A magnetic stirrer or magnetic mixer is a laboratory device that employs a rotating magnetic field to cause a stir bar (also called “flea”) immersed in a liquid to spin very quickly, thus stirring it. The rotating field may be created either by a rotating magnet or a set of stationary electromagnets, placed beneath the vessel with the liquid. Since glass does not affect a magnetic field appreciably (it is transparent to magnetism), and most chemical reactions take place in glass vessels (i.e. see beaker (glassware) or laboratory flasks), magnetic stir bars work well in glass vessels. On the other hand, the limited size of the bar means that magnetic stirrers can only be used for relatively small (under 4 liters) experiments. They also have difficulty dealing with viscous liquids or thick suspensions. For larger volumes or more viscous liquids, some sort of mechanical stirring is typically needed.
ETL-2-Gallon PID Magnetic Stirrer w/ 11″ Heated Plate
Available on backorder