Spectrophotometric determination of cobalt with biacetyl mono(2-pyridyl)hydrazone

Abstract

The absorbance versus pH graphs and stoicheiometry of the complexes formed by biacetyl mono(2-pyridyl)hydrazone (BPH) with cobalt(II), nickel(II), copper(II) and iron(II) have been studied. A method for the spectrophotometric determination of cobalt has been devised. The orange-red chelate is formed at acidities between 2 and 10^–6M(pH 6), in aqueous ethanolic solution, and has λ_max. at 505 nm with a molar absorptivity of 2.3 × 10⁴ l mol^–1 cm^–1. The method has been applied to the determination of cobalt in nitrates and has been compared with other pyridylhydrazone procedures for the spectrophotometric determination of cobalt.