Previous Work on Adsorption

In this section we shall discuss the relationship between the work described in this chapter and that which preceded it. The chief objective will be to compare the techniques, the experimental results, the interpretation of these results, and the theoretical concepts. We shall attempt to point out which results have stood the test of time and which results need to be discarded or modified. This discussion will be limited to the work of the following people and their associates Langmuir, Frankenburg, Roberts and Rideal, and Beeck. In making this selection, we unfortunately exclude many important contributions and for this we apologize in advance. To compensate partially we refer the reader to the excellent and comprehensive books by Adam (20) and Dushman (21). 

Starting about 1911 and extending to about 1935, Langmuir and his associates at the General Electric Research Laboratories published a long series of important articles on adsorption phenomena on metal surfaces at comparatively low gas pressures (20,21). This work has not only 

These and other experiments led Langmuir to develop some fundamental concepts on adsorption. One of these is that the forces involved in adsorption are just as large as those in chemical compounds. These forces are usually short-range forces. If the adatom is removed from the surface 

Another concept is that the electronic work function changes linearly with the amount adsorbed or that the dipole moment is independent of the concentration. The (1 — 0) concept states that the rate of adsorption for a constant arrival rate is proportional to the fraction of the surface which has not yet been covered. The last two concepts permitted Langmuir to derive his famous adsorption isotherm, which has been verified by experiment in many systems (see the discussion in section IV). Langmuir s experimental work for Cs on W convinced him that the (1 — 0) law was not applicable in this system. This work also led to the concept that the energies involved in surface migration were much smaller than the energies involved in evaporation. 

A great many experiments on adsorption and catalysis have been performed on finely divided metal powders, and much useful information 

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