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A stir bar (or flea) is a magnetic bar, used to stir a chemical reaction mixture or solution in a laboratory. The stir bar rotates (and thus stirs) in synch with a separate rotating magnet located beneath the vessel containing the reaction. 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). This allows magnetic stir bars to work well in glass vessels. In physics, magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials. ...
A chemical reaction is a process involving one, two or more substances (called reactants), characterized by a chemical change and yielding one or more product(s) which are different from the reactants. ...
A mixture is a combination of two or more substances, often chemicals, in which the substances remain chemically distinct, retaining their particular composition and properties. ...
Dissolving table salt in water In chemistry, a solution is a homogeneous mixture of one or more substances (the solutes) dissolved in another substance (the solvent). ...
The materials definition of a glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly, thereby not giving enough time for a regular crystal lattice to form. ...
Current flowing through a wire produces a magnetic field (M) around the wire. ...
Illustration of a Beaker A beaker is a type of laboratory glassware which consists of a cylindrical cup with a notch on the top to allow for the pouring of liquids. ...
Stir bars are typically coated in teflon (or less often in glass), so that they are chemically inert and do not contaminate or react with the reaction mixture they are in. They are bar shaped and often octagonal in cross-section (sometimes circular), although a variety of special shapes exist for more efficient stirring. Most stir bars have a ridge around the center (called a pivot ring) on which they rotate. The smallest are only a few millimeters long and the largest a few centimeters. Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910-1994) of DuPont in 1938 and introduced as a commercial product in 1946. ...
Inert is the state of doing little or nothing. ...
The Lachine Canal, in Montreal, is badly polluted Pollution is the release of harmful environmental contaminants, or the substances so released. ...
A stir bar retriever is a separate magnet on the end of a long stick (usually coated with teflon) which can be used to get (or fish) stir bars out of the reaction vessel.
The magnetic stirrer can be as simple as a magnet spun by flowing air or water, on which the reaction vessel containing the stir bar sits. Most magnetic stirrers today spin their magnets with an electric motor. If it also has a heating element, it is referred to as a 'hot plate stirrer'. A magnetic stirrer consists of a small bar magnet, which is normally wrapped in plastics like Teflon and a stand or plate containing a rotating magnet. ...
Electric motors of various sizes. ...
A magnetic stirrer consists of a small bar magnet, which is normally wrapped in plastics like Teflon and a stand or plate containing an electromagnet. ...
Stir bars work best for relatively small reactions (a few liters volume at most) that are not very viscous. For larger volumes or more viscous liquids, some sort of mechnanical stirring is typically needed.
Link to a variety pack of stir bars at Fisher Scientific
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