Abstract The separation of hexacyanoferrate(II) and (III) ions with a TBP-HCl extraction system has been carried out by reversed-phase partition column chromatography. TBP adsorbed on Kel-F powder was used as the stationary phase in the column. Elution was performed with hydrochloric acid of various concentrations and with water, both having been saturated with TBP. The actual separation of hexacyanoferrate(II) and (III) ions from each other was successfully achieved, even in a large volume of a sample solution, by carrying out the elution with 3n HCl. The dependencies of the distribution ratio on the acidity of the solution and on the concentration of TBP in the stationary phase were examined on the basis of the elution curves under various conditions. The liquid-liquid batch extraction was also carried out under the same conditions; it was found an identical relation of distribution between the two phases held in both column and batch extractions. The principal extracted species might be assumed to be a large ion-pair hydrated and solvated.