Tags: Chemical Compound, Chemical Substance.
Ammonium iron(III) sulfate NH4Fe(SO4)2·12 H2O also known as ferric ammonium sulfate (FAS) or iron alum is a double salt in the class of alums which consists of compounds with the general formula AB(SO4)2 · 12 H2O. It has the appearance of weakly violet octahedrical crystals.