Abstract: STUDY ON THE MECHANISM OF THIRD PHASE FORMATION IN NITRIC ACID EXTRACTION BY TRPOLiu Jinchen Liu Zhiping Chen Jian Lu Jiufang(Department of Chemical Engineering,Tsinghua University,Beijing 100084)ABSTRACTThe formation of a third phase is studied in the system of TRPOnoctane(ndodecane) with nitric acid aqueous solution.The acidity of the aqueous phase and the acidity,density and composition of the organic phase are measured.The influences of the diluents on the formation of the third phase are also studied.Proposed mechanism of third phase formation is that the components in the organic phase form a partial miscible system,in which the phase splitting can occur at a certain condition and the third phase can form.The liquidliquid equilibrium phase diagram of the components in the organic phase for the system of TRPOnoctane with nitric acid aqueous solution was given.Key words Third phase TRPO Nitric acid