Our Micromeritics Multypc is an automated gas pycnometer capable of determining absolute density of a wide range of solids to near reference value accuracy following ASTM D4892.
Using ideal gases such as helium, and employing Charles’ Gas Law, a reference volume can be pressurised to a known value before allowing this charge to pass into the unknown chamber of known volume which contains a known mass of the sample. The resulting pressure is the final variable in the equation P1xV1=P2xV2 (for a stable temperature – going back to high school physics here!) which allows the sample volume to be calculated and from the known mass, the density is determined. This is a skeletal or absolute density and considers surface pores accessible to the gas but not internal or ‘locked’ pores. Larger molecule sized gases (eg Ar) and non-ideal gases (eg air) may be used with caution when closed-pore membranes such as some neoprenes are being tested and diffusion through the walls would be possible with helium.
Bulk and tamped densities are tested in accordance with the relevant ASTM/AS standards (eg ASTM C29, D6683, D7481).
