We study the initial behaviour of the characteristics of an hyperbolic system of first-order equations, which models
the diffusion of n species of stable isotopes of the same element in a medium. The model is based on the assumption
that, since the isotopes are chemically indistinguishable, the flux of each isotope depends on the gradient of the total
concentration of the element weighted by the relative percentage of the isotope. We consider here the influence of
initial irregularities of the total concentration on the characteristics.
