Gas pycnometry is recognized as one of the most reliable techniques for obtaining true, absolute, skeletal, and apparent volume and density. This technique is non-destructive as it uses the gas displacement method to measure volume. Inert gases, such as helium or nitrogen, are used as the displacement medium. Density calculations using the gas displacement method are much more accurate and reproducible than the traditional Archimedes water displacement method.
Density Measurement
Density specifies how much of a substance occupies a defined volume at a stated temperature and pressure. The density of a substance can be used to define the substance and it performance character. Controlling the density of finished goods is often desirable for performance as well as economic considerations. For this reason, many manufacturers strive to develop materials that are partially porous yet still fulfill their function while others seek an end product of maximum density. In the manufacture of foams, density is a function of the chemistry used to produce the foam, of additives used to increase the density, and of any additives used to improve the combustion resistance properties of the foam. Accurate density measurements are an important part of characterizing the physical properties of ceramics. Density is used to determine the desired performance of parts created using Additive Manufacturing. It is also a key element utilized in Pharmaceutical Roller Compaction operations and can be used as an indicator of tablet strength and dissolution. Density influences the overall quality of manufactured products and density measurements guide the manufacturing process. For this reason, Micromeritics gas pycnometers (AccuPyc and GeoPyc) are used worldwide to characterize raw materials as well as to determine the density of finished products.
Density Type |
Material Volume |
Open-Pore Volume |
Closed-Pore Volume |
Inter particle Volume |
External Void Volume |
Addressed by |
True (Absolute) The mass of a substance divided by its volume, excluding open and closed (or blind) pores
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AccuPyc II |
Skeletal (Apparent) The ratio of the mass of the solid material to the sum of the volume including closed (or blind) pores
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AccuPyc II |
Envelope The ratio of the mass of a substance to the envelope volume (imaginary boundary surrounding the particle)
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GeoPyc |
Bulk Mass of the material divided by the volume occupied that includes interstitial space
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GeoPyc |
TAP Apparent powder density obtained under stated conditions of tapping
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GeoPyc w
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