A Sedimentation Phenomenon

Abstract

One of us (F. S.) was required some time ago to consider a proposed sedimentation apparatus for particle-size analysis, in which, for reasons beyond the scope of this note, the sedimentation vessel was to be a conical flask. Assuming the motion of each particle to be one of vertical descent, it was shown that an unstable condition would ensue. Suppose time has elapsed for particles of a specified size to fall from AB to A′B′. At this moment, no particle greater than the specified size will be above the surface C′ A′ B′ D′, and the suspension within this region will have a higher specific gravity than the remainder. It was clear, therefore, that some flow of the suspension must occur and that the use of a conical flask would introduce an additional complication into the already difficult problem of particle size analysis.