| Synonyms | Soda alum, sodium alum |
| Definition | |
| Chemical name | Aluminium sodium sulphate |
| Einecs | 233-277-3 |
| Chemical formula | AlNa(SO4)2 · nH2O (n = 0 or 12) |
| Molecular weight | 242,09 (anhydrous) |
| Assay | Content on the anhydrous basis not less than 96,5 % (anhydrous) and 99,5 % (dodecahydrate) |
| Description | Transparent crystals or white crystalline powder |
| Identification | |
A.Positive tests for aluminium, for sodium and for sulphate | |
B.Solubility | Dodecahydrate is freely soluble in water. The anhydrous form is slowly soluble in water. Both forms are insoluble in ethanol |
| Purity | |
| Loss on drying | Anhydrous form: not more than 10,0 % (220 oC, 16h) |
| Dodecahydrate: not more than 47,2 % (50 oC-55 oC, 1h then 200 oC, 16h) |
| Ammonium salts | No odour of ammonia detectable after heating |
| Selenium | Not more than 30 mg/kg |
| Fluoride | Not more than 30 mg/kg |
| Arsenic | Not more than 3 mg/kg |
| Lead | Not more than 5 mg/kg |
| Mercury | Not more than 1 mg/kg |