Calcium citrate

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Calcium citrate

General
Systematic name	2-hydroxy-1,2,3-propane- tricarboxylic acid calcium salt (2:3)
Other names	E333
Molecular formula	Ca₃(C₆H₅O₇)₂
SMILES	C(C(=O)[O-])C(CC(=O)[O-])(C(=O)[O-])O. C(C(=O)[O-])C(CC(=O)[O-])(C(=O)[O-])O. [Ca+2].[Ca+2].[Ca+2]
Molar mass	498.46 g/mol (anhydrous)
Appearance	White powder
CAS number	[813-94-5] (anhydrous) [5785-44-4]
Properties
Density and phase	1.63 g/cm³, solid
Solubility in water	0.095 g/100 ml (25 °C)
Melting point	120 °C (loses water)
Boiling point	Decomposes
Basicity (pK_b)	?
Chiral rotation [α]_D	?°
Structure
Crystal structure	?
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	Irritant
NFPA 704	1 1 0
Flash point	?°C
R/S statement	R: ? S: ?
RTECS number	?
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other cations	Sodium citrate
Related compounds	?
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

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.

1 Chemical properties
2 Production
3 Biological role
4 See also
5 References

[edit] 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.

[edit] Production

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 neutralised 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.

[edit] Biological role

Calcium citrate supplements may increase aluminium 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.