METASTABILITY IN DIFFUSING-REACTING SYSTEMS

Nucleation in non-homogeneous diffusing-reacting systems occurs under a changing supersaturation. Under these conditions, the rate of creation of supersaturation determines the value of the supersaturation threshold at the nucleation time, i.e., the actual maximum metastability level. Measurements of metastable zone-widths and their dependence on the supersaturation rate are here reported for different carbonates and sulphates. By analogy with nucleation behaviour by continuous cooling of saturated solutions, a semiempirical relation appears to govern this dependence. Finally, this relation is checked for solutions doped with additives and metastability measurements in U-tube gel systems are proposed to compare inhibitor effectiveness.