Hot Plate

Hot plates are frequently used in the laboratory to perform chemical reactions, to heat samples, and for numerous other activities. Hot plates are conceptually simple – a flat surface with heating elements. They do not produce open flames and are well suited for oil or sand bath use. But there are key considerations on the proper choice of hot plates and important safety factors that users should be aware of.

 

Features
From a design perspective hot plates can differ in significant ways:

• Some have built-in magnetic stirrers. This is usually desirable if heating liquids since this helps distribute heat and   eliminates the need for an external stirrer.
• Surfaces of hot plates differ but are usually aluminum or ceramic. First, choose a hot plate that is  compatible with the materials you will heat. Next, consider the surface’s heat transfer properties and  the temperature it can handle. Choose a different hot plate if you find yourself using the highest setting frequently.
• Some hot plates have digital read-outs and inputs for thermocouples so you can directly control heat bath temperatures. Some also have built-in safety features that automatically shut-off if the temperature gets outside a set range. These features can improve your process and safety.

Current hot plates have sealed heating elements and have minimal or no sparking. Despite this, they are not explosion proof and should be used in a fume hood when heating organic materials (such as oil baths, or solvents). The air flow in the fume hood will normally keep solvent vapor levels below the flammable range.

Older hot plates are more likely to pose spark hazards due to their on/off switch and the thermostat designs. Bimetallic thermostats in older models can fuse shut and deliver full continuous current to a hot plate.