Bromate-sulfite-ferrocyanide reaction

A Landolt pH-oscillator based on a bromate/sulfite/ferrocyanide reaction has been developed with a room temperature period of 20 minutes and a range of 3.1periodic oscillations in volume in a pH responsive hydrogel. A continuously stirred, constant volume, tank reactor was set-up in conjuction with a modified JKR experiment and is used to show that the combination of a pH oscillator and a pH responsive hydrogel can be used to generate measurable force. 

Eager, M. D. Santos, M. Dolnik, M. Zhabotinsky, A. M. Kustin, K. Epstein, I. R. 1994. Dependence of Wave Speed on Acidity and Initial Bromate Concentration in the Belousov-Zhabotinsky Reaction-Diffusion System, J. Phys. Chem. 98, 10750-10755. Edblom, E. C. Luo, Y. Orban, M. Kustin, K. Epstein, I. R. 1989. Kinetics and Mechanism of the Oscillatory Bromate-Sulfite-Ferrocyanide Reaction, J. Phys. Chem. 93, 2722-2727. 

Indeed, PAAc cryogels coupled with a bromate oscillator oscillated between swollen and collapsed states [31]. The reactions of bromate, sulfite, and ferrocyanide ions were conducted in an open continuously stirred tank reactor. Four feed solutions (potassium bromate, sodium sulfite, potassium ferrocyanide, and sulfuric acid) were supplied continuously to the reactor, during which the pH of the reaction solution was monitored as a function of time. The flow rate of the feed solutions is an important parameter in determining the extent of pH oscillations. In Fig. 21, pH versus time plots are shown for four different reduced flow rates k, defined as the flow rate of the feed solutions divided by the reaction volume. It is seen that the pH of the solution oscillates between 6.2-6.9 and 3.2-3.8. The dissociation degree a of a weak electrolyte relates to pH by ... 

The reactions were conducted in an open continuously stirrer tank reactor (CSTR) at room temperature, with a peristaltic pump supplying the feed solutions of potassium bromate, sodium sulfite, potassium ferrocyanide and sulphuric acid and also pumping out bulk solution to keep the volume in the CSTR constant. Measurements of pH were made using a standard gel-filled probe, and the output from the meter monitored by a PC. A typical pH profile is shown in Figure 1. 

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