Page 221 - Gas Adsorption Equilibria

4. Volumetric – Gravimetric Measurements 207

Figure 4.13. Simultaneous measurements of weights of porous sorbent materials exerted to a
sorptive gas and density of the gas on site were performed for the first time on 11
February 1998 in lab PB-A 0126 at the Institute of Fluid- and Thermodynamics
(IFT) of the University of Siegen. Members of the working group have been R.
Seif (RUBOTHERM), C. Lösch (RUBOTHERM), F. Dreisbach (IFT), and M.
Seelbach (IFT) (from left to right). (Reprint by permission of RUBOTHERM
GmbH.)

After thermodynamic equilibrium is reached, i. e. the pressure (p) and the
microbalance signal are (at least technically) constant, the circulation
pump can be turned off and data (p, T, be registered. These together
with the known concentrations of the sorptive gas mixture originally
supplied to the system, provide the basis from which the masses of
both gas components adsorbed on can be calculated as will be described
in the next section. Naturally, a set of similar step up experiments can be
performed with increasing sorptive gas pressures in the (AC). However, it
should be taken into account that in such a procedure, uncertainties of results
are adding up. Hence it is not recommended to perform more than – say – five
sequential pressure step experiments to keep uncertainties of adsorbed masses
and sorptive gas concentrations below or at 10 %, cp. also Sect. 3.4 of this
chapter.