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The analysis of the distribution of particle-sizes in a powder, or dispersed in a fluid, is important for understanding the chemical and physical properties of the material in question. The particle size distribution (PSD), also known as grain size distribution, that defines this relative frequency of particles, usually given by mass, is expressed as a mathematical function or a list of values.

The PSD is an indication of many different things about the material, including its strength and load bearing capabilities and chemical reactivity, and hence needs to be carefully measured and controlled in the production of many different powdered materials, as well as different products, such as cosmetics and printer toners.

Particle size distribution analysis is carried out using many of the same techniques are ordinary analysis and counting procedures include sieve analysis, sedimentation, light obscuration, electrozone, photozone, photon correlation spectroscopy, air elutriation, air permeability diameter and aerodynamic approaches.

With so many different ways of determining the PSD the measurement presentation usually references the technique used. For example, with sieve analysis the PSD can be expressed as a percentage of material found within a certain size range, the range of the sieve used.

Because of the approach dependency of the PSD measurement, it is important to consider all the different common options e.g. image analysis, laser diffraction and dynamic light scattering before choosing your method.

You need to be aware if there is a historical imperative for a particular technique, perhaps for data compatibility, or whether you need additional information on surface charge, zeta potential or particle shapes. A proper consideration of these aspects will ensure that you do not run into problems, for example, connected with particle resolution.

It is also extremely important to be aware of how different sampling methods e.g. settling chambers, fibre filters or electrostatic precipitators might be skewing the sample size distribution before it is analysed. This can be almost as critical as the actual method picked for arriving at your PSD value.

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