Selective Solvation of Co2+ in Aqueous Ethanol

AbstractSelective solvation of Co 2+ in aqueous ethanol has been studied by measuring visible-region spectra and changes therein upon addition of ZnCl2. The study is based on comparison of spectra in the mixtures with those in the individual neat solvents. Water exhibited stronger selective solvation. On increasing ethanol content absorbance due to organo-complex increased at the expense of the aquo-complex. Only the above two solvation complexes of Co 2+ have been found to co-exist in the system. As a simple model it is suggested that Co 2+ distribute themselves between the two types of solvation spheres. A value of 25±2 has been estimated for the distribution coefficient which is defined as the concentration ratio (caq./corg.). Upon ZnCl2 addition to the Co 2+ solutions in ethanol-rich mixtures (xethanol ≥ 0.6) increase of absorbance for the aquo-complex while simultaneous decrease for the organocomplex indicated more favoured formation of the aquo-complex by Co 2+ as compared to Zn 2+ .

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