Abstract
The particle sizes of various powders measured by the sedimentation, adsorption and air-permeability method were compared with the results by the electronmicroscopy. In the case of the powders having especially uniform shape and size, all of the values of mean particle sizes by various methods, were almost same. For the common powders, however, the values by various methods did not agree. From observation of the particle shape with the electron microscope, it is possible to explain the difference of the apperent particle sizes by various methods has the relation with other properties.
