Formula: (NH4)2Fe(SO4)2·6H2O Double sulfate of divalent iron and ammonium. Naturally occuring, it is known as mineral mohrite.
- Crystal system: monoclynic
- Crystal shape: from pure solution, flat tabular crystals are growing. If solution is conpaminated with Fe3+ ions, then crystals becoming more elongated.
- Color: green
- Stability on air: stable, a rare example of stable Iron (II) compound.
Dissolve equimolar amounts of ammonium sulfate ((NH4)2SO4) and iron (II) sulfate (FeSO4·7H2O) in water with small amount of sulfuric acid, then crystallize.
I used regular evaporation method. On air, solution is prone to slow oxidation, addition of small amount of sulfuric acid suppresses it.
The compound is generally safe, though can ittirate skin.