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ISO 1693:1976

Cryolite, natural and artificial — Determination of fluorine content — Modified Willard-Winter method ISO 1693:1976

Publication date:   Sep 1, 1976

General information

90.93 Standard confirmed   Nov 3, 2020

ISO

ISO/TC 226 Materials for the production of primary aluminium

International Standard

71.060.50   Salts

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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.

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PUBLISHED
ISO 1693:1976
90.93 Standard confirmed
Nov 3, 2020