Micromeritics Gemini VII 2390a, Operator'S Manual

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Gemini VII Appendix C
239-42828-01 - Dec 2012 C-7
Langmuir Surface Area
L
I
P
rel
I
N
ads
I
------------
=
SA
LAN
CSA
6.023 10
23
   
22414
cm
3
STP
 
10
18
nm
2
/
m
2
 
S
 
--------------------------------------------------------------------------------------------------
=
For each point designated for surface area calculations, the Langmuir
3
transformation is calculated as
follows:
where L
I
is in units of g/cm
3
STP
A least-squares fit is performed on the (P
rel
I, L
I
) designated pairs where P
rel
I is the independent vari-
able and L
I
is the dependent variable. The following are calculated:
a.) Slope (S g/cm
3
STP)
b.) Y-intercept (Y
INT
g/cm
3
STP)
c.) Error of the slope (S
ERR
g/cm
3
STP)
d.) Error of the y-intercept (YI
ERR
g/cm
3
STP)
e.) Correlation coefficient
Using the results of the above calculations, the following can be calculated:
Langmuir Surface Area (m
2
/g):
V
M
1
S
---
=
where
CSA = analysis gas molecular cross-sectional area (nm
2
), user-entered on the Adsorp-
tive Properties dialog
Volume of the Monolayer (cm
3
/g STP):
b Y
INT
 
V
M
 
=
Langmuir b Value:
LAN
ERR
SA
LAN
S
ERR

S
-----------------------------------
=
Error of the Langmuir Surface Area (m
2
/g):