An Inexpensive Controller for the Organic Chemistry Laboratory Two years ago we found that our mantle controllers were sparking or not working at all. The sparking was of particular concern because of the fire hazard it presented. Replacement controllers are expensive. We found that aiatisfactory c&troller can be constructed from a light dimmer switch and other locally available materials for less than $15. The controller is constructed of afiher glass double switch box, a receptacle, a light dimmer with integral off-on switch, and a short cord with three-prong plug (see figure). Light dimmer switches are generallyrated at between 500and600 W, whilemost smallmantles draw between 40 and 450 W far 25-mL- and 2-L-size mantles, respectively. Thus, these controllers are of sufficient capacity to handle most mantles used in the typical undergraduate organic chemistry laboratory. the Althoueh -~~~~ " this tvoe of controller works.,one cannot tell when switch is on and when it is off. This difficulty was alleviated by connecting a pilot light t o the output from Lhe dimmer switch (any 120-V ac pilot light should work). This controller has the safety feature of having all electrical contacts enclosed in a nonconducting box. This virtually eliminates the possibility of the controller being a source of ignition. We have used these controllers for more than two years, during which time they have functioned flawlessly.
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Nell Kirkpatrlck. Phlllp Bayless, and Allred R. Conklln. Jr. Wilmington College Wilmington, OH 45177
1110
Journal of Chemical Education
