Cheng/Yang Correction - Micromeritics TriStar II 3020 Operator's Manual

Appendix C
T =
3
T =
4
where

Cheng/Yang Correction

This factor corrects for the nonlinearity of the isotherm. It adds an additional term to the equations for
the different geometrics:
 
P
------ -
ln
 
Po
where
G(L) =

=
C-22
1 1
------------------ - -------------------
–
9 9
   
1 S – 1 +
S
1 1
------------------- ------------------ -
–
8 8
   
1 + 1 S –
S
–
L d
0
--------------
=
S
L
1 1
 
G L   -- - ----------- -
= – 1 – ln
 
 1 
–
one of the Horvath-Kawazoe equations given above
degree of void filling;  is estimated by first computing the monolayer capacity
(V ) with the Langmuir equation over the range of data points from relative
m
pressure 0.02 to 0.2 or the maximum relative pressure included in the Horvath-
Kawazoe analysis.  is computed as the quantity adsorbed over V
TriStar II 3020
.
m
302-42828-01 - Dec 2012