The ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction is a prototypical oscillating chemical reaction system. The unstirred reaction produces waves of blue oxidized ferriin in a red reduced ferroin medium due to complex redox kinetics.  Initial activation is indicated by a clocking wave; one later sees target patterns of outward traveling waves of oxidation.  Two models are proposed to explain the onset of activation.  First, activation might follow a nucleation process due to dust particles or undissolved iron/ferroin particulates.  In this case onset occurs after some average delay, and wait times to the clocking or target waves would follow a normal distribution. Alternatively, activation might be generated by microscopic random thermal fluctuations in concentrations (Hastings, Field, Sobel, J Chem Phys 2003; Sobel, Hastings, Field, J Phys Chem A 2006; Hastings et al., J Phys Chem A 2008).  This mechanism predicts that  activations follow an exponential waiting time model. By timing the onset of activation over a large number of replicates, experimental results can be compared to the theoretical models discussed above.  Preliminary data has shown a correlation with the exponential wait time model for initial activation, while the onset of oscillations show a more normal distribution.  Partially supported by the Camille and Henry Dreyfus Foundation.

Target formation in BZ: Nucleation vs. fluctuation

247th National Meeting (2014)

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