抄録
In chemical industries, the determination of particle size of fine powders play an important part in crushing fine particles its classifying and mixing, its transportation by air and other unit operations.
The photo-extinction method is based upon the determination of the opacity of a suitable dis-persing liquid caused by the suspension of the powder in it.
However, the lack of knowledge of the basic laws of transmission of light through the suspension leaves the method still open to question.
For this reason first we studied the interrelations of optical density, the concentration of the powder, the length of light path through the suspension, the diameter of the particles and the density of the soild particles.
The optical density of the suspension, which is the logarithm of the ratio of intensities of the incident and the transmitted light (I0/I) is proportional to the concentration of the powder (c) and the length of the light path (l) through the suspension, and inverse to the particle size (dx) and the density of the particles. (ρs).
The relationship is expressed by the equation
Secondly, we studied by this photo-extinction method the effects of the dispersion agent, the concentration of powder, the optical filter, the depth of the centre of the beam below the liquid surface, and viscosity, on the particle size distribution of kaolinite. We have found the photoextinction method to be adequate for the determination of particle size with considerable accuracy.
