Picric Acid 1/2/22

History with Richard Bleil

Picric is an interesting little organic chemical, structurally very closely related to tri-nitrotoluene (TNT), but with a hydroxide on it (-OH) rather than a methyl group (-CH3).  If you’re still reading, that information isn’t terribly important, save that both TNT and picric acid are explosive, and that picric acid is actually more powerful.  Picric acid is also a shock-sensitive explosive, so just touching it under the right conditions can set it off.  The US military examined picric acid for potential use in hand grenades, but they couldn’t make it safe enough to kill people with it

When I started teaching in South Dakota, I arrived hearing heroic stories of how they found a bottle of about a liter picric acid solution in a jug dissolved in water with crystals in it, and the bomb squad was called who just picked it up and walked out with it.  What the bomb squad realized is that picric acid, even in the solid form, is actually quite stable and safe if there is water with it (if I am recalling correctly, it is stable with just 5% water.  A jug filled with water that has picric acid crystals is perhaps a skin irritant, but that’s about it. 

My story of picric acid was a little more harrowing.  Prior to working there, I was teaching at a small medical arts college in Ohio.  I’ve never started a new job as a chemist to find the stockroom well documented and organized and took it upon myself to be sure that they were safe and properly catalogued, although this usually took a while to complete.  The first year is typically spent disposing of leftover unknown chemical waste from the previous instructors.  After settling in, getting the lab safe and preparing for the first year of lectures (as the school was in session), then I would do a complete inventory and catalog the chemicals in the storeroom. 

Happily cataloguing the chemicals on a slow day at the small college, I happened on a jar of picric acid.  Unfortunately, it was not a jug.  It was originally a hundred grams of picric acid, shipped in water, but the date on it put it on the shelf through at least three chemistry professors before me, and it had been opened.  What’s worse, it was not sealed properly when it was reclosed, and it was in an amber bottle making it impossible for me to see inside to ascertain if there was still water with it or not.  To figure out if it had water, I would have had to open the jar, but if there were any crystals on the lid, that would have been more than enough to set off an explosion and I would be a stain on the storeroom wall with a commemorative plaque today.  Well, maybe not.  They would have painted over it by now.

The storeroom was locked, so I knew it would remain safe as nobody had the key but me (kind of a lie, but the other people who had the key never went to that side of the storage area).  I ran to the academic vice president (the position would have been “dean” in a larger university) and frantically told him of my find.  “Is it safe?”  I explained that it is since nobody has access.  His reply was perfect.  He said, “good, let’s go and have some tea.”

Brilliant stroke.  He calmed me down to be able to explain in detail the situation, and the danger.  When we got back, we called the bomb squad.  But they didn’t waltz in, pick it up, and walk out.  It took several hours for them to remove the bottle.  See, they didn’t know if it was safe or not, and across the street we had a park.  A little access road ran through the park from the road on the top of a hill on one side to the road that went past the college at the bottom.  Police blocked both entrances to the road as a crew dug a ten-foot hole in the field that was relatively close to the access road.  The college had been evacuated, and I, along with the students, sat in the park (a safe distance) watching the spectacle.  One of the funniest things I ever saw was an arrogant driver who decided that the blockade didn’t apply to him.  He snuck past the police car at the top of the hill, and as he happily drove towards the other, two police cruisers from either side met him in the middle.  They forced him to leave his vehicle and walk back up the hill until the situation was safe.  Yes, I laughed.  But only my ass off.

The process took hours.  They brought a city dump truck filled with sand for this very small bottle of picric acid.  Experts in explosion suits and long tongs carefully picked it up (I had actually picked it up before realizing what it was and set it back down without all of that) and, taking about twenty minutes, carefully took it out of the college and placed it in the truck.  The truck then drove, literally across the street, to the hole.  The only vehicle I had seen move more slowly was the “crawler” that moves the space shuttle from the assembly building to the launch pad.  The truck took about half an hour to cross the street.  The bottle was carefully lowered into the hole along with a remote detonated blasting cap, about the explosive power of a small firecracker.

And we waited.

When they set it off, a fireball erupted from the hole along with an extraordinary boom.  The fireball, based on the trees behind it, looked to reach a height of about ten more feet above the ten-foot hole it was in.  The neighborhood nearby had windows rattle. 

Sometimes I wonder what would have happened had the college not hired me to work there.  Several of my predecessors either didn’t realize it was there or didn’t know of the danger.  Would it still be there today?  Would, in fact, it had exploded in the college by now?  A tearful student stopped by my office the next day to thank me for literally saving her life with my knowledge and actions.  I had a few students ask me what I did when I did find it.  I said, I picked it up, and when I realized what it was, I quickly set it back down.  Then, I immediately picked it up again so I could set it down more gently.

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