On the spot web comic disappearing mercury

Source: © Jane Webster / Debut Art Ltd.

Answer by CLEAPSS:

Mercury has interesting properties that mean ‘curious’ pupils may be tempted to experiment on their own out of lessons. Strict controls should be in place to ensure popular chemicals like this are accounted for before the end of practical sessions. Once the chemical leaves the lab with a pupil, its use is not controlled and could lead to many unwanted situations including poisoning of the pupil or their friends (who will be unware of its risks). Mercury can also be used in tilt switches in bombs, and so disappearances must be reported to the police.

Scenario and solution provided by CLEAPSS