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. 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.".
Other uses include "ceramics, leather tanning (as masking Agent and Synthetic Tanning Agent-SYNTAN), anticaking, setting retarders, flame retardants, paper, anticorrosion pigments, textiles, rubber manufacture, fermentation, antifreeze."Health effects
Polyphosphates are hydrolyzed into simpler phosphates, which in moderate amounts are nutritious.
Salts of polyphosphate anions are moderately irritating to skin and mucous membrane because they are mildly alkaline