Imperfect mixing as a dominant factor leading to stochastic behavior: a new system exhibiting crazy clock behavior

Abstract

It is clearly demonstrated that the arsenous acid-periodate reaction displays crazy-clock behavior when a statistically meaningful number of kinetic runs are performed under "exactly the same" conditions. Both extensive experimental and numerical simulation results gave convincing evidence that the stochastic feature of the title reaction originates from the imperfection of the mixing process, and neither local random fluctuation nor initial inhomogeneity alone is capable of explaining adequately the observed phenomena. Imperfect mixing is manifested-in practice-in the unintentional and inherent formation of dead volumes where the concentration of the reactants may even significantly differ from the ones measured in the case of a completely uniform concentration distribution, and the system may spend enough time there under imperfectly mixed conditions to complete the nonlinear chemical process. Furthermore, it is also shown that a more efficient mixing, i.e. a smaller dead volume size and shorter residence time being spent in the dead volume, does not necessarily mean Landolt times are smaller than the one measured under completely homogeneous conditions. Evidently, the "initial" concentration of the reagents in the dead volume-and of course in the rest of the solution-greatly influences the Landolt time to be measured in the case of an individual kinetic run and may therefore show either positive or negative deviation from the Landolt time for the completely homogeneous state. As a result, less efficient mixing may either accelerate or decelerate the rate of a nonlinear autocatalytic reaction at a macroscopic volume level.

Specific-Ion Effects Unveil a Route for Modulating Oxidatively Triggered Acid Systems for Reservoir Applications

“…It is worth mentioning that the -OTFAc derivative led to inconsistent results, where on occasion the reaction proceeded to completion in as little as 45 min, while on rare occasions it remained unreactive even after heating at 150 °C for 4 days. Unusual reaction rate behavior, so-called crazy-clock behavior, has also been observed in reactions involving periodate and isoelectronic iodate redox systems with arsenous acid and may be the result of imperfect mixing. , Accordingly, the value reported here, i.e., 190 min, was found to be the most common result. The variability observed may be associated with the sensitivity of this system to the presence of additives and/or impurities.…”

“…Unusual reaction rate behavior, so-called crazy-clock behavior, has also been observed in reactions involving periodate and isoelectronic iodate redox systems with arsenous acid and may be the result of imperfect mixing. 40,41 Accordingly, the value reported here, i.e., 190 min, was found to be the most common result. The variability observed may be associated with the sensitivity of this system to the presence of additives and/or impurities.…”

Is Iodine Oxidation with Hydrogen Peroxide Coupled with Nucleation Processes?

“…Besides just analyzed stochastic effects in iodine oxidation by hydrogen peroxide and I → II transitions in the BR oscillator, it is interesting to make some comparisons with stochastic effects in other redox systems mentioned in the introduction of thiosulfate−chlorite reaction, 12 iodide−chlorite system, 13 iodate−arsenous system, 14 periodate−arsenous. 15 Stochastic effects in these systems are well established and connected with various experimental parameters such as rate of mixing, shape of the vessel, reaction volume, diameter of the magnetic stirrer, and reaction composition. In all stochastic systems it is common that some source of inhomogeneity must be present, which is further accelerated by chemical reactions and distributed throughout the whole system.…”

“…Thus, stochasticity of induction times is used as a source of information about the reaction mechanism. Large stochasticity of macroscopic chemical systems is not a common phenomenon in chemistry and only few redox systems with well-confirmed stochastic behavior are presented in literature: thiosulfate−chlorite reaction, 12 iodide−chlorite system, 13 iodate−arsenous system, 14 periodate−arsenous, 15 iodine formation after oscillatory Briggs-Rauscher reaction. 16 An interesting classification of the mentioned systems, in relation with the present results, is discussed.…”

Stochastic Phase Transition Dynamics in Nonequilibrium System: Holographic Study

“…Nonlinear systems are highly sensitive to the concentration of reactants, the geometries of the reaction vessel, mixing conditions, and external influences like light and temperature. ,− Up to now, the time evolution of nonlinear chemical systems has been successfully monitored by potentiometric methods. − However, the electrodes immersed in the solution could give rise to additional effects like catalytic effect, “dead volume” effect (i.e., when diffusion of chemical species is a controlling factor for the reaction), and a lot of other processes highly dependent on the nature of the working electrode. , Furthermore, the main reactant, hydrogen peroxide, could be decomposed on the platinum electrode, which is widely used in potentiometric measurements of oscillatory reactions. In addition, many details of a complex redox system are not fully understood .…”