Abstract
Three basically different principles for density measurement of aerosol particles, based on 1) separate measurements of mass concentration and size distribution, 2) simultaneous measurements of gravitational settling velocity and electrical mobility and 3) balance of gravitational and Coulomb''s force, have been tested. Modifications by combining classification of particles by electric differential mobility analyser to each of the above three methods have also been tested. The easiest and most accurate method has been found to be that based on 3) above, which is similar to Millikan''s experiment for the evaluation of elementary charge, when particles are larger than 0.5 μm. For smaller particles the method based on 1) above is applicable, but there is a problem in accuracy and there is a disadvantage in that the method requires stability in aerosol concentration and size during density measurement.
