Ľudovít Treindl

A new halogen-free chemical oscillator: the reaction between permanganate ion and ninhydrin in a continuously stirred tank reactor

Abstract The reaction between permanganate ion and ninhydrin in the presence of phosphoric acid in aqueous solution shows sustained oscillations in a continuously stirred tank reactor (CSTR). It exhibits a kinetic bistability between an oscillatory and a stationary state. Our new oscillating system seems to be a second permanganate chemical oscillator, thus broadening the small group of non-halogen-based chemical oscillators.

Kinetics of the oxidation of iodine by hydrogen peroxide catalyzed by MoO2−4 ions

Abstract The kinetics of the oxidation of iodine by hydrogen peroxide catalyzed by MoO2−4 ions with a ‘clock’ behaviour is described and the corresponding reaction scheme is proposed. The ‘clock’ behaviour is explained by the assumption that the oxidation of iodine cannot proceed until the iodide concentration drops to a certain treshold, since this reaction can only through the HOI species proceed. The noncatalyzed, direct oxidation of iodine by H2O2 is too slow to become one of the main two processes of the Bray-Liebhafsky oscillatory reaction.

Oxygen-induced excitability of the belousov-zhabotinskii oscillatory system

Abstract The modified Belousov-Zhabotinskii ferroin-catalyzed oscillatory system with the ethyl ester of 3-oxobutanoic acid is described. After an induction period of about 120 s its oscillatory state consisting of four or five oscillations of absorbancy at a wavenumber of 22×10 3 cm −1 can be revived three or four times, if the solution is shaken for 25 s after the oscillatory state has finished. This apparently “mechanical” excitability, which can be observed spectrophotometrically and also polarographically using a rotating platinum disc electrode, proved to be oxygen-induced.

Oscillations in the reduction of permanganate by hydrogen peroxide or by ninhydrin in a batch reactor and mixed-mode oscillations in a continuous-flow stirred tank reactor

Abstract The periodical reduction of permanganate by hydrogen peroxide or by ninhydrin with transient oscillations in a closed system has been observed and discussed in relation to the first two permanganate oscillators described earlier. The mixed-mode oscillations of the permanganate–H 2 O 2 oscillating system in a continuous-flow stirred tank reactor have been described.

Iodide-ion-induced oscillations of the ferroin-catalyzed Belousov-Zhabotinskii reaction

Contrary to “classical” Belousov—Zhabotinskii (BZ) oscillatory systems, consisting of malonic acid, Ce(IV)—Ce(III) or Mn(III)—Mn(II) redox catalyst and KBrO3 in solutions of H2SO4, where in an interval of added iodide initial concentrations 10−4 mol dm−3 < [I−]0 < 10−3 mol dm−3 the oscillations have the same frequency and amplitude as in the absence of iodide, the effect of added iodide on the ferroin-catalyzed BZ system with methyl ester of 3-oxobutanoic acid leads to an increase in the number of oscillations and in the time of their duration. The dependence of this effect on substrate, bromate, iodide, sulfuric acid and ferroin concentrations has been studied. The observations may be explained by a mechanism involving direct reduction of ferroin by iodide, oxidation of iodide to iodate by bromate with a bromide production and eventual faster bromination and iodination of methyl ester of 3-oxobutanoic acid in relation to malonic acid.