Determination of iron with bathophenanthroline following an improved procedure for reduction of iron(III) ions

Bathophenanthroline (4,7-diphenyl-1,10-phenanthroline) forms a red complex with iron(II) but not with iron(III) ions and is used in the determination of total iron when present at low molarities in aqueous solutions. The reduction of iron(III) ions is a critical step in such determinations. A modified procedure is described which brings about a 5-fold increase in the amount of iron(III) ions reduced compared with the original procedure, involving replacement of hydroxylammonium chloride with L-ascorbic acid, addition of concentrated hydrochloric acid and heating the solution in a steam-cabinet.