Pattern Formation in Uncatalyzed Bromate Oscillator with Pyrogallol
Stationary mosaic and trigger wave patterns may spontaneously develop in an unstirred thin film of solution containing bromate, pyrogallol and sulfuric acid (uncatalyzed bromate system). The propagation velocity of the waves was found to depend not only on the initial concentrations of H + and BrO 3 - ions but also on the initial concentration of pyrogallol. For the explanation of the wave velocity dependence, a reaction scheme of the pyrogallol-BrO 3 - system has been proposed. The scheme is based on the well-known bromate chemistry combined with an organic radical control that takes into account the reactions of pyrogallol with BrO 3 - , HBrO 2 and HOBr. Movement of the waves could be recorded also potentiometrically. The kinetics and mechanism of the reaction between pyrogallol and bromate in an H 2 SO 4 medium were studied using a conventional polarographic method.