(NH4)2Fe(SO4)2.6H2O is a blue green crystal at room temperature. It is soluble in water. Its melting point is 100 ̊C (212 ̊F), density 1.86 g/cm3. Mohr's salt may cause burns to eye and skin. It may cause digestive tract irratation if swallowed. It's widely used, such as for water purification or laboratory reagent.