Our air or gas pycnometer is an innovative measuring instrument for the determination of the air-filled pore volume, the solid volume as well as the solid density (dry bulk density) of a substrate sample in the laboratory. Especially the pore volume is a decisive factor for the evaluation of a soil for many questions of water balance, soil management or soil remediation. Air and water conductivity, as well as water and nutrient retention capacity are directly related to pore volume.

How does our air pycnometer work?

The measuring method is based on the fact that only the solid volume VF of a solid sample displaces gas, while pore or void volumes are filled with gas. The air or gas pycnometer consists of a measuring chamber and an additional chamber, which forms the additional volume Vz. The known additional volume is filled with compressed air or the connected gas and connected to the measuring chamber containing the substrate sample via a shut-off valve. Opening the valve results in pressure equalization within the two volumes.

Application areas

Our air or gas pycnometers are suitable for undisturbed soil samples as well as for bulk materials such as sands, gravels or plant granules.

• UGT air pycnometer uses atmospheric air compressed inside the instrument and does not require an external gas supply line like a gas pycnometer. An air pycnometer is thus somewhat faster and less complex to operate than a gas pycnometer. For soil samples with a very high percentage of fines, the applicability of the air pycnometer may be limited, in part because nitrogen will attach to the soil particles and distort the measurement result (Amoozegar et al. 2022). Air pycnometers are therefore only suitable for samples with coarse to medium pores. The same applies when using a gas pycnometer with nitrogen.
• The use of the UGT gas pycnometer with external gas connection enables the measurement with gases with defined properties under exclusion of influences by air components and air humidity (absorption and corrosion). This is particularly recommended for soil samples with a high fine content (such as clay).

The large measuring chamber with a volume of approx. 2100 cm³ enables the examination of correspondingly large samples.

For air as well as gas pycnometer are included:

• Mains cable
• Closing bracket with clamping screw
• Cover sample chamber
• Sealing ring

Required accessories for gas pycnometer: Supply hose for external gas

Optional accessories: Additional volume 100 cm³ for air pycnometer (Art.-No.: 1480100)