A hot plate stirrer or a hot plate magnetic stirrer is a laboratory instrument that is typically used to stir and heat the solution simultaneously. This helps the person performing the experiment speed up the reaction and properly dissolve the solute in the solvent.
Working of Hot Plate Stirrer
A hot plate stirrer typically works on the basis of a rotating electromagnetic field. The internal structure of the hot plate is embedded with a number of electromagnets. A magnetic bar, also known as a stir bar, is placed in the container that contains the solution. The bar is coated with a non-reactive material; therefore, is chemically inert in nature. It is required to be properly immersed into the solution. The beaker or flask containing the solution and the stir bar is placed on the top of the hot plate. The hot plate stirrer is equipped with two controlling knobs. One of the knobs is used to adjust the temperature of the device, while the other knob is used to control the speed of rotation. When the main switch of the hot plate stirrer is turned on, the heating mechanism and the electromagnets get activated. The heating mechanism heats up the solution and an electromagnetic field builds up. This electromagnetic field produced by the device interferes and interacts with the still magnetic field of the bar magnet causing the solution to rotate and get mixed up properly. Thereby, causing the solution to mix and heat up at the same time. For proper and even stirring, the container must be placed in the centre of the hot plate. The size of the magnetic bar should be selected on the basis of the viscosity and volume of the solution.
Advantages and Uses of Hot Plate Stirrer
1. A hot plate stirrer is used in biology and chemistry labs to speed up reactions.
2. Hot plate stirrers are being used in place of mechanical stirrers as they reduce effort, do not produce noise, and are comparatively more efficient.
3. Hot plate stirrers have less wear and tear as they do not make use of movable mechanical components.
4. A hot plate stirrer is compact and portable in nature.
Disadvantages of Hot Plate Stirrer
1. The size of the magnetic bar is required to be varied again and again as per the nature of the solution.
2. The size of the bar is limited. Hence, the device can only be used for small scale experiments.