| Definition | |
| Chemical name | Sodium sulphite (anhydrous or heptahydrate) |
| Einecs | 231-821-4 |
| Chemical formula | Anhydrous: | Na2SO3 |
| Heptahydrate: | Na2SO37H2O |
| Molecular weight | Anhydrous: | 126,04 |
| Heptahydrate: | 252,16 |
| Assay | Anhydrous: | Not less than 95 % of Na2SO3 and not less than 48 % of SO2 |
| Heptahydrate: | Not less than 48 % of Na2SO3 and not less than 24 % of SO2 |
| Description | White crystalline powder or colourless crystals |
| Identification | |
A.Positive tests for sulphite and for sodium | |
B.pH of a 10 % solution (anhydrous) or a 20 % solution (heptahydrate) between 8,5 and 11,5 | |
| Purity | |
| Thiosulphate | Not more than 0,1 % based on the SO2 content |
| 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 |
