OXIDATION OF COBALT(II) DURING ITS SOLVENT-EXTRACTION WITH ACETYLACETONE

During the solvent extraction of cobalt(II) with acetylacetone, benzoylacetone, dibenzoylmethane, and benzoyltrifluoroacetone in toluene, oxidation of the metal ion was found only with acetylacetone. The oxidation was assumed to be caused by dissolved atmospheric oxygen in the organic solvent. The rate of oxidation was first order with respect to the acetylacetone concentration, and was nearly the same when the diluent was carbon tetrachloride. This oxidation was slowed down by the addition of trioctylphosphine oxide. The shape of the extraction curve of cobalt(II) with acetylacetone as a function of the hydrogen-ion concentration was different when the time for the two-phase agitation was one hour,one day,and one week. The reason for this is discussed from the stand point of the slow oxidation of cobalt(II) and of the acetylacetone concentration in the organic phase.