Applicable to Fe contents, expressed as Fe2 O3 , equal to or more than 0.005 % (m/m). Specifies the preliminary reduction of iron (III) by means of hydroxylammonium chloride. Formation of the iron(II)-1,10-phenanthroline complex in a buffered (pH value between 3.5 and 4.2). Photometric measurement at a wavelength of about 510 nm. Replaces ISO Recommendation R 805/1968.