Extraction—spectrophotometric determination of traces of antimony as the ferroin—hexachloroantimonate(V) complex

The sparingly soluble scarlet precipitate formed by the interaction of ferroin and antimony(V) in strong hydrochloric acid medium is soluble in nitrobenzene. The composition of the complex is [Fe(phen)₃] [SbCl₆]₂. The percentage extraction into nitrobenzene, determined by tracer techniques, reaches a maximum (98%) at 8–9 M hydrochloric acid. The advantages of this procedure over those employing dyes as reagents are discussed. Antimony(V) can be determined in the range 2.5–24μg ml^-1. Interferences are described.