Chemistry Reference
In-Depth Information
25
4
CH
4
CO
2
H
2
S
H
3
BO
3
NH
3
CH
4
CO
2
H
2
S
H
3
BO
3
NH
3
20
2
15
10
0
5
0
600
-2
700
800
900
1000
100
200
300
400
500
Water Density, ρ°
2
(kg∙m
-3
)
Water Density, ρ°
2
(kg∙m
-3
)
(a)
(b)
FIGURE 9.3
Variations of Krichevskii function,
A
Kr
, for various small solutes in
water; (a) for high solvent densities, (b) for lower densities. Symbols for data, lines for
Equation 9.25. (Reprinted with permission from J. P. O'Connell, A. V. Sharygin, and R. H.
Wood, 1996, Infinite Dilution Partial Molar Volumes of Aqueous Solutes over Wide Ranges
of Conditions,
Industrial and Engineering Chemistry Research
, 35, 2808. With permission
from ACS Publishing.)
conditions. This behavior has led to extensive models for thermodynamic proper-
ties and phase behavior of dilute aqueous systems (Plyasunov, O'Connell, and Wood
2000; Plyasunov et al. 2000, 2001; Sedlbauer, O'Connell, and Wood 2000; Plyasunov,
Shock, and O'Connell 2006; Majer, Sedlbauer, and Bergin 2008; Plyasunov 2011).
Details of these models are described below.
9.2.4 P
arTial
m
olar
v
olumes
aT
F
iniTe
c
oncenTraTions
One issue associated with the above systems is defining the mole fraction of solute
where infinite dilution is no longer a satisfactory assumption. Liu (Liu and O'Connell
1998; O'Connell and Liu 1998) investigated this in the context of supercritical chro-
matography measurements for partial molar volumes. Expanding the DCFI in solute
mole fraction about infinite dilution shows that irst-order terms can be significant
even at mole fractions of the order of 10
-3
. This suggests that common conditions and
literature treatments of data could be unreliable. The analysis was extended to solu-
bilities in supercritical fluids, noting that at least one set of data did not display the
required thermodynamic consistency for phase equilibria and volumetric behavior.
9.3 FLUCTUATION SOLUTION THEORY MODELING OF PHASE
EQUILIBRIA INVOLVING DILUTE SOLUTIONS
Issues in dilute solution modeling have been discussed extensively (Cabezas and
O'Connell 1993). The application of FST to these systems provides a powerful
