A new ternary synergistic extracting system composed of two chelate extracting ligands and one ion assooiation ligand, namely AAC species, has been studied. As a preliminary study, uranyl perchlorate was extracted by the binary system of thenoyltrifluoroacetone (HTTA) and of 1-phenyl-3-methyl-4-benzoyl-pyrazol-5-one (HPMBP) with tetraphenylarsonium chloride(C_6H_5)_4 AsCl in chloroform solution. The binary synergistic equilibrium constants were determined to be log β_(AIC)=3.97 [HTTA+(C_6H_5)_4AsC1 system] ...