34.2: Measuring Particle Size Using Sieves

The particulates in a solid matrix are separated by size using one or more sieves (Figure \(\PageIndex{1}\)). Sieves are available in a variety of mesh sizes, ranging from approximately 25 mm to 40 μm. By stacking together sieves of different mesh size—with the largest mesh at the top and the smallest mesh at the bottom—we can isolate particulates into several narrow size ranges. Using the sieves in Figure \(\PageIndex{1}\), for example, we can separate a solid into particles with diameters >1700 μm, with diameters between 1700 μm and 500 μm, with diameters between 500 μm and 250 μm, and those with a diameter <250 μm. The sample is place in the uppermost sieve and mechanical shaking used to effect the separation.

Because we cannot use more than a limited number of sieves in a single stack, the methods for analyzing the particle size data presented in Chapter 34.1 will be discrete in nature instead of continuous; thus, histograms will have a relatively small number of bins and a cumulative distribution will consist of a discrete number of points. One limitation to a sieve is that irregularly shaped particles are sized based on their two smallest dimensions.

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