Page 107 - Gas Adsorption Equilibria

2. Volumetry / Manometry 93

with the total mol number again being obtained from the EOS

including the compressibility factor

Inserting Eqs. (2.21-2.25) into the mass balance (2.20) and taking Eq. (2.3)
into account we get the equations

with

being the “reduced mass” of component i in the sorbate phase, a quantity
which according to its definition (2.28) can be calculated from measured
experimental parameters of the adsorption system. In order to calculate
from (2.27) we must introduce an approximate value for Choosing
again the helium volume approximation (2.7), the adsorbed mass indeed is the
Gibbs surface excess mass of component (i), cp. Chap. 1, for which we get
from (2.27)

or in view of (2.28, 2.21, 2.24),

Choosing for in (2.27) instead of (2.7) the approximation (2.9) we get
for the absolute adsorbed masses of components i = 1...N in view of
(2.21-2.25, 2.30), the relations