Interference patterns with Liesegang rings

Abstract

Anyone who is experimentally familiar with the production of Liesegang rings in gelatine films and other allied phenomena might well feel tempted to believe that such periodical precipitates are to be regarded as wave-patterns. Indeed, several workers in the field appear to have felt that the analogy between the Liesegang phenomenon and a wave-effect is not merely superficial, and have sought for more positive evidence in support of it. Leduc and others, for example, claimed that Huygens' well-known optical principle gives an explanation of the form of the rings observed when a precipitating agent diffuses through a narrow aperture in an obstacle cutting across the film. More recently, some Russian workers have gone further and suggested that the periodic precipitation itself is to be explained in terms of the de Broglie waves associated with the movement of the precipitating agent, and claim to have been able to measure the 'refractive index' of such waves in passing across a boundary separating regions of different concentration of the gelatine.