Watson:
For surface tension
s
for the liquid/gas interface
ln(
s
/
s
o
) = a
1
+
å
a
i
×
T
r
i-1
×
ln(1-
T
r
) , where the summation is from
i = 2
to
nTerms -1
T
r
=
T/T
c
,
T
c
is the critical temperature, and
s
o
= 1 N/m
