Micromeritics ASAP 2460, Operator'S Manual

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ASAP 2460 Operator’s Manual Appendix C
246-42800-01 - Aug 2013 C-37
Dubinin-Radushkevich
The Dubinin-Radushkevich
13
equation is:
where:

= the affinity coefficient of analysis gas relative to Po gas (for this application

is taken to be 1)
B = a constant
Po = saturation vapor pressure of gas at temperature T
P = equilibrium pressure
Q = quantity adsorbed at equilibrium pressure (cm
3
/g STP)
Q
0
= the micropore capacity (cm
3
/g STP)
T = analysis bath temperature ( K ), from the
Po and Temperature Options
win-
dow

For each point designated for Dubinin-Radushkevich calculations, the following calculations are done:
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):
Q
 
log Q
0
 
BT
2

---------
Po
P
------- log

2
– log =
LV Q
 
log =
LP
Po
P
-------
 
 
2
log =
Q
0
10
YI
=