Magnetic stirrers are of numerous sizes. Each size is best suited for a particular range of applications. When selecting one for your application, there are several factors to consider. Here are some things you need to think about.
The Volume of Fluid You’re Stirring
If you are dealing with smaller volumes and vessels, the magnetic stirrer should be small enough so it won’t touch the sides of the vessel while spinning. On the other hand, it’s advisable to get a larger stir bar when dealing with larger volumes. Larger magnetic mixdrive stirring drives deliver more motion, boosting mixing efficiency.
The Shape of the Vessel and Opening Size
Before you choose a magnetic stirrer, you should consider the shape and opening size of the vessel. For instance, if you want to stir the contents of a round-bottomed flask that has a wider diameter in the middle, you will still need a smaller bar.
This is done so there is no catching near the bottom on the sides of the flask. On the other hand, you may also have some vessels that have a small opening. This means the desired bar won’t be able to fit. While this is rare, you will have to go smaller if it happens.
The Size of the Internal Drive Magnet
The drive magnet size also determines the stir bar size. It’s important to ensure that the length of the bar is almost the same as the magnet size. This will help to avoid spinouts. Spinout happens when the stirrer loses its coupling with the internal magnet.
The result is that the bar will stop spinning altogether. Apart from that, stir bars that are a bit longer than the internal magnet can lower the maximum spinning speed of the bar. These are some factors to consider when selecting the right size of magnetic stirrer.