Abstract: The extraction behavior of iron(Ⅲ), cobalt(Ⅱ) and nickel(Ⅱ) by 1,9-bis (1'-phenyl-3'-methyl-5'-oxopyrazole-4'-yl)-1, 9-nonanedione (abbreviated as H₂A) in chloroform rom sodium nitrate and HAc-NaAc buffer medium has been studied. Their pH_1/2 values were found to be 2.43, 5.08 and 4.51,respectively. Therefore, it is possible to separate ironfrom cobalt and nickel by extraction with H₂A. The compositions of the extracted comple-xes were determined by the slope method as Fe₂A₃; CoA and NiA respectively. Their extrac-tion equlibrium constants (lgK_ex) were calculated to be 2.44±0.11, -7.33±0.18, -6.63±0.11 respectively. The solid ferric complex synthesised has been characterized by elemental,thermal analyses and IR measurement.

Key words: Extraction separation, Chelating extractant, Iron, Cobalt, Nickel