Components:
(1) Ammonium dihydrogenphosphate,
NH4H2PO4; [7722-76-1]
NIST WebBook
(2) Diammonium dihydrogendiphosphate,
(NH4)2H2P2O7; [13597-86-9]
NIST WebBook
(3) Water,
H2O; [7732-18-5]
NIST WebBook
Original Measurements
Kuznetsova, A. G.; Il'ina, T. L.; Zh. Prikl. Khim. 1982, 55, 1153.
Variables:
Ambient temperature: Composition at 0 °C
Prepared by:
Method/Apparatus/Procedure:
The isothermal method was used. The system was equilibrated for 4 hrs. Liquid phases and wet residue were analyzed for total P2O5 and P2O5 in ortho form spectrophotometrically.1.
Source and Purity of Materials:
- Chemically pure NH4H2PO4 was used. (NH4)2H2P2O7 was prepared by heating (NH4)4P2O7 at 110°C for 46 hours. The product contained 91.9% (NH4)2H2P2O7 and 4.4% NH4H2PO4. Paper chromatography2 showed the absence of any more condensed polyphosphates.
Estimated Errors:
Ambient temperature: No information is given.
Mass concentration (m/v) (1): No information is given.
References
1
Metody Analiza Fosfatnogo Syrya, Fosfornykh i Kompleksnykh Udobreniy, Kormevykh Fosfatov, Moscow 1975.
2
Ionova, L. A.; Postnikov, N. N.; Khim. Prom. 3, 198 (1969).
Experimental Values:
Note: Remarks: The solubility isotherm for the NH4H2PO4-(NH4)2H2P2O7-H2O system at 0°C is given in graphical form and described verbally as follows:Solubility of NH4H2PO4 is virtually constant in the concentration range of 0 mass % to 19.5 mass % of (NH4)2H2P2O7, then decreases slightly.
Solubility of (NH4)2H2P2O7 increases in the concentration range of 0 mass % to 6.3 mass % of NH4H2PO4, but decreases in the concentration range of 6.3 mass % to 13.6 mass % NH4H2PO4.
The composition of the eutonic point is 13.6 mass % NH4H2PO4 (2.5 mol/kg--compiler), 38.2 mass % (NH4)2H2P2O7 (3.7 mol/kg--compiler), 48.2 mass % H2O.
The total plant food (N + P2O5) in the system under consideration is in the range of 13.7 to 40.6 mass %, the ratio N/P2O5 being constant at 1:5.
The authors linearized the dependence of total plant food on total P2O5 content in the form y = 0.05 + 1.195x where y is the total plant food (N + P2O5) and x is the total P2O5 content.
