Simultaneous size and thickness measurements for heterogeneous micrometre-sized particles

The size of anisodiametric particles is commonly expressed in terms of the diameters of equivalent spheres. A theoretical comparison is made between the equivalent rotating sphere and the equivalent sedimenting sphere. The ratio of these diameters is a function of the axial ratio alone for ellipsoids, rods and discs. A method is proposed for simultaneous measurement of the variability in both the major and minor dimension of a heterogeneous sample. Illustrative data on two kaolinite clay samples are given.