1 | Appearance | White crystalline powder. | White or almost white to yellowish crystalline powder or colorless crystals. |
2 | Solubility | Complies | Freely soluble in water. Slightly soluble in ethanol (96%) and in alcohol. |
3 | Identification A (By pH) | 4.4 | 3.5 to 5.0 |
4 | Identification (Reaction of sulfates) | Complies | White precipitate should form |
5 | Identification (Reaction of sodium) | Complies | A dense white precipitate should form |
6 | Identification (Sulfite) | Complies | A filter paper moistened with mercurous nitrate solution should blacken |
7 | Appearance of solution | Complies | Clear and colorless solution |
8 | pH | 4.4 | 3.5 to 5.0 |
9 | Thiosulfates | Complies | The solution should remain clear for at least 15 min |
10 | Limit of Thiosulfate | Less than 0.05% | NMT 0.05% |
11 | Iron (Fe) | Less than 20ppm | NMT 20ppm (0.002%) |
12 | Limit of Chloride | Less than 0.05% | NMT 0.05% |
13 | Assay (as SO2) | 65.8% | 65.0%- 67.4% |
14 | Assay | 97.7% | 95.0% - 100.5% |