A Simple, Inexpensive Laboratory Stirring Motor While designing an advanced organic chemistry laboratory, it was thought desirable t o provide student exposure of as many modernlaboratory methods as possible. One very common device, the mechanical stirrer, has often proved too expensive t o be included in the student's list of personal equipment. (The most inexpensive stirrer marketed a t the moment costs over $30.) In an effort t o provide an effective yet very inexpensive mechanical stirrer t o fill this gap, the following device was designed and constructed. The design shown in the diagram and photograph fulfilled our expectations admirably. This machine has a total of only six parts which must be machined, all of which can be fabricated from aluminum in a shop equipped with a mill and a lathe. The total work time involved in machining these parts is 5 hr. All added parts such as the motor, bearings, etc., are commercially available a t a total cost of $14. The drive wheel is replaceable being a piece of small diameter rubber tubing, and this whole assembly can be adjusted t o allow fitting of larger or smaller shaft wheels for varying the stirring speed. We use two shaft wheels for speeds of 150 and 300 rpm which are suitable for most laboratory applications. The stirrer's action is silent, and although we have not measured the torque output we have had no trouble stirring very thick solutions such as polyphosphoric acid or cold concentrated sulfuric acid. The electric motor used in this device is of the ac induction variety (Dayton #3M-201, 1/70 hp, 0.75 amp, 1500 rpm) and therefore sparkless, and our students have had no difficulty in the operation of this stirring motor.
726
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Journal of Chemical Education
