| Appearance: | Pale violet crystals |
| Assay: | 98.5-102.0% NH4Fe(SO4)2 · 12(H2O) |
| MAXIMUM ALLOWABLE | |
| Insoluble matter: | 0.01% |
| Chloride (Cl): | 0.001% |
| Nitrate (NO3): | 0.01% |
| Copper (Cu): | 0.003% |
| Zinc (Zn): | 0.003% |
| Ferrous iron (Fe++): | Passes test |
| Substances not precipitated by ammonium hydroxide: | 0.05% |