The conditions under which a stable Belousov-Zhabotinskii (BZ) oscilla
ting reaction can exist in H2SO4 and HNO3 extraction systems are deter
mined. The Ce and Eu distribution coefficients are related to the pote
ntial of the Pt-electrode in the extraction systems such that D(Ce) in
creases whereas D(Eu) decreases as the potential increases and vice ve
rsa. This phenomenon can probably be used to develop new methods for s
eparating elements with similar chemical properties.