  Theoretical models of the Liesegang phenomena are studied and simple
expressions for the spacing coefficients characterizing the patterns are
derived. The emphasis is on displaying the explicit dependences on the
concentrations of the inner- and the outer-electrolytes. Competing theories
(ion-product supersaturation, nucleation and droplet growth, induced sol-
coagulation) are treated with the aim of finding the distinguishing features of
the theories. The predictions are compared with experiments and the results
suggest that the induced sol-coagulation theory is the best candidate for
describing the experimental observations embodied in the Matalon-Packter law.
