Page 66 - BOLA Catalogue

STIRRING AND MIXING
BOLA Stirring Bars
Magnetic stirring and mixing
What you should know about
For optimum results, both drive magnet and stirring bar are decisive. For optimum efficiency, the distance between the magnetic poles of
the drive magnet and the length of the stirring bar should be equal. A magnetic stirring bar which is too small will eventually gravitate toward one of the poles of the drive magnet. Stirring efficiency is influenced by the material, by the thickness of the cover plate and the thickness of the vessel. For the best magnetic coupling, the distance between the magnets should be minimized.
The choice of stirring bars – What you should know about
Improperly selected stirring bars often cause flickering
of the bars in the vessel, respectively ineffective mixing of the product. You can find an overview of the most common stirring bars here below:
Cylindrical Magnetic Stirring Bars:
They are the most commonly used magnetic stirring bars. Due to their simple shape they can be offered at very attractive prices. Cylindrical magnetic stirring bars offer excellent centering and smooth running characteristics.
Power Magnetic Stirring Bars:
Due to special magnetic material, their torque loads are larger than those of conventional magnetic stirring bars. Power magnetic stirring bars are mainly used for agitating viscous liquids or for bridging larger distances between the magnetic stirring machine and the magnetic stirring bar.
Magnetic Stirring Bars with Pivot Ring:
Their interrupted surface provides greater surface area and added turbulence. Only their pivot ring and one end of the magnetic stirring bar touch the bottom of the vessel. Therefore these magnetic stirring bars have a more steady spinning position and a better longevity.
HELPFUL: page 354
Detailed information on magnetic stirring
Square Magnetic Stirring Bars:
They are particularly suitable for big vessels due to the high magnetic force. Solids are released or removed from the bottom of the vessel.
Egg-Shaped Magnetic Stirring Bars:
They are particularly suitable for round-bottom flasks. Their sha- pe mimics that of the flasks and assures complete mixing. Those magnetic stirring bars have an egg-shaped magnetic core which assures a better force transmission than a cylindrical core.
Triangular Magnetic Stirring Bars:
Such magnets are useful for mixing reagents which resist dis- solving or for avoiding any residues at the bottom of the vessels. They provide strong turbulence at relatively low speeds.
Glass Magnetic Stirring Bars:
They have a non-porous and smooth glass-coating. All following processes are not affected by any carry-over. There is an increa- sed abrasion between glass vessels and glass stirring bars.
Star Head Magnetic Stirring Bars:
Optimum stirring in tall, narrow diameter vessels. Ideal stirring bar for cuvettes or test tubes.
Centre Magnetic Stirring Bars:
These magnetic stirring bars provide better stirring action and a more stable spinning position due to the punctual position.
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