Reversible flocculation of silica colloids in liquid mixtures

We report some observations concerning the reversible flocculation of silica colloids in reentrant liquid mixtures of 3-methylpyridine plus water plus heavy water and 2,6-lutidine plus water. Our research involved a detailed determination of the line of flocculation temperatures for phase-separating as well as non-phase-separating mixtures. We find that the flocculation temperature is more influenced by the impurities in the suspension rather than the concentration and size of the spheres. For a fixed volume fraction and diameter of the colloids, we notice a close similarity between the dome of flocculation temperatures and the bulk-coexistence surface but with different amplitudes and exponents in each case.