Old sample of acid detonated in Wis.

It's not often that a bomb squad is asked to help clean up a pharmacy. But experts say a 2-ounce sample of picric acid in the basement of Sharrow Drug Store packed the punch of nearly half a stick of dynamite.

Store employees found the sample Thursday as they were cleaning out old chemicals. Store owner Nick Sharrow is relieved that the local bomb squad safely destroyed the sample Friday, saying its explosive capability was stunning.

"This is very similar to TNT," Sharrow said.

Picric acid isn't volatile as a liquid. But as it ages, it can form highly explosive crystals, Sharrow said. The sample discovered on the basement shelf dated back to around World War I.

The sample was probably overlooked when employees disposed of the rest of its picric acid supply in 1984, a process that also required the assistance of a bomb squad.

Picric acid was used as an antiseptic and in medical formulations to treat such afflictions as malaria, herpes and smallpox.

Authorities decided to remove the acid Friday around 8:15 a.m. because traffic would be light and school buses would have already passed.

The drug store and its second-story apartments were evacuated, as were neighboring businesses. The street was also closed to traffic during the removal.