STPP is one of the most important ingredients in detergent powder formulation. Its chemical formula is Na5P3O5. The STPP preparation process is composed of three steps: preparation of phosphoric acid from phosphate rocks, sodium pyrophosphate from neutralization of the acid, and finally the formation of STPP by condensation and polymerization of the sodium pyrophosphate. There are two processes now in common use for preparing STPP: 1. Wet process Converse ingredients in the phosphate rocks into their corresponding sulfuric salt and phosphoric salt. The liquid phosphoric acid is neutralized in next section into sodium pyrophosphate, then the phosphate to be condensed and polymerized into STPP. 2. Thermal process Feed phosphate rocks, coke and silicate rocks into an electric furnace to obtain phosphorus. The phosphorus is burned, and phosphorus pentoxide is formed. The later is hydrated and polymerized into STPP.