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Sodium Tripolyphosphate (Tech Grade) CAS: 7758-29-4
Na5 P3 O10
Sodium triphosphate (STP, sometimes STPP or sodium tripolyphosphate or TPP) is an inorganic compound with formula Na5P3O10. It is the sodiumsalt 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.
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.
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 numberE451. 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".
Polyphosphates are hydrolyzed into simpler phosphates, which in moderate amounts are nutritious. For example, ATP, a related derivative of triphosphate, is essential for life. Thus, the toxicity of polyphosphates is low, as the lowest LD50 after oral administration is >1,000 mg/kg body weight.[clarification needed] Similarly, no mutagenic or carcinogenic effects nor reproductive effects have been noted. Salts of polyphosphate anions are moderately irritating to skin and mucous membrane because they are mildly alkaline.
Effects of wastewater containing phosphorus
Detergents containing phosphorus contribute together with other sources of phosphorus to the eutrophication of many fresh waters. Eutrophication is an increase in chemical nutrients—typically compounds containing nitrogen or phosphorus—in an ecosystem. It may occur on land or in water. The term is however often used to mean the resultant increase in the ecosystem's primary productivity (excessive plant growth and decay), and further effects including lack of oxygen and severe reductions in water quality, fish, and other animal populations.
Phosphorus can theoretically generate its weight 500 times in algae (Wetzel 1983). Whereas the primary production in marine waters is mainly nitrogen limited, freshwaters are considered to be phosphorus limited. A large part of the sewage effluents in many countries is released untreated into freshwater recipients, and here the use of phosphorus as complexing agents is still an environmental concern.
Category: Other Chemical Products