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  • Scienceware 371130208 PTFE Round Spinbar Magnetic Stirrer Bar, with Tapered Ends, 20mm Length, 8mm Diameter
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Scienceware 371130208 PTFE Round Spinbar Magnetic Stirrer Bar, with Tapered Ends, 20mm Length, 8mm Diameter

1 customer review

Price: $6.49 + $2.99 shipping
In stock.
Usually ships within 4 to 5 days.
Ships from and sold by OpticsPlanet, Inc.
20mm Length x 8mm Diameter
  • Round shape with tapered ends has a rounded pivot point to reduce friction and wear while spinning
  • Teflon (PTFE) casing is chemically inert, can be used with corrosive chemicals, and helps reduce friction and wear while spinning
  • Smooth surface provides quicker cleanup and less risk of cross-contamination than bars with pivot rings
  • Internal magnet made from alnico V, an alloy of aluminum, nickel, iron, and cobalt
  • Casing material is FDA approved for use in food, drug, and cosmetic applications
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$6.49 + $2.99 shipping In stock. Usually ships within 4 to 5 days. Ships from and sold by OpticsPlanet, Inc.

Product Description

Size:20mm Length x 8mm Diameter

Bel-Art Spinbar Stir Bar Round 20X8MM F371130208

Product Information

Size: 20mm Length x 8mm Diameter
Technical Details
Brand NameBel-Art Products
Item Weight2 pounds
Product Dimensions4.5 x 4.5 x 3 inches
Item model number371130208
Material TypePTFE (Polytetrafluoroethylene)
Number of Items1
Size20mm Length x 8mm Diameter
Manufacturer Part Number371130208
Additional Information
Best Sellers Rank #208,083 in Office Products (See top 100)
Shipping Weight2 pounds (View shipping rates and policies)
Domestic Shipping Item can be shipped within U.S.
International Shipping This item is not eligible for international shipping. Learn More
Date First AvailableNovember 3, 2009
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From the Manufacturer

Magnetic Stirring

Magnetic Stirring Bar Selection & Use

Magnetic stirring is used in a number of common laboratory procedures, yet the importance of selecting the best stirring bar for each particular application is often overlooked. The drive magnet, vessel shape, viscosity and abrasiveness of the materials should all be considered when choosing the size, shape and materials (coating and magnet) of the magnetic stirring bar in order to achieve effective, efficient stirring results.

First, let’s discuss magnetism. On the most basic level, we know that opposite poles attract. A magnetic stirrer has a drive magnet, generally a bar or U-shaped made of a metallic alloy or a ceramic which rotates powered by a drive motor. The magnetic poles of the drive magnet are typically about two inches apart in bench top models, and can be up to six inches apart in larger units used to mix 50 gallons of liquid solution. For optimum magnetic coupling the distance between the magnetic poles of the drive magnet and the length of the stirring bar should be equal. Bars too long or too short in proportion to the drive magnet will not have optimum coupling which is important to reduce spin-out.

Once a magnetic stirring bar has been placed in a container with solution, it should be positioned directly over the center of the drive magnet. The stirring speed should be increased slowly, until the desired vortex pattern is achieved. Should the magnetic stirring bar lose its coupling with the drive magnet because of the speed of the drive magnet, viscosity of the fluid, or an improperly selected stirring bar length, it is said to have 'spun-out'.

Vertical distance between the drive magnet and the stirring bar should be kept to a minimum for the best coupling and stirring efficiency. Therefore, the containing vessel should be as thin as practical.

The selection of the shape of the magnetic stirring bar also influences the resulting vortex in that multi-sided shapes may be more efficient in moving solutions and certain shapes have been designed to provide a tailored fit in specialty vessels such as test tubes, cuvettes and spectrophotometer cells.

Magnetic stirring bars are generally made of ALNICO (an alloy of aluminum, nickel, iron and cobalt) magnets encapsulated in an FDA approved PTFE coating. In addition, magnetic stirring bars also use high energy magnetic materials, such as Samarium Cobalt which increases strength of coupling with a drive magnet and helps to reduce spinout when mixing viscous solutions or mixing at high speeds.

Newer to the market, the Bel-Art Products Spinfinity magnetic stirring bars, use ALNICO magnets encapsulated in plastic for increased durability in granular slurries.

Use for General Stirring Applications Use for High Temperature Stirring Applications Use for Viscous Solutions High Speed Stirring Applications Use for Abrasive Slurries Extended Stirring Applications
Brand / Type Spinbar Teflon PTFE Spinbar Pyrex Glass Spinbar Rare Earth Samarium Cobalt Spinfinity
Magnetic Type Alnico Alnico Samarium Cobalt Alnico
Covering Teflon PTFE Clear Pyrex Glass Teflon PTFE Plastic
Features / Benefits Wide selection of shapes and sizes to fit vessels of all types; Individual shapes create different vortexes for efficient and effective stirring Heated stirring applications up to 274°C (525°F) Reliable Magnetic Coupling – Superior magnetic energy reduces frequency of spinout in the most vigorous applications Durable – Last 2.5 to 3 times longer under conditions known to traditionally cause material breakdown
FDA grade Teflon PTFE low friction coating is durable and inert Glass casing has zero absorption and porosity FDA Grade Teflon PTFE low friction coating is durable and inert Outer shell made from FDA approved materials
Color selection for color-coding work processes Distinct Color – Green color lets you quickly identify Spinbar Rare Earth Samarium Cobalt Distinct Color – Quickly identify the Spinfinity difference by its purple color
Round spinbar, magnetic stirrer bar, stir bar with tapered ends

Round Spinbar Magnetic Stirring Bars with Tapered Ends

Round Spinbar Magnetic Stirring Bars with Tapered Ends

Round magnetic stirring bars with tapered ends have a naturally centered pivot point, eliminating the need for a separate pivot ring.

  • Smooth surface and the slightly raised ends on these bars facilitate efficient movement through solutions
  • End diameters are 1mm less than center diameter
  • Alnico magnet encapsulated in FDA Grade, USP Class VI Teflon PTFE low friction coating; durable and inert
  • Manufactured in a registered ISO 9001:2008, as verified by SGS certification
  • Autoclavable
F37113-0208 F37113-0309 F37113-0409 F37113-0509
Size (L x Center Diameter) .787" x .315" (20 x 8mm) 1.181" x .354" (30 x 9mm) 1.575" x .354" (40 x 9mm) 1.969" x .354" (50 x 9mm)

Technical Details

Size: 20mm Length x 8mm Diameter
  • Brand Name: Bel-Art Products
  • Part Number: 371130208
  • Material Type: PTFE (Polytetrafluoroethylene)
  • Number of Items: 1
  • Item Package Quantity: 1

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Most Helpful Customer Reviews

Size: 40mm Length x 9mm Diameter Verified Purchase
Ended up returning this. The two halves that were put together to make up the one I got were slightly misaligned. This caused the bar to get thrown after less than five minutes. I think if you were to get a properly assembled one that it would work great.
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