A boiling chip, boiling stone, or anti-bumping granule is a tiny, unevenly shaped piece of substance added to liquids to make them boil more calmly. Boiling chips are frequently employed in distillation and heating. When a liquid becomes superheated, a particle of dust or a stirring rod can cause flash boiling. This very rapid boiling can be extremely violent and cause reagents to splatter, possibly causing severe burns, ruining an experiment, and damaging equipment. Boiling chips work by providing nucleation sites so the liquid boils smoothly without becoming superheated or bumping.
The structure of a boiling chip traps liquid while in use, meaning that they cannot be re-used in laboratory setups.
Boiling chips are typically made of a porous material, such as alumina, calcium carbonate, calcium sulfate, porcelain or carbon, and often have a nonreactive coating of PTFE. 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 porcelainware or glassware are often used.
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