Sodium triphosphate (STP), also sodium tripolyphosphate (STPP), or tripolyphosphate (TPP),) is an inorganic compound with formula Na 5 P 3 O 10.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.t 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.