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IUPAC-NIST Solubility Database
NIST Standard Reference Database 106
Solubility System:
Ammonium dihydrogenphosphate with Urea phosphate and Water
Components:
(1) Ammonium dihydrogenphosphate; NH4H2PO4; [7722-76-1]
NIST Chemistry WebBook
for detail
(2) Urea phosphate; CO(NH2)2.H3PO4; [4861-19-2]
NIST Chemistry WebBook
for detail
(3) Water; H2O; [7732-18-5]
NIST Chemistry WebBook
for detail
Original Measurements:
Kummel, R.; Fahsl, R., Z. Anorg. Allg. Chem. 1973, 402, 305.
Variables:
Concentration = Composition at 20 ºC and 40 ºC.
Prepared By:
J. Eysseltová
Experimental Data:
(Notes on the Nomenclature)
(Please see footnotes following the table(s).)
Solubility isotherms in the NH
4
H
2
PO
4
-CO(NH
2
)
2
·H
3
PO
4
-H
2
O system.
t/°C
Chemical
1
10
2
* Mass Fraction w
1
m
1
[mol/kg]
(a)
Chemical
2
10
2
* Mass Fraction w
2
m
2
[mol/kg]
(a)
Chemical
3
10
2
* Mass Fraction w
3
Solid Phase(s)
(b)
ρ [g/cm3]
20
CO(NH2)2.H3PO4
44.35
6.03
NH4H2PO4
9.08
1.69
H2O
46.57
A
1.2833
20
CO(NH2)2.H3PO4
41.05
5.94
NH4H2PO4
15.21
3.02
H2O
43.74
A
1.3062
20
CO(NH2)2.H3PO4
38.59
6.27
NH4H2PO4
22.46
5.01
H2O
38.95
A + B
1.3409
20
CO(NH2)2.H3PO4
28.78
3.88
NH4H2PO4
24.24
4.49
H2O
46.98
B
1.2877
20
CO(NH2)2.H3PO4
16.26
1.74
NH4H2PO4
24.60
3.62
H2O
59.14
B
1.2255
20
CO(NH2)2.H3PO4
5.63
0.516
NH4H2PO4
25.40
3.20
H2O
68.97
B
1.1737
20
CO(NH2)2.H3PO4
0.000
0.000
NH4H2PO4
25.50
2.98
H2O
74.50
B
1.1518
40
CO(NH2)2.H3PO4
58.94
10.92
NH4H2PO4
6.91
1.76
H2O
34.15
A
-
40
CO(NH2)2.H3PO4
55.05
11.01
NH4H2PO4
13.31
3.66
H2O
31.64
A
-
40
CO(NH2)2.H3PO4
44.35
10.17
NH4H2PO4
28.06
8.84
H2O
27.59
A + B
-
40
CO(NH2)2.H3PO4
35.22
6.18
NH4H2PO4
28.70
6.91
H2O
36.08
B
-
40
CO(NH2)2.H3PO4
23.39
3.22
NH4H2PO4
30.67
5.80
H2O
45.94
B
-
40
CO(NH2)2.H3PO4
11.78
1.35
NH4H2PO4
33.01
5.20
H2O
55.21
B
-
40
CO(NH2)2.H3PO4
0.000
0.000
NH4H2PO4
36.20
4.93
H2O
63.80
B
-
Notes:
Table 1
a
These values were calculated by the compiler.
Table 1
b
The solid phases are: A=CO(NH
2
)
2
·H
3
PO
4
; B=NH
4
H
2
PO
4
.
Method/Apparatus/Procedure:
Mixtures of the components were stirred vigorously and allowed to equilibrate for 15 hrs to 25 hrs. The equilibrium was checked by repeated analysis of the liquid phase. PO
4
3–
content was determined by precipitation titration with La(NO
3
)
3
using Chromazurol S as indicator; NH
4
+
was determined, after removal of phosphate ions, with the aid of anion exchange resin by formol tritration. Urea was determined gravimetrically as dixanthedrylurea or after enzyme decomposition as NH
3
. The composition of the solid phases was determined by the method of Schreinemakers.
Source and Purity of Materials:
The ammonium phosphate was recrystallized several times before use. The urea phosphate was synthesized from urea and an equivalent amount of phosphoric acid and recrystallized several times.
Estimated Errors:
Solubility: No information is given.
Temperature: The temperature was kept constant to within ±0.05 K.