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    Self-diffusion and Conduction in Hydrogen-Bonded Solids: Part 1.—Labile Proton Diffusion in Pivalic Acid
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (4), 1972) Hood, G. M.; Lockhart, N. C.; Sherwood, J. N.
    A study has been made of the self-diffusion of labile protons in the plastic phase of pivalic acid using (CH3)3CCOO3H as the tracer. The carboxyl protons diffuse approximately 103 times more rapidly than the molecules and with a significantly different activation energy. Both differences arc confirmed by high-resolution n.m.r. measurements. Conductimctric measurements show that the proton migration is not accompanied by an equivalent charge transport. This leads to the conclusion that the proton migrates via an exchange mechanism which involves molecular rotation.
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    Self-diffusion and Conduction in Hydrogen Bonded Solids: Part 2.—Self-diffusion of C6H514COOH and C6H5COO3H in Single Crystals of Benzoic Acid
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (3), 1972) McGhie, A. R.; Sherwood, J. N.
    A study has been made of the self-diffusion of the labelled species C6H514COOH and C6H5COO3H in single and polycrystallinc specimens of benzoic acid. The two tracers diffuse in a similar manner in the latter where grain-boundary diffusion may predominate. In the pure single crystals the tritium tracer diffuses more rapidly than the 14-carbon tracer and by a different mechanism. The 14-carbon labelled tracer diffuses with the characteristics of molecular vacancy self-diffusion. From a consideration of the effects of ambient conditions and the residual concentration of water in the samples, it is concluded that the rapid tritium diffusion process is extrinsic in nature and that it is a consequence of the exchange of the labile proton with included water coupled with the interstitial diffusion of the water molecule in the lattice.
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    Pressure and Temperature Dependence of the Self-diffusion of Benzene
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (8), 1972) McCool, M A; Collings, A F; Woolf, L A
    The self-diffusion coefficient of liquid benzene has been measured with a modified diaphragm cell. The cell incorporates a bellows in one compartment and the technique for its use makes allowance for bulk flow effects due to changes in pressure. Results have been obtained at 288, 298, 313 and 328 K over the pressure ranges 1-283, 1-645, 1-975 and 1-1496 bar, respectively and used to calculate activation energies and volumes. In contrast to earlier (less accurate) data the present results indicate a non-linear dependence of log D on pressure. The results are used to test a quasi-lattice model of the liquid. The Stokes-Einstein relation is obeyed over only a narrow density range.
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    Pressure and Temperature Dependence of the Self-diffusion of Carbon Tetrachloride
    (Journal of the Chemical Society : Faraday Transaction - I. The Chemical Society, London. 1972, 68 (10), 1972) McCool, M. A.; Woolf, L. A.
    A modified diaphragm cell method 1 has been used to measure the self-diffusion coefficient of carbon tetrachloride at 283, 298, 313 and 328 K over the pressure ranges 1-769, 1-1216, 1-1469 and 1-1475 bar, respectively. These results arc compared with less extensive data from other methods and used with data reported elsewhere for benzene 2 and cyclohexane 3 to test some current theories of transport. In a test of the Stokes-Einstein relation best agreement between theory and experiment was obtained for the pseudo-spherical molecules of carbon tetrachloride for which constancy of (Dtj/T) is maintained over the full range of temperature and pressure. A comparison of the present results with literature values calculated from molecular dynamics of hard spheres shows that the density dependence is not the same and the two cannot be reconciled by a temperature dependent hard sphere diameter. Internal pressures calculated from the data are not dependent on a model of the liquid and are in reasonable agreement with directly determined values.