ISO 983:1974

Sodium hydroxide for industrial use — Determination of iron content — 1,10- Phenanthroline photometric method

Specifies a method that is more sensitive and more widely used than the 2,2′-bipyridyl method. It is applicable to products having iron contents equal to or greater than 0.5 mg/kg. The principle is based on the reduction of trivalent iron by hydroxylammonium chloride, formation of a bivalent iron/1,10-phenanthroline complex in a buffered system. Photometric measurement of the coloured complex at a wavelength of about 510 nm. This method has also been approved by the IUPAC. – Cancels and replaces ISO Recommendation R 983-1969.