The Belousov−Zhabotinsky reaction (bromate−malonic
acid−ferroin) exhibits regular sequences of complex
(large and small amplitude) transient oscillations in a CSTR as well as
in a batch reactor. General features
of the dynamics in both type experiments are explained in a qualitative
way using a simple model proposed
recently for batch conditions.
Complex periodic oscillations with small amplitude oscillations close to the maximal value of a large amplitude
oscillation followed by other small amplitude oscillations close to the minimal value of the next largest
amplitude oscillation are found in the Belousov−Zhabotinsky (B−Z) reaction (bromate−malonic acid−ferroin)
in CSTR. Oscillations showing identical patterns are obtained in a simple model proposed recently for a
qualitative description of transient and asymptotic oscillations observed in the B−Z system.
We have studied the effect of oxygen on the time-dependent bifurcations of transient oscillations in the Belousov-Zhabotinsky oscillating chemical reaction in a closed system. Experiments show that oscillations disappear through different bifurcations depending on the oxygen concentration in gas phase above the reaction solution. Oscillations disappear through the time-delayed Hopf bifurcation at low oxygen concentrations, whereas at high oxygen concentrations they disappear through the time-dependent SNIPER (saddle-node infinite period) bifurcation. We propose a kinetic scheme that describes the effects observed in experiments. Good agreement between the experimental data and simulations is obtained.
The specific heat is measured as a function of temperature for [Ni(H2O)6](ClO4)2. Two anomalies of specific heat are revealed, at (311.40 ± 0.93) K and (361.05 ± 0.01) K. The entropy changes associated with these anomalies have the values of (2.26 ± 0.15) cal/mol K and (6.02 ± 0.13) cal/mol K, respectively.
The behaviour of a system composed of malonic acid (MA), KBrO 3 , H 2 SO 4 , and ferroin was investigated in batch experiments at various concentrations of oxygen above the chemical mixture when changing the concentration of MA. We could observe that at 10% of oxygen or more and for initial concentrations of malonic acid [MA] 0 between 0.15 M and 0.6 M the system attains an equilibrium by some of mixed mode oscillations. Such a behaviour of the system could be described by a model used lately. Additionally for [MA] 0 = 0.1 M or less at 0 -20% of oxygen a region of sequential oscillations was discovered (observed for the first time in the system with ferroin) and a trial of understanding of the event is suggested. For rather small [MA] 0 ca. 0.025 M no mixed mode oscillations, no sequential ones but the so-called relaxation oscillations were observed.
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