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 |
Einecs | 231-545-4 |
Chemical name | Silicon dioxide |
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 | |
---|---|
Test for silica | Positive |
Purity | |
Loss on drying | Not more than 2,5 % (fumed silica, 105 °C, 2 hours) Not more than 8,0 % (precipitated silica and silica gel, 105 °C, 2 hours) Not more than 70 % (hydrous silica, 105 °C, 2 hours) |
Loss on ignition | Not more than 2,5 % after drying (1 000 °C, fumed silica) Not more than 8,5 % after drying (1 000 °C, 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 |