Disodium phosphate

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	7558-79-4 ; 10028-24-7 (dihydrate) ; 7782-85-6 (heptahydrate) ; 10039-32-4 (dodecahydrate) ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:34683 ;
ChEMBL	ChEMBL1060 ;
ChemSpider	22625 ;
ECHA InfoCard	100.028.590
EC Number	231-448-7;
E number	E339(ii) (antioxidants, ...)
PubChem CID	24203;
RTECS number	WC4500000;
UNII	22ADO53M6F ; 94255I6E2T (dihydrate) ; 70WT22SF4B (heptahydrate) ; E1W4N241FO (dodecahydrate) ;
CompTox Dashboard (EPA)	DTXSID1026039 ;
	InChI InChI=1S/2Na.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q2+1;/p-3 Key: BNIILDVGGAEEIG-UHFFFAOYSA-K ; InChI=1/2Na.H3O4P/c;;1-5(2,3)4/h;;(H3,1,2,3,4)/q2+1;/p-3 Key: BNIILDVGGAEEIG-DFZHHIFOAK;
	SMILES OP(=O)([O-])[O-].[Na+].[Na+];
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/cm3
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)	−56.6·10−6 cm3/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)	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 [77 °F], 100 kPa). verify (what is ?) Infobox references

Disodium phosphate (DSP), or disodium hydrogen phosphate, or sodium phosphate dibasic, is an inorganic compound with the chemical formula Na₂H P O₄. 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⁻

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