| Synonyms | Silica, silicium dioxide |
| Definition | Silicon dioxide is an amorphous substance, which is produced synthetically by either a vapour-phase hydrolysis process, yielding fumed silica, or by a wet process, yielding precipitated silica, silica gel, or hydrous silica. Fumed silica is produced in essentially an anhydrous state, whereas the wet-process products are obtained as hydrates or contain surface absorbed water |
| Chemical name | Silicon dioxide |
| Einecs | 231-545-4 |
| Chemical formula | (SiO2)n |
| Molecular weight | 60,08 (SiO2) |
| Assay | Content after ignition not less than 99,0 % (fumed silica) or 94,0 % (hydrated forms) |
| Description | White, fluffy powder or granules |
| Hygroscopic |
| Identification | |
A.Positive test for silica | |
| Purity | |
| Loss on drying | Not more than 2,5 % (fumed silica, 105 oC, 2h) |
| Not more than 8,0 % (precipitated silica and silica gel, 105 oC, 2h) |
| Not more than 70 % (hydrous silica, 105 oC, 2h) |
| Loss on ignition | Not more than 2,5 % after drying (1 000 oC, fumed silica) |
| Not more than 8,5 % after drying (1 000 oC, hydrated forms) |
| Soluble ionisable salts | Not more than 5,0 % (as Na2SO4) |
| Arsenic | Not more than 3 mg/kg |
| Lead | Not more than 5 mg/kg |
| Mercury | Not more than 1 mg/kg |
