Sodium triphosphate (STPP), 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.
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.
Used in water softening, heavy-duty fabric washing, automatic dish washing, drilling fluid cleaning, and liquid cattle feed supplements; Also used as a peptizing, emulsifying, and dispersing agent; a preservative, sequestrant, and texture-modifier in foods; a sealant for leaking farm ponds; and a calcium and magnesium chelating agent; [HSDB] Used in paper pulping, paper coatings, clay and textile processing, and ore flotation; Also used as a hydrogen peroxide solution stabilizer and to make rubber and paint.