Formation of Liesegang patterns in an electric field

Abstract

Evolution of Liesegang patterns in an electric field was studied experimentally in the AgNO₃/K₂Cr₂O₇/gelatine system. The distance of the last (nth) band as a function of their appearance time can be described by the equation X_n = c₁t^1/2 + c₂t + c₃. A numerical model, based on Ostwald's supersaturation theory, predicted the same functional law. Experiments showed that the ratio of the distances of two consecutive rings, the spacing coefficient, decreases with increasing electric field strength and this behaviour was also reproduced by the numerical model.