The BET method involves the adsorption of a gas, typically nitrogen, on the surface of a solid material at low temperatures. The amount of gas adsorbed is measured as a function of pressure. The BET equation is then applied to this data to calculate the specific surface area. The equation is:
where \( v \) is the volume of gas adsorbed, \( P \) is the equilibrium pressure, \( P_0 \) is the saturation pressure, \( v_m \) is the monolayer adsorbed gas volume, and \( C \) is the BET constant.
