Sodium pyrophosphate

Sodium pyrophosphate

Other names	tetrasodium pyrophosphate, tetrasodium phosphate
Identifiers
CAS number	[7722-88-5]
Properties
Molecular formula	Na₄P₂O₇
Molar mass	265.90 g/mol
Appearance	Colourless crystals
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Sodium pyrophosphate, also called tetrasodium pyrophosphate or tetrasodium phosphate, is a slightly toxic and mildly irritating colorless transparent crystalline chemical compound with the formula Na₄P₂O₇ and CAS number 7722-88-5. It contains the pyrophosphate ion. Toxicity is approximately twice that of table salt when digested orally.^[1]. There is a hydrated form, Na₄P₂O₇.10(H₂O) which has the CAS number 13472-36-1.^[2]

Sodium pyrophosphate is used as a buffering agent, an emulsifier, and a thickening agent, and is often used as a food additive. Common foods containing sodium pyrophosphate include chicken nuggets, marshmallows, pudding, crab meat, imitation crab, canned tuna, and soy-based meat alternatives. It is the active ingredient in Bakewell, the substitute for baking powder's acid component marketed during shortages in World War II.

In toothpaste, sodium pyrophosphate acts as a tartar control agent, serving to remove calcium and magnesium from saliva and thus preventing them from being deposited on teeth. Sodium pyrophosphate is sometimes used in household detergents to prevent similar deposition on clothing, but due to its phosphate content it causes eutrophication of water, promoting algae growth.