An emergency alert was issued in Halifax on January 22 following what was believed to be a formaldehyde spill at the Bedford Institute of Oceanography, but turned out to be picric acid.
Firefighters found a 250 ml container of dry picric acid on site. Transport Canada says the compound must be stored with at least 10% moisture content. In a dry state, the chemical is highly explosive. A 250-metre evacuation order, which included a portion of the MacKay Bridge, was put in place around the institute by Halifax Regional Fire and Emergency officials.
In online discussion forums, the alert led many observers to recall the historic Halifax explosion of 1917, when a boat collision occurred with one vessel fully loaded with TNT, picric acid, benzol and guncotton. The Halifax Harbour incident remains one of the largest non-nuclear explosions on record and led to the death of some 1,782 people.
Often phased out of use and replaced with safer alternatives in modern times, picric acid may still be used at the institute for cell staining, as a chemical reagent, or as a preservative for certain fish organs.
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“The wetted product is significantly less shock sensitive than the dry acid,” states Transport Canada in handling guidelines. “Picric acid is highly reactive with a wide variety of chemicals and forms explosive picrate salts easily. Many of these salts are even more reactive and shock sensitive than the acid itself.”
Transport Canada considers picric acid, or 2,4,6-trinitrophenol, to be one of the most dangerous chemicals used in chemistry labs.
