Diffusion plausible explanation

In a recent experimental study of the adsorption of methanol in a large crystal of CrAPO by interference microscopy, Lehmann et al. [36] observed that, even at equilibrium, the distribution of sorbate through the crystal is far from uniform. It seems clear that access is controlled lai ely by the defect structure and the growth planes of the crystal. This observation may provide a plausible explanation for the discrepancies observed between different diffusion measurements. The impact of the defect structure... 

In soil suspensions at low salt concentrations, extraneous (junction) potentials can affect pH readings (Appendix 10,1). The most plausible explanation for junction potentials is that K ions in the KC1 bridge of the reference electrode diffuse more rapidly, and Cl ions less rapidly, when negatively charged soil particles are near the bridge. One answer is to place the reference electrode in the clear supernatant solution and the glass electrode in the settled clay suspension (where H+ is concentrated) to obtain valid soil pH measurements. Junction potentials are essentially eliminated at salt concentrations greater than 0.01 M. 

Indeed, plausible explanations of the effects of halogen and Mg/RX in terms of the proposed surface chain mechanism are not obvious. According to this mechanism, the lifetime of R-. and therefore the extent to which it cyclizes, will be halogen-independent, contrary to observation. Also, if the intermediates remain at the surface, the same mechanism predicts that the product distribution will be independent of the area of Mgz (Section 7.2.13). The observed effects suggest that intermediates diffuse in solution. 

Several authors, however, have reported a minor caveat in relation to the reversibility (Napper, 1968b Everett and Stageman, 1977 1978a Clarke and Vincent, 1981a Buscall, 1981). This is that if the particles are allowed to remain flocculated for relatively long periods (say, an hour or more), redispersion is no longer complete. The reasons for this aging effect are unknown. One plausible explanation for the irreversibility involves the slow diffusion of the stabilizer away from the stress zones that are created by the close approach of the particles. 

For a given particle size of 30-50 pm, the influence of pore diffusion on selectivity can be excluded, as proved by additional experiments discussed in Section 14.4.2.4. On the basis of our current knowledge, the only plausible explanation is that the IL changes the chemical properties of the Ni catalyst and acts as a cocatalyst, for example, by the hindrance of the (re) adsorption of COE (or hydrogen) on the active Ni sites. 

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