Home Specific surface (BET)

Illustration of the absorption of nitrogen on a powder surface According to a method of Brunauer, Emmett and Teller* the surface of a (ceramic) powder can be calculated from the N2-isotherm, which is observed at the boiling point of liquid nitrogen. By the analysis of the adsorption curves within the relative pressure ranges  p/p0 ~ 0,05 and p/p0 ~ 0,2 the volume Vm is determined, which according to the theory of Brunauer, Emmett and Teller corresponds to the quantity of nitrigen, which is necessary for a monomolecular layer. The surface needed for one nitrigen molecule is 16,2Å2. From this value the specific surface of the sample can be determined in m2/g.

* Brunnauer, S., P.H. Emmett und E. Teller: J. Amer. Chem. Soc. 60 (1938) 309. 

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