DIRECT MEASUREMENT OF CONCENTRATION AND SIZE FOR PARTICLES OF DIFFERENT SHAPES USING LASER LIGHT DIFFRACTION.

The laser diffraction technique has now been developed so that not only the particle size distribution but also the true volume concentration may be measured for solid particles suspended in liquid. Data from the diffraction rings, giving relative concentration of particles of different sizes, has been combined with information from the undiffracted light beam to give the absolute concentration of particles. Particle shape has been corrected by using the theorem that the average geometical projected area of a convex particle with random orientation is one quarter of the total surface area. The correctness of the analysis and the applicability of the new technique have been confirmed by experiment, using glass spheres and crystals of potassium iodide, potassium aluminium sulphate and sucrose.