Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

Extraction of hafnium(IV) was studied from solutions of mixtures of perchloric and nitric acids and of perchloric and hydrochloric acids for constant ionic strength, I = 2, 4, 6, or 8, and for c_Hf 4 . 10^-4 mol l^-1. The organic phase was constituted by solutions of some acidic or neutral organophosphorus reagents or of 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, or N-benzoyl-N-phenylhydroxylamine in benzene, chloroform, or n-octane. A pronounced synergic extraction of hafnium proceeds only on applying organophosphorus reagents from an aqueous phase whose acidity is not lower than 3M-(HClO₄ + HNO₃) or 5M-(HClO₄ + HCl). The synergic effect was not affected markedly by a variation of the initial concentration of hafnium in the range 1 . 10^-8 -4 .10^-4 mol l^-1, it lowered with increasing initial concentration of the organophosphorus reagent and decreasing concentration of the H⁺ ions. It is suggested that the hafnium passes into the organic phase in the form of mixed complexes, the salting-out effect of perchloric acid playing an appreciable part.