Explanation : A gas pycnometer is a laboratory device used for measuring the density - or more accurately the volume - of solids. The devise employs use of some method of gas displacement and the volume-pressure relationship known as Boyle's Law. A gas pycnometer is also sometimes referred to as a helium pycnometer. While pycnometer (of any type) is recognized as density measuring devices, they are in fact devices for measuring volume only. ....Read more