Micromeritics TriStar II 3020 - Dubinin-Radushkevich

TriStar II 3020 Appendix C
302-42828-01 - Dec 2012 C-27
Dubinin-Radushkevich
Vlog Vo
BT
2


---------------
Po
P
-------log
2
–log=
The Dubinin-Radushkevich
13
equation is as follows:
where:
V
= volume adsorbed at equilibrium pressure (cm
3
/g STP)
Vo = the micropore capacity (cm
3
/g STP)
Po = saturation vapor pressure of gas at temperature T (mmHg)
P = equilibrium pressure (mmHg)
B = a constant
 = the affinity coefficient of analysis gas relative to Po gas
(for this application  is taken to be 1)
T = analysis bath temperature (K), from the Po and Temperature Options dialog
For each point designated for Dubinin-Radushkevich calculations, the following calculations are done:
LV = log (V)
LP
Po
P
-------


2
log=
The intercept, log(Vo) can be found by performing a least-squares fit on the (LP,LV) designated pairs
where LP is the independent variable and LV is the dependent variable. Assuming the adsorption of
gas is restricted to a monolayer, Vo is the monolayer capacity. Based on this assumption, the following
are calculated:
a.) Slope (S cm
3
/g STP)
b.) Y-intercept (YI cm
3
/g STP)
c.) Error of the slope (S
ERR
cm
3
/g STP)
d.) Error of the y-intercept (YI
ERR
cm
3
/g STP)
e.) Correlation coefficient
Using the results of the above calculations, the following can be calculated:
Monolayer Capacity (cm
3
/g STP):
Vo = 10
YI