Figure 4: Qualitative calculation of the OD of a mixture using the binary model.The optical density of a mixture calculated thanks to the binary model is represented versus the increasing number of particles P2. The minimum is ocated at the intersection of two line segments. This figure is the theoretical equivalent of experimental figure (Figure 1). It is obvious that the binary model approximation is only applicable in the region of the minimum, which corresponds to the complete complexation of particles 1. Apart from this zone, other interactions and/or other types of particles are required to account for the profile