What is "pyrophosphate"

Pyrophosphate \Pyr"o*phos"phate\, n. (Chem.) A salt of pyrophosphoric acid.

n. (context inorganic chemistry English) Any salt or ester of pyrophosphoric acid.

n. a salt or ester of pyrophosphoric acid

In chemistry, pyrophosphate is a phosphorus oxyanion. Compounds such as salts and esters are also called pyrophosphates. The group is also called diphosphate or dipolyphosphate, although this should not be confused with phosphates. As a food additive, diphosphates are known as E450. A number of hydrogen pyrophosphates also exist, such as NaHPO, as well as the normal pyrophosphates.