Calcium citrate

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Calcium citrate
Chemical formula Ca3(C6H5O7)2
OTP appearance white solid 
Molar Mass(g/mol) 498 
Melting Point(°C) 120 
Boiling Point(°C) decomposes 
Density(g/cc) 1.6 
Solubility in water(g/L) 0.8 
Solubility in ethanol(g/L) non
NFPA 704
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Calcium citrate is an important salt of calcium for nutritional supplementation, and a stable compound for storage of citrate.

Uses

Primary

  • Feedstock for oral rehydration salts
  • Storage of citrate for other uses
  • Intermediate in purification of citric acid from citrus juice

Natural Occurrence

  • Does not occur naturally

Hazards

  • GRAS, food supplement

Production

Extraction

citrus fruits contain two main acids: citric acid and ascorbic acid. Extraction and isolation of calcium citrate occurs as follows:

  1. Filter juice of citrus fruit
  2. Discard residue
  3. Acidify to pH ~2 with hydrochloric acid
  4. Filter
  5. Discard residue
  6. Basify to pH 8-9 via sodium hydroxide
  7. Filter
  8. Discard residue
  9. Add calcium chloride in proportion to the sodium hydroxide used (1:2 molar) while warming, precipitating calcium citrate
    2 Na3C6H5O7(aq) + 3 CaCl2(aq)
    {
    Δ}
    3 Ca2C6H5O7(s) + 6 NaCl(aq)
  10. Filter
  11. Discard filtrate

Testing

Purification

Storage

Disposal

See Also

References