where J is the total current density, Qj the rate of change in charge density accounting for current sources, σ the electrical conductivity, j the imaginary unit, ω the angular frequency, εo vacuum permittivity, εr the relative permittivity of the material, E the electric field, Je the externally generated current density and V the electric potential.
Electric properties of the solution, electrode and temperature sensor probe materials are summarized in Table 1. Geometry of the model is illustrated in Fig. 2 (a). The reaction solution was considered in macroscopic terms as a bulk dielectric medium with frequency-dependent ohmic losses to account for its resistance and capacitive properties. For the sake of simplicity, only the initial solution composition was considered (aqueous solution of pure Ca(NO3)2). Only the parts of electrodes and probes immersed in the solution volume were regarded in the model in order to reduce mesh size. The glass walls of the beaker and surrounding air were assumed to be perfect insulators. The curvature of the solution surface due to gentle stirring and solvent evaporation were neglected in the calculation. Geometries of excitation electrodes and temperature probe were approximated with cylindrical shapes and positioned within the solution volume according to the experimental setup geometry. The extremely fine physics-controlled mesh was utilized to obtain optimal accuracy of the electric field calculation. Working electrode was set at the fixed electric potential of 10 V while the counter electrode was set at the ground potential. The current conservation equation was solved in the frequency domain for the frequency of 1 kHz.