Explanation of Spatial Band Propagation in the Belousov Reaction

BELOUSOV1 reported that the ratio [Ce(IV)]/[Ce(III)] undergoes repeated temporal oscillations in a stirred sulphuric acid solution containing bromate ion and malonic acid. Busse2 and Zaikin and Zhabotinsky3 reported that spatial bands of alternating oxidizing and reducing character propagated through an unstirred solution if it were initially subject to a concentration gradient. Existence of these bands was demonstrated by the redox indicator ferroin (the 1,10-phenanthroline complex of ferrous ion), and bands could be generated in the absence of cerium ions if indicator were present, because the ferroin indicator itself serves as an oxidation-reduction couple in the absence of cerium ions.