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remarkably different from those of ambient water. The solubility of nonpolar spe-
cies increases, whereas that of ionic and polar compounds decrease. As a result of
the drop of the polarity of water, the molecular mobility increases due to a decrease
in the solvent viscosity (
). Drastic changes of ionic hydration are brought about by
the decrease in the dielectric constant (
η
). Table 1.5 gives the
values of dielectric constant, density, and viscosity of water varying with tempera-
ture and pressure in comparison with the ambient values of 78.3, 0.997 g/cm 3 , and
0.890 mPa, respectively [113] . The temperature dependence of the saturation vapor
pressure is illustrated up to the critical point
ε
) and density (
ρ
in Figure 1.8 [113] . Below
200 C, the saturation vapor pressure is relatively low. Above this tempera-
ture, however, the vapor pressure rises rather sharply. Such anamolous properties
of water with pressure
150
temperature variations are associated with the hydrogen
bonding, which has attracted the attention of solution chemists. Thus, recent
advances in hydrothermal solution chemistry have paved a new path to materials
processing techniques with minimum energy consumption in comparison with
larger energy consumption to create melt, vapor, gas, or plasma. Figure 1.9 shows
free energy versus temperature diagram in a single component system. Similarly,
Table 1.5 Values of ε r , ρ (g/cm 3 ), and η (mPa/s) of Water at High Temperatures and High
Pressures
p (MPa)
t ( C)
Parameter
200
250
300
350
400
450
10
ε r
35.1
27.4
20.4
1.2
1.2
1.1
ρ
0.871
0.806
0.715
0.045
0.038
0.034
η
0.136
0.108
0.087
0.022
0.025
0.027
20
ε r
35.3
28.0
21.2
14.1
1.6
1.4
ρ
0.878
0.816
0.733
0.600
0.101
0.079
η
0.139
0.110
0.091
0.070
0.026
0.028
30
ε r
35.9
28.4
22.0
15.7
5.9
2.1
ρ
0.885
0.826
0.751
0.646
0.357
0.148
η
0.141
0.113
0.094
0.076
0.044
0.031
40
ε r
36.3
28.9
22.6
16.7
10.5
3.8
ρ
0.891
0.835
0.765
0.672
0.523
0.271
η
0.114
0.115
0.097
0.080
0.062
0.039
50
ε r
36.6
29.3
23.1
17.6
12.2
6.6
ρ
0.897
0.843
0.777
0.693
0.278
0.402
η
0.146
0.118
0.099
0.083
0.068
0.051
60
ε r
37.0
29.7
23.6
18.2
13.3
8.5
ρ
0.903
0.850
0.788
0.711
0.612
0.480
η
0.148
0.120
0.101
0.086
0.073
0.059
70
ε r
37.3
30.0
24.0
18.8
14.2
9.9
ρ
0.909
0.857
0.798
0.726
0.638
0.528
η
0.150
0.122
0.104
0.089
0.077
0.065
Source: Cited from Ref. [113] .
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