Abstract: In a slightly acidic solution buffered at pH 2,an ionic association complex was formed by the reaction of Pd(Ⅱ) with potassium bromide and tetrabutyl ammonium bromide (abbreviated as PdBr2-4·2TBAB+),which is water-insoluble and floated on the surface of the aqueous phase frominga clear interface between the liquid and solid phases.Concentrations of KBr and TBAB necessary for the floatation reaction were chosen at 1.5×10-2mol·L-1 and 2.0×10-3mol·L-1 respectively.Foreign ions,i.e.,Hg(Ⅱ),Pb(Ⅱ),W(Ⅵ) and V(Ⅴ) coexisted,did not form similar complexes and hence,did not floated with Pd(Ⅱ).Floatation separation of Pd(Ⅱ) from Hg(Ⅱ),Pb(Ⅱ),W(Ⅵ) and V(Ⅴ) was attained quantitatively by this method,and the rate of floation of 99.7% was obtained when 100 μg of Pd(Ⅱ) were separated from binary mixed solutions containing the co-existing ions of Hg(Ⅱ),Pb(Ⅱ),W(Ⅵ) and V(Ⅴ).