1.1 ,This test method covers the determination of the particle size distribution of alumina or quartz powders in the range from 0.5 to 50 μ,m and having a median particle diameter from 2.5 to 10 μ,m using a sedimentation method. This test method is one of several found valuable for the measurement of particle size. Instruments used for this test method employ a constant intensity X-ray beam that is passed through a sedimenting dispersion of particles.