Portugaliae
Electrochimica Acta

Research over more than 150 years has made clear that many electrochemical systems exhibit highly exotic behaviour. In the past few decades detailed dynamic studies of these interesting results often reveal oscillations, which vary from periodic to quasi-periodic to chaotic. The application of linear theory of the irreversible thermodynamics to a variety of electrochemical problems demonstrates its utility, but the time evolution of certain phenomena must be modelled by non-linear equations to characterize their dynamic behaviour. The new ideas and solution methods in non-equilibrium phenomena, that are revolutionizing dynamic systems theory, provide the framework for understanding the nature of electrochemical dynamics. The extremely complex structures generated by certain systems, are analysed in terms of fractals, one of the most rewarding scientific developments of recent years. The concept of fractal, their dimensions and the relations between fractal character of the phenomena and the dynamics of the processes are object of today's fundamental research. In this work a quick overview is presented of some recent developments related to electrochemical dynamical systems. Attention is focused predominantly on the typical tools that are useful in the study of these systems. A summary of some oscillatory phenomena from different areas of electrochemistry is presented. Emphasis will be placed on those aspects that may prove beneficial for electrochemists.

Insulin-zinc suspensions are more electroactive on the hanging mercury drop electrode (hmde) when the protein is in amorphous state. Reduction and reoxidation of disulphide bridges depend on the Zn(II) present in buffer solutions. The influence of the insulin adsorption on the reduction process of zinc at the hmde, can be explained by variation oi the exchange- current, density with a change in the surface fraction covered by the protein on the electrode.

Prussian blue (PB) has been electrodeposited on ITO-glass coated electrode. Electrochromism effect, stability of the film against continued ciclation of potential and influence of nitrate and chloride ions has been studied.

A critical review of the ca.. 100 papers in which ion-selective electrodes (ISEs) are used as detectors in flow-injection analysis (FIA) systems is presented, with the purpose of identifying systematic patterns of utilization. Three points, the insertion of the ISEs in F IA systems, the characteristics of F IA systems in which ISEs are used, and their analytical applications, are considered in turn.