A NEW SIZING TECHNIQUE OF AEROSOL-PARTICLES - LINE START SEDIMENTATION TYPE USING AN ULTRAMICROSCOPE

A new line start sedimentation type sizing technique of aerosol partic les using an ultramicroscope has been developed to determine the numbe r density distribution of particle size in a direct manner. Aerosol sa mpled into a closed cell forms a thin layer at the top of the cell and then the particles settle toward the particle free space by gravity. The number of particles settling in the visual field of an ultramicros cope at a known depth of the cell is counted. This method has some adv antages: (1) it directly gives the number density distribution of part icle size; (2) it is suitable for aerosols having a high fluctuating s ize distribution with time; and (3) it permits a quick measurement in a few minutes, This sizing technique is useful for the size measuremen t of aerosol panicles of around 1 mu m in diameter and a high number c oncentration.