A Quasi Universal Matalon-Packter Law for a Periodically Precipitating System of Iron(II) Hydroxide Involving Volumes...

The Matalon-Packter (MP) empirical law of periodically precipitating (Liesegang phenomenon) systems under non-equilibrium conditions describes the dependence of the periodicity (spacing coefficient) on the initial concentration of the outer electrolyte. We aim to present the MP law in a more generalized form using a realistic approach wherein mass transfer in the gel column plays a role instead of the initial concentrations. This work is an attempt to make such progress. The Liesegang bands of Fe(OH)₂ were studied by varying the reservoir concentrations (c) and volumes (V) of the outer electrolyte (NH₄OH). The spacing coefficient was found to be a function of the volume and concentration of the outer electrolyte. It was observed that the amount of chemical substance (cV) and the average molar diffusion flux (F_diff) of the ions of the outer electrolyte could be a unifying quantity for expressing the MP law instead of the initial electrolyte concentration. We demonstrated that a single model is possible for a system, irrespective of the V value. Three different volumes were employed, and the calculations were performed under small, intermediate, and larger reservoir volume regimes. Interestingly, a single model was observed for the diffusion coefficients for all of the F_diff values.