MEASUREMENT OF PARTICLE-SIZE DISTRIBUTIONS WITH A DISK CENTRIFUGE - DATA-ANALYSIS CONSIDERATIONS

The disc centrifuge with an optical detector measures particle size distributions of various types of particles over a wide dynamic size range, .01 to 50-mu-m based on Stokes' Law for centrifugation. Generally the extinction efficiency of particles is a function of particle size, refractive index and an optical correction based on Mie scattering theory is required to ensure that the photodetector response is proportional to particle concentrations. It is shown that such corrections can be simplified if experimental conditions are adjusted to prevent the largest particles from sedimenting in short spin times. When this is done, data acquired on an equal time interval basis can be used to obtain valid particle size distribution averages.