Magnetic stirrer

November 2, 2021

Magnetic stirrers are electronic equipment that use a magnetic bar to stir a substance. It is equipment that minimizes reagent contamination and operates quietly.

What is it?

It is an equipment that consists of a magnetic bar, known as a stirring bar, covered with a Teflon layer and a plate underneath in which there is a rotating magnet or electromagnets arranged in a circular shape that form a rotating magnetic field. This magnetic field makes it possible to mix a solvent and one or more solutes.

Some plates have electrical resistances to provide heat for some chemical solutions that need it.

For its operation, the container is placed on the plate, usually a flask or beaker, and the stirring bar is placed inside the liquid, the rotating magnet exerts its influence on the bar and promotes its rotation inside the liquid.

Arthur Rosinger was the one who obtained the patent of the magnetic stirrer on June 6, 1944 and its first application was on October 5, 1942. The plastic coating of the bar was created by Edward McLaughlin employee of the Torpedo Experimental Establishment (TEE) laboratories.

Characteristics

The magnetic stirrer is made up of magnetized bars covered with Teflon or glass (this coating is used in cases of liquid alkali metals and alkali metal solutions in ammonia) both layers are inert and do not contaminate or react with the mixture.

The bars are elongated and have an octagonal section, some are specially shaped for more efficient stirring. They have a rim around the center that they rest on when turning.

The stirrer also has a plate that contains magnets or an electromagnet that provides the necessary magnetic field to cause the stirrer to start rotating.

It also has a stirrer magnet recuperator. It is made up of a magnet attached to a Teflon-coated rod. It is used to recover the stir bar from inside the container.

This equipment works with small amounts of mixture, which do not exceed a certain number of liters, and substances that are not very viscous.

Advantage

  • They are quiet, efficient equipment and do not have moving parts that can wear out, with the exception of the stir bar.
  • Due to the small size of the bar, it is easier to clean than other equipment.
  • It does not contaminate the mixture because it does not require the use of lubricants.

Disadvantages

It must be used in laboratory-level experiments and chemical analysis due to its inability to mix highly viscous liquids, large amounts of mixtures, and thick suspensions.

How is it used?

  • Place the beaker or flask with the contents on the stir plate.
  • The bar is introduced into the container.
  • The hob is turned on and the speed is adjusted, starting with the lowest until the appropriate speed is reached.
  • Check that the liquid does not leak out of the container.
  • At the end, the speed is adjusted to its initial position and the hob is turned off.
Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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