Sizing and size particles distribution is very important in materials technological characterization. In general the particles have irregular shape, so the methods used to determine the particle size are based on geometrical similarity, like equivalent diameter that are determined by techniques that use the Stoke's law. This law is applied only in laminar flow. With nowadays technological development is possible to analyze sizes until 0.1 mum using the sedigraph analyzer that apply the Stoke's law plus the X-ray absorption by dispersion of particles in water environment. In order to use correctly these methods it is very important that the material have to be pure or if there are more than one phase the density of those should be very close. So the calculation of particles size present will be correct.
Stokes' law; settling; size analysis
