Disodium pyrophosphate

Disodium pyrophosphate or sodium acid pyrophosphate (SAPP) is an inorganic compound with the chemical formula Na2H2P2O7. It consists of sodium cations (Na+) and dihydrogen pyrophosphate anions (H2P2O2−7). It is a white, water-soluble solid that serves as a buffering and chelating agent, with many applications in the food industry. When crystallized from water, it forms a hexahydrate, but it dehydrates above room temperature. Pyrophosphate is a polyvalent anion with a high affinity for polyvalent cations, e.g. Ca2+.

Disodium pyrophosphate
Names
IUPAC name
Disodium dihydrogen diphosphate
Other names
Diphosphoric acid, disodium salt
Disodium dihydrogen pyrophosphate
Disodium diphosphate
Sodium acid pyrophosphate, SAPP
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.941
EC Number
  • 231-835-0
E number E450(i) (thickeners, ...)
UNII
  • InChI=1S/2Na.H4O7P2/c;;1-8(2,3)7-9(4,5)6/h;;(H2,1,2,3)(H2,4,5,6)/q2*+1;/p-2 N
    Key: GYQBBRRVRKFJRG-UHFFFAOYSA-L N
  • InChI=1/2Na.H4O7P2/c;;1-8(2,3)7-9(4,5)6/h;;(H2,1,2,3)(H2,4,5,6)/q2*+1;/p-2
    Key: GYQBBRRVRKFJRG-NUQVWONBAI
  • [Na+].[Na+].[O-]P(=O)(O)OP([O-])(=O)O
Properties
Na2H2P2O7
Molar mass 221.936 g·mol−1
Appearance White odorless powder
Density 2.31 g/cm3
Melting point > 600 °C
11.9 g/(100 mL) (20 °C)
1.4645 (hexahydrate)
Hazards
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
2650 mg/kg (mouse, oral)
Related compounds
Other anions
Other cations
Related compounds
 Tetrasodium pyrophosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

Disodium pyrophosphate is produced by heating sodium dihydrogen phosphate:

2 NaH2PO4 → Na2H2P2O7 + H2O
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