Solution in the Adsorbent Catalyst

It is an important fact that in many cases the rate of diffusion of the dissolved atoms in the metals is high as compared with the rate of dissolution of the gases into the metal or the rate of desorption from the 

Molecular hydrogen does not dissolve easily into iron with a smooth surface at temperatures below 200°C. Atomic hydrogen, however, enters the iron easily even at room temperature (218). In the case of molecular hydrogen it is the activation energy at the surface which governs the process. On a smooth or contaminated iron surface, it is the rate of chemisorption which governs the total rate. We shall return to this special case in Sec. X,4. 

Oxygen may be taken up by platinum. A study of this reaction has revealed that at some stages at not too high temperatures, e.g., 200°C., there may be a temporary increase of the work function of the platinum, showing that some of the oxygen is still at the surface after some time the work function returns to the proper value for platinum, the oxygen atoms having diffused into the metal (219). 

Oxygen and nitrogen may also dissolve in the lattice of zirconium or titanium, where again they are situated at interstices of the metallic lattice. In these metals the atoms are too strongly bound to be of any value for catalytic purposes. 

Physical Adsorption Phenomena at High Degrees op Occupation 

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