Micromeritics ASAP 2460 - Calculations

Appendix C ASAP 2460 Operator’s Manual
C-16 246-42800-01 - Aug 2013
Calculations
The quantities adsorbed (Qa) are converted to the liquid equivalent volumes (Vl, cm
3
/g):
where V
mol
is the liquid molar volume from the fluid property information.
The relative pressure (P
i
) is assumed to be close to unity so that substantially all the pores in the sam-
ple are filled.
The corresponding Kelvin core radius is calculated. Only pores smaller than this size will be included:
where
A = adsorbate property factor (from the BJH Adsorptive Options window)
F = fraction of pores open at both ends (from the BJH Adsorption Report
Options window or the BJH Desorption Report Options window); assumed
to be zero for desorption
Rc = Kelvin radius (Å) of core
This radius will be adjusted for the thickness of the adsorbed layer during subsequent calculation steps.
The following calculations (a-c) are made for each relative pressure interval based on the increment of
volume desorbed during that interval:
where
i = interval number, that is i=1 for the first interval from P
1
to P
2
, and so on
j = each previous interval during which new pores were found
k = the total number of intervals in which new pores have been found. It is also
the number of lines reported on the BJH table for collected data
Vl
i
Q
i
V
mol
22414cm
3
STP
-------------------------------------
=
Rc
i
A–
1 F+P
i
ln
---------------------------------
=