MOTAT was the latest museum in Aotearoa to remove picric acid (an explosive) from its
collection last week. The suspect was a 45-gram vial of 5-gram silver picrate once used as an antiseptic in a historic first aid kit.
MOTAT Conservation Manager, Kristie Short-Traxler said, “The recent findings at Otago Settlers and Waikawa reminded us to revisit and have a look for this particular risk.”
The museum’s collection team has been slowly and systematically reviewing hazards and risks over the past three years and this includes identifying collections that are made from or contain hazardous substances. We must review our collection regularly to ensure our staff, items, and community are safe.
Short-Traxler said, “Picric acid and derivatives are included in a group of compounds known as contact explosives which can be triggered by relatively small amounts of energy such as shock, pressure, or temperature.”
“Picric acid contains nitrogen groups. The triple bonds between nitrogen molecules in a compound are very stable but the bonds between nitrogen and other molecules in the same compound are not as stable. When compounds deteriorate, the strong bonds in nitro groups are broken and a significant amount of energy can be released, which most people know as an explosion.”
Picric acid is just one of the many hazards that we have identified in our collections. The important thing is for museums to move it out of the too-hard basket and to methodically put together a program to assess and mitigate the risk.
If you come across anything that lists picric acid as an ingredient, leave them alone and contact your nearest Police or Fire service. If the disposal is necessary, the emergency services team will contact the New Zealand Defence Force Explosive Ordnance Disposal to arrange removal.
For suspected items with no ingredients list? There is no need to panic and dispose of everything as the EOD can analyse the unknowns on the spot with a portable Raman spectrometer which will provide a chemical identification and assist you in making further decisions.