The structures of three colloidal liquids at their triple points are studied. The interparticle attraction in these liquids, induced by the depletion effect of free polymer, has variable range. In one case, the liquid state is "marginal"-in the phase diagram the critical point lies nearly on the line of triple coexistence. Structure factors of the liquids, measured by anew application of two-color dynamic light scattering, show that their local structures are similar, while long-range fluctuations increase as the liquids become more marginal. [S0031-9007(98)08136-8].
- POLYMER MIXTURE