  We investigate polydispersity effects on the average structure factor of
colloidal suspensions of neutral particles with surface adhesion. A sticky hard
sphere model alternative to Baxter's one is considered. The choice of
factorizable stickiness parameters in the potential allows a simple analytic
solution, within the ``mean spherical approximation'', for any number of
components and arbitrary stickiness distribution. Two particular cases are
discussed: i) all particles have different sizes but equal stickiness (Model
I), and ii) each particle has a stickiness proportional to its size (Model II).
The interplay between attraction and polydispersity yields a markedly different
behaviour for the two Models in regimes of strong coupling (i.e. strong
adhesive forces and low temperature) and large polydispersity. These results
are then exploited to reanalyze experimental scattering data on sterically
stabilized silica particles.
