Chemistry Reference
In-Depth Information
∆
G
11
∆
G
22
∆
G
33
0.12
0.8
20
0.6
15
0.08
0.4
10
0.04
5
0.2
1
3
0
0
0
2
∆
G
12
∆
G
13
∆
G
23
0.2
2
0
1.5
0.1
-0.5
-1
1
0
-1.5
0.5
-0.1
-2
0
-2.5
FIGURE 4.2
Corrected KBIs (Δ
G
ij
, Equation 4.29) for the ternary system 2-methoxyethanol(1)
+ tetrahydrofuran(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.
same orientation in order to facilitate comparison among them, but with different
scales for the
z
-axis. Because of the huge difference in the magnitudes of some Δ
G
ij
,
the use of the same scale would have compressed the images with small Δ
G
ij
values
with the consequence of practically hiding their features.
Figure 4.4 through Figure 4.6 show the plots of all δ
x
ji
values (Equation 4.30)
for systems I-III. The surfaces in a row show the excess composition of the solva-
tion shell of the same central species; their comparison indicates which compounds
the solvaton prefers to be solvated by. Alternatively, by comparing the pictures in a
column, information can be inferred on which solute a component prefers to solvate.
It should be noted that for system I (Figure 4.4) and system II (Figure 4.5), the
model for calculating
V
cor
finds a solvation shell composed of two layers, but only one
layer for system III (Figure 4.6). It must also be mentioned that this model is some-
what empirical because it was founded on reasonable, but not rigorous, assumptions
and other different, more scientifically valid, methods to calculate
V
cor
could be put
forward. Therefore, the values of the excess local composition so obtained should not
be given a quantitative meaning. However, they can be safely used for comparison
since, as the form of Equation 4.25 suggests, the
V
cor
value cannot change the relative
magnitude of δ
x
ji
.
