IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

Glass Ball as Bullet Solubility System: Ammonium dihydrogenphosphate with Diammonium dihydrogendiphosphate and Water

   (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.


   Concentration = Composition at 0 °C

Prepared By:
   J. Eysseltová

Experimental Remarks:

        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.

Experimental Data:   (Notes on the Nomenclature)

   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:
   Solubility: No information is given.
   Temperature: No information is given.

   1Metody Analiza Fosfatnogo Syrya, Fosfornykh i Kompleksnykh Udobreniy, Kormevykh Fosfatov, Moscow 1975.
   2L. A. Ionova and N. N. Postnikov, Khim. Prom. 3, 198 (1969).