This standard was last reviewed and confirmed in 2018. Therefore this version remains current.
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.
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|std 1 40|
|std 2 40||Paper|
A standard is reviewed every 5 years
Stage: 90.20 (Under review)
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