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Pentasodium triphosphate

Sodium triphosphate
Sodium tripolyphosphate.svg
Names
IUPAC name
Pentasodium triphosphate
Other names
sodium tripolyphosphate, polygon, STPP
Identifiers
ECHA InfoCard 100.028.944
E number E451 (thickeners, ...)
PubChem CID
RTECS number YK4570000
UNII
Properties
Na5P3O10
Molar mass 367.864 g/mol
Appearance white powder
Density 2.52 g/cm3
Melting point 622 °C (1,152 °F; 895 K)
14.5 g/100 mL (25 °C)
Hazards
Safety data sheet ICSC 1469
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions
Trisodium phosphate
Tetrasodium pyrophosphate
Sodium hexametaphosphate
Other cations
Pentapotassium triphosphate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Sodium triphosphate (STP), also sodium tripolyphosphate (STPP), or tripolyphosphate (TPP),) is an inorganic compound with formula Na5P3O10. It is the sodium salt of the polyphosphate penta-anion, which is the conjugate base of triphosphoric acid. It is produced on a large scale as a component of many domestic and industrial products, especially detergents. Environmental problems associated with eutrophication are attributed to its widespread use.

Sodium tripolyphosphate is produced by heating a stoichiometric mixture of disodium phosphate, Na2HPO4, and monosodium phosphate, NaH2PO4, under carefully controlled conditions.

In this way, approximately 2 million tons are produced annually.

STPP is a colourless salt, which exists both in anhydrous form and as the hexahydrate. The anion can be described as the pentanionic chain [O3POP(O)2OPO3]5−. Many related di-, tri-, and polyphosphates are known including the cyclic triphosphate P3O93−. It binds strongly to metal cations as both a bidentate and tridentate chelating agent.

The majority of STPP is consumed as a component of commercial detergents. It serves as a "builder," industrial jargon for a water softener. In hard water (water that contains high concentrations of Mg2+ and Ca2+), detergents are deactivated. Being a highly charged chelating agent, TPP5− binds to dications tightly and prevents them from interfering with the sulfonate detergent.

STPP is a preservative for seafood, meats, poultry, and animal feeds. It is common in food production as E number E451. In foods, STPP is used as an emulsifier and to retain moisture. Many governments regulate the quantities allowed in foods, as it can substantially increase the sale weight of seafood in particular. The United States Food and Drug Administration lists STPP as "generally recognized as safe."


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