Piette. metie +. 18 14. Marshall, J. H. J. Theoret. Biol. 6, 386 (1964). 15. Bowen, H. J. M. Trace Klemenis in Biochemistry, Academie Press, London, 1966, p. 19. 16. Mietanen, S. and Sillen, L. Ct. eta Chem. Scand. 13, 533 (1959). 17. Blake, C. A., Coleman. C. F., Brown, K. B., Will. D. G., 18. 19. 20. 21. 2. to 11. Aleem, A. A. J. Ecol. 38, 75 (1950). 12. van Overbeek, J., personal communication. 13. Revelle, R. and Fairbridge, R. Geol. Soc. Aomerica, Memoir 67.1, 239 (1957). Lowrie, R.S., and Schmitt, J. M. J. Am. Chem. Soc. 78 5978 (1956). Fuller, W. H. and Hardcastle, J. E. Soil Set. Soc. Am. Prov 31, 772 (1967). Koezy, F. F. and Titze, H. J. Marine Res. 17, 302 (1958 Lowenstam, H. A. J. Geol. 62, 284 (1954). Emery, K. O., Tracey, J. L., and Ladd, H. 8. U. 8. Geo) Survey Prof. Paper 260A (1954+). Thomson, T. G. and Chow, T. J. Papers in Marine Biolog and Oceanography, Suppl. to Deep Sea Res. 3, 20 (1955 SEPARATION OF CESIUM AND RUBIDIUM BY THE FERROCYANIDES OF COPPER, ZINC, AND ZIRCONIUM DN, Edgington, M.A. Thommes, and L. £. Harrison* The suitability of several metal ferrocyanides for ion exchange separation of cesium and rubidium has been studied. Both cesium and rubidium are satisfactorily absorbed on zine ferrocyanides and could be recovered in separate fractions by elution with solutions of nitrate jon. Zirconium ferrocvanide absorbs cesium strongly and is well suited to concentrate ce- sium when subsequent clution is not required, e.g., to separate fallout *"Cs from sea water. Copper ferrocyanide absorbs both cesium and rubidium strongly. but is of little value in analysis becauseof difficulties in elution of adsorbed species. Extensive measurements of the concentration of radioactive *'Cs in the biosphere have been made in order to understand more fully the behavior of this fission product in terrestrial and aquatic environ- ments, as well as in man. While most elements are discriminated against with incrcasing trophic level, Gustafson has shown that the ratio of *7Cs to potas- sium increases in the aquatic environment.” Folsom has measured the concentration of this radionuclide and stable cesium in salt water fish@) and sea water.) Recently, Edgington and Lucas have shown that there is also an increase in rubidium concentration with increasing trophic level in freshwater fish.“ It would be interesting to know whetherstable cesium exhibits the same inerease in coneentration with trophic level as its radioactive isotope. In order to determine the concentration of cesium in water and biota, its separation by ion exchange and solvent extraction has been extensively studied.) On the other hand, very little has been published concerning the separation of rubidium. Because solvent extraction and anion exchange processes are not effective for univalent cations, much attention has been focused on the development of cation exchange materials for their separation. Such an ex- changer would be useful for concentrating trace * ANL-CSUI Honor Student. Spring, 1969. amounts of these elements in the biota for analysi- measurement of 7Cs from fallout, and the separa tion of radioactive cesium and rubidium from mix tures of nuclides produced by neutron activation o biological or other samples. For these purposes it is desirable to use a catia: exchanger which will not only concentrate trac amounts of eesium and rubidium, but will also al low them to be eluted as weil with a high percentag of recovery. The organic ion exchangers, Dowe 50W-X12, sodium form,‘® and Amberlite TR-100," have been used, but they require large columns an are time consuming in operation. Many highly in soluble inorganic compounds have also been investi gated. The compoundsof zirconium,‘® the heteropoly acids,!*") ammonium phosphomolybdate,2%!) an various cobalticyanides“+.) and ferrocyanides (hex acyanoterrates) 74 16-19) have been shown to hav: exchange properties for cesium and rubidium. Th ferroeyanides have a high specificity in particular fo cesium, but have to be destroyed using the concen trated sulfurie acid to get the cestum back into solu tion. Therefore, the present study is being conducte: in order to obtain a greater understanding of the io exchange behavior of the zinc, copper, and zirconiun ferrocyanides, and to evaluate their usefulness a> exchangers for ion exchange chromatography of the=: two elements, METHODS AND MATERIALS Analytical grade reagents were used in the following preparations. Preparation of Heavy Metal Ferrocyanides Zinc ferrocyanide was prepared as described by Kourim, Rais and Million,“but on a larger seale Fight hundred milliliters of 0.1 M potassium ferro-