Ammonium iron(III) sulfate, NH4Fe(SO4)2·12 H2O, or NH4[Fe(H2O)6](SO4)2·6 H2O, also known asferric ammonium sulfate (FAS) oriron alum, is adouble salt in the class ofalums, which consists of compounds with the general formula AB(SO4)2 · 12 H2O.[2] It has the appearance of weakly violet, octahedricalcrystals. There has been some discussion regarding the origin of the crystals' color, with some ascribing it to impurities in the compound,[3] and others claiming it to be a property of the crystal itself.[4]
FAS can be prepared by crystallization from a solution offerric sulfate andammonium sulfate. Iron(II) in ferrous sulfate is oxidized to ferric sulfate by addition ofsulfuric andnitric acid. Upon addition of ammonium sulfate to the solution and damping in of the solution, ferric ammonium sulfate crystals precipitate. Equations for these conversions ignore thedegree of hydration of the material.
^Considine, Douglas M:Chemical and process technology encyclopedia, McGraw-Hill, New York, 1974, p. 993
^Christensen, Odin T. "On the Cause of the Amethyst Color of Ferric Alum and of Mixed Crystals of Ferric and Manganic Alum".Chem. Lab. Roy. Vet. Agr. Hochschule, KGL. Danske Vidsk. Selsk. Forh.1906:173–95.
^Cooke, Meyer; Wolf (1956). "The Specific Heats of Three Paramagnetic salts at Very Low Temperatures".Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences.237 (1210):395–403.Bibcode:1956RSPSA.237..395C.doi:10.1098/rspa.1956.0185.S2CID97076961.
^Wang, Fei; et al. (2008). "Microcalorimetric investigation of the toxic action of ammonium ferric(III)sulfate on the metabolic activity of pure microbes".Environmental Toxicology and Pharmacology.25 (3):351–357.Bibcode:2008EnvTP..25..351W.doi:10.1016/j.etap.2007.11.004.PMID21783873.
^abcWiley Encyclopedia of inorganic chemistry: Volume 4, p. 1704:
^Chen et al.:United States Patent 5518131 – "Etching molydbenum with ferric sulfate and ferric ammonium sulfate"
^Grant W. Wilson, Peter T. Timbie: "Construction techniques for adiabatic demagnetization refrigerators using ferric ammonium alum".Cryogenics, Volume 39, Number 4, (1999), pp. 319–322
^J. C. Whitehorn: "A system of blood analysis. Supplement II. Simplified method for the determination of chlorides in blood or plasma".Journal of Biological Chemistry (1921), 45 p. 449–60.
^Yu, Shanxin; et al. (2005). "Application of ammonium ferric sulfate dodecahydrate in organic synthesis".General Review.17 (1):27–30.
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