Geoscience Reference
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facilitate direct visibility of the growth medium just as in any other low-
temperature solution growth. This has greatly attracted the attention of crystal
growers in the last 2 years and a great variety of compounds which hitherto were
produced only at high temperature and high pressure have been today obtained at
lower PT conditions. Hence, the mineralizer plays an important role in the hydro-
thermal growth of crystals and it has changed the tendency and perspective of the
method. All these aspects can be very well described with reference to quartz, ber-
linite, sodalite, and
-TeO 2 . The reader is advised to refer to the works of Pearson
[96,97] regarding the empirical selection of solvents based on the hard and soft
acids and bases.
α
Solubility of Zincite
The solubility of zincite has been studied in great detail during the 1970s by several
workers [72,73,89] . Measurements of the solubility of zincite has been performed
first
in noncomplexing solutions
(HTr, NaTr)
at various
ionic
strengths
290 C) to determine the equilibrium
(0.03
1.0 mol NaTr) and temperatures (50
2
quotient of the following reaction:
Zn 2 1 1
2H 1 !
ZnO cr 1
H 2 O
ð
4
:
25
Þ
Figure 4.14 represents an example of the solubility obtained at 200 C and
0.1 mol by approaching equilibrium from undersaturation (triangles), whereby the
pH was changed by titration of acid into the cell during the experiments. The solid
-2.0
200 ° C
I = 0.1 m
-2.2
Solubility in presence
of chloride
-2.4
-2.6
Solubility in presence
of sulfate
-2.8
Solubility without
complexing ligands
-3.0
-3.2
-3.4
-3. 4.0
4.2
4.4
4.6
4.8
5.0
-log (H + )
Figure 4.14 Solubility of zincite obtained at 200 C [98] .
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