University Chemistry ›› 2022, Vol. 37 ›› Issue (1): 2104049.doi: 10.3866/PKU.DXHX202104049

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Discussion on C in BET Equation

Weiqing Zhang, Bin Huang, Guping Hu()   

  • Received:2021-04-23 Accepted:2021-07-02 Published:2021-07-12
  • Contact: Guping Hu


In this paper, the physical meaning of C in BET equation is introduced from the view of kinetics and statistical thermodynamics. The influence of the size of C on the shape of adsorption isotherm is analyzed. The relationship between the inflection point, the position of B point and the size of C on the adsorption isotherm is deduced, and the relationship between C and relative pressure, the fraction of covered surface when the adsorption capacity reaches one-way, is also deduced. This paper introduces the method to ensure the positive value of C by mathematical method, explains a common phenomenon in data analysis, and discusses the lower limit of C from the mathematical form and physical meaning of BET equation.

Key words: BET equation, Adsorption isotherm, Inflection point