Acceleration of chemical reaction fronts

Influence of Oxygen on Chemoconvective Patterns in the Iodine Clock Reaction

“…The IS reaction has a mechanism similar to the iodate–arsenous acid (IA) reaction with arsenous acid as the reductant in place of sulfite; the IA reaction is also autocatalytic in both acid and iodide, and the behavior depends on the stoichiometric ratio of the reductant to iodate: R = [H 3 AsO 3 ] 0 /[IO 3 – ] 0 . , In thin layers in a Petri dish (0.8 mm depth), when R < 3, the IA reaction supports propagating fronts of iodine, whereas for higher arsenous acid concentrations, R ∼ 3, a narrow band or pulse of iodine may be obtained. , …”

“…46,47 In thin layers in a Petri dish (0.8 mm depth), when R < 3, the IA reaction supports propagating fronts of iodine, whereas for higher arsenous acid concen-trations, R ∼ 3, a narrow band or pulse of iodine may be obtained. 46,48 The transition from iodine fronts to pulses in the IS reaction occurred at S > 3.4, where S = [SO 3…”

“…In the IA reaction, acceleration of fronts in horizontally propagating fronts in Hele-Shaw cells or a Petri dish with an open air interface were attributed to a Marangoni instability driven by the formation of iodine. , Pulses propagated with a constant velocity of the order of 1 mm min –1 , whereas acceleration of the fronts was observed at R < 2.8 during the initial and late phases of the reaction. During the intermediate phase, the velocity was constant and of the order of 8 mm min –1 for R = 2.6 as presumably, evaporation of iodine matched its production.…”

The Briggs–Rauscher Reaction: A Demonstration of Sequential Spatiotemporal Patterns

“…The periodic color changes seem almost magical. , Furthermore, coupling between chemical oscillations and transport processes can generate spatial symmetry-breaking and pattern formation, such as traveling waves or patterns, − which enhance the visual and intellectual appeal and inspire students to connect their observations with similar complex spatiotemporal behaviors in nature. Moreover, chemical reactions lead to changes in physical properties, such as density, temperature, and surface tension, which may elicit hydrodynamics flows leading to new patterns. − For example, if a denser solution overlies a less dense one as a result of reaction, this density difference can trigger buoyancy-driven convection in the gravity field, which can generate traveling convective fingers, breaking the transverse symmetry in oscillatory systems . In a horizontally arranged shallow liquid layer open to the atmosphere or a Hele–Shaw cell, surface tension and density gradients induced by reaction may also contribute to pattern formation. − In the excitable BZ reaction system, segmentation waves have been obtained from the interaction of Marangoni (surface tension-driven) and buoyancy-driven flows …”