Solvent extraction equilibria of bis-Hg(II) benzoylacetonate and benzoyltrifluoroacetonate complexes and their adducts with trioctylphosphine oxide

The solvent extraction equilibria of Hg(II) in 1 mol dm⁻³ (Na, H)ClO₄ with benzoylacetone and benzoyltrifluoroacetone in carbon tetrachloride containing trioctylphosphine oxide (TOPO) have been measured at 25°C. The stability constants of the complexes in the aqueous phase, the two-phase partition constants, and the adduct formation constants with TOPO of the bis-complexes have been computed from the data. It is concluded that Hg(II) forms very stable β-diketonates and the bis-complexes form stable TOPO adducts in the organic phase. However, the partition constants of the bis-complexes are much lower than those of many other metal ions and this is the reason for the poor extraction of Hg(II) with these reagents.