Gazpyknometria

Gazpyknometria, also called gas pycnometry, is an analytical technique used to determine the volume and density of solid materials by measuring gas displacement in a calibrated chamber. The method relies on the principle of gas behavior under pressure, typically employing helium due to its small molecular size. By recording pressure changes as known reference volumes are evacuated and filled with gas at a controlled temperature, the volume of the sample can be calculated. The density is then obtained by dividing the sample mass by this volume, yielding a true or skeletal density that reflects the solid material.

Procedure in brief: a dry, pre-weighed sample is placed in a pycnometer, and the system is evacuated. Gas is introduced, and pressure readings are taken at several steps. Using calibration data and Boyle’s law, the sample’s volume is determined. Temperature control is essential, and results are reported with an associated uncertainty. Gas choice (commonly helium) allows access to interconnected pores, enabling assessment of porosity when combined with complementary bulk density measurements.

Applications: gazpyknometria is widely used in materials science and engineering to characterize ceramics, powders, minerals, catalysts, polymers, and pharmaceuticals. It provides a rapid, non-destructive means to determine true density and to infer porosity, quality, and consistency across production batches or processing conditions.

Advantages and limitations: the method is fast, requires only small samples, and is solvent-free. Limitations include sensitivity to moisture or chemical reactivity with the test gas, strict temperature control requirements, and potential interpretation challenges for materials with significant closed or inaccessible porosity. Proper calibration and sample preparation are essential for reliable results.

See also: pycnometry, skeletal density, true density, porosity.