The magnetic stirrer, also referred to as the magnetic mixer, is a piece of equipment commonly used in the laboratory to mix and stir liquids automatically. It is an important device used in laboratories dealing with chemicals, biology, and quality assurance because of its unique stirring capacity.

How does it work?

The operation of a magnetic stirrer is based on magnetic forces that cause the rotation of a small bar within the solution without the necessity of using shafts.

• Stirrer base: In the main body of the stirrer, there is a stationary motor that turns a permanent magnet, or rather creates a rotating magnetic field through electromagnets, located close to the top plate of the unit.
• The Stir Bar (Flea): The stir bar is a tiny magnet that is coated with plastic and is placed directly into the vessel that contains the liquid substance, usually the beaker.
• Coupling: The stir bar is connected to the rotating magnet present in the base when the beaker is set onto the top plate. As the magnet rotates, the stir bar rotates at an equal pace.

Main Types of Magnetic Stirrers

1. Standard Magnetic Stirrers

• They are simple devices meant for the stirring of liquids at room temperature. They are very effective when stirring low-viscosity solutions.

2. Hot Plate Magnetic Stirrers

This is the most widely used type of laboratory magnetic stirrer. It incorporates both a heater and a stirring system. It enables the heating of the liquid to the desired temperature and also helps stir the liquid.

3. Multi-Position Stirrers

They have a wider top plate where there are various magnetic field positions beneath that enable stirring of several containers, including flasks and test tubes, at once. They stir these containers with uniform speed and temperature.

Important Parts of a Magnetic Stirrer

• Magnetic Stir Bar: Also known as a "flea," it consists of a magnetic stir bar that is enclosed in an inert substance, usually PTFE (Teflon), since it will not interact with chemicals while stirring. These stir bars are available in different shapes and sizes according to the size of the container and the thickness of the fluid.
• Control for Speed and Temperature: There are mechanical controls that adjust the speed, measured in revolutions per minute, and the temperature.