Abstract
Narrow forward angle transmission of a monochromatic light beam through an aqueous suspension of dust particles during and after settling was used to obtain particle projected area. Measurements were alternately made in two mutually perpendicular directions, i.e., horizontal and vertical. Random orientation was characterized by equal particle projected areas in these two directions. Narrow size range samples of suspensions of quartz, bituminous coal, anthracite coal and diamond were evaluated. The apparatus is briefly described and results are discussed in terms of commonly employed particle sizing procedures.