LABORATORY FURNITURE

A magnetic stirrer or magnetic mixer is a laboratory device that employs a rotating magnetic field to cause a stir bar (or 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. It is used in chemistry and biology where other forms of stirring, such as motorized stirrers and stirring rods, may not be viable.

A magnetic stirrer consists of a magnetic bar placed within the liquid which provides the stirring action. The stir bar’s motion is driven by another rotating magnet or assembly of electromagnets in the stirrer device, beneath the vessel containing the liquid. Stir bars are typically coated in PTFE, or, less often, in glass; the coatings are intended to be chemically inert, not contaminating or reacting with the reaction mixture they are in. Glass may be viable as an alternative if PTFE is unsuitable due to high temperature or chemical attack. In dissolving metal reductions that use an alkali metal dissolved in a primary amine, PTFE may be attacked to some extent.  Birch reductions (a common dissolving metal reduction) are often conducted in a glass vessel, thus indicating that a glass stir bar would likewise be compatible. Glass can be attacked by strong alkali (such as lye) depending on heat, exposure time, and concentration.