Chemistry Reference
In-Depth Information
Since the
G
i
ij
have magnitudes on the order of the molar volumes, the correction is
important for systems showing a behavior near to ideality. However, it is negligible
for large parts of the composition domain if the system presents strong deviations
from ideality.
In a similar way, the corrected local excess composition, δ
x
ji
, is calculated by
subtracting from the local composition that of the corresponding ideal system,
id
L
L,id
δ
x
′
=− =−
δ
x
δ
xxx
(4.30)
ji
ji
ji
ji
ji
where
x
j
L,id
is obtained with the same procedure as
x
j
L
(Equation 4.24) but assuming
G
E
=
V
E
= 0 for the system under examination. Also, the preferential solvation can be
corrected for the volume contribution by using δ
x
ji
instead of δ
x
ji
in Equation 4.26,
∆ps
i
jk
,
=
δ
x
′ −
δ
x
′
(4.31)
ji
ki
4.6 PRESENTATION AND DISCUSSION OF THE RESULTS
All Δ
G
ij
(Equation 4.29) values for the three ternary mixtures are shown in
Figure 4.1 through Figure 4.3. Note that the units are dm
3
mol
-1
for systems I and II,
and cm
3
mol
-1
for system III. The surfaces of Δ
G
ij
have been depicted with almost the
∆
G
11
∆
G
22
∆
G
33
0.16
14
0.4
12
0.12
0.3
10
8
0.08
0.2
6
4
0.04
0.1
1
2
3
0
0
0
2
∆
G
12
∆
G
13
∆
G
23
2.5
0.15
2
0
0.1
1.5
-0.2
0.05
1
-0.4
0
0.5
-0.6
-0.05
0
-0.1
-0.5
-0.8
FIGURE 4.1
Corrected KBIs (Δ
G
ij
, Equation 4.29) for the ternary system ethanol(1) + tetra-
hydrofuran(2) + cyclohexane(3) at 298.15 K. Units are dm
3
mol
-1
. For all pictures, components
correspond to the three corners of the composition triangle as illustrated in the first panel.
