Slow coagulation of aqueous α-Fe2O3 dispersions studied by electric light scattering

Abstract The slow coagulation of monodisperse spherical α-Fe 2 O 3 particles in the presence of a bivalent electrolyte (MgSO 4 ) is studied electro-optically. The saturation value of the electro-optical effect and the decay process are used. The electro-optic coagulation curves are calculated theoretically, assuming two types of aggregates, linear and compact. Agreement between experimental and theoretical calculation is found for small aggregates, i.e., doublets. Some reasons for the discrepancy between results from extinction and electro-optical measurements are discussed.