Influence of particle size on angle of repose (a), and on internal frictional coefficient (μ1) and cohesive force (C1) obtained by shear strength method was discussed for white alundum. Presence of critical particle size was confirmed at 45-50 μ, and a, C1, and μ1 increase markedly with the decrease of particle size in the region smaller than this size. Cohesive force (C1) is proportinal to μ1 and linearly related to C/Mg calculated from the data of angles of repose. It is concluded that cohesive force is negligibly small in the region above the critical size, but in the region below this size it affects the physical properties of powders, such as angle of repose.
