Fractal Structures in PbF2/Pb(NO3)2 Precipitate Systems

Abstract

Tree-like aggregates (dendrites) have been reported in a variety of precipitate systems. We here explore different routes for the growth of dendrites of PbF 2 and Pb(NO 3 ) 2 . The PbF 2 ramifications form via the interdiffusion of coprecipitates (F - into Pb 2+ ) in microslides (Liesegang-type experiments) and via the infiltration of electrolyte through cracks, thus simulating geochemical fractals. The Pb(NO 3 ) 2 dendrites are grown by evaporation of dilute solutions of the salt. Images of the various patterns obtained are analyzed and their fractal dimensions are determined. The location of the edges of successive "cascades" in dendritic patterns obeys a spacing law similar to that of Liesegang bands.