Introduction of the Surface Complexation Model into the Theory of Colloid Stability*

This article shows that the introduction of the Surface Complexation model into the »family« of theories that comprise the Theory of Colloid Stability makes that theory »absolute«. This means that one characterizes the electrical interfacial layer, e.g. by adsorption measurements, and calculates the equilibrium parameters, such as the equilibrium constants of protonation and deprotonation of amphoteric surface OH groups, equilibrium constants of the association of counterions, capacitances of inner and outer interfacial layers and the total concentration of surface sites. From these equilibrium parameters one evaluates the potential at the onset of the diffuse layer ( d) and calculates the electrostatic interaction energy yielding the rate constant of aggregation and the stability coefficient. It is shown that counterion association plays an important role in the aggregation phenomena by reducing the value of potential d.