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How to choose a magnetic stir bar
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How to choose a magnetic stir bar

Views: 34     Author: Site Editor     Publish Time: 2020-07-21      Origin: Site

Introduction of Magnetic Stirrer

Common magnetic stirrers are glass magnetic stirrers and polyethylene tetrafluoroethylene magnetic stirrers. Glass magnetic stirrers are made of high temperature resistant glass to seal the permanent magnets, while polyethylene PTFE magnetic stirrers are made of polyethylene tetrafluoroethylene. The material seals the permanent magnet. Long-term use will cause the accumulative wear of the stir bar to change the status quo, thereby affecting the vortex formed when the magnetic stir bar works. The conventional stir bar will gradually demagnetize under high temperature conditions.

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Temperature, magnetic field and iron materials will all affect the residual magnetism of the magnetic stirrer, which will affect the stirring effect of the magnetic stirrer. Therefore, it is recommended to replace the magnetic stir bar in time and regularly. By observing the shape of the stirrer, if there is obvious wear, it should be replaced. If you need to check the magnetic force of the permanent magnet in the stir bar, you need to use a magnetometer to detect the remanence of the magnetic stir bar.

Magnetic stir bar storage

Due to the magnetic substance of the magnetic stirrer, it should be kept away from iron and other magnetic materials, because these materials will affect the magnetic properties of the magnetic stirrer, and cause the magnetic attenuation of the magnetic stirrer to affect the performance of the magnetic stirrer during use.

Selection of conventional magnetic stir bar

The magnetic stirrer puts the container of the liquid to be stirred into the stirrer on the base of the magnetic stirrer. When the magnetic stirrer is energized, a rotating magnetic field is generated near the base to drive the stirrer into a circular motion, so that the liquid in the container A vortex is formed to achieve the purpose of stirring the liquid. Therefore, if you want to achieve a better stirring effect, you must choose a good stirrer magnetic force. 

There are many types of stirrers used in magnetic stirrers. If the selected stirrer does not match the stirrer, it will run asynchronously during stirring and cause the phenomenon of magnetic jump. When this phenomenon occurs, the user may think that this is a malfunction of the magnetic stirrer. In fact, this is caused by the mismatch between the stirrer and the stirrer. How to choose the stirrer that matches the stirrer?

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The selection method is as follows:

1. Generally speaking, the smaller the contact area between the stirrer and the bottom of the container, the better, because the friction between the stirrer and the container is small, but the stirrer itself is required to have a high degree of balance; a large contact area is good for stability, so the two should be balanced. .The round-bottomed container has a convergent effect on the small stirrer, which makes its rotation stability better. The oil bath of the flat-bottomed container does not have this effect, so the small stirrer is prone to revolution while autobiography. Therefore, the round-bottomed container should use type A (olive type) stir bar. The flat-bottomed container does not use the olive-type stirrer, and chooses to use the B-type(cylindrical with collar)stirrer. C-type (polygonal, cylindrical) magnetic stirrer is suitable for use in low-concentration flat-bottomed cylindrical beakers.

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2. Select the stir bar according to the capacity: the capacity is within 1000mL, and the stir bar is 15mm in length. Use a stirrer with a length of 300mm within 3000mL.

3. Choose a stir bar according to the viscosity of the liquid: If the viscosity of the liquid is grease, use a strong magnetic stir bar. ...

In addition to the above selection essentials, when choosing a magnetic stirrer, you should also check the maximum stirring capacity of the stirrer. Small magnetic stirrers are used for small magnetic stirrers, and longer magnetic stirrers are used for large-capacity magnetic stirrers. If a small magnetic stirrer uses a large-capacity magnetic stirrer, there is a possibility that the magnetic stirrer may be burned because of the excessive charge.


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