Effects of the Anion on the Extraction of Cobalt with 8-Quinolinol into Chloroform

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Abstract
The effects of the anions, especially the perchlorate ion, on the extraction of cobalt into chloroform with 8-quinolinol (Hql) were examined. Two kinds of cobalt(II) 8-quinolinol complexes, species A and B, are extracted into the chloroform phase from the aqueous cobalt(II) solution containing perchlorate ions. Species A contains no perchlorate ion and is extracted above pH 7.7; species B is an ion-pair complex containing a perchlorate ion and is predominantly extracted below pH 5.1. The compositions of species A and B were estimated to be Co2ql4(Hql)2 and Co2ql3(Hql)3ClO4, respectively. These dimer complexes are related by the following equilibrium, with logKAB=−7.2: