Determination by Analytical Sieving

ow that some of the general precepts of particle size and shape have been outlined (1) and the all-important topic of powder sampling has been addressed (2), it is appropriate to move into a discussion of the experimental methods used to deduce information about particle size. Analytical sieving is one of the most conceptually simple methods for deducing the particle-size distribution of a powdered solid. In sieving analysis, one simply passes the sample through wire meshes that have openings of various sizes and then measures how much of the sample is retained on each sieve. Sieving is one of the fundamental methods for the classification of powders, and it is the method of choice for determining the size distribution of coarse powders. Although sieving is most suitable for powders whose average particle size exceeds 25–50 m, it can be used for finer grades of powders if the method is properly validated and executed. Sieving analysis is difficult to perform for oily or cohesive powders because they tend to clog sieve openings.