Magnetic Stirring Bars Made Easy Most chemical laboratories find it difficult ta maintain an adequate supply of magnetic stirring bars, and would really like to have an inexpensive, unlimited supply readily available. This paper will describe a method for making stirring bar magnets which meet all of the above criteria. Refrigerator doors have an iron oxide magnetic strip which is responsible for door closure. This strip can be removed from an old door or it can be purchased from a repair shop. The magnetic strip from one door can be cut into 70 or 80 2-in. magnet bars. The magnetic bars are then sealed in a Tygon tube using a soldering iron. The ends of the tube can be sealed by cutting circular Tygon pieces with cork borers. The sealing is best accomplished if a slight excess in length is allowed when the Tygon tubing is cut so that about 1 mm excess extends beyond each end. The seal can be checked by placing the bar under water and squeezing. One interesting aspect of these stirring bars is the fact that the polarization is lateral rather than longitudinal, and the stirring pattern can be varied as the^ speed of the rotor varies. The use of two bars simultaneously results in a roll and turn motion which is most effective when solid material is to be dissolved from the bottom of a vessel. The total cost per magnetic stirring bar should not exceed $0.10 if the magnetic strip has to be purchased. With this method of production it should now be possible t o use stirring bars in every reaction run a t temperatures below the melting paint of Tygon tubing. New York State University
College a t Buffalo Buffalo. 14222
264
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Journal ot Chemical Education
Albert A. Himmel
