By Paul Webb, Micromeritics
There are a number of manual and automated methods for determining volume and density. This article, however, focuses on laboratory methods that are most often used in research and quality control applications. Another large area of application is on-line monitoring in production control. An excellent overview of density determinations in this application is by Capano.
The Density Enigma
When first introduced to density, perhaps in grade school, we were taught that it simply is the mass of an object divided by its volume. We thought that was pretty much the whole story, but sooner or later we discovered that this
definition was only the beginning. The difficulty in defining density is exemplified by the American Society for Testing and Materials' book of standard definitions (1) where one finds over forty definitions based on mass per unit volume. The British Standards Institute (2) has narrowed it down to fourteen types of densities.
Determining the mass of an object is rather straightforward; it is the determination of volume that conceals the difficulty. The ‘volume' of a solid object, whether a single piece or a mass of finely divided powder, is one of those concepts that can't be bundled up into a
single, neat definition.
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