Page 147 - Gas Adsorption Equilibria

3. Gravimetry 133

From the measured quantities we can calculate the reduced
mass adsorbed, i. e. the quantity, cp. (3.5),

via eqs. (3.26-3.29) as

The letter “G” in the abbreviation symbol is indicating gravimetric
measurements, contrary to volumetric/manometric measurements, cp. Chap.
2, eq. (2.5).

If the sorbent mass in the basket is replaced by a dense ballast or tare
or sinker of mass and well known volume weighing of the
suspension in the sorptive gas delivers instead of (3.26) the result

Similarly, a vacuum measurement of this “sinker configuration” leads instead
of (3.28) to

Combining eqs.(3.31), (3.32) and taking (3.27), (3.29) into account we can
calculate the sorptive gas density by

Introducing again the so-called helium hypothesis, i. e. approximating the
volume in the reduced adsorbed mass eq. (3.5) by the helium
volume of the sorbent, i. e. cp. (3.13), we can calculate the Gibbs
excess mass adsorbed from (3.30) and (3.33) as