gaspyknometer

A gas pyknometer is a laboratory instrument used to determine the density of a solid or liquid by measuring the volume of a gas that displaces a known mass of the substance. This method is particularly useful for porous or finely powdered solids that are difficult to measure accurately with traditional liquid displacement methods. The pyknometer typically consists of a sealed container with a known volume and a mechanism for introducing the sample and a non-reactive gas, often helium.

The principle behind the gas pyknometer relies on the ideal gas law. By measuring the pressure and temperature of the gas before and after it fills the volume occupied by the sample, the volume of the solid can be calculated. First, the volume of the empty pyknometer is calibrated. Then, a known mass of the sample is introduced, and the gas is allowed to fill the remaining volume. By observing the pressure change, the volume of the sample can be determined. Knowing the mass and volume of the sample, its density can be calculated. This technique avoids issues associated with gas adsorption or reaction with the sample, as helium is chosen for its inertness. Gas pyknometry is a precise method for characterizing materials where accurate volume determination is crucial.