Periodic and complex precipitation pattern of catechol-lead complex in agaragar gel media

Abstract

Periodic and complex patterns of precipitation have been obtained when a lead acetate solution diffuses into agar-agar gel containing catechol to form lead(IV)-catechol complex. Location of various normal-spaced bands from the initial junction has been measured and plotted as a function of the number of bands. The data are best fitted by the empirical equation X_n = Ce^mn where X_n is the location of the band n from the junction. m. and log C are slope and intercept respectively of the plot of log X_n versus n. Changes in potential and <i>p</i>H during the reaction process have been monitored as a function of time. Results lead to the conclusion that the phenomena involve the transition from one stable state to another state. Influences of the electrolyte concentration, diameter and orientation of the tube on the precipitation patterns have also been studied. The reaction product, obtained in the form of red spherical crystals, has been characterized by far IR and mass spectroscopy, and microanalytical techniques.