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The impact of perchlorate ions and acetonitrile medium on copper redox couple was investigated. The acetonitrile solvent and perchlorate ions were found to synergistically increase the redox potential of Cu(II)-Cu(I) couple, thereby increasing its ability to oxidize more systems and expand the copper redoxi metric analysis window. The difference in the behavior of thiourea towards copper(II) salts in aqueous and non aqueous media was also explored. Based on the synergistic effect, an electroanalytical method for com position analysis of copper(I) thiourea complexes was proposed. Kinetic and quantum chemical studies have been used for mechanistic insight into synergistic effect of acetonitrile and perchlorate ions on copper redox couple.

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Abstract. The objective of this study is to develop a simple, environmentally benign alternate analytical method for simultaneous estimation of iron oxidation states. This proposed method of iron speciation is based on 1,10-phenanthroline (phen) modified redox potential of transition metal ions. In a pre-step excess cerium(IV) oxidizes iron(II) in sample to iron(III). Initial back titration of un-reacted cerium(IV) with cobalt(II) in presence of phen gives amount of iron(II) in sample, reduction of iron(III) with cobalt(II) is then used to estimate total iron as iron(III). The potentiometric titration method has been successfully tested for determinations of iron(II) and total iron in synthetic and natural samples and represents a distinctively green alternative to other reported protocols of iron speciation analysis.

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A detailed investigation on resorcinol as the Belousov-Zhabotinsky (BZ) oscillator in manganese(II) ion catalyzed reaction system with inorganic bromate (oxidant) and acetone (cosubstrate) was carried out in aqueous sulfuric acid medium (1.3 M). The aforesaid reagents were mixed with various concentrations to evolve the effective concentrations at which the reaction system exhibited better oscillations. The various oscillatory parameters such as time period (t p ), induction period (t in ), frequency (v), amplitude (A), and number of oscillations (n) were derived, and the dependence of concentration of the reacting species on these oscillatory parameters was interpreted on the basis of the Field-Koros-Noyes mechanism.

O estudo diz respeito ao comportamento oscilatório de resorcinol como substrato orgânico na reação de Belousov-Zhabotinsky (BZ) em presença de diferentes íons metálicos como catalisadores no meio aquoso ácido. ). On varying the aqueous acid media, it is observed that protonated species with respect to organic substrate (resorcinol) is more easily formed in aqueous sulfuric acid, owing to which maximum number of oscillations are observed in this medium. Moreover, the effect of different anions like acetate, carbonate and sulfate associated with the same metal ion (Mn 2+ ) as catalyst on the oscillatory behavior of the reaction system was also studied. Mixed mode oscillations are seen while changing concentration of aqueous sulfuric acid medium.

In the present paper a thorough study of temperature dependence on oscillatory behaviour of the Belousov-Zhabotinsky (BZ) system containing the isomers of hydroxybenzoic acids + BrO3-+ Mn(II) in aqueous acid medium (1.0 M H2SO4) at a fixed concentration of reacting species has been reported. On varying temperature, the oscillatory parameters like induction time, time period and number of oscillations show marked changes. These changes arise due to the position and number of hydroxyl groups in these isomers which affect the oscillations. Experimental observations have satisfactorily been explained by FKN mechanism and kinetic parameters. The oscillatory characteristics depend on the temperature dependence of the rate constant of the reaction controlling the inhibitory reaction steps (negative feedback)