pycnometeri

Pycnometeri is a term sometimes used to refer to pycnometers, specialized laboratory instruments used to determine the density and volume of solids, powders, and porous materials by liquid or gas displacement. In standard English texts, the instrument is called a pycnometer, and the plural is pycnometers; the form pycnometeri may appear in some non-English contexts or Latinized usage.

There are two main variants: gas pycnometers and liquid pycnometers. Gas pycnometers determine true density by measuring the volume of a sample with a gas in a sealed chamber at controlled temperature and pressure, applying the principles of gas behavior (typically Boyle’s law). The chamber has a known fixed volume, and changes in gas pressure are used to calculate the sample’s volume; density is then obtained from the sample mass divided by this volume. Liquid pycnometers determine density by immersing the solid in a reference liquid of known density and measuring the volume displaced. The method relies on Archimedes’ principle: the volume of liquid displaced equals the volume of the solid, allowing calculation of true density from the mass of the solid and the displaced liquid.

Typical procedure for a liquid pycnometer involves cleaning and drying the apparatus, weighing the empty pycnometer, calibrating with the reference liquid to establish its volume, and weighing the sample. The solid is introduced into the pycnometer with the liquid, and the masses are recorded to compute the density. Gas pycnometer procedures emphasize stabilizing temperature, sealing the chamber, and recording pressure changes to deduce volume.

Applications include determining true densities of powders, ceramics, polymers, and minerals, assessing porosity and material quality, and comparing manufacturing batches. Limitations include chemical incompatibility between the sample and the reference liquid, effects of surface tension, and the need for careful temperature control.