A Simple Method of Gas Evolution Measurement Suitable for Analysis of Batch Oscillating Reactions: Briggs−Rauscher System with Acetone Revisited

Szabo, Erik; Ševčı́k, Peter

doi:10.1021/jp809969e

Cited by 11 publications

(8 citation statements)

References 31 publications

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“…Approximated from previous results, ,, k 12 = 2.74 × 10 −4 s −1 was considered for circular surface with 2 cm radius representing S ∞ = 12.57 cm 2 , affording the surface-independent rate constant k 12 ′ = 2.18 × 10 −5 cm −2 s −1 . With this rate constant fixed, the course of reaction was observed with respect to varying radius r of the particles of dispersed oxygen, at the same time calculating the total amount of iodine trapped with the oxygen d n false( I 2 ( g h l d ) false) d t = S h l d S h l d + S ∞ v 12 V r x n − k 13.2 n false( I 2 ( g h l d ) false) from which its average concentration [I 2 ( g hld )] in the total volume V hld was also determined.…”

Section: Formulation Of the Modelmentioning

confidence: 96%

“…10,11 Growing attention has recently also been dedicated to the production of gas, [12][13][14] to some extent accompanying a vast majority of oscillating reactions, however, with particularly dramatic examples in the family of the BR reaction and its substitutions or additions. 8,[15][16][17] The BR reaction with acetone as the organic substrate has already been considered for its exceptionally well-defined oscillations in the rate of gas production and their practical measurement 18 and effects of the interphase transport of oxygen and iodine on the reaction have been modeled, 19 suggesting a possible interplay of the physical process of gas production and the chemistry of the reaction, which is normally neglected.…”

Section: Introductionmentioning

confidence: 99%

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Modeling of Interactions Between Iodine Interphase Transport and Oxygen Production in the Modified Briggs−Rauscher Reaction with Acetone

Szabo

Ševčı́k

2010

J. Phys. Chem. A

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Novel aspects of influence of gas evolution on oscillating chemical reaction are considered on a model of the modified Briggs-Rauscher reaction with acetone. The mechanism proposed by Noyes with Furrow and De Kepper with Epstein, adapted for acetone and expanded with oxygen evolution and first-order escape of iodine by interphase transport, was subjected to further extension, and calculations assuming direct proportionality of the rate of iodine escape on the surface area of the oxygen gas trapped in the solution as well as calculations considering first-order back-flow of iodine from the gas phase into the solution were performed. Furthermore, the concentrations of iodine vapors were considered to be variable within the bubble population, as all the bubbles are not in contact with the reaction mixture for the same length of time. Distribution functions of the surface size over the range of concentrations of iodine in the contacting gas phase were introduced and derived, and whereas they were proved not to play any role in the total intensity of iodine return when it is first-order, the article also demonstrates their explicit consideration in calculations to be essential if the dependence of the rate of iodine return into the solution on its concentration is not linear, for example, in future extensions of the model with bubble radius also considered variable.

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Section: Formulation Of the Modelmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Modeling of Interactions Between Iodine Interphase Transport and Oxygen Production in the Modified Briggs−Rauscher Reaction with Acetone

Szabo

Ševčı́k

2010

J. Phys. Chem. A

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“…We have recently demonstrated, that the role of varying amounts of gaseous products in oscillating reactions should not be underestimated . We also have good experience in highly precise closed-system real-time measurements of gases by simply weighing of liquid they displace, and we were convinced, that this method could be improved, so that even very small amounts of gases would be measurable precisely.…”

Section: Introductionmentioning

confidence: 93%

“…We have recently demonstrated, that the role of varying amounts of gaseous products in oscillating reactions should not be underestimated. 49 We also have good experience in highly precise closed-system real-time measurements of gases by simply weighing of liquid they displace, 48 and we were convinced, that this method could be improved, so that even very small amounts of gases would be measurable precisely. Therefore, we decided to undertake the task of applying the method in quantifying gas evolution from some examples of UBOs, hoping to contribute to verifying their reputation as gas-free oscillators.…”

Section: Introductionmentioning

confidence: 99%

Are Uncatalyzed Bromate Oscillators Truly Gas-Free?

2011

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Gas evolution is a common byproduct of chemical oscillations but is seldom treated as anything but a complication. Its precise quantification is usually underestimated, and if not obvious enough, gaseous products are easily neglected completely. Reported herein is how evolution of gas from uncatalyzed bromate oscillators with pyrocatechol, pyrogallol, and 1,4-cyclohexanedione was measured by a high-precision batch-mode gasometric method, and the data obtained with unprecedented time resolution are presented. Even though within this completely closed arrangement of measurement no oscillations in rate of gas evolution were observed, it is verified that neither of the substrates can be considered totally free of gas production. Nevertheless, the amount of gas evolved from 1,4-cyclohexanedione was confirmed to be very small, and near negligible, if only oscillatory phase is of interest. Conversely, under identical conditions, the peak rates of gas evolution from the other substrates were reached much sooner, and even though the results in all three cases suggest some extent of suppression of gas production by oscillations, as much as 1 equiv of gas in total can be produced from the phenols, especially from pyrogallol, where the degradation was measured to be approximately twice as extensive. Greater caution is, therefore, recommended whenever the gas-free nature of these oscillators is considered.

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“…Molecular iodine is also formed by oxidation of iodide or reduction of iodate, and the hydrolysis of iodine produces hypoiodous acid (I 2 + H 2 O ⇆ HOI + I – + H + ), which in turn is an important intermediate in the formation of iodine organic compounds and has a particularly important role in the exchange of iodine between seawaters and the atmosphere. − HOI is also a component of the waste streams from nuclear reactors . On the other hand, hypoiodous acid is a crucial intermediate in complex systems like the Bray–Liebhafsky (BL) − and Briggs–Rauscher (BR) − oscillating reactions. Kinetic studies and modeling of all these systems would benefit greatly from a sensitive device measuring the concentrations of HOI.…”

Section: Introductionmentioning

confidence: 99%