| Definition | |
| Chemical name | Calcium sulphite |
| Einecs | 218-235-4 |
| Chemical formula | CaSO3·2H2O |
| Molecular weight | 156,17 |
| Assay | Content not less than 95 % of CaSO3·2H2O and not less than 39 % of SO2 |
| Description | White crystals or white crystalline powder |
| Identification | |
A.Positive tests for sulphite and for calcium | |
| Purity | |
| Iron | Not more than 50 mg/kg based on the SO2 content |
| Selenium | Not more than 10 mg/kg based on the SO2 content |
| Arsenic | Not more than 3 mg/kg |
| Lead | Not more than 5 mg/kg |
| Mercury | Not more than 1 mg/kg |
| Heavy metals (as Pb) | Not more than 10 mg/kg |