Tetrasodium pyrophosphate

Tetrasodium pyrophosphate
Names
	IUPAC name Tetrasodium diphosphate
	Other names Pyrophosphate, Sodium pyrophosphate, Tetrasodium pyrophosphate (anhydrous), TSPP
Identifiers
CAS Number	7722-88-5 ; 13472-36-1 (decahydrate) ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:71240;
ECHA InfoCard	100.028.880
EC Number	231-767-1;
E number	E450(iii) (thickeners, ...)
PubChem CID	24403;
RTECS number	UX7350000;
UNII	O352864B8Z ; IY3DKB96QW (decahydrate) ;
CompTox Dashboard (EPA)	DTXSID9042465 ;
	InChI InChI=1S/4Na.H4O7P2/c;;;;1-8(2,3)7-9(4,5)6/h;;;;(H2,1,2,3)(H2,4,5, 6)/q4*+1;/p-4;
	SMILES [O-]P(=O)([O-])OP(=O)([O-])[O-].[Na+].[Na+].[Na+].[Na+];
Properties
Chemical formula	Na4O7P2
Molar mass	265.900 g·mol−1
Appearance	Colorless or white crystals
Odor	odorless
Density	2.534 g/cm3
Melting point	988 °C (1,810 °F; 1,261 K) (anhydrous) ; 79.5 °C (decahydrate)
Boiling point	decomposes
Solubility in water	2.61 g/100 mL (0 °C) ; 6.7 g/100 mL (25 °C) ; 42.2 g/100 mL (100 °C)
Solubility	insoluble in ammonia, alcohol
Refractive index (nD)	1.425
Structure
Crystal structure	monoclinic (decahydrate)
Thermochemistry
Heat capacity (C)	241 J/mol K
Std molar; entropy (S⦵298)	270 J/mol K
Std enthalpy of; formation (ΔfH⦵298)	−3166 kJ/mol
Gibbs free energy (ΔfG⦵)	−3001 kJ/mol
Hazards
Flash point	Non-flammable
	NIOSH (US health exposure limits):
PEL (Permissible)	none
REL (Recommended)	TWA 5 mg/m3
IDLH (Immediate danger)	N.D.
Related compounds
Other anions	Trisodium phosphate; Pentasodium triphosphate; Sodium hexametaphosphate
Other cations	Tetrapotassium pyrophosphate
Related compounds	Disodium pyrophosphate
	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

Tetrasodium pyrophosphate, also called sodium pyrophosphate, tetrasodium phosphate or TSPP, is an inorganic compound with the formula Na₄P₂O₇. As a salt, it is a white, water-soluble solid. It is composed of pyrophosphate anion and sodium ions. Toxicity is approximately twice that of table salt when ingested orally. Also known is the decahydrate Na₄P₂O₇ · 10(H₂O).