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What Is a Pycnometer?

Mal Baxter
Mal Baxter

A pycnometer is a piece of laboratory equipment or glassware used to measure material properties of substances. It may resemble a measurement bottle with a hole or protruding glass stopper, a sealed steel gravity cup, or even a high-tech kitchen blender, with a vessel sitting on a base with readout controls. This vessel performs fast, precision measurement of density or specific gravity of a liquid.

The bottle uses standard measurements and calculates volume by displacement of its liquid. Forcing a liquid out a small hole via gas or pressure allows instant comparisons to be made between volume measurements. This allows rapid assessment of the porous nature of substances possible, and makes this labware a powerful addition to a facility.

Scientist with beakers
Scientist with beakers

Multiple characteristics of the liquid volume can be measured and compared before and after displacement. These may also be understood by calculating comparisons to a water-filled vessel. Liquid factors may include density, time-related pressure equilibrium, proportional solids content, and overall pore volume. The pycnometer performs most of its analyses in minutes to provide a host of content calculation profiles. Its speed and accuracy contribute to time-critical lab processes and benefit reporting time and productivity.

Using a pycnometer provides quick measurements through a minimal number of steps. These may consist of filling the device with water to get a weight measurement to calculate volume and then comparing that result to the vessel filled with the target substance. Accuracy and precision are vital to such processes, so some equipment is designed especially to withstand pressures from gas and liquid viscosities in order to completely fill the bottle. Some components are manufactured from solid bar metals in order to prevent liquid from entering the bottle's threads and also to eliminate surface imperfections that could affect accuracy.

Types of pycnometer bottles differ in some ways, depending not only on material but also in the size of sample chambers. Some models use computer software to process their analysis modules. These can be linked with chambers of varying dimensions integrated into one analysis process. This permits increased throughput of materials ranging from liquids and powders to solids and slurries. Such flexibility can ensure that testing is not complicated by inconsistencies.

The degree of performance of a pycnometer may range from low tech to high tech. Some devices are capable of enhanced operational ranges and automation. Pre-programmed sample standards may assist in the analysis; the procedure can be further simplified through the use of a software interface that groups varying samples in a clear manner. Some also permit the control of temperature variables or operation in a glove box for analysis in a controlled environment.

Discussion Comments


The botte pycnometer is out of date. Most scientists are using the gas pycnometer G-DenPyc 2900 to test the density, by the gas displacement principle.

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      Scientist with beakers