Chemistry Department, Faculty of Science, Ain Shams University, Cairo-Egypt Manuscript received 16 June 1978, accepted 22 December 1978 From the distribution of cobalt(II) acetyl acetonate in different diluents, the com­position of the extractable complexes and the extraction constants were calculated. The results indicate that acetyl acetone forms complexes with Co(II) of the type [Co(AcAc)2]4 which is a tetramer.