A new ternary synergistic extracting system composed of 2 chelate extracting ligands and 1 ion association ligand (AAC species) was studied. The UO2(ClO4)2 was extracted by the binary system of thenoyltrifluoroacetone (HTTA) and of 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HPMBP) with Ph4AsCl in CHCl3. The binary synergistic equilibrium constants are log bA1C = 9931 [HTTA + Ph4AsCl system] and log bA2C = 4.86 [HPMBP + Ph4AsCl system], resp. The synergic effect occurred udring the extration of UO2(ClO4)2 by a CHCl3 solution of HTTA + HPMBP + Ph4AsCl. The principle of min. d. of elec. charge plays an important role in this system. The formation of a ternary extracted complex [Ph4As]UO2ClO4(TTA)(PMBP) was confirmed by the methylene blue spectrophotometric method. The equilibrium constant is bA1A2C = 5.52.

Key words: URANIUM, TERNARY SYSTEM, URANYL COMPOUNDS, PYRAZOLONE P, 2-THENOYL-TRIFLUORO-ACETONE, PERCHLORATE, SYNERGIC SOLVENT EXTRACTION, ARSENIC CHLORIDE