EDMOND, Oklahoma - Classes are back in session at the University of Central Oklahoma after a highly explosive chemical forced the evacuation of two buildings.

According to university officials, a visiting scholar discovered a crystallized form of picric acid just before 2:00 p.m. Wednesday. It was discovered while the staff was taking inventory of the lab to prepare for an upcoming remodeling job.

Picric acid in its liquid form is flammable, but when it becomes solid and crystallized, it's highly explosive. Howell Hall and an adjacent building were evacuated.

A bomb squad was called in to diffuse the situation. Around 2:40 p.m., university officials told News 9 that the chemical was removed in a jar, put into a containment vehicle and removed from campus.

No one was injured in the incident.

Picric Acid:

Picric acid is the chemical compound formally called 2,4,6-trinitrophenol (TNP). This yellow crystalline solid is one of the most acidic phenols. Like other highly nitrated compounds such as TNT, picric acid is an explosive.

The chemical is commonly present in many laboratories, for use as a chemical reagent. Water is added to picric acid to act as a desensitizer. The wetted product is significantly less shock sensitive than the dry acid. One of the largest use of picric acid has been in munitions and explosives.

It is recommend that picric acid be stored wet. Glass bottles are required, as picric acid can form metal pi crate salts that are even more sensitive and hazardous than the acid. However, it is not acidic enough to cause chemical burns. If physical contact is made, the acid can react with proteins in the skin to give a dark brown color that may last as long as a month.