Other Surface Area Methods

Because of its simplicity and straightforward applicability, the BET theory is almost universally employed for surface area measurements. However, other methods [e.g., 1, 2] including methods based on small angle x-ray scattering and small neutron scattering [3] have been developed. Whereas the scattering methods cannot be used in routine operations (to date at least), immersion calorimetry and in particular permeability measurements are more frequently used in various applications. We will discuss below some aspects of the latter two methods together with the so-called Harkins Jura relative method, which is based on gas adsorption and is applied in a relative pressure range P/P₀, which is similar as in case of the BET theory (i.e., 0.05 – 0.3). However, no attempt is made to derive and discuss these alternate methods completely, but rather to present their essential features and to indicate how they may be used to calculate surface areas.