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Recently we reported [1] on a fast and simple procedure for separating quantitatively americium (and/or curium), berkelium, and californium by extraction chromatography. Dilute (0.5 M) HCl was used to successively elute tracer quantities of these elements (in the trivalent state) from kieselguhr columns loaded with di-(2-ethylhexyl)orthophosphoric acid (HDEHP). Adsorption took place from 0,1 M HCl solution and no oxidizing or reducing agents were used in the procedure. As a further demonstration of the possibilities offered by this technique results are now presented on one of the most delicate separations in heavy element chemistry : that between tracer amounts of berkelium and macroamounts of cerium. ProcedureThe 200^400 mesh fraction of a commercial kieselguhr was made hydrophobic with dimethyl dichloro silane and loaded to a kieselguhr/HDEHP ratio of 8.5 from chloroform solution (2:15) by stirring to dryness and heating over night at 50° C. The commercial HDEHP was purified following standard procedures. Columns (4 mm diameter, 150 mm high) were prepared from the fraction precipitated after cooling of a mixture of 1 gram of treated kieselguhr and 20 ml of 1.5 M HCl which has been brought to a near boil. During filling a slight pressure is applied by a glassrod. The density of the column filling was adjusted so that an overpressure of approximately 40 cm of water gave a flowrate of one drop of ~42 λ each 45 seconds. The free column volume of the column amounted to 22 drops at the operating temperature (87° C).

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