90.93 Standard confirmed Nov 3, 2020
ISO
ISO/TC 226 Materials for the production of primary aluminium
International Standard
71.060.50 Salts
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.
PUBLISHED
ISO 1693:1976
90.93
Standard confirmed
Nov 3, 2020