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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 25 (1996), S. 541-553 
    ISSN: 1572-8927
    Schlagwort(e): Potassium ; cesium ; fluoride ; halide ions and perchlorate ; methanol ; water ; molar conductivities ; ion association ; Gibbs energies of transfer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Electrolytic conductivities of KF and CsF in methanol solution have been determined at 25°C. The single ion molar conductivities of the fluoride ion, obtained from the two salts are in excellent agreement and indicate that the F− ion is highly solvated in methanol (MeOH). Combination of the present and literature data for related salts in both water and MeOH indicate that while the primary solvation of ions may be more extensive in H2O there is considerable enhancement of the secondary solvation sheath in MeOH. Recalculation of high precision literature conductivity data using a consistent mathematical approach indicates that ion pair formation constants for simple 1:1 electrolytes in MeOH are 1 or 2 orders of magnitude greater than in H2O. This is shown to be entirely due to the less favorable solvation of ions in MeOH, as the Gibbs energies of transfer of the neutral ion pairs MX from H2O to MeOH are also unfavorable. Calculations also show that ion association in MeOH is strongly influenced by coulombic interactions whereas in H2O short range interactions are generally more important.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1572-8927
    Schlagwort(e): Electrolytic conductance ; molar conductance ; ion pair formation ; complex formation ; 18-crown-6 ; calix[4]arene-bis-crown-6 ; lithium perchlorate ; sodium perchlorate ; potassium perchlorate ; rubidium perchlorate ; cesium perchlorate ; acetonitrile ; methanol ; propylene carbonate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Résumé The interactions of Li+, Na+, K+, Rb+, and Cs+ with the “double-crown calix,” calix[4]arene-bis-crown-6, have been studied in methanol, acetonitrile, and propylene carbonate at 25°C using precise conductivity measurements. For Li+ and Na+ in solutions containing this calix[4]arene, only 1:1 cation:ligand complexes are formed which permit the determination of the thermodynamic complexation formation constants,K f. The conductivity data strongly suggest that 2:1 cationcalixarene complexes form with K+, Rb+, and Cs+. The existence of 2:1 complexes was experimentally confirmed for the potassium systems by a mass spectroscopic method.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1434-601X
    Schlagwort(e): 25.70.Np
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report a preliminary measurement of coincident neutron-proton pairs emitted at 45° in the interaction of 400, 530, and 650 MeV/A neon beams incident on uranium. Charged particles were identified by time of flight and momentum, as determined in a magnetic spectrometer. Neutral particles were detected using a thick plastic scintillator, and their time of flight was measured between an entrance scintillator, triggered by a charged particle, and the neutron detector. The scatter plots and contour plots of neutron momentum vs. proton momentum appear to show a slight correlation ridge above an uncorrelated background. The projections of this plane on then-p momentum difference axis are essentially flat, showing a one standard deviation enhancement for each of the three beams energies. At each beam energy, the calculated momentum correlation function for the neutron-proton pairs is enhanced near zero neutron-proton momentum difference by approximately one standard deviation over the expected value for no correlation. This enhancement is expected to occur as a consequence of the attractive final state interaction between the neutron and proton (i.e., virtual or “singlet” deuterons). The implications of these measurements are discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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