Improvements in the measurement of contact angles at heterogeneous surfaces
and their interpretation were applied to mineral flotation systems where a
hydrophilic solid surface is covered by a hydrophobic collector and forms
a heterogeneous pattern. The examination of the contact-angle hysteresis an
d the contact-angle vs. drop-size relationship for the fluorite-carboxylate
and apatite-carboxylate systems supports the model of nonuniform formation
of adsorbed layers through nucleation and growth of hemimicelles at the mi
neral surface.