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Disodium phosphate

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Disodium phosphate
Structural formula of disodium phosphate
Ball-and-stick model of the component ions of disodium phosphate
  Sodium, Na  Phosphorus, P  Oxygen, O  Hydrogen, H
Names
IUPAC name Disodium hydrogen phosphate
Other names
  • Acetest
  • Dibasic sodium phosphate
  • Disodium hydrogen orthophosphate
  • Disodium hydrogen phosphate
  • Disodium phosphate
  • Sodium phosphate dibasic
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.028.590 Edit this at Wikidata
EC Number
  • 231-448-7
E number E339(ii) (antioxidants, ...)
PubChem CID
RTECS number
  • WC4500000
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/2Na.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q2*+1;/p-3Key: BNIILDVGGAEEIG-UHFFFAOYSA-K
  • InChI=1/2Na.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q2*+1;/p-3Key: BNIILDVGGAEEIG-DFZHHIFOAK
SMILES
  • OP(=O)()..
Properties
Chemical formula Na2HPO4
Molar mass
  • 141.96 g/mol (anhydrous)
  • 177.99 g/mol (dihydrate)
  • 268.07 g/mol (heptahydrate)
Appearance White crystalline solid
Odor Odorless
Density 1.7 g/cm
Melting point 250 °C (482 °F; 523 K) Decomposes
Solubility in water 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
Magnetic susceptibility (χ) −56.6·10 cm/mol
Refractive index (nD) 1.35644 to 1.35717 at 20°C
Hazards
Occupational safety and health (OHS/OSH):
Main hazards Irritant
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
1 0 0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose) 17000 mg/kg (rat, oral)
Safety data sheet (SDS) ICSC 1129
Related compounds
Other anions sodium phosphite
Other cations Dipotassium phosphate
Diammonium phosphate
Related compounds Monosodium phosphate
Trisodium phosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). ☒N verify (what is  ?) Infobox references
Chemical compound

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.

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

It 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:

CaHPO4 + NaHSO4 → NaH2PO4 + CaSO4

In the second step, the resulting solution of monosodium phosphate is partially neutralized:

NaH2PO4 + NaOH → Na2HPO4 + H2O

Uses

It 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. 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. It is also found in some detergents and cleaning agents.

Heating solid disodium phosphate gives the useful compound tetrasodium pyrophosphate:

2 Na2HPO4 → Na4P2O7 + H2O

Laxative

Monobasic and dibasic sodium phosphate are used as a saline laxative to treat constipation or to clean the bowel before a colonoscopy.

References

  1. "Physical data (pdf)" (PDF). Archived from the original (PDF) on 2011-07-17. Retrieved 2007-03-06.
  2. ^ 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
  3. "MSDS". Archived from the original on 2017-10-28. Retrieved 2011-09-26.
  4. "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

  • Media related to Disodium phosphate at Wikimedia Commons solubility in Prophylaxis alcohol
Sodium compounds
Inorganic
Halides
Chalcogenides
Pnictogenides
Oxyhalides
Oxychalcogenides
Oxypnictogenides
Others
Organic
Phosphates
H3PO4

 He
Li3PO4 Be BPO4
+BO3 		C (NH4)3PO4
(NH4)2HPO4
NH4H2PO4
-N 		O +F Ne
Na3PO4
Na2HPO4
NaH2PO4 		Mg3(PO4)2 AlPO4 Si P +SO4
-S 		Cl Ar
K3PO4
K2HPO4
KH2PO4 		Ca3(PO4)2 ScPO4 Ti VPO4 CrPO4 Mn3(PO4)2
MnPO4 		Fe3(PO4)2
FePO4 		Co3(PO4)2 Ni3(PO4)2 Cu3(PO4)2 Zn3(PO4)2 GaPO4 Ge As -Se Br Kr
Rb3PO4 Sr3(PO4)2 YPO4 Zr3(PO4)4 Nb Mo Tc Ru Rh Pd Ag3PO4 Cd3(PO4)2 InPO4 Sn SbPO4
-SbO4 		Te I Xe
Cs3PO4 Ba3(PO4)2 * LuPO4 Hf Ta W Re Os Ir Pt AuPO4 Hg Tl3PO4 Pb3(PO4)2 BiPO4 Po At Rn
Fr Ra ** Lr Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
 
* LaPO4 CePO4 PrPO4 NdPO4 PmPO4 SmPO4 EuPO4 GdPO4 TbPO4 DyPO4 HoPO4 ErPO4 TmPO4 YbPO4
** AcPO4 Th3(PO4)4 Pa U(PO4)2 Np PuPO4 AmPO4 CmPO4 Bk Cf Es Fm Md No
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