A pycnometer is a common science equipment found in laboratories. It is used to measure the density or rather volume of solids. It uses an inert gas such as helium or nitrogen. Hence, sometimes it is also known as helium pycnometer. A pycnometer can measure solids that are porous/non-porous, regularly shaped, granular, powdered, monolithic and even comminuted.
This laboratory equipment is based on Boyle’s Law which determines the volume-pressure relationship.
How is Pycnometer Useful?
A pycnometer makes the process of measurement simple and quick. It doesn’t require enough manpower to operate. It is also very affordable equipment.
What are the Applications of a Pycnometer?
A pycnometer is used for characterizing:
- Metal Powders
- Heterogeneous catalysts
- Petroleum coke
- Pharmaceutical ingredients
- Other construction materials
It is also used to determine the density of viscous materials.
What are Different Types of Pycnometers?
There are broadly two types of pycnometers:
Gas Expansion Pycnometer
Also known as constant volume gas pycnometer, it comprises two chambers – sample and reference. A sample is put in the sealed chamber located in the pycnometer. Then, the pressure is applied as per the target measure. The readings are recorded. The opening of the expansion valve situated between the sample chamber and the reference chamber let the gas expand to the reference chamber. This, in turn, creates a pressure drop ratio which verifies the density/volume of the said sample. It does so by comparing the recorded readings to the volume of a standard measured earlier through a similar process.
Variable Volume Pycnometer
Also known as gas comparison pycnometer, it consists of single or dual variable volume chambers. The cell volume for the sample can vary according to types and size. After the sample is placed in the sample chamber, a piston is placed at the initial position simultaneously. Then the valve is opened and gas is filled in pycnometer. The valve is closed after which the initial gas pressure in the pycnometer is measured using an absolute pressure transducer. The piston is moved to another position to measure the final pressure.
A pycnometer is a very important science laboratory equipment for scientific and many other types of research.
Also Read: What are Hydrometers and it's uses