Crystal growth in gels and Liesegang ring formation: II. Crystallization criteria and successive precipitation

Abstract

This paper considers the conditions under which two diffusing reagents can form precipitates (continuous or periodic) in a gel, on the basis of numerical solutions obtained in Part I. For a precipitate to form, not only must the local concentration product exceed a certain value K′ s, but the two reacting entities A and B must be nearly equal to form nuclei of structure AB. With these dual conditions, the behavior of gel-diffusion systems is correctly reproduced. The periodic nature of their fulfillment (Liesegang Ring formation) is demonstrated. As a demonstration of principle, ring masses and ring spacings are calculated on the basis of a simple algorithm, suitable for microcomputers.