D2dsymmetry was used instead of the real S4one) can

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940510

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe elementary reactions of F and Cl atoms with CH2CO were studied in an isothermal flow reactor with a mass spectrometric detection device. The atoms were produced in a microwave discharge of F2/He and Cl2/Ar mixtures respectively. — For the reactions of F and Cl atoms with CH2CO, applying pseudo first order conditions ([F]0→ [CH2CO]0and [Cl]0→ [CH2CO]0respectively, the second order rate constantswere found. — The following mechanism was obtained for the F atom reaction:The abstraction channel to form HF and CHCO was calibrated to contribute 20% to the overall reaction. — For the Cl reaction the two main reaction pathwayswere d

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940511

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

年代:1990

数据来源: WILEY