Ferrous ammonium sulfate - Fe (NH4)2 (SO4)2·6H2O
Ferrous ammonium sulfate is a so-called double salt. It is not a complex, but contains free ferrous ions and ammonium ions. It is a useful substitute for ferrous sulfate. The compound is much less air sensitive than ferrous sulfate and keeps well. This sample nicely shows the light blue/green color of ferrous ions.