THE BRAY-LIEBHAFSKY AND BRIGGS-RAUSCHER OSCILLATING REACTIONS Guy Schmitz a and Stanley Furrow b a Faculty of Applied Sciences, Université Libre de Bruxelles, CP165/63, Av. F. Roosevelt 50, 1050 Brussels, Belgium. E-mail: gschmitz@ulb.ac.be b Penn State Berks College, The Pennsylvania State University, Reading, Pennsylvania 19610. E-mail: f13@psu.edu ABSTRACT The common points and differences between the Bray-Liebhafsky and Briggs- Rauscher reactions are discussed. The reactants of the non-catalyzed version of the Briggs-Rauscher reaction being the same as those of the Bray-Liebhafsky reaction plus a reducing organic compound, the mechanisms of these two systems must have several common points. The marked difference between the oscillating behaviours comes from radical reactions that could be initiated by the new pathway of the iodate reduction by hydrogen peroxide at high concentrations. FOREWORD … to conduct my thoughts in such order that, by commencing with objects the simplest and easiest to know, I might ascend by little and little to the knowledge of the more complex… René Descartes (1596–1650). Discourse on Method. COMPARISON OF THE BL AND BR REACTIONS The Bray-Liebhafsky (BL) [1] reaction is the decomposition (1) of hydrogen peroxide catalyzed by iodate in acidic solutions. 2 H 2 O 2 3 IO ,H - + → 2 H 2 O + O 2 (1)