Tortuosity of sedimentation beds was measured by the electrical conductivity method for aqueous suspension of variously shaped particles (sphere, glass and nylon; irregular shape, calcium carbonate and chloramphenicol ; rod, glass, salycylic acid, and benzoic acid; plate, mica and naphthalene). Tortuosity at the upper part of the sedimentation beds showed low values for calcium carbonate of primary particle size γ
0=3.3 μm which constitutes an aggregated settling system, and high values for glass sphere of γ
0=22.5 μm which constitutes a monodispersed settling system. As for porosity (ε), vertical tortuosity (q
V) and horizontal tortuosity (q
H), the values obtained by the gravitational and centrifugal sedimentation methods were the same for glass spheres but were different, depending on the mode of sedimentation, for glass rods and nylon spheres. In the case of sedimentation beds of rod- and plate-shaped particles, decrease of q
V was more notable than that of q
H with increase of ε. The data plotted to see the relation between q and ε fell on different lines for coarse particles, but fell on the same line for fine particles of calcium carbonate and chloramphenicol whose γ
0 is about 0.8 μm. The ratio of q
V/q
H, which represents anisotropy of the sedimentation bed, was about 1 for glass spheres, constant independent of ε for fine particles of γ
0=0.8 μm, and decreased with increase of ε for other particles. It was concluded that the anisotropy of sedimentation beds is caused by nonspherical nature of primary particles and or aggregated secondary particles.
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