POLAROGRAPHIC BEHAVIOUR OF METALLIC COMPLEXES WITH PYROPHOSPHATE.Part -I.

Abstract

Employing sodium pyrophosphate as the complexing agent a systematic study has been made on the polarographic ehaviour of iron. It has been noticed that the polarograms consist of two waves both corresponding to the rednction of ferric to ferrous. With a decrease in pH, the height of the first wave increases, then remains constant, and again increases. These resuits are explained on the assumption of the formation of different species in sluggish equilibrium at different pH values.It has been noticed that the first wave is reversible while the second wave is irreversible. The addition of potassium nitrate suppresses the first wave. The formula of the ferric pyrophosphate is found to be (FeP20,).In presence of ammonia-ammonium chloride the formation of a new amino-pyrophosphate complex has been established. Solutions containing sodium carbonate and pyrophosphate are yellow in colour due to the formation of colloidal ferric oxide. It has been suggested that a combination of potassium nitrate with gelatin can be employed to estimate iron polarographically in presence of pyrophosphate.