Gázpycnometria

Gázpycnometria, also known as gas pycnometry, is a technique used to determine the absolute true density of a solid material. It works by measuring the volume of a solid sample by displacing a gas, typically helium. The principle is based on Boyle's Law, which states that for a fixed amount of gas at constant temperature, the pressure and volume are inversely proportional.

In a gas pycnometer, the sample is placed in a chamber of known volume. This chamber is then filled with a gas, and the pressure is recorded. The gas expands into an empty reference chamber that is connected to the sample chamber. By measuring the change in pressure as the gas expands, the volume occupied by the solid sample can be calculated. The density is then determined by dividing the mass of the sample by its measured volume.

This method is particularly useful for porous or irregularly shaped solids where traditional liquid displacement methods are difficult or inaccurate. The gas can penetrate into small pores and crevices, providing a more precise measurement of the true skeletal volume and thus the true density of the material. Gas pycnometry is widely used in various fields, including materials science, pharmaceuticals, and food science, for characterizing powders, ceramics, catalysts, and other solid materials. It is a non-destructive technique, meaning the sample is not altered during the measurement process.