Micromeritics ASAP 2460, Operator'S Manual

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ASAP 2460 Operator’s Manual Appendix C
246-42800-01 - Aug 2013 C-11
Temkin Isotherm
The Temkin isotherm has the form
where
A = a
0
exp , where

0
and a
0
are adjustable constants
P = equilibrium pressure measured by gauge at temp T
amb
q
0
= the differential heat of adsorption at zero surface coverage
Q = quantity of gas adsorbed
Q
m
= quantity of gas in a monolayer
R = molar gas constant
T = bath temperature
In terms of quantity adsorbed
Thus, the plot of the natural log of absolute pressure vs. quantity adsorbed yields a straight line with
slope and intercept .
Q
Q
m
--------
RT
q
0

---------
A
0
P
 
ln =
q
0
–
RT
--------
 
 
 
8.31441 10
3 –
kJ
mol K
--------------

Q
RTQ
S
q
0

--------------
A
0
P
P
0
------
 
 
ln + ln =
RTQ
m
q
0
---------------
A
RTQ
m
q
0
a
---------------
ln