Inexpensive Alternative to Purchasing Immersion Heaters Immersion heaters, which are capable of rapid heating, are useful for Lecture demonstrations and in student laboratories where time is a factor. Burners may be dangerous and hot plates are somewhat expensive and slow. Immersion heaters, however, are safe as well as efficient, hut usually prove too costly far use in laboratory applications where several heaters are used. Here is a simple method for fabricating an immersion heater that casts no more than $15 versus those commercially produced, which typically range from $30 to $100 and which can deliver up to 4500 W (much more than usually needed). This assembly requires only about 15-20 min to complete. We have been using several of these "homemade" immersion heaters in our physical chemistry labs for the past few years without problems. Construction details are shown in the figure. The heater itself is a 4500-W, 220-V ac replacement heater designed for use in electric hot water heaters. It can he purchased a t a hardware or building supply for about $15. The protective cap is a PVC pipe cap or a polyethylene bottle, which has been drilled through the top to accommodate the 120-V ac line cord. The electrical connections are made to the heater using the screws supplied by the manufacturer. The exposed connections are thoroughly coated with hot glue, which serves to insulate them electrically. The cap is then filled with hot glue and affixed to the top of the heater. The unit may be connected directly to a 120-V ac outlet or powered with apowerstat-type transformer. Since the circuit does not provide temperature control, this must be done manualIv. We have used this device successfullv in a Gav-Lussae's law lecture demonstration and in an experiment on the thermody&nics oicells by simply starting out at about 5' C (using which was eontrnllcrl hv . - ice) . and followed hv heatine " at a moderate rate. ~~~~~, -. the setting on a powerstat, to various temperatures up to about 80 OC. Important: Notice t h a t t h e heater must be immersed when operated. Otherwise, i t will be destroyed. ~
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Schematic of the immersion heater. (1) Hot water heater element.. 12) , , oower -~ card attachment. (3) PVC pipe cap or honh .an. old ..nn~vemv~ana ..,....,.. .... ..... , IAI ,.,to ..-. ..-. source. (5)seal with hot glue or silicon. (6)clamp attachment point, and (7)end view. ~
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D. Dewayne Garret1 M. C. Banta
Sam Houston State University Huntsville, TX 77341
976
Journal of Chemical Education
