IUPAC-NIST Solubilities Database

IUPAC-NIST Solubility Database
NIST Standard Reference Database 106

Solubility System: Ammonia with Diphosphorus pentoxide and Water

Components:
   (1) Ammonia; NH3; [7664-41-7]  NIST Chemistry WebBook for detail
   (2) Diphosphorus pentoxide; P2O5; [1314-56-3]  NIST Chemistry WebBook for detail
   (3) Water; H2O; [7732-18-5]  NIST Chemistry WebBook for detail

Evaluator:
   J. Eysseltová; Charles University; Prague, Czech Republic

Critical Evaluation:

   Oligophosphate Systems

Chulanova, et al., ^1,2 published solubility data for the following three systems:

1. NH₄H₂PO₄-(NH₄)₄P₂O₇-H₂O;
2. NH₄H₂PO₄-(NH₄)₂H₂P₂O₇-H₂O;
3. (NH₄)₂HPO₄-(NH₄)₂H₂P₂O₇-H₂O.
The compounds chosen as components in the first system cannot coexist in a saturated solution. Perhaps there was an error in identifying the solid phases at equilibrium. In the third system, the authors observed a crystallization field for (NH₄)₃HP₂O₇·H₂O as a product of reaction between the compounds chosen as components. Therefore, the solubility data in Ref. 1 are rejected.
The data in Ref. 2 can be compared with the 0 °C isotherm of the NH₄HPO₄-(NH₄)₂H₂P₂O₇-H₂O system reported by others³, see Fig. 2. The data points for 50 °C and 70 °C on Fig. 2 were found by extrapolation from the solubility isotherms². The variation of composition with temperature shown in Fig. 2 appears to be reasonable. Consequently, the data can be accepted tentatively.
A research group at the Tennessee Valley Authority in the USA studied the following systems:^4-6:NH₃ - H₂P₂O₇ - H₂O;
NH₃ - H₅P₃O₁₀ - H₂O;
NH₃ - H₆P₄O₁₃ - H₂O.
The solubility data presented for these systems cannot be critically evaluated because of the absence of other, similar experimental work. The same research group also made a detailed study of multicomponent systems consisting of di-, tri- and tetra- phosphoric acid, the corresponding ammonium salts (and, in one case also, with potassium salts).^7-19 They used a petrographic examination of the solid phases as the main criterion of equilibrium. In these works they report more solid phases than are allowed by the Phase Rule. The solubility information presented in these articles may be useful for fertilizer production. However, there is real doubt that true equilibrium was established in the experimental work and, therefore, these articles are neither compiled nor critically evaluated in this volume.

Experimental Data: (Notes on the Nomenclature)

View Figure 1 for this Evaluation

View Figure 1 for this Evaluation

References: (Click a link to see its experimental data associated with the reference)

   1  Chulanova, G.A.; Shipyatskaya, R.I.; Mukhina, L.S., Zh. Prikl. Khim. (Leningrad) 1974, 47, 1637.
   2  Chulanova, G.A.; Mukhina, L.S.; Shipyatskaya, R.I.; Taran, A.I., Zh. Prikl. Khim. (Leningrad) 1976, 49, 1933.
   3  Kuznetsova, A.G.; Il'ina, T.L., Zh. Prikl. Khim. (Leningrad) 1982, 55, 1153.
   4  Farr, T.D.; Fleming, J.D., J. Chem. Eng. Data 1965, 10. 20.
   5  Farr, T.D.; Fleming, J.D.; Hatfield, J.D., J. Chem. Eng. Data 1967, 12, 141.
   6  Farr, T.D.; Willard, J.W.; Hatfield, J.D., J. Chem. Eng. Data 1972, 17, 313.
   7  Slack, A.V.; Hatfield, J.D.; Shaffer, H.B.; Driskell, J.C., J. Agr. Food Chem. 1959, 7, 404.
   8  Slack, A.V.; Potts, J.M.; Shaffer, H.B., J. Agr. Food Chem. 1964, 12, 154.
   9  Slack, A.V.; Potts, J.M.; Shaffer, H.B. Jr., J. Agr. Food Chem. 1965, 13, 165.
   10  Farr, T.D.; Willard, J.W., J. Chem. Eng. Data 1969, 14, 367.
   11  Farr, T.D.; Willard, J.W., J. Chem. Eng. Data 1971, 16, 67.
   12  Farr, T.D.; Willard, J.W., J. Chem. Eng. Data 1972, 17, 317.
   13  Frazier, A.W.; Dillard, E.F.; Thrasher, R.D.; Waerstad, K.R., J. Agr. Food Chem. 1973, 21, 700.
   14  Willard, J.W.; Dillard, E.F., J. Chem. Eng. Data 1975, 20, 436.