| Synonyms | Potassium alum, potash alum |
| Definition | |
| Chemical name | Aluminium potassium sulphate dodecahydrate |
| Einecs | 233-141-3 |
| Chemical formula | AlK(SO4)2 · 12 H2O |
| Molecular weight | 474,38 |
| Assay | Content not less than 99,5 % |
| Description | Large, transparent crystals or white crystalline powder |
| Identification | |
A.Positive tests for aluminium, for potassium and for sulphate | |
B.pH of a 10 % solution between 3,0 and 4,0 | |
C.Solubility | Freely soluble in water, insoluble in ethanol |
| Purity | |
| 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 |