A sedimentation method for the determination of the particle size of finely divided materials (such as hydrated lime)

Abstract

This paper reports a comparison between a sedimentation method of determining particle size distribution and a microscopic method and also some data on hydrated lime. Glass spherules were prepared from pyrex glass and fractionated so that most of the particles had a diameter within 2 microns of the average di-ameter of the fraction. These particles were then dispersed in a liquid and weighed as they settled out of suspension with an automatic-weighing device. From this sedimentation record the particle size distribution was calculated. The same sample was then used to determine the particle size distribution by measuring the diameters of several hundred particles with a microscope. In making the microscopic measurements the glass spherules were mounted in liquids of various refractive indices and it was found that differences in refractive index of the mounting medium produced appreciable changes in the apparent diameter (more than 20 percent in some cases). The microscopic and sedimentation measurements showed similarly shaped distribution curves but there was some variation between them. Particle size distributions of hydrated lime are also reported