Ammonium ferric citrate
Crystal structure of (NH4)5Fe(C6H4O7)2·2H2O
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Ammonium ferric citrate has the formula (NH4)5Fe(C6H4O7)2. A distinguishing feature of this compound is that it is very soluble in water, in contrast to ferric citrate which is not very soluble.
In its crystal structure each citric acid moiety has lost four protons, and the deprotonated hydroxyl groups act as ligands together with four caboxylate groups; two carboxylate groups are not coordinated to the ferric ion.
Ammonium ferric citrate has a range of uses, including:
- As a food additive, where it has the E number E381, and is used as an acidity regulator.
- Water purification
- As a reducing agent of metal salts of low activity like gold and silver.
- With potassium ferricyanide as part of the cyanotype photographic process.
- Used in Kligler iron deeps to determine hydrogen sulfide production in microbial metabolism.
- In medical imaging, ammonium ferric citrate is used as a contrast medium.
- As a hematinic.
- Matzapetakis, M.; Raptopoulou, C. P.; Tsohos, A.; Papaefthymiou, V.; Moon, N.; Salifoglou, A. (1998). "Synthesis, Spectroscopic and Structural Characterization of the First Mononuclear, Water Soluble Iron−Citrate Complex, (NH4)5Fe(C6H4O7)2·2H2O". J. Am. Chem. Soc. 120 (50): 13266–13267. doi:10.1021/ja9807035.
- Budavari, Susan, ed. (2001), The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (13th ed.), Merck, ISBN 0911910131