New apparatus for determination of size distribution of particles in fine powders

Every year a greater need for accurate analysis of the size distribution of subsieve material is being felt by the engineer, because of the increasingly vital part it plays in the manufacture of cement, pigments, and other powdered products. Sieves are a satisfactory means of obtaining this information as long as the material is relatively coarse, but when from 70 to 95 per cent of the sample passes the 200-mesh screen (the finest one giving consistent reading), some new scheme of analysis must be used. Several methods of analyzing this fine fraction have been developed. For example, Professor Work at Columbia has perfected an excellent microscope technic. Elutriation and sedimentation methods employing various fluid media have been shown to be feasible, and additional methods are constantly being developed, but most of them are slow and tedious.