Pore analysis by adsorption

Abstract

Adsorption studies leading to measurements of pore size and pore-size distributions generally make use of the Kelvin⁴⁵ equation which relates the equilibrium vapor pressure of a curved surface, such as that of a liquid in a capillary or pore, to the equilibrium pressure of the same liquid on a plane surface. Equation (8.1) is a convenient form of the Kelvin equation:

$$ \ln \frac{P}{{P_0 }} = - \frac{{2\gamma \bar V}}{{rRT}}\cos \theta $$

(8.1)

where P is the equilibrium vapor pressure of the liquid contained in a narrow pore of radius r and P₀ is the equilibrium pressure of the same liquid exhibiting a plane surface. The terms γ and $\bar V$are the surface tension and molar volume of the liquid, respectively, and θ is the contact angle with which the liquid meets the pore wall.