Role of heterogeneous reactions in generating chaos and noise in oscillatory chemical reactions†

Abstract

In view of the importance of noise in physiology, information processing and finance, studies on chaos and noise have been undertaken. Detailed studies on the following oscillatory reactions have been undertaken: (i) thiophenol + BrO₃^- + H₂SO₄, (ii ) frutose + BrO₃^-+ H₂SO₄ + Ce⁴⁺, and (iii) iodate + arsenite, which can serve as a model system for this purpose. Aperiodic oscillations have been observed in these systems. Analysis of phase plane plots yields complex attractors, which are quite different from strange attractor indicating the occurrence of random noise. Power spectra also indicate chaos with a broad band not necessarily the deterministic chaos. For the reactions (i) and (iii), a mechanism has been proposed involving precipitation of C₆-H₅-S-C₆H₅ and iodine, respectively: while in case of reaction (ii), gaseous evolution of Br₂ has been invoked. Experimental studies on sedimentation of C₆-H₅-S-C₆H₅ and Br₂ evolution confirm that such heterogeneous reactions play an important role in generating noise in oscillations.