Abstract: STUDIES OF THE EXTRACTION BEHAVIOR OF Am~(3＋) AND LANTHANIDES WITH 7804 EXTRACTANT Ⅱ．COMPLEX STRUCTURE AND ANALYSIS OF EXTRACTION MECHANISMHOU RUIQIN（Nothwest institute of Nuchnology，P.O. Box 69，Xi′an 710024）JIAO RONGZHOU；ZNU YONGJUN（Institute of Nuclear Energy Technology，Tsinghua UniversiYy，P.O.Box 1021，Beijing 102201）ABSTRACT The IR and hypersensitive spectra of the complex Nd~(3+)-7804 and the diluting IR spectrumof 7804 extractant are measured．The complex structure is deduced and the extraction mechanismis discussed．The extraction equilibrium constants of americium and lanthanides are calculated. Key words Americium Lanthanides Extraction 2-hydroxy-5-alkylacetophenone oxime（7804）