Determination of particle size distribution by number

Little difficulty is likely to be experienced in carrying out a number count since the same total area is used for all size classes and the minimum number of particles, namely 625, that it is necessary to count is specified in advance [equation (3.3)]. Let there be j classes of particles of interest. For 

The class that contains the highest number concentration of particles (usually the smallest size class) is taken as the control size class. 

The dispersion technique should give about 3 particles per field of view for these particles and at least 96 fields of view should be examined. At lower magnifications it is usual both to increase the area of the field of view and decrease the number of fields examined. 

The expected standard error s p ) of the percentage by number in each size class, out of the total number in all size classes, is given by  

Circle Size Total area Number Cumulative Number Expected 

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