Division Purity
United Kingdom
| Chlorides | Not more than 1 % |
| Nitrogen | Not more than 8 % |
| Loss on drying (105 °C for 6 hours) | Not more than 10 % |
| Mercury | Not more than 0,1 mg/kg |
| Arsenic | Not more than 1 mg/kg |
| Cadmium | Not more than 1 mg/kg |
| Chromium | Not more than 10 mg/kg |
| Lead | Not more than 0,5 mg/kg |