Calcium citrate

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Calcium citrate
Calcium citrate.PNG
IUPAC name 2-hydroxy-1,2,3-propane- tricarboxylic acid calcium salt (2:3)
Other names E333
CAS number 813-94-5
SMILES C(C(=O)[O-])C(CC(=O)[O-])(C(=O)[O-])O.
Molecular formula Ca3(C6H5O7)2
Molar mass 498.46 g/mol (anhydrous)
Appearance White powder
Density 1.63 g/cm3, solid
Melting point

120 °C (loses water)

Boiling point


Solubility in water 0.095 g/100 ml (25 °C)
MSDS External MSDS
Main hazards Irritant
Related Compounds
Other cations Sodium citrate
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]


Calcium citrate is the calcium salt of citric acid. It is commonly used as a food additive (E333), usually as a preservative, but sometimes for flavor. In this sense, it is similar to sodium citrate. Calcium citrate is also used as a water softener because the citrate ions can chelate unwanted metal ions. Calcium citrate is also found in some dietary calcium supplements.

Chemical properties

Like citric acid, calcium citrate has a sour taste. Like other salts, however, it also has a salty taste. For this reason, citrates such as sodium and calcium citrate are commonly known as sour salt.


Calcium citrate is an intermediate in the isolation of citric acid from the fermentation process by which citric acid is produced industrially.[1] The citric acid in the broth solution is neutralized by calcium hydroxide, precipitating insoluble calcium citrate. This is then filtered off from the rest of the broth and washed to give clean calcium citrate.

The calcium citrate thus produced may be sold as-is, or it may be converted to citric acid using dilute sulfuric acid.

Biological role

Calcium citrate supplements may increase aluminum toxicity. Patients with renal disease are at an increased risk of toxicity.

Bioavailability is 2.5 times higher than calcium carbonate. For this reason, patients who have undergone the Roux-en-Y variety of weight-loss surgery (also known as gastric bypass) are usually instructed to take calcium citrate as a dietary supplement.


  1. "Use of Lime in the Chemical Industry". National Lime Association. Retrieved 2006-11-25. 
de:Calciumcitratit:Citrato di calcio