Experimental investigations on the light scattering of colloidal spheres *1I. The specific turbidity

Abstract

Specific turbidities were measured on 23 nearly monodisperse polystyrene and polyvinyltoluene latices containing rigid spherical particles. The uniform diameters varied systematically from 45 to 824 millimicrons. The particle diameters calculated from the turbidity data by means of the Mie theory agreed so well with electron microscopic diameters that the results can be regarded as a conclusive proof of the Mie theory. A precision apparatus and the general experimental technique are described which allow one to determine particle diameters with a precision of better than 0.33%, which far exceeds the precision obtainable with the electron microscope. It is shown that the refractive index of the scattering spheres must be determined very exactly in order to obtain, in addition, highly accurate particle diameters. Evaluation of the turbidity data by means of the Rayleigh-Gans theory shows that it can give quantitatively significant particle diameters only for a very limited size range if the relative refractive index is near 1.2.