Wicking rate experiment

The pore size distribution in a porous medium is determined by measuring the counterdiffusion rates of two gases across the medium in a Wicke-Kallenbach experiment (Brown and Travis, 1983). The experiments are carried out without a temperature or pressure gradient across the pellet. 

Peters and Krabetz [43] measured reaction rates at 1 atm on AI2O3 promoted iron catalysts with varying particle size (0.5-5.2 mm) and mean pore radius (110-310 A). The effective diffusion coefficient of NH3 was also measured in a Wicke-Kallenbach experiment. They also found good agreement between the measured and calculated data using a pseudo first-order approach. 

The Washburn model is consistent with recent studies by Rye and co-workers of liquid flow in V-shaped grooves [49] however, the experiments are unable to distinguish between this and more sophisticated models. Equation XIII-8 is also used in studies of wicking. Wicking is the measurement of the rate of capillary rise in a porous medium to determine the average pore radius [50], surface area [51] or contact angle [52]. 

Fig. 13. Relationship between the normalized apparent dissolution rate of HT materials, r(glaxs)l1(lnn and their free energy of hydration, ACh>lir. calculated for the pH values measured after one day and 10 days of corrosion. For comparison, the literature-extracted results (Plodinec and Wicks 1994) obtained for 115 glasses of different origins corroded under the conditions of the MCC-I test are reproduced. For simplicity, data obtained after three days of corrosion are not shown their linear fit lies between the ones of the one-day and the 10-day corrosion experiments.

A phase change scheme similar to those described above was proposed by Schwartz and Schmidt 141,142) on the basis of LEED experiments, and by Schiith and Wicke (91,101) on the basis of IR measurements for the oscillatory CO/NO reaction on Pt(lOO). The experiments of Schwartz and Schmidt demonstrated that the transition from the high- to the low-reaction-rate state was accompanied by a change from the 1 x 1 to the hex phase in LEED patterns. The position of the L-CO band in the IR spectra recorded during oscillations varied between the high- and low-reaction-rate states with a relatively high absorption band below 2050 cm present in the low-reaction-rate state, which is characteristic of CO on the Pt(lOO) hex surface. Further proof was provided by Clausius-Clapeyron plot of the conditions for the occurrence of oscillations, which yielded points near the isostere associated with the hex 1 x 1 phase transition (Fig. 14). 

It is well established that many animal tissues can oxidize ketone bodies (Snapper and Grunbaum, 1927 Wick and Drury, 1941 Williamson and Krebs, 1961), and this has led to the concept that it is a physiological function of ketone bodies to serve as a fuel of respiration when carbohydrate is in short supply (Krebs, 1961). Experiments have shown that increased production of ketone bodies is closely matched by increased utilization (Bates et al., 1968). These authors suggest the sequence of events leading to "physiological ketosis" as a consequence of hormonal interrelationships a low blood sugar concentration causes an increase in adipose tissue lipolysis and a rise in the concentration of free fatty acids in the plasma. This in turn results in an increased rate of ketogenesis in the liver, which is followed by a rise in blood ketone-body concentrations, and an increased rate of peripheral utilization. 

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