gázpycnométer

A gas pycnometer is an analytical instrument used to determine the true density of solid materials, powders, and porous substances. The device operates on the principle of measuring the volume displaced by the sample when saturated with an inert gas, typically helium, under controlled temperature and pressure conditions. The apparatus is composed of a sealed measurement chamber, a gas filling line, a gauge system for pressure and temperature monitoring, and a calibration system that allows for precise volume determinations.

During measurement, the chamber is first evacuated to remove ambient air, then filled with a known quantity of helium. The sample is introduced into the chamber, and the pressure rise due to the displaced gas is recorded. By applying the ideal gas law and accounting for the temperature of the system, the exact volume occupied by the sample can be computed. The true density is then calculated by dividing the mass of the sample—measured with an analytical balance—by this volume. Because helium atoms are small and inert, they penetrate virtually all types of pores, providing a highly accurate representation of the material’s void space.

Gas pycnometers find widespread use in pharmaceutical, polymer, metallurgy, and geology industries for quality control, property characterization, and research. They are crucial in determining intrinsic material properties such as mechanical strength, optical characteristics, and porosity, all of which depend on accurate density measurements. Modern devices offer automation, digital readouts, and connectivity to laboratory information systems, thereby improving throughput and data integrity. International standards such as ASTM D2874 and ISO 8318 provide guidance on test procedures to ensure comparability and reproducibility across laboratories.