LIGAND EFFECT ON REDOX REACTION OF METAL-IONS AND ITS APPLICATION TO POTENTIOMETRIC TITRATION OF CHROMIUM(VI) AND COPPER(II) WITH IRON(II)

The effect of complexing agents on the titration of chromium(VI) and copper(II) with iron(II) was studied. In general, iron(III) forms more stable complexes than iron(II), so that the potential of the system Fe(III)/ Fe(II) is lower in the presence of a complexing agent than in its absence. Thus the addition of a complexing agent increases the sharpness of the end point of titration with iron(II). The presence of pyrophosphate improves the potential break at the equivalence point of chromium(VI) with iron(II). The use of neocuproine together with pyrophosphate is very effective in the titration of copper(II) with iron(II). © 1990, The Japan Society for Analytical Chemistry. All rights reserved.