Magnetic stirrer

Magnetic stirrer

A Magnetic Stirrer is a laboratory device used to mix liquid samples with a rotating magnetic field. It consists of a small bar magnet and a plate containing a rotating magnet. The bar magnet, often coated with plastic or glass, is immersed in the liquid to be stirred. The plate, usually powered by an electric motor, generates a rotating magnetic field that causes the bar magnet to spin and stir the liquid. Magnetic stirrers are preferred over mechanical stirrers in many laboratory applications because they reduce the risk of contamination and can be used in closed systems.

History

The invention of the magnetic stirrer is attributed to Arnold O. Beckman, a prominent American chemist, and inventor. Beckman developed the first magnetic stirrer as part of his work in the 1940s. The device simplified many laboratory procedures and has since become a staple in laboratories around the world.

Design and Operation

A typical magnetic stirrer consists of a flat plate with a rotating magnet beneath it. The user places a container with the liquid on the plate and immerses a magnetic stir bar in the liquid. When the device is turned on, the rotating magnet beneath the plate creates a magnetic field that causes the stir bar to rotate, thereby stirring the liquid. Some advanced models of magnetic stirrers include heating elements, allowing the user to control the temperature of the liquid being stirred. These models are known as hotplate stirrers and are particularly useful in experiments where temperature control is crucial.

Applications

Magnetic stirrers are widely used in chemistry and biology laboratories for mixing solutions, dissolving solids in liquids, and promoting chemical reactions by ensuring homogeneous liquid samples. They are essential tools in research and development, quality control, and education.

Advantages

Magnetic stirrers offer several advantages over traditional mechanical stirrers:

• Reduced risk of contamination, as the stir bar can be easily sterilized and is the only part of the stirrer that comes into contact with the liquid.
• The ability to stir closed systems without the need for a seal that could potentially leak.
• Precise control over stirring speed.
• Simplicity and ease of use.

Limitations

Despite their advantages, magnetic stirrers have limitations:

• They are less effective for stirring viscous liquids or large volumes.
• The magnetic coupling between the stir bar and the rotating magnet can be disrupted, causing the stir bar to stop spinning.
• Stir bars can be lost or damaged, requiring replacement.

See Also

• Laboratory equipment
• Stirring rod
• Vortex mixer