pyknometrin

Pyknometrin is a term often used to refer to a pycnometer, a laboratory instrument designed to measure the density of liquids and solids by determining volume electronically or by displacement. In some languages the word pyknometrin denotes the same device or the method of pycnometry, and it is used in chemistry, materials science, and related fields to obtain accurate density or specific gravity values.

The basic principle relies on the relationship between mass, volume, and density. A known volume vessel is weighed empty, then filled with a liquid or with a sample and liquid, and weighed again. For liquids, the density is determined directly from the mass of liquid in a known volume. For solids, a sample is introduced into the pycnometer filled with a liquid; the mass difference between filled and empty states allows calculation of the sample’s volume via buoyancy and displacement, from which the density of the solid can be derived. Temperature control is essential, as liquid density and the volume of the vessel change with temperature.

There are two common variants. Gas pycnometers use a calibrated chamber and a reference gas (often helium) to determine volume from gas compression and expansion, offering very precise solid-volume measurements. Liquid pycnometers use immersion or displacement with a liquid of known density, commonly water or organic solvents, which may require careful drying of the sample and solvent compatibility considerations.

Applications include determining the true density of powders, grains, polymers, ceramics, and metals; assessing porosity and moisture content; and supporting quality control and material characterization in research and industry. Standards from various regulatory bodies describe recommended procedures for pycnometry and related density measurements.