Compilation - Diammonium hydrogenphosphate with Disodium hydrogenphosphate and Water (IUPAC SDS Volume 66)
SDS Volume (2925)
Volume 66. Ammonium Phosphates, p None
Original Measurements
Platford, R. F.; J. Chem. Eng. Data 1974, 19, 166.
Variables:
Room Temp: Composition at 25 °C
Prepared by:
Method/Apparatus/Procedure:
Conventional measurements were made on aliquots of saturated solutions. The ammonium salt was determined gravimetrically as ammoniumtetraphenyl borate [1] and the total salt content was determined by evaporation to constant weight in vacuum over $\ce{H2SO4}$. The sodium salt was then estimated by difference. The composition of the eutonics was determined by an isopiestic method [2].
Source and Purity of Materials:
- The AR grade phosphates were recrystallized once from water. The $\ce{Na2HPO4}$ was dried at 105°C. The $\ce{(NH4)2HPO4}$ was dried in vacuum over sulfuric acid at room temperature.
Estimated Errors:
Ambient temperature: No information is given.
Mass concentration (m/v) (1): No information is given.
References
1
Vogel, A. I.; Quantitative Inorganic Analysis, Wiley, New York, p. 566 (1961).
2
Platford, R. F.; Amer. J. Sci. 272, 959 (1972).
Components:
- Diammonium hydrogenphosphate, $\ce{ (NH4)2HPO4 }$; [7783-28-0] NIST WebBook
- Disodium hydrogenphosphate, $\ce{ Na2HPO4 }$; [7558-79-4] NIST WebBook
- Water, $\ce{ H2O }$; [7732-18-5] NIST WebBook
Experimental Data
Solubility in the Na2HPO4-(NH4)2HPO2-H2O system at 25°C
| 100w1 | w2 | m1 (mol/kg) | m2 (mol/kg) | Phase (s) () |
|---|---|---|---|---|
| 10.4 | 0.00 | 0.82 | 0.00 | A |
| 12.3 | 2.0 | 1.01 | 0.18 | A |
| 16.0 | 3.3 | 1.39 | 0.31 | A + B |
| 15.6 | 4.6 | 1.38 | 0.44 | B |
| 13.6 | 5.9 | 1.19 | 0.55 | B |
| 11.3 | 7.0 | 0.97 | 0.65 | B |
| 10.5 | 8.9 | 0.92 | 0.84 | B |
| 9.7 | 12.8 | 0.88 | 1.25 | B |
| 9.1 | 14.4 | 0.84 | 1.42 | B |
| 8.2 | 18.0 | 0.78 | 1.85 | B |
| 8.4 | 20.4 | 0.83 | 2.17 | B |
| 8.0 | 25.5 | 0.85 | 2.90 | B |
| 7.8 | 31.2 | 0.90 | 3.87 | B |
| 8.5 | 40.1 | 1.16 | 5.91 | B + C |
| 7.1 | 41.3 | 0.97 | 6.06 | C |
| 4.8 | 40.8 | 0.62 | 5.68 | C |
| 1.8 | 41.3 | 0.22 | 5.50 | C |
| 0.0 | 41.5 | 0.00 | 5.37 | C |
(a) The molalities were calculated by the compiler.
(b) The solid phases are: A = Na2HPO4·12H2O; B = NaNH4HPO4·4H2O; C = (NH4)2HPO2.
