Reference number
ISO 2833:1973
ISO 2833:1973
© ISO 2025
International Standard
ISO 2833:1973
Sodium fluoride for industrial use — Determination of fluorine content — Modified Willard-Winter method
Edition 1
1973-12
1973-12
ISO 2833:1973
7830
Published
(Edition 1, 1973)
This publication was last reviewed and confirmed in 2023.
Therefore this version remains current.
Abstract
The principle consists in separation of the fluorine from a test portion by distillation with sulphuric acid or perchloric acid. Titration with thorium nitrate solution using sodium alizarinsuphonate and methylene blue as indicators. Alternatively the thorium nitrate titration may be carried out using sodium alizarinsuphonate alone as indicator, the end-point being determined spectrophotometrically under carefully defined conditions. The absorbance at a wavelength of 525 nm shall reach the arbitrary value of 0.6. Has also been approved by the IUPAC.