Page 148 - Gas Adsorption Equilibria

134 Chapter 3

If the volume of the adsorbed phase is taken into account, i. e. is
approximated by eq. (3.15), the absolute mass adsorbed again can be
calculated from as given by (3.34) via eq. (3.16).

Hint: From the gas density calculated by eq. (3.33) the sorptive gas
pressure inside the adsorption vessel can be calculated via an
accurate thermal equation of state. That is, the MSB also can be used as a
(fairly sensitive) manometer, especially at very high and very low pressures
[3.6, 3.26].

2.2.3 Uncertainties or Errors of Measurements

The uncertainty of measurement represented by its dispersion or mean
square deviation (MSD) of the Gibbs excess mass can be calculated
from eq. (3.18) which results from eq. (3.14) or (3.34) by applying the Gauss
law of propagation of uncertainties:

However, here the MSD of has to be calculated from eq. (3.30).
Hence we have

The dispersions of the sorptive gas density and of sorbent’s helium

volume occurring in eq. (3.35) are given by expressions (3.21) and
(3.22), ( 3.23) respectively, cp. Sect. 2.1.3. For sake of clarity we list all
parameters and quantities to be measured in a table:

The symbol indicates any of the vertical forces defined by eqs. (3.26-
3,29) and measured at the MSB. The uncertainties of measurement of all these
forces have been assumed to be equal, cp. eq. (3.36). This assumption