A pycnometer is typically a glass container whose known volume is used to determine the density of liquids, powders, and granules. By placing both the powdered sample and a liquid of a known volume into the pycnometer, the density, or volume, of the sample can be determined through a series of equations.
First, the combined mass of the sample and liquid is subtracted from the previously measured mass of the sample, in order to determine the mass of the liquid. This calculated mass is then divided by the known density of the liquid to determine the volume of the fluid within the pycnometer. Finally, the density of the powdered sample is calculated by the difference between the total volume of the pycnometer and the volume of the fluid.