Hot Air Baths and Tube Furnaces

Perhaps the most common types of electrical equipment found in a laboratory are the devices used to supply the heat needed to effect a reaction or a separation. These include ovens, hot plates, heating mantles and tapes, oil baths, salt baths, sand baths, air baths, hot-tube furnaces, hot-air guns, and microwave ovens. The use of steam-heated devices rather than electrically heated devices is generally preferred whenever temperatures of 100 °C or less are required. Because they do not present shock or spark risks, they can be left unattended with assurance that their temperature will never exceed 100 °C. 

Input Plug Double-Pole Switch Output Receptacle 

Schematic diagram of properly wired variable autotransformers. 

The external cases of all variable autotransformers have perforations for cooling by ventilation, and some sparking may occur whenever the voltage adjustment knob is turned. Therefore, these devices should be located where water and other chemicals cannot be spilled onto them and where their movable contacts will not be exposed to flammable liquids or vapors. Variable autotransformers should be mounted on walls or vertical panels and outside of hoods they should not simply be placed on laboratory benchtops. 

Electrically heated ovens are commonly used in the laboratory to remove water or other solvents from chemical samples and to dry laboratory glassware. Never use laboratory ovens for human food preparation. 

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