Micromeritics TriStar II 3020 - BET Surface Area

Appendix C TriStar II 3020
C-6 302-42828-01 - Dec 2012
BET Surface Area
SA
BET
CSA 6.023 10
23

22414 cm
3
STP10
18
nm
2
/m
2
SY
INT
+
------------------------------------------------------------------------------------------------------------------------
=
C
SY
INT
+
Y
INT
--------------------
=
V
M
1
CY
INT

---------------------
1
SY
INT
+
--------------------
==
BET
ERR
SA
BET
S
ERR
2
YI
ERR
2
+
0.5

Y
INT
S+
----------------------------------------------------------------------------
=
For each point designated for surface area calculations, the BET
2
transformation is calculated as
follows:
where B
I
is in units of g/cm
3
STP.
A least-squares fit is performed on the (P
rel
I
,B
I
) designated pairs where P
rel
I
is the independent vari-
able and B
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 (Cc)
Using the results of the above calculations, the following can be calculated:
BET Surface Area (m
2
/g):
where
C
SA = analysis gas molecular cross-sectional area (nm
2
), user-entered on the Adsorp-
tive Properties dialog
BET C value:
Volume of the Monolayer (cm
3
/g STP):
Error of the BET Surface Area (m
2
/g):
B
1
P
rel
1
1.0 P
rel
1
–N
ads
1

-------------------------------------------------
=