Quick Optical Measurement of Particle Distribution in a Sedimentation Apparatus

The determination of the particle size distribution of a powder may last up to 14 hours with standard sedimentation techniques such as an Andreasen pipette. If, in a photosedimentometer, not only the one sensor close to the bottom is incorporated but a number of sensors positioned at different heights, the time required for determining the particle size distribution of a powder may be reduced to 15 minutes. For each sensor there is an optimum location, which is determined both by the distance from the surface to the lowest and the highest sensor and by the number of sensors. The instrument, equipped with three measuring sensors and a reference sensor is connected to a personal computer. The measured particle size distributions are reproducable with a standard deviation of less than 2%. Agreement with a Sedigraph or a sedimentation balance is about the same as the agreement of these two instruments with each other. The time required for the determination of a particle size distribution of a quartz powder suspended in water with particle diameters from 1.5 to 60 μ is 15 minutes.