Before investigating the finer details of particle size analysis, the first question to ask is 'Why do you need to know the particle size?' A knowledge of particle size is only the first step towards the use, performance, final application or properties of those particles. For example, sieving was first recorded over 6000 years ago in ancient Egyptian times in the manufacture of beer. In this instance a classification of particles was required to remove the unwanted hops after the fermentation. Here the 'particles' could be seen with the naked eye so it was comparatively easy to specify a mesh that would remove those particles. At the other end of the time and size spectrum, we are becoming increasingly concerned about the presence of nano particles in our environment. Silver in particular is being used increasingly in medical applications and can enter sewerage treatment systems and kill off bacterial action, even though they may only be present in parts per billion.
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