calcium citrate calcium citrate 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 found in some dietary calcium supplements (e.g. citracal or caltrate). calcium makes up 24.1% of calcium citrate (anhydrous) and 21.1% of calcium citrate (tetrahydrate) by mass. the tetrahydrate occurs in nature as the mineral earlandite. calcium citrate 2d structure of calcium citrate calcium citrate tetrahydrate calcium citrate tetrahydrate names iupac name 2-hydroxy-1,2,3-propane-tricarboxylic acid calcium salt (2:3) other names e333, tricalcium dicitrate identifiers cas number 813-94-5 y5785-44-4 (tetrahydrate) y 3d model (jsmol) interactive image chebi chebi:190513 chembl chembl2106123 chemspider 12584 y drugbank db11093 echa infocard 100.011.265 ec number 212-391-7 e number e333 (antioxidants, ...) pubchem cid 13136 unii 86117bwo7p ymlm29u2x85 (tetrahydrate) y comptox dashboard (epa) dtxsid7061148 inchi inchi=1s/2c6h8o7.3ca/c2*7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h2*13h,1-2h2,(h,7,8)(h,9,10)(h,11,12);;;/q;;3*+2/p-6 ykey: fnaqsuugmsobhw-uhfffaoysa-h yinchi=1/2c6h8o7.3ca/c2*7-3(8)1-6(13,5(11)12)2-4(9)10;;;/h2*13h,1-2h2,(h,7,8)(h,9,10)(h,11,12);;;/q;;3*+2/p-6key: fnaqsuugmsobhw-cyfpfddlaz smiles ...o=c()cc(o)(c()=o)cc(=o).c(=o)c(o)(cc()=o)cc()=o properties chemical formula ca3(c6h5o7)2 molar mass 498.4334 g/mol (anhydrous) 570.4945 g/mol (tetrahydrate) appearance white powder odor odorless density 1.63 g/cm3 (anhydrous) 2.00 g/cm3 (tetrahydrate) melting point decomposes boiling point decomposes solubility in water 0.85 g/l (18 °c) 0.95 g/l (25 °c) solubility insoluble in alcohol structure crystal structure triclinic (tetrahydrate) space group p1, no. 2 lattice constant a = 0.59466(4) nm, b = 1.02247(8) nm, c = 1.66496(13) nmα = 72.213(7)°, β = 79.718(7)°, γ = 89.791(6)° hazards occupational safety and health (ohs/osh): main hazards irritant nfpa 704 (fire diamond) 1 1 0 related compounds other cations magnesium citratestrontium citrate except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). n verify (what is yn ?) infobox references in 2020, calcium was the 204th most commonly prescribed medication in the united states, with more than 2 million prescriptions. chemical properties calcium citrate is sparingly soluble in water. needle-shaped crystals of tricalcium dicitrate tetrahydrate ·2h2o were obtained by hydrothermal synthesis. the crystal structure comprises a three-dimensional network in which eightfold coordinated ca2+ cations are linked by citrate anions and hydrogen bonds between two non-coordinating crystal water molecules and two coordinating water molecules. production calcium citrate is an intermediate in the isolation of citric acid from the fungal fermentation process by which citric acid is produced industrially. the citric acid in the broth solution is neutralized by limewater, precipitating insoluble calcium citrate. this is then filtered off from the rest of the broth and washed to give clean calcium citrate. 3 ca(oh)2(s) + 2 c6h8o7(l) → ca3(c6h5o7)2(s) + 6 h2o(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 in many individuals, bioavailability of calcium citrate is found to be equal to that of the cheaper calcium carbonate. 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. calcium carbonate is harder to digest than calcium citrate, and calcium carbonate carries a risk of "acid rebound" (the stomach overcompensates by producing more acid), 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, 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.