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IUPAC-NIST Solubility Database
NIST Standard Reference Database 106
Solubility System:
Diammonium hydrogenphosphate with Urea and Water
Components:
(1) Diammonium hydrogenphosphate; (NH4)2HPO4; [7783-28-0]
NIST Chemistry WebBook
for detail
(2) Urea; CH4N2O; [57-13-6]
NIST Chemistry WebBook
for detail
(3) Water; H2O; [7732-18-5]
NIST Chemistry WebBook
for detail
Original Measurements:
Vereshchagina, V.I.; Endovitskaya, M.P., Zh. Neorg. Khim. 15, 2818 (1970).
Variables:
Concentration = Temperature and composition.
Prepared By:
J. Eysseltová
Experimental Data:
(Notes on the Nomenclature)
(Please see footnotes following the table(s).)
Composition and crystallization temperature of invariant points in the (NH
4
)
2
HPO
4
-CO(NH
2
)
2
-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)
16
CO(NH2)2
45.0
16.7
(NH4)2HPO4
10.0
1.68
H2O
45.0
A + B + C
-6
CO(NH2)2
26.0
7.80
(NH4)2HPO4
18.5
2.52
H2O
55.5
A + C + D
-16
CO(NH2)2
27.0
7.75
(NH4)2HPO4
15.0
1.96
H2O
58.0
A + D + E
-17
CO(NH2)2
26.0
7.0
(NH4)2HPO4
12.5
1.54
H2O
61.5
A + D + ice
In addition to the above data, the authors also give the following data for the binary system (NH
4
)
2
HPO
4
-H
2
O.
t/°C
Chemical
1
10
28
* Mass Fraction w
1
m
1
[mol/kg]
(a)
Solid Phase(s)
-5.5
(NH4)2HPO4
28.0
2.94
ice + (NH4)2HPO4.2H2O
15.2
(NH4)2HPO4
39.5
4.94
(NH4)2HPO4.2H2O + (NH4)2HPO4
Notes:
Table 1
a
These values were calculated by the compilers\.
Table 1
b
The solid phases are: A=β-urea; B=γ-urea. C=(NH
4
)
2
HPO
4
; D=(NH
4
)
2
HPO
4
·2H
2
O; E=α-urea.
Table 2
a
These values were calculated by the compiler.
Method/Apparatus/Procedure:
A visual polythermic method was used.
1
Solid carbon dioxide was sued as the cooling agent. The temperature was measured with the aid of Assman's thermometer, the scale of which was divided in steps of 0.2 K.
Source and Purity of Materials:
No information is given
Estimated Errors:
Temperature: The temperature was constant to within ± 0.40 °C.
References:
1
A. G. Bergman and N. P. Luzhnaya, Fiziko-Khimicheskie Osnovy Izucheniya I Ispol'zovaniya Solyanykh Mestorozhdeniy Khlorid-Sul'fatnogo Tipa, Moscow, IAN SSSR (1951).