Geoscience Reference
In-Depth Information
Table 5.6 Comparative Data of Solubility
T
(
C)
Solvent
P
(kpsi)
Time (days)
Remarks
3 M HCOOH
300
1
5
3.05 M NaOH
170
10
3
Residue not AlPO
4
2MNH
4
Cl
300
1
5
High solubility
4.62 M Na
3
PO
4
300
10
3
Residue not AlPO
4
2 M HCOOH
300
11
5
Good solubility
3MNa
2
HPO
4
300
10
5
1% solubility
2.5 M NH
4
Cl
300
1
5
Fairly good solubility
3.05 M CH
2
COOH
170
10
3
Negligible solubility
2 M NaHCO
3
300
1
5
Fairly good solubility
2 M NaCl
300
1
5
Negligible solubility
3.05 M NaCl
170
10
3
4% solubility
2 M NaF
300
1
5
Good solubility
2 M KF
300
1
5
Good solubility
2 M LiF
300
1
5
Good solubility
3.05 M NH
4
HF
2
300
10
5
Residue not AlPO
4
2MNH
4
H
2
PO
4
300
1
5
Negligible solubility
2 M HCl
300
1
5
Good solubility
3.05 M NH
4
HF
2
170
10
5
Residue not AlPO
4
3.05 M HNO
3
170
10
5
Negligible solubility
3.05 M NaCl
300
10
4
Negligible solubility
1.0 M Na
2
CO
3
300
1
5
Negligible solubility
[76,85
87]
. Normally, high-purity alumina is used as the nutrient, because of the
purity of the grown crystals. The crystallization reaction is:
Al
2
O
3
1
2H
3
PO
4
!
2AlPO
4
1
3H
2
O
These fine crystals of aluminum orthophosphate are in turn used as the nutrient
to grow bigger single crystals of berlinite.
The TC of solubility of AlPO
4
is negative in the temperature
pressure range
below 300
C. Thus, in the usual hydrothermal temperature gradient where the
bottom of the autoclave is hotter than the top, AlPO
4
would be expected to nucleate
preferably in the bottom region, so one would like to place the seed in the lower
hotter region and nutrient in the upper cooler region.
The most important modifications suggested from time to time in the growth of
berlinite crystals are as follows:
i. Crystal growth by slow heating method
ii. Crystal growth by composite gradient method
iii. Crystal growth by temperature gradient
iv. Growth on seeds.
Chai et al.
[86]
suggested the following nutrient preparation conditions for large
(kg) quantities, where the temperature is cycled:
