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Magnetic stirrers

A magnetic stirrer consists of a small magnetic bar (called a stirring bar) that is normally covered by a layer of plastic (usually Teflon) and a plate under which is a rotating magnet or a series of electromagnets arranged in a circular shape in order to create a rotating magnetic field. It i...

A magnetic stirrer consists of a small magnetic bar (called a stirring bar) that is normally covered by a layer of plastic (usually Teflon) and a plate under which is a rotating magnet or a series of electromagnets arranged in a circular shape in order to create a rotating magnetic field. It is very common for such a plate to have an assembly of electrical resistances in order to provide it with the necessary heat to heat some chemical solutions. During the operation of a typical magnetic stirrer, the magnetic stirring bar (also colloquially called flea, fly, bean or magnetic bullet) is slipped into a container either a flask or beaker – preferably borosilicate glass – containing some liquid to shake it. The container is placed on top of the plate where the magnetic fields or the rotating magnet exert their influence on the coated and promote its mechanical rotation.

Magnetic stirrers are preferable over gear mechanism ones because they are quieter, more efficient, and have no moving parts that can break or wear (only the stirring bar itself). Due to its small size, the stirring bar is easier to clean and sterilize than other stirring appliances.

Magnetic stirrers solve two major problems by being used in place of motorized stirrers. First, motorized agitators require the use of lubricants, which at any given time can contaminate the reagents. Second, in a motorized agitator it can be a problem to hermetically seal the rotating mechanical connection of the motorized agitator in the case of a closed system (because it requires environmental regulation or because it is a process in which there must be an absence of dust, water or oxygen).

A magnetic stirrer magnet or stirring bar is a small magnetic bar or magnet used to remove a liquid mixture or solution, when placed inside a container arranged over a magnetic stirrer,usually in a laboratory.

Operation

The circular motion of the magnetized bar is driven by another magnet or set of electromagnets (i.e. coils), located below the surface on which the vessel containing the liquid rests and possessing a rotational motion, the speed of which can be controlled. Since glass does not appreciably affect a magnetic field (it is transparent to magnetism), and most chemical reactions take place in glass vessels (beakers, Erlenmeyer flasks, etc.), these magnetic stirring rods work well in those glass containers.

Structure

These magnetized bars are usually coated with Teflon, or less often glass. Glass coatings are used for liquid alkali metals (except bleach, which corrodes glass), and solutions of alkali metals in ammonia. Both layers are chemically inert and do not contaminate or react with the reaction mixture inside.

They are shaped like an elongated bar with octagonal section, and often circular, although there are a variety of special shapes for more efficient agitation. Most stirring bars have a flanting around the center (called a pivot ring) on which they rest when rotating. The smallest are only a few millimeters long and the largest can be a few centimeters long.

An agitator magnet recuperator is made up of a magnet attached to the end of a long rod (usually coated with Teflon), which can be used to capture or retrieve the stirring bar inside the container.

A magnetic stirrer can be as simple as a rotating magnet, under the container containing the stirring bar. Most magnetic stirrers spin their magnets with an electric motor, and some also have a heating element.

Stirring bars work best with relatively small amounts of liquid (a few liters of volume at most) that are not very viscous. For larger volumes or more viscous liquids, some kind of mechanical agitation is usually necessary.

Agitador magnético PCE-MSR 50 Agitador magnético PCE-MSR 50

PCE-MSR 50

Agitador magnético PCE-MSR 50

Agitador magnético con capacidad de 1 l. Ajuste de la velocidad de agitación.
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Product Data Sheet:

pdf PCE-MSR-50.pdf

Price:

€42.23 (inc. VAT)
€34.90 (Excl. VAT)
5 Available
2-3 business days
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