Chemistry Reference
In-Depth Information
Δ
ij
are unknown, it could be successfully used to derive analytical expressions for
the solubility of gases and large molecules of biomedical and environmental sig-
nificance including proteins in aqueous media (Ruckenstein and Shulgin 2009). In
addition, Equation 10.8 could be used to identify whether a cosolvent is a salting-out
or salting-in agent (Ruckenstein and Shulgin 2002b).
10.3 SOLUBILITY OF GASES IN BINARY MIXED SOLVENTS
The solubility of gases (component 2) in the mixed solvent 1-3 can be expressed
via the Henry constant
H
2
t
(O'Connell 1971a). In order to obtain the composition
dependence of the Henry constant in a binary solvent, one should consider either the
derivative
∂
ln
H
x
2t
t
∂
3
t
pT x
,,
=
0
2
or the derivative
∂
ln
H
x
2t
t
∂
1
t
pT x
,,
=
0
2
which can be obtained starting from the following expression for the Henry constant
in a binary solvent (O'Connell 1971a),
2
0
ln
H
=
limln
γ
+
ln(,)
f
pT
(10.10)
2, t
2,t
t
x
→
0
2
where
f
i
0
(
p
,
T
) is the fugacity of component
i
(Prausnitz, Lichtenthaler, and Gomes
de Azevedo 1999). The combination of Equations 10.8, 10.9, and 10.10 and the inte-
gration of the obtained equation provides the following relation for the composition
dependence of the Henry constant in a binary solvent mixture, at constant tempera-
ture and pressure (Shulgin and Ruckenstein 2002b),
(
∆∆
−
)
b
,
13
−
∂
ln
γ
3
(
)
∫
12
23
t
x
=
0
b
,
13
−
b
,
13
−
0
0
ln
H
=−
c
+
c
1
+
x
dx
+
2
2t
1
3
3
b
,
13
−
3
2
∂
x
3
pT
,
(10.11)
1
2
(
)
+
b
,
13
−
b
,
13
−
+
ln
γ
+
ln
γ
A
1
3
where
A
(
p
,
T
) is a composition-independent integration constant and
x
i
b, 1-3
and γ
i
b, 1-3
are the mole fraction and the activity coefficient of component
i
(
i
= 1 or 3) in the
gas-free binary solvent 1-3. One can note that Equation 10.11 contains, with the
