ISO 1693:1976
Cryolite, natural and artificial; Determination of fluorine content; Modified Willard-Winter method
- Standard No.
- ISO 1693:1976
- Release Date
- 1976
- Published By
- International Organization for Standardization (ISO)
- Latest
- ISO 1693:1976
- Scope
- Specifies the determination for natural and synthetic materials having a molar ratio sodium fluoride/aluminium trifluoride between 3 and 1,7 approximately. The principle consists in fusion of a test portion with sodium carbonate, separation of fluorine by distillation with sulphuric acid or perchloric acid. Titration with thorium nitrate solution in presence of sodium alizarinsulphonate/methylene blue as indicator. Alternatively, the thorium nitrate titration may be made using only sodium alizarinsulphonate, the end-point being; spectrophotometrically determined at 525 nm.
ISO 1693:1976 history
- 1976 ISO 1693:1976 Cryolite, natural and artificial; Determination of fluorine content; Modified Willard-Winter method
