Particle Size Distribution Measurement by Automated Dual Wavelength Turbidimetry

Abstract Numerous methods have been reported in the literature for the measurement of (submicron) particle size distribution by turbidimetry. Attempts to apply some of these to coupler dispersions (oil‐in‐water emulsions of importance in the photographic industry) have not in general proved satisfactory, however, because small experimental errors lead to relatively large errors in the calculated distribution. In order to reduce this problem a turbidimetric technique involving measurements at two widely separated wavelengths, 400 nm and 2.22 μm, has been developed. Its accuracy has been demonstrated using polydisperse polystyrene latexes of known size distribution. With the aid of simple, purpose‐built equipment, linked to a desktop computer, the technique has been largely automated so that it is suitable for use by an unskilled operator working in a factory environment.