Chemical Concepts Demonstrated: Exothermic reactions that require heat for activation, "dangerous" chemical compounds
A fairly spectacular explosion takes place.
Picric acid is in the same family of nitroaromatic explosives as trinitrotoluene (TNT). It is no longer used as an explosive because of this type of reaction. A shock-insensitive explosive compound that forms shock-sensitive explosive salts with metals (such as lead) is too unwieldy for most usual applications.
Several years ago, someone realized that many high school chemistry classrooms in the midwest portion of the United States contained picric acid. Bomb squads were sent into several of these schools to remove this "dangerous explosive." This demonstration has been used to help students understand that compounds such as picric acid can be dangerous, but they can be handled safely if care is taken.