Disodium phosphate (DSP), or disodium hydrogen phosphate, or sodium phosphate dibasic, is an inorganic compound with the chemical formula Na2HPO4. It is one of several sodium phosphates. The salt is known in anhydrous form as well as hydrates Na2HPO4·nH2O, where n is 2, 7, 8, and 12. All are water-soluble white powders. The anhydrous salt is hygroscopic.[1]
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| Names | |
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| IUPAC name
Disodium hydrogen phosphate
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Other names
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3D model (JSmol)
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| ECHA InfoCard | 100.028.590 |
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| E number | E339(ii) (antioxidants, ...) |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| Na2HPO4 | |
| Molar mass |
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| Appearance | White crystalline solid |
| Odor | Odorless |
| Density | 1.7 g/cm3 |
| Melting point | 250 °C (482 °F; 523 K) Decomposes |
| 7.7 g/(100 ml) (20 °C) 11.8 g/(100 ml) (25 °C, heptahydrate) | |
| Solubility | Insoluble in ethanol |
| log P | −5.8 |
| Acidity (pKa) | 12.35 |
| −56.6·10−6 cm3/mol | |
Refractive index (nD)
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1.35644 to 1.35717 at 20°C |
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Main hazards
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Irritant |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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17000 mg/kg (rat, oral) |
| Safety data sheet (SDS) | ICSC 1129 |
| Related compounds | |
Other anions
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sodium phosphite |
Other cations
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Dipotassium phosphate Diammonium phosphate |
Related compounds
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Monosodium phosphate Trisodium phosphate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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The pH of disodium hydrogen phosphate water solution is between 8.0 and 11.0, meaning it is moderately basic:
- HPO2−4 + H2O ⇌ H2PO−4 + OH−
Production and reactions
editIt can be generated by neutralization of phosphoric acid with sodium hydroxide:
- H3PO4 + 2 NaOH → Na2HPO4 + 2 H2O
Industrially It is prepared in a two-step process by treating dicalcium phosphate with sodium bisulfate, which precipitates calcium sulfate:[2]
- CaHPO4 + NaHSO4 → NaH2PO4 + CaSO4
In the second step, the resulting solution of monosodium phosphate is partially neutralized:
- NaH2PO4 + NaOH → Na2HPO4 + H2O
Uses
editIt is used in conjunction with trisodium phosphate in foods and water softening treatment. In foods, it is used to adjust pH. Its presence prevents coagulation in the preparation of condensed milk. Similarly, it is used as an anti-caking additive in powdered products.[3] It is used in desserts and puddings, e.g. Cream of Wheat to quicken cook time, and Jell-O Instant Pudding for thickening. In water treatment, it retards calcium scale formation.[citation needed] It is also found in some detergents and cleaning agents.[2]
Heating solid disodium phosphate gives the useful compound tetrasodium pyrophosphate:[citation needed]
- 2 Na2HPO4 → Na4P2O7 + H2O
Laxative
editMonobasic and dibasic sodium phosphate are used as a saline laxative to treat constipation or to clean the bowel before a colonoscopy.[4]
References
edit- ^ "Physical data (pdf)" (PDF). Archived from the original (PDF) on 2011-07-17. Retrieved 2007-03-06.
- ^ a b Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann "Phosphoric Acid and Phosphates" in Ullmann’s Encyclopedia of Industrial Chemistry 2008, Wiley-VCH, Weinheim. doi:10.1002/14356007.a19_465.pub3
- ^ "MSDS". Archived from the original on 2017-10-28. Retrieved 2011-09-26.
- ^ "Sodium Phosphate, Dibasic, Sodium Phosphate, Monobasic Oral solution". Krames Patient Education. Archived from the original on 2013-01-28. Retrieved 2009-10-29.
External links
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Media related to Disodium phosphate at Wikimedia Commons solubility in Prophylaxis alcohol
