Economical and Safe Laboratory Heat Control Providing controllable heat sources in the undergraduate chemistry laboratory has traditionally heen difficult, often entailing expensive or hazardous solutions. Organic chemistry labs present special difficultiei because of fire hazards. We suggest a much more economical and potentially safer means of heat control, using a solid-state control commonly sold as alamp dimmer for about $5, with asoft heatingmantle. They typically have capacities of 600 W, more than adequate for ordinary small heating mantles; they are compact and light. The plastic housings lend themselves to being easily sealed; less expensive models lack "push-on push-off' switching and are less apt to produce sparking. It should he noted that these dimmers are designed for control of resistive loads and cannot he used for control of inductive loads (such as variahle-speed universal motors.) A typical circuit1 can be modified using components with greater power-handling capacity and then substituted for sparking-type heat controls in hotplates drawing 1 kW or more. '"Solid State Projects from Motorola," 2nd ed., Motorola Ine., 1968, p. 51. Brandeis University Waltham, Massachusetts 02154
Robert Rothchild
Volume 55, Number 8. August 1978 / 501
