The bomb squad had to be called in to carry out a controlled explosion on unstable chemicals found in a lab at the Royal College of Surgeons in Dublin.
The Army unit was dispatched to the building on Dublin's Stephen's Green after in-house checks revealed the picric acid.
The Defence Forces experts said the chemicals were unsafe to transport and made them safe on waste ground near the college.
The RCSI said the acid was found during a routine health and safety self-assessment.
"The necessary precautions were immediately taken in order to stabilise the chemical. In the interest of health and safety the building was evacuated as a precautionary measure," a spokeswoman said.
It was the 150th call out for the Defence Forces bomb squad this year.
Picric acid is used as a reagent in organic chemistry experiments and is also an explosive. It becomes unstable when it dries out and crystallises.