Studies on the System Iron‐DTPA

Abstract

The iron‐diethylenetriaminepentaacetic acid (DTPA) system has been investigated polarographically over the pH range 3–10 in the absence of maximum suppressor. The iron (III) complex is reversibly reduced at the dropping mercury electrode. Polarograms of mixtures of iron (III) and iron (II) yield a composite cathodic / anodic wave in the presence of excess DTPA. The half wave potential of the system is constant in the pH region 5.5–9, and from this the ratio of the stability of iron (III) DTPA to iron (II) DTPA has been evaluated. The stability constant of the ferric complex has been obtained from a spectrophotometric analyse of its dissociation equilibrium in 0.4–1.0 M perchloric acid medium at wavelength 380–520 mμ. μ dependence of the acid dissociation constant of DTPA verified that the Davies quation can be extended to μ = 1.0