Particle size and sol stability in metal colloids

It is shown experimentally that the stability of metal sols depends on particle size. Sols with small particles are more stable against electrolyte coagulation than coarser suspensions. It is possible to separate metal particles of different radii by fractionated coagulation. Results are explained from the diminishedvan der Waals attraction between small particles. Consequences for the repeptization of metal sols and for the measurement ofHamaker constants are discussed. It is concluded that the smallness of the particles is a decisive factor for the stability of metal colloids.