Tw
1
HP1
HP2
Pr
1
ln
-------------------
HP3
=
Tw
1
HJ1
HJ2 Pr
1
log–
--------------------------------------
HJ3
=
Tw
I 1+
HP1
HP2
Pr
I 1+
ln
-------------------------
HP3
=
CSA
J
Rc
j
Tw+
2
Rc
j
2
–10
16–
cm
2
/A
2
=
Appendix C TriStar II 3020
C-12 302-42828-01 - Dec 2012
The thickness of the remaining adsorbed layer at this relative pressure is calculated:
where
HP1, HP2, and HP3 are Halsey Parameters 1, 2, and 3 (respectively) from the Halsey Thickness Equa-
tion dialog.
These calculations illustrate the use of the Halsey thickness equation. If the Harkins/Jura equation was
selected, substitute the following wherever the thickness equation appears:
where
HJ1,
HJ2, and HJ3 are Harkins-Jura Parameters 1, 2, and 3 (respectively) from the Harkins-Jura Thick-
ness Equation dialog.
The following calculations (a-c) are made for each relative pressure interval based on the increment of
volume desorbed during that interval. The variable I refers to the interval number, that is I=1 for the
first interval from Pr
1
to Pr
2
, and so on. J refers to each previous interval during which new pores were
found. K refers to the total number of intervals in which new pores have been found. K is also the num-
ber of lines reported on the BJH table for collected data.
a.) The thickness of the adsorbed layer at the end of the interval is calculated as follows:
(For the last pressure interval from the lowest Pr
I
to zero relative pressure, Tw
I+1
= 0.)
For the first pressure interval, there are no previously opened pores so the volume desorbed
from walls of previously opened pores is zero (Vd
1
= 0), and the remainder of Step (a) is
skipped.
The change in thickness of the wall layer due to desorption from previously opened pores is
calculated:
The annular cross-sectional area of the wall layer desorbed
is calculated for all previously
opened pores:
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