In September of 2021, a fellow explorer and I went to investigate rumors of an abandoned steel mill near the Third Ward in Milwaukee during the revival of the WIpex regional meetup. Employing just over 100 workers, this steel mill closed in 2019 when the corporate office decided to relocate a product line to an unspecified city.
This particular mill used a process knowing as casting, in which molten steel is poured into molds and allowed to cool in order to mass produce metal parts- in this case, components for engines. Pretty much all of the equipment had been removed leaving just an industrial shell behind, so we weren't expecting to find anything too dangerous inside.
We were wrong.
One side section of the building off the main mill had been set aside as a chemistry lab. Though much of the laboratory equipment had removed, some had been left behind- including dangerous reagents such as a liter of nitric acid missing its lid. But perhaps most alarming was a bottle with a name I didn't recognize.
Picric acid, also known as 2,4,6-trinitrophenol (TNP), is a white phenol crystal typically stored in powdered form. In steel mills such as this one, it has metallurgical uses for determining the grain of ferritic steels and etching of magnesium alloys. But that's just a minor secondary use.
It's primarily been used as a military grade high explosive.
Picric acid is a highly unstable, shock sensitive explosive with an explosive yield 1.25 times greater than that of dynamite. It is one of the primary ingredients in Shellite, an explosive used in the Royal Navy during WWII before being phased out of service as too unstable for military applications. Typically it is stored in water to render it inert. However, when improperly stored like this jar was, that water can evaporate off leaving pure picric acid behind. Setting it down too hard can be enough to trigger an explosion, and many a chemist has caused a detonation merely by opening a bottle of picric acid and causing the fraction of a gram of residual powder on the lip to go off.
Not knowing the danger, I picked up the bottle to read the label and gave it a swirl to see if there was anything inside. There was, but it wasn't a liquid. I casually set the bottle down and sent a picture to a chemistry grad student friend of mine to ask for information, who promptly freaked out when he saw the label. According to him, picric acid is semi-frequently found in old chemistry labs, and 30 grams is enough to warrant a bomb squad visit. Furthermore, the lid of the bottle was metal. When stored in containers with metal lids, picric acid can build up on the underside of the lid and form picrate salts, which are even more unstable and are the primary ingredient in dunnite (aka Explosive D), another military grade explosive.
I had been holding a pound of dried, purified crystals in my hand. That is the equivalent of 1.25 pounds of dynamite with the fuse lit. Had that bottle detonated, the explosion would have certainly killed me and quite possibly have collapsed the entire laboratory section. Quite frankly, it was pure luck that the bottle didn't go off in my hands.
Upon being informed by my chemist student friend just what we were dealing with, my fellow explorer and I made the call to leave the building with haste. We also knew we couldn't just leave the picric acid there- we'd already seen evidence of local kids getting inside and smashing up other reagent bottles, and it was only a matter of time before somebody threw the bottle of picric acid at a wall and got themselves killed.
After we left I left an anonymous tip with the Milwaukee Police Department, detailing the picric acid bottle and the likelihood of an accidental explosion. I finished the tip with a request for a bomb squad intervention at the soonest possible time. One week later I found that somebody had their eye on the plant, so hopefully my tip got through.
Finding that bottle was a sobering lesson on the inherent hazards of this hobby, and a reminder not to shake strange bottles in derelict places. This was the closest call I've ever had in eight years of exploring, and quite possible will remain my closest call ever.
