Laser Diffraction Spectrometers/Experience in Particle Size Analysis

Over the past few years, laser diffraction spectrometry has become a very important method of particle size analysis. Typical features include the large measuring range, the simplicity of operation and the speed with which analyses can be carried out. The principle of measurement and the set-up of three commerical instruments are described. The following points are discussed, with reference to examples: –Relevant parameters, such as particle shape, shape of distribution curve or dispersion, bution curve or dispersion, –reproducibility, comparison of the results obtained with different types of apparatus between one another and with other, analytical methods, and –on-line use of the instruments for the measurement of dynamic processes, eg. flocculation and dispersion processes. Operating experience gained with six instruments over a number of years is discussed. The measuring method which is described here is in a stage of rapid development and dissemination. It is for this reason that recent improvements and new developments cannot be dealt with here. For example, an apparatus named Helos from Sympatec GmbH, Remlingen, has appeared on the market. The external appearance of the instruments marketed by the Malvern and Leeds and Northrup companies has changed somewhat. The author's practical experience (in some instances extremely wide-ranging) with these devices is presented here in summary form.