Particles are far from identical whether in solid or liquid form, and therefore the particle size distribution and average particle size become the important measurements. Manufactured materials are typically polydisperse (or polysized), i.e. composed of particles of varied size and mass.
As it is not usually possible in a commercial environment to measure every individual particle in a sample it is important to design the correct sampling devices and methods. Adhering to statistical sampling theory all particles must be given the same probability of being selected.
The international standard used for particle size analysis is ISO 9276 - Representation of results of particle size analysis - which is broken down into six parts:
Part 1: Graphical representation
Part 2: Calculation of average particle sizes/diameters and moments from particle size distributions
Part 3: Adjustment of an experimental curve to a reference model
Part 4: Characterization of a classification process
Part 5: Methods of calculation relating to particle size analyses using logarithmic normal probability distribution
Part 6: Descriptive and quantitative representation of particle shape and morphology