| White crystalline powder | Complying |
| Assay (T) | 99.0-102.0%w/w |
| pH (5% in water) | 4.2-4.5 |
| Reducing substances | Complying |
| Water insolubles | <= 0.2% |
| Loss on drying (130°C) | 21.5-24.0% |
| Arsenic (As) | <= 0.0002% |
| Chloride (Cl) | <= 0.005% |
| Heavy metals (as Pb) | <= 0.001% |
| Iron (Fe) | <= 0.0005% |
| Sulfate (SO4) | <= 0.02% |