Abstract
The alumina particles were ground with an annular type beads mill, and the effect of dispersing agent (sodium hexametaphosphate, abbre. S. H.) on the grinding process and the particle size measurement were examined. The following results were obtained: (1) Almost the same 50% particle size change with the grinding time was obtained regardless of the initial S. H, conc. in grinding when 3mol/m3 conc. at S. H. solution was used as a dispersing medium for particle size measurement: (2) Reversed grinding(that is, flocculation) apparently occurred at the lower initial S. H. conc. in grinding using pure water as the dispersing medium: (3) The existence of S. H. gave the lower specific surface area measured by the B. E. T. method: and (4) The X-ray diffraction analysis showed that other crystalloid materials were not formed with the existence of S. H. although the ground particles become partially amorphous.
