Tetrasodium pyrophosphate

Tetrasodium pyrophosphate

Names
IUPAC name Tetrasodium diphosphate
Other names Pyrophosphate, Sodium pyrophosphate, Tetrasodium pyrophosphate (anhydrous), TSPP[1]
Identifiers
CAS Number	7722-88-5 13472-36-1 (decahydrate)
3D model (Jmol)	Interactive image
ECHA InfoCard	100.028.880
EC Number	231-767-1
PubChem	24403
RTECS number	UX7350000
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	265.90 g·mol^−1
Appearance	Colorless or white crystals[2]
Odor	odorless
Density	2.534 g/cm^3
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
Specific heat capacity (C)	241 J/mol K
Std molar entropy (S^o298)	270 J/mol K
Std enthalpy of formation (ΔfH^o298)	-3166 kJ/mol
Gibbs free energy (ΔfG˚)	-3001 kJ/mol
Hazards
Flash point	Non-flammable
US health exposure limits (NIOSH):
PEL (Permissible)	none[2]
REL (Recommended)	TWA 5 mg/m^3[2]
IDLH (Immediate danger)	N.D.[2]
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).
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Infobox references

Tetrasodium pyrophosphate, also called sodium pyrophosphate, tetrasodium phosphate or TSPP, is a colorless transparent crystalline chemical compound with the formula Na₄P₂O₇. It is a salt composed of pyrophosphate and sodium ions. Toxicity is approximately twice that of table salt when ingested orally.^[3] There is also a hydrated form, Na₄P₂O₇ · 10(H₂O).^[4]

Tetrasodium pyrophosphate is used as a buffering agent, an emulsifier, a dispersing agent, and a thickening agent, and is often used as a food additive. Common foods containing tetrasodium pyrophosphate include chicken nuggets, marshmallows, pudding, crab meat, imitation crab, canned tuna, and soy-based meat alternatives and cat foods and cat treats where it is used as a palatability enhancer.

In toothpaste and dental floss, tetrasodium pyrophosphate acts as a tartar control agent, serving to remove calcium and magnesium from saliva and thus preventing them from being deposited on teeth. Tetrasodium pyrophosphate is used in commercial dental rinses before brushing to aid in plaque reduction.

Tetrasodium pyrophosphate is sometimes used in household detergents to prevent similar deposition on clothing, but due to its phosphate content it causes eutrophication of water, promoting algae growth.

Production

Tetrasodium pyrophosphate is produced by the reaction of furnace-grade phosphoric acid with sodium carbonate to form disodium phosphate, which is then heated to 450 °C to form tetrasodium pyrophosphate.

Alternatively, it can be created by the molecular dehydration of dibasic sodium phosphate at 500 °C (932 °F).

References

1. CDC - NIOSH Pocket Guide to Chemical Hazards
2. "NIOSH Pocket Guide to Chemical Hazards #0606". National Institute for Occupational Safety and Health (NIOSH).
3. Handbook of food toxicology, S. S. Deshpande, page 260
4. D.L. Perry S.L. Phillips (1995) Handbook of inorganic compounds CRC Press ISBN 0-8493-8671-3