11), hydrophobic interaction (12, 13), secondary minimum The influence of particle size on the kinetics of slow Brownian coagulation (6-8, 14-16), slow equilibration of the surface coagulation is studied. Colloidal gold was chosen as a model syscharge during the collisions (17, 18), etc.-into traditional tem of spherically shaped colloidal particles with a rather sharp DLVO theory. Some of these effects have indeed been found particle size distribution. An experiment shows that dispersions experimentally. They can affect the details of coagulation with particle sizes of nanometer scale may deviate from expected in special cases. But still, the repairs of the discrepancy, behavior according to DLVO theory. This experiment confirms between the theoretical predictions of the particle size effect rather well the expectation of a qualitative influence of surface and the experimental observations that it does not exist, have irregularities on log W -log c diagrams. The surface roughness remained unsuccessful. Specific effects that might apply in effect has been described in such a way that a transition in the character of the stability diagram would be expected at L Γ
l 2 /dd certain colloids under certain conditions offer no explanation Γ
1. This parameter compares the particle diameter with surface for the lack of sensitivity in experimental coagulation rates roughness characteristics l (half-wave) and d (half-amplitude). with particles of different sizes that is found in many, widely This indicates that the surface features commensurate with the differing classes of colloids.
range of interparticle forces are more important in determining
In a preceding paper (19) we considered which length the rate of slow Brownian coagulation of electrostatically stabilized scales are relevant in the potential energy of two colliding colloids than the average particle size.