Adsorption of gases on solids using the BET equation

Stephen Bmnauer (1903-1986), Paul Emmett and Edward Teller (1908-2003) developed a theoretically based adsorption theory known by the initials of their 

The parameter C of BET is a measure of the difference in the heat of adsorption of the 2nd, 3rd and so on layer compared to the heat of the creation of the first layer. With the exception of the first layer, all other layers are assumed to have the same heat of adsorption. The first layer is characterized by a much higher heat of adsorption compared to the other layers. 

The BET equation has found widespread use in adsorption studies. For example, the model has been used for the characterization of porous materials, i.e. getting information about the surface area and the nature of the surface. Using Equation 7.3, the specific surface area of solids can be estimated from the V parameter of BET  

195 nm for Kr). Nitrogen is the standard gas used in BET measurements of the specific surface area of solids. Further support of the BET theory arises when the adsorption of different gases on the same solid yields (using Equation 7.3) the same specific surface area for the solid. Based on an lUPAC Project (1970), BET is recommended as the standard for Aspec measurements. 

Moreover, as we will see next, when the specific surface area of a solid is known (using the technique 

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