The Transition from pH Waves to Iodine Waves in the Iodate/Sulfite/Thiosulfate Reaction–Diffusion System

Gao, Qingyu; Xie, Rongyong

doi:10.1002/cphc.200800002

Cited by 7 publications

(8 citation statements)

References 32 publications

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“…When the two fronts collide, there is no more possibility for oscillations, since thiourea does not consume protons any more. A seemingly similar phenomenon, separated iodine and pH fronts, is observed in the iodate−sulfite−thiosulfate reaction under batch conditions …”

Section: Discussionsupporting

confidence: 69%

Spatiotemporal Dynamics of Mixed Landolt Systems in Open Gel Reactors: Effect of Diffusive Feed

2010

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In this report we present an experimental study on the spatiotemporal dynamics of the iodate-sulfite-ferrocyanide and the iodate-sulfite-thiourea systems. Both systems are capable of producing nontrivial reaction-diffusion patterns when they are operated in a one-side-fed open spatial reactor. An important parameter of these types of reactors is the time scale of the diffusive feed, which is determined by the "thickness" of the gel and diffusion coefficients of the chemicals. A conical shape gel is used to study the effect of the thickness gradient on the dynamics. We show that spatiotemporal oscillations stop below a critical thickness. It is demonstrated that the period of the oscillations is determined by the time scale of the inhibitory kinetics and the time scale of the diffusive feed together. In the case of the iodate-sulfite-thiourea system we observed the appearance of a stationary iodine front in the presence of the oscillating pH front. An experimentally supported kinetic explanation is given to account this phenomena.

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Section: Discussionsupporting

confidence: 69%

Spatiotemporal Dynamics of Mixed Landolt Systems in Open Gel Reactors: Effect of Diffusive Feed

2010

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“…These systems are often called mixed Landolt reactions. As an example, the iodate–sulfite–thiosulfate (IST) reaction is autocatalytic with respect to hydrogen and iodide ions and shows complex pH oscillations, − temperature oscillations in closed and/or CSTR system and presents pH- and iodine waves in a reaction–diffusion system . Skeleton mechanism of the reaction has been proposed and used to describe the phenomena mentioned above. − , More recently, Liu et al found different spatiotemporal structures like iodine patterns, pH patterns, cellular fronts and Turing structures and proposed a mechanism with positive and negative feedback processes for explaining the pattern formation.…”

Section: Introductionmentioning

confidence: 99%

A Possible Candidate to Be Classified as an Autocatalysis-Driven Clock Reaction: Kinetics of the Pentathionate–Iodate Reaction

Horváth

2014

J. Phys. Chem. A

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The pentathionate-iodate reaction has been investigated by spectrophotometrically monitoring the formation of the total amount of iodine at 468 nm in the presence of phosphoric acid/dihydrogen phosphate buffer. We noticed that iodine forms only after a fairly long time lag, and the inverse of time necessary to produce a certain amount of iodine is linearly proportional to the initial concentration of iodate ion and the square of the hydrogen ion concentration, while depending complexly on the concentration of substrate pentathionate. This reaction can therefore be treated as a clock reaction but differs from the original Landolt reaction in the sense that substrate pentathionate and the clock species iodine coexist for a relatively long time--due to their relatively slow direct reaction--depending on the experimental circumstances. Furthermore, we also provided experimental evidence that iodide ion acts as an autocatalyst of the system. A 14-step kinetic model is proposed in which the mechanisms of the pentathionate-iodine, bisulfite-iodate, and the well-known Dushman reactions are combined. A thorough analysis revealed that the direct pentathionate-iodate reaction plays a role only to produce iodide ions via a finite sequence of reactions, and once its concentration reaches a certain level, the reaction is almost exclusively governed by the pentathionate-iodine and the Dushman reactions. As expected, a strong catalytic effect of the buffer composition is also found that can readily be explained by its well-known catalytic influence on the original Dushman reaction.

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“…The skeleton mechanism of these combined systems has been accepted , and even a temperature oscillation could be explained in case of the iodate−sulfite−thiosulfate system . More recently, these systems are thoroughly studied to produce different spatiotemporal structures and may thus have potential applications in designing chemical waves, Turing structures, and even pH responsive gels with rhythmical motions. − Therefore, to gain deeper insight into the intimate details of the Landolt reaction perturbed by thiosulfate we decided to investigate the later phase of thiosulfate−iodate reaction. Although the detailed kinetics and the mechanism of the thiosulfate−iodate reaction was already studied 80 years ago by Rieder, recent studies have pointed out ,, that the reaction cannot exclusively produce tetrathionate, sulfite has to be formed as well to explain adequately the batch pH oscillatory behavior.…”

Section: Introductionmentioning

confidence: 99%

Complex Kinetics of a Landolt-Type Reaction: The Later Phase of the Thiosulfate−Iodate Reaction

Varga

Nagypál²,

Horváth³

2010

J. Phys. Chem. A

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The thiosulfate-iodate reaction has been studied spectrophotometrically in slightly acidic medium at 25.0 +/- 0.1 degrees C in acetate/acetic acid buffer by monitoring the absorbance at 468 nm at the isosbestic point of iodine-triiodide ion system. The formation of iodine after the Landolt time follows a rather complex kinetic behavior depending on the pH and on the concentration of the reactants as well. It is shown that the key intermediate of the reaction is I(2)O(2), its equilibrium formation from the well-known Dushman reaction along with their further reactions followed by subsequent reactions of HOI, HIO(2), S(2)O(3)OH(-), and S(2)O(3)I(-) adequately accounts for all the experimentally measured characteristics of the kinetic curves. A 19-step kinetic model is proposed and discussed with 13 fitted and 7 fixed parameters in detail.

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The Transition from pH Waves to Iodine Waves in the Iodate/Sulfite/Thiosulfate Reaction–Diffusion System

Cited by 7 publications

References 32 publications

Spatiotemporal Dynamics of Mixed Landolt Systems in Open Gel Reactors: Effect of Diffusive Feed

Spatiotemporal Dynamics of Mixed Landolt Systems in Open Gel Reactors: Effect of Diffusive Feed

A Possible Candidate to Be Classified as an Autocatalysis-Driven Clock Reaction: Kinetics of the Pentathionate–Iodate Reaction

Complex Kinetics of a Landolt-Type Reaction: The Later Phase of the Thiosulfate−Iodate Reaction

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