Vätskepycnometers

A pycnometer, often referred to as a *vätskepycnometer* in Swedish (literally "liquid pycnometer"), is a laboratory instrument used to measure the density of liquids and solids with high precision. The term "pycnometer" originates from the Greek words *pyknós* (dense) and *métron* (measure). This device operates on the principle of displacement, where the volume of a known mass of a substance is determined to calculate its density.

The most common type of pycnometer is a glass bottle with a ground-glass stopper, often featuring a capillary tube to allow air bubbles to escape during filling. The bottle is typically calibrated to a specific volume, usually around 25 to 100 milliliters. To measure the density of a liquid, the pycnometer is first weighed empty, then filled with the liquid, and weighed again. The difference in mass divided by the known volume yields the density. For solids, the sample is placed inside the pycnometer, and the remaining space is filled with a liquid of known density (such as water or a solvent), allowing for indirect density calculation.

Pycnometers are widely used in chemistry, materials science, and quality control to ensure accurate density measurements, which are critical for applications like pharmaceutical formulations, petroleum products, and food science. They are particularly valuable when high precision is required, as they minimize errors associated with manual volume measurements. Modern variations include automated pycnometers that use digital scales and temperature control for enhanced accuracy and repeatability.