Gas pycnometry is a common analytical technique that uses a gas displacement method to measure volume accurately. Inert gases, such as helium or nitrogen are used as the displacement medium. The sample is sealed in the instrument compartment of known volume. The appropriate inert gas is admitted and then expanded into another precision internal volume. The pressure before and after expansion is measured and used to compute the sample volume. Dividing this volume into the sample weight gives the gas displacement density.
Reproducibility typically to within ± 0.01% of the nominal full-scale sample cell chamber volume, 1 cm3.
Reproducibility guaranteed to within ±0.02% of the nominal full-scale volume on clean, dry, thermally equilibrated samples using helium.
In house: AccuPyc II 1340 Micromeritics