Micromeritics ASAP 2460 - Alpha-S Method

ASAP 2460 Operator’s Manual Appendix C
246-42800-01 - Aug 2013 C-13
Alpha-S Method
The alpha-S curve is calculated from the reference isotherm by dividing each quantity adsorbed by the
quantity adsorbed at 0.4 relative pressure.
where Q
0.4
is found by linear interpolation.
A least-squares analysis fit is performed on the (α
i
,Q
ads,i
) data pairs where α
i
is the independent vari-
able and Q
ads,i
is the dependent variable. The following are calculated:
a.) Slope (S cm³/g STP)
b.) Y-intercept (Q
0
cm³/g STP)
c.) Error of the slope (cm³/g STP)
d.) Error of the Y-intercept (cm³/g STP)
e.) Correlation coefficient
Surface area is calculated as:
Pore size is calculated as:
where V
mol
is liquid molar volume from the fluid property information.
a
i
Q
i
Q
0.4
----------
=
A
A
ref
S
Q
0.4
-------------
=
Q
0
V
mol
22414cm
3
STP
-------------------------------------