NationMaster - Encyclopedia: Magnetic stirrer

A magnetic stirrer is a type of laboratory equipment consisting of a rotating magnet or stationary electomagnets creating a rotating magnetic field. The stirrer is used to cause a stir bar, immersed in a liquid to be stirred, to spin very quickly, stirring it. Often, the stirrer can provide heating. Image File history File links Metadata Size of this preview: 450 Ã— 600 pixelsFull resolution (1536 Ã— 2048 pixel, file size: 216 KB, MIME type: image/jpeg) File historyClick on a date/time to view the file as it appeared at that time. ... A stir bar (or flea) is a magnetic bar, used to stir a chemical reaction mixture or solution in a laboratory. ... A Mini-Vortexer with micro-centrifuge tube. ... Three static mixers: The top is an alternating spiral with each spiral offset by 90Â°; the second is the above in a delivery tube, such as for epoxy; the last is a larger metal mixer used to divide a flow into streams that intersect at 90Â°. - Static Mixers use the... For other uses, see Magnet (disambiguation). ... A stir bar (or flea) is a magnetic bar, used to stir a chemical reaction mixture or solution in a laboratory. ...

Stirrers are often used in laboratories, especially in the field of chemistry. They are preferred over gear-driven motorized stirrers in chemical research because they are quieter, more efficient, and have no moving parts to break or wear out (other than the simple bar magnet itself). Due to the small size, the stirring bar is more easily cleaned and sterilized than other stirring devices. For other uses, see Chemistry (disambiguation). ...

Magnetic stirrers solve two major problems with using motorized stirrers. Firstly, motorized stirrers use lubricants, which can contaminate the vessel and the product. Secondly, in motorized stirrers, the sealing of the connection between the rotating shaft of the stirrer and the vessel can be a problem, especially if a closed system is needed (e.g. due to OSHA, or environmental regulations, or because a process works only if oxygen, water or dust is absent). If you are searching for the organization, click OSHA. Osha (Ligusticum porteri) is a perennial herb used for its medicinal properties. ...

The magnetic stirrer also has its drawbacks: the limited size of the stirring bar means it can only be used for lab size experiments. In addition, viscous liquids or thick suspensions are extremely difficult to stir using this method, although there are some models with special magnets to overcome this problem.

History

Arthur Rosinger of Newark, New Jersey, U.S.A. obtained US Patent 2,350,534, titled Magnetic Stirrer on 06 June 1944, having filed an application therefor on 05 October 1942. Mr. Rosinger's patent includes a description of a coated bar magnet placed in a vessel, which is driven by a rotating magnet in a base below the vessel. Mr. Rosinger also explains in his patent that coating the magnet in plastic or covering it with glass or porcelain makes it chemically inert.

The plastic-coated bar magnet was independently invented in the late 1940s by Edward McLaughlin, of the Torpedo Experimental Establishment (TEE), Greenock, Scotland, who named it the 'flea' because of the way it jumps about if the rotating magnet is driven too fast. This article does not cite any references or sources. ... For other uses, see Greenock (disambiguation). ... This article is about the country. ...

An even earlier patent for a magnetic mixer is US 1,242,493, issued 09 October 1917 to Richard H. Stringham of Bountiful, Utah, U.S.A. Mr. Stringman's mixer used stationary electromagnets in the base, rather than a rotating permanent magnet, to rotate the stirrer.

The first multipoint magnetic stirrer was developed and patented by Salvador Bonet of SBS Company in 1977. He also introduced the practice of noting the denomination of stirring power in "liters of water", which is a market standard today.

External links

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