Tetrasodium pyrophosphate, also called sodium pyrophosphate, tetrasodium phosphate or TSPP, is a colorless transparent crystalline chemical compound with the formula  Na₄P₂O₇. It contains the pyrophosphate ion and sodium cation. Toxicity is approximately twice that of table salt when ingested orally. There is also a hydrated form, Na₄P₂O₇10(H₂O).