Share

Magnetic Stirrer: Definition, Working Principle, Types, And How-To-Use It

Resource Description

Table of contents

What is a magnetic stirrer?

A magnetic stirrer is a device that is designed for stirring a liquid using a rotating magnetic field. It is a piece of lab equipment that is widely used for the preparation of solutions, especially for low viscosity fluid mixing. Magnetic stirrers are used in chemical and biological laboratories, in the food industry, etc.

What are the elements of a magnetic stirrer?

Let’s consider the elements of a magnetic stirrer with a hot plate.

  • A stir bar is a portable magnet that is immersed in the liquid.
  • A beaker with a cover (optional) on it is placed on the hot plate.
  • On the magnetic stirrer,there is a display (optional) and heat & rotation regulators to control the process.

A magnetic stirrer without a hot plate does not have a heat regulation knob.

How does a magnetic stirrer work?

The working principle of a magnetic stirrer is pretty simple.

A stir bar is immersed in a beaker with a liquid and a rotating magnetic field makes this stir bar rotate. Thus, the liquid is stirred.

It is recommended to use glass or other non-metal vessels so there is no interference with the magnetic field.

Choosing a magnetic stirrer

When deciding which magnetic stirrer to select, consider the following characteristics:

  • capacity - decide what capacity you need for your application, avoid exceeding the limit so you don’t damage your stirrer;
  • speed - it is stated in rotations per minute (or RPMs);
  • temperature - there are temperature ranges (specified by the manufacturer) within which your magnetic stirrer can be used;
  • size of the mounting surface - the bigger it is, the bigger vessel you can place on it;
  • stir bars should be suitable for the vessel you use. See the “Types of stir bars” section to select the best options for excellent performance.

Types of magnetic stirrers

If you are on the hunt for a magnetic stirrer, you know that there are plenty of options available. Let’s take a closer look at them.

Depending on the volume of liquid you are going to stir, there are:

If we consider how many stirring positions a magnetic stirrer has, there are:

You can also choose from magnetic stirrers with additional features:

There are also:

  • battery-powered or corded magnetic stirrers - battery-operated stirrers are perfect for places where there is no electrical outlet;
  • air-driven turbine magnetic stirrers that utilize low-pressure air supply to power the stirrer; one of their benefits is that the sparkling hazard from electrical sources is eliminated.

Types of stir bars

As a rule, stir bars are coated with glass or Teflon so they are not chemically reactive.

It is important to choose the right magnetic stirrer bar. Stirring magnets have different shapes, sizes, in addition, they are made of different materials.

A bone stir bar provides excellent stirring and high levels of stability even when the speed is slow. A great choice for a vessel with an arched bottom.

If you are using a flat-bottomed vessel, a round stir bar is a perfect option.

For vessels with a curved or uneven bottom, use a slide round stir bar.

A cross stir bar is ideal for stable stirring at high speeds.

An ellipse stir bar (also called an egg-shaped stir bar) is best suitable for use in beakers with a round bottom.

A prism (or triangular) stir bar can be effective even if the speed is slow. Thanks to its shape, it helps with dissolution, preventing sedimentation, etc.

A crown stir bar is perfect for use in cuvettes or test tubes. You can use other containers too.

How to use a magnetic stirrer? (a step-by-step guide)

To use a magnetic stirrer, follow a few simple steps.

(Optional) If your magnetic stirrer has a support stand, set it up. Just screw the 2 rods together, thus you will create 1 support rod. Then, insert the slotted end of the rod into the holder on the back of the base. After that, slip the right angle clamp onto the support rod. Tighten the knob. If there is a thermometer holder, slide it in, and tighten the other knob.

2. Place a beaker with a liquid on top of the stirrer platform.

3. Immerse a stir bar into the liquid.

4. Use the knob(s) on the magnetic stirrer to control the process.

WARNING: When using a magnetic stirrer with hot plate, the vessel (e.g. beaker, which must be suitable for hot plates) should be filled with a liquid, do not let the vessel boil dry.

In addition, when the hot plate is turned on, do not touch it to avoid burns.

PROS & CONS of a magnetic stirrer

As most things, magnetic stirrers have their advantages and disadvantages.

Pros

  • Magnetic stirrers offer a quieter and more efficient operation compared to other stirrer types.
  • In addition, such devices do not have moving external parts that are attached to them, there is just a magnetic stir bar that is portable and immersed in the solution for stirring.
  • As a result, we have less parts that can be worn out.
  • Magnetic stirrers are easy to clean and sterilize if necessary. The construction of a magnet stirrer does not require any lubricants that can contaminate the product and the vessel.
  • Thanks to its compact size, a magnetic stirrer doesn’t require much storage space.

Cons

  • They are not suitable for all applications. For most non-demanding stirring tasks, a magnetic stirrer is a great option. However, for large volumes and for viscous liquids, it is better to use an overhead stirrer, for example.

Conclusion

A magnetic stirrer is a device for stirring low-viscosity liquids. There are different types available. However, besides the selection of the stirrer for your needs, don’t forget to get the most suitable stir bars for the vessel you are going to use. After reading this article, you understand how a magnetic stirrer works and how to use it. In addition, knowing the types and the pros & cons of this device, you will get the best magnetic stirrer for your application. Shop with Mega Depot!

Related Products