Boiling chips, also known as boiling stones, boileezers or anti-bumping granules, are small, irregularly shaped stones added to liquids to make them boil more smoothly mainly in distillation. They provide nucleation sites so the liquid boils easily without becoming superheated. Without boiling chips, a liquid heated in a smooth container can become superheated and release vapor suddenly, sometimes violently. This sudden bubble of gas can cause the solution and reagents to be thrown out of the beaker, possibly causing severe burns, ruining an experiment, or simply making a mess.[1]
Boiling chips are typically made of a porous material, such as alumina, calcium carbonate, porcelain or carbon, and often have a nonreactive coating of PTFE (Teflon). This ensures that the boiling chips will provide effective nucleation sites, yet are chemically inert. In less demanding situations, like school laboratories, pieces of broken ceramic crucibles are often used.
Boiling chips should not be added to liquid that is already near its boiling point, as it could cause a large amount of vapor to form all at once. This could cause hot liquid to be expelled from the container, possibly causing heat or chemical burns.[1]
References
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