ISO/R 909:1968

Hydrochloric acid for industrial use — Determination of iron content — 2,2′- Bipyridyl spectrophotometric method

The principle consists in evaporation of the test portion, taking up by means of hydrochloric acid and reduction of iron(III) by means of hydroxylammonium chloride. Formation of an iron(II)-2.2′-bipyridyl complex in a buffered medium at a pH value between 4.5 and 6. Photometric measurement of the coloured complex at a wavelength of about 522 nm.