Geoscience Reference
In-Depth Information
Table 9.1 Hydrothermal Experimental Conditions of Synthesis of Hydroxides
[37]
T
(
C)
Hydroxide
Solvent
P
(atm)
Be(OH)
2
H
2
O
100
175
4000
Mg(OH)
2
3% NaOH
450
600
Ca(OH)
2
3% NaOH
550
650
Cd(OH)
2
35% NaOH
450
1000
Mn(OH)
2
5% NaOH
450
1000
Co(OH)
2
1% NaOH
280
3500
Ni(OH)
2
1% NaOH
280
3500
TR(OH
3
)
15% NaOH
350
600
TR
5
La
Gd
TR
5
Dy, Er, Yb
15% NaOH
450
600
Cr(OH)
3
3% NaOH
300
1500
In(OH)
3
40% NaOH
400
400
Al(OH)
3
H
2
O
,
150
39
In(OH)
3
H
2
O
185
275
50
75
In(OD)
3
D
2
O
180
210
18
50
InOOH
H
2
O
325
410
120
800
InOOD
D
2
O
360
380
320
400
α
-ScOOH
H
2
O
162
350
6
170
β
-ScOOH
H
2
O
350
160
Y(OH)
3
H
2
O
300
85
CrOOH
H
2
O
450
2700
GdOOD
D
2
O
600
1400
SmOOH
H
2
O
600
1400
Sr
3
Cr
2
(OH)
12
H
2
O
150
200
hydroxides. The oxyhydroxides (MeOOH) often crystallize at relatively higher tem-
peratures. Among these, the polymorphism is very common, and it depends upon
the temperature, for example, in rare earth hydroxides
[38]
.
Similar to the alkali solutions in the synthesis of metal hydroxides, acid solu-
tions, particularly chloride solutions, are also used. Thus, in this case, an increase
in the concentration of the solution forms hydroxyl chlorides, often with 100%
output. Their synthesis takes place as a result of the substitution of one hydroxyl
group with chloride as follows:
Me
ð
OH
Þ
3
1
HCl
!
Me
ð
OH
Þ
2
Cl
1
H
2
O
ð
9
:
4
Þ
In this way, Demianets and Emelyanova
[39]
have obtained hydroxyl chlorides
of neodymium, Nd(OH)
2
Cl, under hydrothermal conditions using aqueous solutions
of NH
4
Cl (concentration 7 wt%) at temperatures 450
480
C. At 500
C, rare earth
hydroxyl chlorides, R(OH)
2
Cl, where R
La, Ce, Pr, Nd, Sm, and Gd, have been
obtained by Kletsov et al.
[40]
. Similarly, Carter and Levinson
[41]
have obtained
hydroxyl chlorides containing La, Nd, Sm, Gd, and Y, and the more complex
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