Boiling Chip

Many experiments will ask you to add a boiling chip.

These tiny boiling chips are very porous rocks which release bubbles of entrapped air to the solution being heated. These bubbles provide a path by which the vapour of the boiling liquid can be smoothly led to the surface and released. It should be noted here that a boiling chip may not be used twice; it must never be added to a hot solution (near its boiling point) since violent frothing will occur.