Portugaliae
Electrochimica Acta

Modern theory of ionic solutions depends upon information on a variety of experimental methods for a realistic adjustment of parameters. Hamiltonian models yield reliable equations for various solution properties with a unique set of basic parameters resulting from fits of different appropriate experiments, thus permitting the simulation of the properties of other electrolyte solutions for which data are not available. In this way knowledge-based data bases provide the property profiles of electrolyte solutions for applied research and technology. A survey is given of the information on structure and dynamics of electrolyte solutions obtained from high frequency permittivity measurements and of chemical models at McMillan-Mayer level permitting the calculation of electrolyte solution properties. The interplay of thermodynamic, transport, spectroscopic, kinetic and computer simulation methods is stressed. Illustrative examples are quoted.

The principle of fast techniques in direct electrochemistry is presented, and the domain of their applicability is examined on the basis of classical theories. In this process two series of factors are identified which limit the method. In the one hand, ohmic drop, capacitive phenomena and coupling of diffuse and diffusion layers are intrinsic factors. They lead to built-in limitations of the time scale range of the method. These limits cannot be trespassed without the necessity of introducing severe modifications of the available theories of molecular electrochemistry. On the other hand, other limitations exist which are only due to the present technology, and are therefore expected to be broken in the future.

An electroanalytical study of the cytarabine reduction process at a dropping mercury electrode in aqueous supporting electrolyte solution using direct current polarographic technique has been carried out. The optimum parameters were found as 1000 dyne.cnr2 pressure on the mercury reservoir, Is drop time, 4 mV.s"1 scan rate and 5.50-6.60 pH range. The reversibility of the reduction on the mercury electrode was ascertained as quasi-reversible and the polarographic current was mainly diffusion controlled. The results obtained by DC, SIAP and DP polarography allowed a method developed for the determination of cytarabine in the lxlO-4 - 5xl04 mol.L"1 concentration range. Good results were obtained by applying the DC polarographic technique to the determination of cytarabine in a pharmaceutical preparation.

The experimental conclusions on the chemical-kinetic process of the chemical plating on ABS surface, one of the plastics materials more widely used, are presented, describing each step of the process

In the anodic methanol oxidation in aqueous sulphuric acid on smooth R-electrodes using the chronopotentyometric method, oscillations of potential in the V=V(t)-curves have been observed. The evolution of such potential oscillations with the value of the current impulse imposed on the electrodes has been discussed and a reaction mechanism of the methanol oxidation has been proposed in accordance with the experimental results