Magnetic Stirrer- Principle, Parts, Types, Uses, Examples


A magnetic stirrer is a laboratory device that uses a rotating magnetic field to make a stir bar or rod immersed in a liquid spin very quickly, thus stirring or mixing it . The magnetic field may be created by a rotating magnet or a set of stationary electromagnets under the vessel . A magnetic stirrer may have a heating system to heat the liquid . It is used in chemistry and biology where other forms of stirring may not be viable. It can have different speeds, volume capacities, and positions, and be powered by battery or plug-in.

A magnetic stirrer consists of a magnetic bar placed within the liquid which provides the stirring action. The stir bar`s motion is driven by another rotating magnet or assembly of electromagnets in the stirrer device, beneath the vessel containing the liquid . Stir bars are typically coated with PTFE or glass, so they are chemically inert and do not contaminate or react with the solution they are in . Their shape may vary to increase efficiency during stirring. Their size varies from a few millimeters to a few centimeters. The smaller sizes are often referred to as "fleas".

Magnetic stirrers are simple, silent, and easy to use devices that can mix liquids for various purposes. They can also heat the liquids if needed. They are widely used in laboratories for chemical experiments and synthesis, microbiology, biochemistry, oil analysis, soil suspending, buffer solutions preparation, pH measurement, and more . They have many advantages over other stirring methods, such as preventing intense boiling, boosting reaction rate and evaporation rate, allowing stirring in closed systems without isolation, reducing contamination risk, and occupying less space . However, they also have some limitations, such as being ineffective for dispersing nanoparticles, viscous liquids or thick suspensions, and large volumes .

In this article, we will discuss the principle, parts, types, uses, examples, advantages, limitations, and precautions of magnetic stirrers in detail.