Synonyms: Ammonium ferrous sulfate hexahydrate, Ammonium iron(II) sulfate, Mohr's salt, Ammonium iron(II) sulfate hexahydrate CAS: 7783-85-9 Molecular Formula: Fe(NH4)2(SO4)2 · 6H2O Molecular Weight: 392.14 g/mol Test Specification Description Pale-green mixture of fine crystals & larger regular pieces Assay [Fe(NH4)2(SO4)2 · 6H2O] 98.5 to 101.5% Calcium (Ca) 0.005% max. Copper (Cu) 0.003% max. Magnesium (Mg) 0.002% max. Ferric Iron (Fe+3) 0.01% max. Insoluble Matter 0.01% max. Manganese (Mn) 0.01% max. pH of 5% Solution at 25°C 3.0 to 5.0 Potassium (K) 0.002% max. Sodium (Na) 0.02% max. Phosphate (PO4) 0.003% max. Zinc (Zn) 0.003% max.