Page 46 - Gas Adsorption Equilibria
P. 46
32 Chapter 1
1. Mercury intrusion porometry
2. Helium measurements
3. Gas adsorption Ar,
A variety of fairly accurate and reliable instruments for all of these
methods is available commercially today, some of which are listed in
Table 1.5 below.
Additionally it should be mentioned that calorimetric measurements in gas
adsorption systems can also be very well used to characterize the porosity of a
sorbent material. As this field is well presented in the literature [1.3, 1.29,
1.61, 1.62] we do not go into details here but refer the reader to the (few)
examples presented at the end of Chap. 2.
4.1 Mercury Intrusion Porosimetry
The porous material is immersed in a non-wetting liquid, preferably
mercury (Hg). Increasing the pressure in the liquid will cause it to penetrate
into the pores of the solid until equilibrium against the surface tension in
the smaller and smaller pores is attained. The respective mechanical
equilibrium condition leads to the so-called Washburn equation for the
limiting pore radius (r) into which mercury at pressure (p) can penetrate [1.1,
1.2, 1.43, 1.44]:
