Volumetric methods for low surface areas

Wooton and Brown [134] used this low pressure method to measure the surface area of oxide coated cathodes (c. 100 cm2) by adsorption 

Lister and McDonald [135] have described in detail the construction and calibration of low temperature ethylene adsorption apparatus. In measurements of such low pressures, two obvious risks must be considered namely the desorption of water and thermal transpiration. By heating the entire system for a short while, or by permanently keeping the system under vacuum, most of the adsorbed vapors from the glass walls should be removed. Otherwise the slowly desorbing vapors will increase the pressure in the system during adsorption measurements leading to erroneous results. When low pressure measurements are made on a gauge held at a different temperature from that part of the apparatus where the adsorption takes place, correction for thermal molecular flow also needs to be considered. To obtain accurate results Lister and McDonald prepared and used correction data. 

In most low pressure measurements the correction for unadsorbed gas is negligible so that no effort needs to be made to minimize the dead space volume. 

Aylmore and Jepson [136] used a novel method of krypton adsorption with labeled krypton ( Kr) as adsorbate and, from the measure of activity, they calculated pressures. 

The field of low surface area determination has been reviewed by Choudhary [137], 

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