Citric acid is a weak organic tricarboxylic acid having the chemical formula C6H8O7. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the metabolism of all aerobic organisms. More than a million tons of citric acid are manufactured every year. It is used widely as an acidifier, as a flavoring and chelating agent. A citrate is a derivative of citric acid; that is, the salts, esters, and the polyatomic anion found in solution. An example of the former, a salt is trisodium citrate; an ester is triethyl citrate. When part of a salt, the formula of the citrate ion is written as C6H5O73− or C3H5O(COO)33−.
1,2,3-Propanetricarboxylic acid, 2-hydroxy-
Appearance & Physical State
White crystalline powder
309.6ºC at 760 mmHg
750 g/L (20 ºC)
Stable. Incompatible with bases, strong oxidizing agents, reducing agents, metal nitrates.