Calcium citrate

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Calcium citrate
Calcium citrate
Identifiers
CAS number 813-94-5 N5785-44-4 (tetrahydrate)
PubChem 13136
ChemSpider 12584 YesY
EC number 212-391-7
ATC code A12AA13
Jmol-3D images Image 1
Properties
Molecular formula Ca3(C6H5O7)2
Molar mass 498.4334 g/mol (anhydrous)
570.49452 g/mol (tetrahydrate)
Appearance White powder
Odor odorless
Density 1.63 g/cm3, solid
Melting point 120 °C (loses water)
Boiling point Decomposes
Solubility in water 0.085 g/100 mL (18 °C)
0.095 g/100 mL (25 °C)
Solubility insoluble in alcohol
Hazards
MSDS External MSDS
Main hazards Irritant
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Other cations Sodium citrate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox 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 (e.g. Citracal). Calcium makes up 24.1% of calcium citrate (anhydrous) and 21.1% of calcium citrate (tetrahydrate) by mass.

Chemical properties[edit]

Calcium citrate is an odorless white powder, practically insoluble in cold water.

Production[edit]

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.

3Ca(OH)2(s) + 2C6H8O7(l) → Ca3(C6H5O7)2(s) + 3H2O(l)

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

Biological role[edit]

In many individuals, bioavailability of calcium citrate is found to be equal to that of the cheaper calcium carbonate.[2] However, alterations to the digestive tract may change how calcium is digested and absorbed. Unlike calcium carbonate, which is basic and neutralizes stomach acid, calcium citrate has no effect on stomach acid.[3] Calcium carbonate is harder to digest than calcium citrate,[3] and calcium carbonate carries a risk of "acid rebound" (the stomach overcompensates by producing more acid),[3] so individuals who are sensitive to antacids or who have difficulty producing adequate stomach acid may choose calcium citrate over calcium carbonate for supplementation. According to recent research into calcium absorption after gastric bypass surgery,[4] calcium citrate may have improved bioavailability over calcium carbonate in Roux-en-Y gastric bypass patients who are taking calcium citrate as a dietary supplement after surgery. This is mainly due to the changes related to where calcium absorption occurs in the digestive tract of these individuals.

References[edit]

  1. ^ "Use of Lime in the Chemical Industry". National Lime Association. Archived from the original on 2006-09-29. Retrieved 2006-11-25. 
  2. ^ Heaney RP, Dowell MS, Bierman J, Hale CA, Bendich A (June 2001). "Absorbability and cost effectiveness in calcium supplementation". Journal of the American College of Nutrition 20 (3): 239–46. doi:10.1080/07315724.2001.10719038. PMID 11444420. Retrieved 2009-11-03. | PMID 11444420
  3. ^ a b c "What you need to know about calcium". Harvard Health Publications. Retrieved 4 August 2014. 
  4. ^ Tondapu, P. and Provost, D. and Adams-Huet, B. and Sims, T. and Chang, C. and Sakhaee, K. (June 2009). "Comparison of the Absorption of Calcium Carbonate and Calcium Citrate after Roux-en-Y Gastric Bypass". Obesity Surgery 19 (9): 1256–1261. doi:10.1007/s11695-009-9850-6. PMID 19437082. Retrieved 2010-08-11. 

External links[edit]