摘要:

AbstractThe paper reports absolute measurements of the thermal conductivity of mixtures of hydrogen and nitrogen in the pressure range 0.7 to 10 MPa at a nominal temperature of 27.5 °C. The experimental results have an estimated uncertainty of ±0.3%. The mixture thermal conductivity in the limit of zero‐density can be described with the aid of the available kinetic theory only if empirical adjustments are made to some of the collision‐integral ratios characteristic of the unlike interactions. The need for these adjustments is taken as evidence that the available kinetic theory formulae are not sufficiently accurate for gas mixtures in which the mass ratio of the molecules is large. At elevated densities the calculation scheme of Mason and his coworkers cannot provide a description of the experimental data within their uncertainty, even when empirical adjustments of a parameter characteristic of the unlike interactions are al

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860302

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

年代:1982

数据来源: WILEY

摘要:

AbstractA recently constructed isoperibol calorimeter has been modified to measure the spontaneous reactions of Li2O, Na2O, CaO, and BaO with As2O5after ignition. Thus, the heats of formation from the component oxides have been determined for Li3AsO4, Na3AsO4, Ca3As2O8, and Ba3As2O8.

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860303

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe mass density ρ and the dynamic viscosity ρ of eleven binary liquid mixtures were measured as a function of concentration and temperature, in order to study the influence of the entropy of mixing on the viscosity of athermal liquid mixtures.—ζ was determined via an Ubbelohde micro‐viscosimeter and ρ via a vibrating densimeter.—The species of the mixtures differ to a large extent in size and in mass only (Si‐, Sn‐, and Ti‐Tetraalkyl and Tetraalkoxy compounds).—With the Grunberg‐Nissan equation the experimental data can be described in good approximation. As a measure for the non‐ideal behaviour of the mixtures, the Grunberg‐Nissan Parameter ρ is correlated with the difference of the molecular diameter of the components, and wi

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860304

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

年代:1982

数据来源: WILEY

摘要:

AbstractCalorimetric studies of transformations have been carried out in single crystals of Ag2+δS and Ag2+δSe of coulometrically controlled compositions. The entropy changes accompanying the α‐β transitions of these solids with different degrees of non‐stoichiometry are discussed in the light of crystal structures and statistical ar

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860305

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe mechanism of intermolecular proton transfer AH + A ⇋ A + HA in solution is studied in terms of a model in which the motion of the molecule A is treated as a classical random motion while the proton behaves quantum mechanically. The proton moves in a symmetrical double well potential which is stochastically time dependent. The energy splitting due to the coupling of the AH stretching vibration in different molecules is assumed to depend only on the distance between diffusing molecules but not on their relative orientation.—Using a first order perturbation approach the transfer rate is found to be inversely proportional to the diffusion coefficient. The proton transfer rates are calculated for two limiting cases corresponding to a WKB type and a Franck Condon type coupling t

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860306

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

年代:1982

数据来源: WILEY

摘要:

AbstractPotential curves of the eight lowest singlet and eight lowest triplet states for the isomerization reaction of stilbene have been calculated by CI including triply excited configurations. The CI was based on MO's evaluated by a CNDO method. A ground state activation energy of the isomerization of 259 k J/mol was calculated. The lowest excited singlet state has a minimum at the perpendicular geometry and an activation energy of 50 kJ/mol for the trans cis isomerization in this state was found. It is shown, that this activation energy originates from an avoided crossing with a higher lying singlet state. Isomerization in the triplet manifold should occur preferentially via the lowest triplet state.

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860307

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

年代:1982

数据来源: WILEY

摘要:

AbstractAnalysis of the1H‐17O dipolar contribution to the proton longitudinal relaxation rate in17O‐enriched water yields a correlation time for re‐orientation of the O–H vector τrOH= (1.71 ± 0.07) ps in H2O at 25 °C. This result is insensitive to uncertainties in the calculated intermolecular relaxation contribution. From1H, D, and17O relaxation rates in H2O/D2O mixtures deuterium isotope effects on the correlation times were estimated. The quadrupole coupling constants of D and17O in liquid water were

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860308

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

年代:1982

数据来源: WILEY

摘要:

AbstractA1H (90 MHz) NMR study shows that ligand (L) exchange on [BeL4]2+is characterised by the rate law: exchange rate = 4(k1+k2[L]free)[BeL2+4] when L = O = CMe(NMe2), O = CMe(NHMe), or O = CH(NMe2) in the non‐coordinating solvents CD3NO2and CD3CN, and also in CD2Cl2in the case of O = CH(NMe2). The kinetic parameters observed for these systems are exemplified by those characterising [Be(O = CMe(NMe2))4]2+in CD3NO2solution which are:k1(340 K) = 7.3 ± 0.7 s−1, ΔH#1= 56.9 ± 1.5 kJ mol−1, ΔS#1= −62.1 ± 4.6 J K−1mol−1,k2(340 K) = 10.5 ± 1.0 dm3mol−1s−1, ΔH#2= 66.7 ± 2.6 kJ mol−1, and ΔS#2= −30.1 ± 7.4 JK−1mol−1. Thek1andk2rate constants are interpreted in terms of dissociative (D) and associative (A) (or interchange (I)) ligand exchange mechanisms and are discussed in conjunction with previously reported dat

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860309

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

年代:1982

数据来源: WILEY

摘要:

AbstractRelative fluorescence intensities of anthracene, fluorene, and 9,10‐dimethylanthracene in aqueous solutions of cetyltrimethylammonium bromide (CTAB) and cetyltrimethylammonium chloride (CTAC) have been measured as functions of surfactant concentrations. Fluorescence was found to be quenched by bromide but not by chloride ions. At low total concentrations (cs0.3 M are connected with changes in micelle shape (rod for

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860310

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

年代:1982

数据来源: WILEY

摘要:

AbstractThe magnetic circular dichroism (MCD) spectra of the bridged tropylium cations have been measured at room temperature. Very weak MCD bands have been observed in the longest wavelength region and assigned to the intramolecular charge‐transfer (CT) transitions arising from the electronic excitations from the highest occupied MO(HOMO) of the remote chromophore to the lowest vacant MO(LVMO) of the tropylium cation. In the shorter wavelength region, four distinct MCD bands with alternating sign have been detected, clarifying four π→π* transitions in the perturbed tropylium m

ISSN:0005-9021    

DOI:10.1002/bbpc.19820860311

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

年代:1982

数据来源: WILEY