Sodium triphosphate (STP, sometimes STPP or sodium tripolyphosphate or 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 is attributed to its widespread use.
Preparation and properties
Sodium tripolyphosphate is produced by heating a stoichiometric mixture of disodium phosphate, Na2HPO4, and monosodium phosphate, NaH2PO4, under carefully controlled conditions.
2 Na2HPO4 + NaH2PO4 → Na5P3O10 + 2 H2O
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.
25 MT, 25 kgs bags per 20'ft container
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 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", along with salt, vinegar, and baking powder.
Other uses (hundreds of thousands of tons/year) include "ceramics, leather (as Synthetic Tanning Agent), anticaking, setting retarders, flame retardants, paper, anticorrosion pigments, textiles, rubber manufacture, fermentation, antifreeze."