It has been shown by Stell (1991, J. statist. Phys., 63, 1203) that at low
temperature monodisperse sticky spheres collapse to form coexisting close-p
acked solid and infinitely dilute gases. We show that polydisperse sticky s
pheres also collapse and calculate the collapse temperature. The polydisper
se spheres separate into fractions with narrower polydispersities which can
then solidify. This is perhaps the first example of a single-peaked polydi
sperse mixture phase solidifying and separating. It implies that a mixture
of polydisperse large hard spheres with much smaller hard spheres does not
show fluid-fluid coexistence.