Abstract: A NEW TERNARY SYNERGISTIC EXTRACTION SYSTEM FOR URANIUM（Ⅵ）DU JIASHENG（Department of Chemistry,Yunnan University,Kunming 650091）ABSTRACT The synergistic extraction for U（Ⅵ） from nitric acid solution is studiedied using 4，4＇-decane-dioyl-bis-（ 1- phenyl- 3－methyl- 5-pyrazolone）as chelate extractant，TBP and Pyridine as the firstand second neutral synergistic extractants. The constituent of the extracted complex is confirmedto be UO_2A·TBp·Py by the usual slope methed，The equilibrium constant of this ternary syner-gistic extraction reaction is evaluated. Elemental analyses，IR and ~1HNMR are made for the solidextracted compound isolated.Key words Ternary synergistic extraction 4，4＇-decane－dioyl-bis-（ 1- phenyl- 3-methyl-5-pyrazolone）TBP Pyridine Uranium（Ⅵ）