Lateral hydrogen concentration

Fig. 8. Variation of the lateral hydrogen concentration and normalized oxygen concentration as a function of distance from the edges of Pd strips. The plot for the lateral hydrogen concentration from the left ( ) and the right ( ) Pd strips (schematic diagram of the sample and the corresponding optical image after a few weeks of H loading at 373 K is shown in the inset) and the average H profile (A) are shown. The different YH phases have been indicated by...

The model for slurry hydrogenation is based on the three steps involving hydrogen mass transfer and reaction. The surface reaction is assumed first order to hydrogen, so the rate constant can be combined with the mass transfer coefficients in a simple equation. Step 3 is omitted, since the bulk concentration of B is normally much greater than the hydrogen concentration in the liquid. Step 5 is not included in the model but will be considered later, in the discussion of selectivity with consecutive reactions. Because of... 

One important variation of the hydrogen concentration cell, the flowing emf cell was developed by Sweeten et al. for studies of volatile reactants. The cell, shown in Fig. 16, comprises of two electrode chambers and a hquid junchon chamber. The lateral holes in the bottom of each piece allow solution to come in from each electrode chamber and then flow upwards into grooves cut in... 

In the later work by Jahn [11] quoted in [6, 12] low hydrogen concentration mixtures were not considered (investigated hydrogen concentrations were 30% and higher), and maximum burning velocities (267 cm/s) were less than those measured by Michelson (281 cm/s). Kozachenko L.S. [13] replicated the Michelson measurements using a fantail burner the results were close to those obtained by Michelson. 

In a later paper Chouinard and Gustafson (1971) reported angular correlations of positron annihilation in erbium, gadolinium, holmium and ytterbium hydrides. The correlations were again claimed to be consistent with the predictions of the protonic model. Recent studies on yttrium dihydride (Sabin et al., 1972 Rozen-feld and Debowska, 1975) were interpreted on the basis of the proton model, but it was pointed out that the model fails for higher hydrogen concentrations, i.e. YH2-YH3 (Rozenfeld and Debowska, 1975). 

We can use this relation and the techniques developed later in this book to correlate our experiments with only one parameter, the diffusion coefficientZ). We then can correctly predict the hydrogen uptake versus time and the hydrogen concentration in the gas. As a dividend, we get the hydrogen concentration at all positions and times within the metal. 

Forests can act as sources of some of the trace gases in the atmosphere, such as hydrocarbons, hydrogen sulfide, NO, and NH3. Forests have been identified as emitters of terpene hydrocarbons. In 1960, Went (10) estimated that hydrocarbon releases to the atmosphere were on the order of 108 tons per year. Later work by Rasmussen (11) suggested that the release of terpenes from forest systems is 2 x 10 tons of reactive materials per year on a global basis. This is several times the anthropogenic input. Yet, it is important to remember that forest emissions are much more widely dispersed and less concentrated than anthropogenic emissions. Table 8-2 shows terpene emissions from different types of forest systems in the United States. 

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