Reasonable choice of magnetic stir bar

The magnetic stirrer is suitable for liquids or solid-liquid mixtures that are not very viscous. It can be stirred separately or heated and stirred at the same time. It uses the continuous circular motion of a magnetic stirrer placed in the liquid in a rotating magnetic field to achieve the purpose of stirring the liquid. It has been widely used in laboratories in various universities, environmental protection, scientific research and health, epidemic prevention, petroleum, metallurgy, chemical, medical and other industries.

There are many factors that affect the working state of the mixer, and we can only list some of the more important factors here. such as:

1) The shape of the stir bar. 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.

2) The relationship between the amount of solution and the length of the stirring bar. Use a small stirrer for small capacity and a large stirrer for large capacity.

3) The shape of the bottom of the container. The round-bottomed container has a convergent effect on the small agitator, making it more stable in rotation; the flat-bottomed container does not have this effect, so the small agitator is prone to revolution while rotating.

4) Whether the bottom surface of the flat-bottomed container is flat. Obviously, the uneven bottom surface will cause the revolution phenomenon.

5) The internal structure design of the magnetic stirrer. A common design is to place a magnet of appropriate size under the disk surface, which is good for the uniformity of the magnetic field of the entire disk surface, and the rotation stability of the longer stirrer is good. We have also noticed that some domestic magnetic stirrers use two small magnet balls that are very close to each other, so that the limited magnetic field is completely concentrated in the center of the working plate. Therefore, it is more suitable for small stirrers to run stably, but larger specifications. It cannot operate normally.

6) The effect of high temperature conditions on the stir bar. At present, the commonly used stir bar will gradually demagnetize under high temperature conditions, so after using it for a period of time, confirm whether it has enough magnetism.