Light scattering by aggregates of large colloidal particles

Information theory and the Rayleigh-Gans-Debye and anomalous diffraction approximations are used to obtain criteria for choosing an aggregate model. They suggest a simple one with appropriate gross features. The hollow sphere of equal mass and total volume is chosen, actually a slightly heterogeneous population of hollow spheres. The average sphere volume is that of the aggregate; the volume and refractive index of the coat are those of the particles; the volume and refractive index of the sphere core are those of the spaces between the particles. The effects of aggregation on transmitted and scattered light were measured with two transmittance photometers and a 90° scattering photometer. Observed effects of aggregation are qualitatively accounted for with this method of predicting aggregate scattering. The method is also used to survey predicted effects of aggregation of blood platelets on suspension transmittance.