摘要:

AbstractThe limitsnαmaxandnβminof the two‐phase region of PdHncan only roughly be estimated from the shape of the equilibrium isotherms pH2(n). Other methods applied so far do not yield more accurate results. More precise values can be obtained, however, from measurements of the magnetic susceptibility x as a function of the hydrogen contentnat various temperatures.Such x(n) isotherms have been measured at temperatures between 20 and 300°C and H2pressures up to 140 atm (0 · n · 0.8), using samples of Pd wire (1 mm) and Pd foil (33 μm). In the homogeneity range isotherms for adsorption and desorption were identical, in the two‐phase region, however, hysteresis was always observed. Here the desorption curve was taken as the equilibrium isotherm, and was applied to determine the values ofnαmaxandnβminby extrapolation.Measurements on Pd black in the same region of pressure and temperature showed a number of peculiarities, for instance smaller values of susceptibility and smaller hysteresis loops as compared with bulk Pd. These can be attributed to the large specific surface area of Pd black as well as to its strongly distorted lattice structure.By means of the measurements on bulk Pd the position of the critical point of the palladium‐hydrogen system could be redetermined with rather high precision:Tc= 291 ± 2°C;nc= 0.250 ± 0.005 mol H/mol Pd;Pc= 19.7 ± 0.2 atm H2.The measurements on Pd‐black yielded within the limits of error the same values for the critical temperature and the critical pressure, whereas the value of the H/Pd ratio, properly corrected, was found to be a bit higher, name

ISSN:0005-9021    

DOI:10.1002/bbpc.19730770112

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

年代:1973

数据来源: WILEY

摘要:

AbstractA chemical relaxation study of base pairing through self‐association of 1‐isobutyl‐6‐methyl‐uracil (I) and its hetero‐association with 5‐O‐acetyl‐2′,3′‐O‐isopropylidene‐adenosine (II) in benzene has been carried out by means of the dipolar chemical field effect. The measurements have been interpreted in terms of kinetic parameters as well as with respect to the structures of these hydrogen bonded complexes. The rate constants and dipole moments are:the self‐association being a dimerization process. The dimerization constant (K0= 1151/mol) has been checked by i.r. spectrophotometric measurements, and a comparison has been made between I and 5′‐O‐acetyl‐2′,3′‐O‐isopropylidene‐uridine in tetrachloromethane, chloroform, and benzene. In benzene, the dimer of I acquires most probably structure IV, and the A = U‐bas

ISSN:0005-9021    

DOI:10.1002/bbpc.19730770113

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

年代:1973

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19730770114

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

年代:1973

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19730770116

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

年代:1973

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19730770117

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

年代:1973

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19730770101

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

年代:1973

数据来源: WILEY