Propagating reaction front in ‘frozen’ phase

Szirovicza, Lajos; Nagypál, Ištván; Bárdi, István

doi:10.1002/kin.550230109

Cited by 12 publications

(11 citation statements)

References 3 publications

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“…Polythionates are well-known long-lived intermediates produced from the oxidation of thiosulfate by different oxidants, leading eventually to sulfate ion. , Their further reactions with the corresponding oxidants sometimes display fascinating kinetics and may contribute to the appearance of a rich variety of exotic nonlinear dynamical phenomena. − Hexathionate, being one of the important intermediates in redox transformations or metabolism of sulfur-containing compounds in various environmental, industrial, and biological systems, , is often reported to be produced in numerous oxidation processes of thiosulfate. , It is also well-known that hexathionate is unstable in weakly alkaline conditions and degradation of the sulfur–sulfur bond eventually leads mainly to the formation of elemental sulfur and thiosulfate …”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of the Concurrent Reactions of Hexathionate with S(IV) and Thiosulfate in a Slightly Acidic Medium

Pan

Kégl

et al. 2019

J. Phys. Chem. A

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Reactions of hexathionate with thiosulfate and sulfite have been investigated by high-performance liquid chromatography via monitoring the concentration–time series of tetrathionate, pentathionate, hexathionate, and thiosulfate simultaneously within the pH range of 4.0–5.0. In both reactions, elementary sulfur forms; more significant sulfur precipitation may be observed in the case of the hexathionate–thiosulfate reaction, but slight turbidity in the other system means that elementary sulfur also appears in a detectable amount in the hexathionate–sulfite reaction. Initial rate studies have revealed that the formal kinetic orders of both reactants in both systems are clearly unity but pH-dependence can only be observed in the case of the hexathionate–sulfite reaction. The proposed kinetic model appears to suggest that nucleophilic attack of sulfite and thiosulfate may also occur on the β- or γ-sulfur of the polythionate chain and breakages of the α–β, β–γ, and γ–γ′ bonds are all conceivable possibilities to drive the reactions. Consequently, the generally accepted sulfur-chain elongating effect of thiosulfate on longer polythionates is also proven to be accompanied by sulfur-chain shortening pathways, eventually leading to the formation of elementary sulfur.

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Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of the Concurrent Reactions of Hexathionate with S(IV) and Thiosulfate in a Slightly Acidic Medium

Pan

Kégl

et al. 2019

J. Phys. Chem. A

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“…The oscillation frequency increase has been explained by the formation of crystals and interfacial phenomena during freezing. This might be partly supported by experiments with chlorite–thiosulphate system frozen to −34°C [55]. There, a velocity of wavefronts is increased because en route to total freezing the reaction occurs only in the thin liquid layer, at the periphery of the solid domain, where concentrations of chemicals are temporarily higher.…”

Section: Introductionmentioning

confidence: 93%

Thermal switch of oscillation frequency in Belousov–Zhabotinsky liquid marbles

et al. 2019

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External control of oscillation dynamics in the Belousov–Zhabotinsky (BZ) reaction is important for many applications including encoding computing schemes. When considering the BZ reaction, there are limited studies dealing with thermal cycling, particularly cooling, for external control. Recently, liquid marbles (LMs) have been demonstrated as a means of confining the BZ reaction in a system containing a solid–liquid interface. BZ LMs were prepared by rolling 50 μl droplets in polyethylene (PE) powder. Oscillations of electrical potential differences within the marble were recorded by inserting a pair of electrodes through the LM powder coating into the BZ solution core. Electrical potential differences of up to 100 mV were observed with an average period of oscillation ca 44 s. BZ LMs were subsequently frozen to −1°C to observe changes in the frequency of electrical potential oscillations. The frequency of oscillations reduced upon freezing to 11 mHz cf. 23 mHz at ambient temperature. The oscillation frequency of the frozen BZ LM returned to 23 mHz upon warming to ambient temperature. Several cycles of frequency fluctuations were able to be achieved.

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“…It is generally well-known that oxidation of thiosulfate ion by different oxidizing agents leads finally to sulfate ion via formation of different polythionates as long-lived intermediates. These reactions of thiosulfate, for example, with chlorite, bromate, and periodate, exhibit several exotic nonlinear dynamical phenomena such as autocatalysis under batch condition, − bistability and complex periodic and aperiodic behavior − in a continuously stirred tank reactor (CSTR), and an appearance of varieties of different reaction–diffusion patterns (chemical waves and chemical reaction fronts) in unstirred system. − It seems to be well-established that formation of polythionates and their further reactions with the corresponding oxidants sometimes displaying fascinating kinetics play a substantial role in the appearance of these exotic behaviors. Recently, a series of investigations confirmed that besides the sulfate ion, polythionates − (such as tri-, tetra-, and pentathionate) and chlorine dioxide are also produced during the oxidation of thiosulfate by chlorite ion.…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of the Oxidation of Pentathionate Ion by Chlorine Dioxide in a Slightly Acidic Medium

Csekõ

Petz

et al. 2014

J. Phys. Chem. A

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The chlorine dioxide-pentathionate reaction has been studied at a slightly acidic medium by conventional UV-vis spectroscopy monitoring the absorbance at 430 nm. We have shown that pentathionate was oxidized to sulfate, but chlorate is also a marginal product of the reaction besides the chloride ion. The stoichiometry of the reaction can be established as a linear combination of two limiting stoichiometries under our experimental conditions. Kinetics of the reaction was found to be also complex because initial rate studies revealed that formal kinetic orders of both the hydrogen ion and chlorine dioxide is far from unity. Moreover, log-log plot of the initial rate against pentathionate concentration indicated a nonconstant formal kinetic order. We also observed a significant catalytic effect of chloride ion. Based on our observations and simultaneous evaluation of the kinetic curves, an 11-step kinetic model is obtained with 6 fitted rate coefficients. A relatively simple rate equation has also been derived and discussed.

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Propagating reaction front in ‘frozen’ phase

Abstract: It is reported and explained that the front-like reaction sustains, and its velocity is enhanced in frozen phase in the chlorite-thiosulphate system.

Cited by 12 publications

References 3 publications

Kinetics and Mechanism of the Concurrent Reactions of Hexathionate with S(IV) and Thiosulfate in a Slightly Acidic Medium

Kinetics and Mechanism of the Concurrent Reactions of Hexathionate with S(IV) and Thiosulfate in a Slightly Acidic Medium

Thermal switch of oscillation frequency in Belousov–Zhabotinsky liquid marbles

Kinetics and Mechanism of the Oxidation of Pentathionate Ion by Chlorine Dioxide in a Slightly Acidic Medium

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