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IUPAC-NIST Solubility Database
NIST Standard Reference Database 106
Solubility System:
Ammonium dihydrogenphosphate with Diammonium dihydrogendiphosphate and Water
Components:
(1) Ammonium dihydrogenphosphate; NH4H2PO4; [7722-76-1]
NIST Chemistry WebBook
for detail
(2) Diammonium dihydrogendiphosphate; (NH4)2H2P2O7; [13597-86-9]
NIST Chemistry WebBook
for detail
(3) Water; H2O; [7732-18-5]
NIST Chemistry WebBook
for detail
Original Measurements:
Kuznetsova, A.G.; Il'ina, T.L., Zh. Prikl. Khim. (Leningrad) 1982, 55, 1153.
Variables:
Concentration = Composition at 0 °C
Prepared By:
J. Eysseltová
Experimental Remarks:
Remarks: The solubility isotherm for the NH
4
H
2
PO
4
-(NH
4
)
2
H
2
P
2
O
7
-H
2
O system at 0 °C is given in graphical form and described verbally as follows:
Solubility of NH
4
H
2
PO
4
is virtually constant in the concentration range of 0 mass % to 19.5 mass % of (NH
4
)
2
H
2
P
2
O
7
, then decreases slightly.
Solubility of (NH
4
)
2
H
2
P
2
O
7
increases in the concentration range of 0 mass % to 6.3 mass % of NH
4
H
2
PO
4
, but decreases in the concentration range of 6.3 mass % to 13.6 mass % NH
4
H
2
PO
4
.
The composition of the eutonic point is 13.6 mass % NH
4
H
2
PO
4
(2.5 mol/kg--compiler), 38.2 mass % (NH
4
)
2
H
2
P
2
O
7
(3.7 mol/kg--compiler), 48.2 mass % H
2
O.
The total plant food (N + P
2
O
5
) in the system under consideration is in the range of 13.7 to 40.6 mass %, the ratio N/P
2
O
5
being constant at 1:5.
The authors linearized the dependence of total plant food on total P
2
O
5
content in the form y = 0.05 + 1.195
x
where y is the total plant food (N + P
2
O
5
) and
x
is the total P
2
O
5
content.
Experimental Data:
(Notes on the Nomenclature)
Method/Apparatus/Procedure:
The isothermal method was used. The system was equilibrated for 4 hrs. Liquid phases and wet residue were analyzed for total P
2
O
5
and P
2
O
5
in ortho form spectrophotometrically.
1
.
Source and Purity of Materials:
Chemically pure NH
4
H
2
PO
4
was used. (NH
4
)
2
H
2
P
2
O
7
was prepared by heating (NH
4
)
4
P
2
O
7
at 110 °C for 46 hours. The product contained 91.9 % (NH
4
)
2
H
2
P
2
O
7
and 4.4 % NH
4
H
2
PO
4
. Paper chromatography
2
showed the absence of any more condensed polyphosphates.
Estimated Errors:
Solubility: No information is given.
Temperature: No information is given.
References:
1
Metody Analiza Fosfatnogo Syrya, Fosfornykh i Kompleksnykh Udobreniy, Kormevykh Fosfatov
, Moscow 1975.
2
L. A. Ionova and N. N. Postnikov, Khim. Prom.
3
, 198 (1969).