How are particles dispersed when using the wet method?

In laser diffraction particle size analysis, inaccurate results can be caused by particle agglomerating in the suspension, especially when they are fine. Therefore, a full dispersion of the sample prior to measurement is essential. 

Three effective methods are available for the sample dispersion when using the wet method. Primary dispersion of aggregates can be achieved by circulating the suspension through a wet flow path containing a stirring blade. In addition, variable levels of ultrasonication can be helpful in deagglomeration. Thirdly in some systems, the downward slope of the circulation tank and a higher pump speed can effectively prevent the precipitation of particles with a higher specific gravity or larger particle size in the wet flow path, leading to a complete dispersion and hence a statistically good representation of the particles. For particles that float on the meniscus of the water, an appropriately diluted surfactant may be necessary to lower the surface tension. Hence the particles can be absorbed into the water.

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