Oscillation system of Belousov-Zhabotinskii type in presence of Cl- ions

A modified Belousov-Zhabotinskii oscillation system involving ethyl ester of 3-oxobutanoic acid and Fe(phen) 3 2+ - Fe(phen) 3 3+ as redox catalyst is remarkable in that it shows an oxygen-induced excitability. The oscillating state, involving 4-5 oscillations in the absorbancy of Fe(phen) 3 2+ ions, comes soon to its end but can be restored by shaking the reaction system, thus incresing the transport of oxygen from the air. This phenomenon is not influenced by Cl - ions in a low concentration, but if this is equal to 10 -3 mol dm -3 or higher, no oscillations are observed, the increase of the concentration of Fe(phen) 3 2+ ions is autocatalytic in character and can be reproduced several times by shaking or stirring the solution. These phenomena are discussed in terms of a probable reaction mechanism.