Ammonium ferric citrate has the formula (NH4)5[Fe(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.
Structure of ammonium ferric citrate
Crystal structure of (NH4)5[Fe(C6H4O7)2]·2H2O
2-Hydroxypropane-1,2,3-tricarboxylate, ammonium iron(3+) salt
Ferric ammonium citrate
Ammonium iron(III) citrate
Ammonium ferric citrate
Iron ammonium citrate
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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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In its crystal structure each moiety of citric acid has lost four protons. The deprotonated hydroxyl group and two of the carboxylate groups ligate to the ferric center, while the third carboxylate group coordinates with the ammonium.
Ammonium ferric citrate has a range of uses, including:
- As a food ingredient, it has an INS number, and is used as an acidity regulator. Most notably used in the Scottish beverage Irn-Bru.
- 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's Iron Agar (KIA) test to identify enterobacteriaceae bacteria by observing their metabolism of different sugars, producing hydrogen sulfide
- 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.
- "KEGG DRUG: Ferric ammonium citrate".
- Aryal, Sagar. "Kligler's Iron Agar Test – Procedure, Uses and Interpretation". MicrobiologyInfo.com. Retrieved 5 November 2021.
- Budavari, Susan, ed. (2001), The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (13th ed.), Merck, ISBN 0911910131