Measurement of adsorbed volume

Measuring the rate of adsorption by noting changes in the adsorbed volume is in principle quite simple. A known mass of gas is admitted to the system and the 

The essential parts of a volumetric apparatus are a closed system of known volume, a source of adsorbate and a pressure measuring device. This type of apparatus is more commonly used for the determination of adsorption isotherms, but kinetics can be measured provided that the adsorbent surface is large and the response of the pressure measuring device is much faster than the rate of adsorption. These criteria are usually only satisfied by powders or films which show activated adsorptions. Bond has discussed the phenomenon of activated adsorption. Although the results may often be ascribed to contamination or incorporation into the bulk of the material, in other instances a genuine activated chemisorption is found. 

Although part of the data for activated adsorption, particularly on metal surfaces, can be ascribed to contamination or diffusion effects, there are some experimental results which cannot be explained in this way. The theoretical reasons for this type of behaviour have been discussed by Bond and by Hayward and Trapnell. In general, such chemisorptions obey the Elovich equation 

As noted in Section 2.1.2, measurement of the kinetics of chemisorption on clean metal surfaces generally requires ultra high vacuum techniques, in order to accomplish the experiment in a reasonable period of time. The variant of the classical adsorption method known as the flash-filament technique has been developed by several groups of workers and recently summarised by Ehrlich . 

The kinetic data obtained from the flash filament technique depend on three parameters, the absolute rate of adsorption AdNjdt) occurring on a sample of 

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