Sodium fluoride for industrial use — Determination of fluorine content — Modified Willard-Winter method
NORMA vydána dne 1.12.1973
Označení normy: ISO 2833:1973
Datum vydání normy: 1.12.1973
Počet stran: 5
Přibližná hmotnost: 15 g (0.03 liber)
Země: Mezinárodní technická norma
Kategorie: Technické normy ISO
Description / 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.