“The kind of whistling you would rather not hear in a chemistry lab”

From a reddit forum, a rather dramatic tale of what happens when nitric acid and ethanol are combined in a waste container:

There were no empty nitric bottle in lab so rather than go get a new one 4 floors down, I grabbed a common use waste bottle. These are 4 liter glass bottles with a screw on cap.6 Usually they are used to collect organic waste, brought to a central facility where they are emptied and then thoroughly cleaned. University protocol is that they are first cleaned with ethanol, then water. The idea is that the only remnants in these bottles should be water. I happened to pick a bottle that had not been washed with water. Knowing that nitric acid was dangerous, I visually checked the bottle to make sure it was empty. There was a little bit of water (or so I thought)7 in the bottom, which did not concern me because nitric acid and water are fine to mix.8 I proceeded to clean my glass using a total of 30-50 mL of nitric acid, which I disposed of in the waste container. Knowing that nitric acid could react with organics, I left the waste bottle un-capped in my fumehood for about 60 seconds after I put the nitric in. Seeing no reaction, I then capped the waste bottle loosely. This probably saved me a trip to the hospital.

Now, the astute chemist reading this may have figured out what happened next.9 Nitric acid and ethanol (remember this bottle was supposed to be washed with water, but never was) react very violently to produce heat and a large amount of gas. This reaction has an incubation time of a few minutes before it really kicks in. So 20 or so seconds after capping this bottle, I hear an ominous whistling sound. The kind of whistling you would rather not hear in a chemistry lab. I look at my fume hood and saw a very large and copious amount of brown gas (NOx) billowing out from my loosely fitted cap. As the whistling increased to a truly terrifying pitch, I had a few seconds to dive behind a wall before the waste bottle exploded with a force much larger than that mortar from the front page yesterday.10,11,12 Here I fucked up again as despite my 10 or so second lead time, I did not warn anyone that a glass shrapnel bomb was about to go off. I am so fucking lucky that no one decided to come around the corner at that moment. As the nitric acid tinged glass rained down upon me, my lab mates rushed to see what was wrong. I yelled for them to evacuate the lab as a billowing cloud of brownish green gas (a toxic mix of nitric acid, nitrous oxide, ethyl nitrate and the various other chemicals in my hood which were vaporized and atomized) was spewing forth from my fumehood. Alarms were going off, lights in the ceiling were blown out and haphazardly hanging from their sockets, I’m pretty sure an undergraduate was crying…

Go read the full thing for more; photos of the damage are here. There are some additional stories in the comments, too. Reading the piece myself, I particularly appreciated the point about what could have happened to this chemist’s labmates. This is why you should always wear PPE in the lab, even if you’re just updating your notebook or working on a computer. What your labmate is doing may be far more dangerous.

Author: Jyllian Kemsley

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  1. When you hear the waste bottle whistling, it is time to re-enact one of the Monty Python film scenes —

    “Run away, run away, …”

  2. The unusual part of this incident is that the person who made the mistake admitted it. Because of the induction period, these events usually occur hours after the actual mixing and no one “did it.”

    There is a good lesson to be learned in this self-report. When using concentrated nitric, always start with containers you know are clean – you cleaned them yourself.

    The person who self-reported is to be commended. Yes, mistakes occurred, but he shared the incident widely and thus made it a teaching moment. I am confident that as he moves forward in his career, the moment will be shared with many students and colleagues.

    Working together, we can reduce the frequency of nitric acid incompatibility incidents.

  3. Holy crap on a cracker! I was going to put in a rather pedestrian piece on sociology of experience in this month’s newsletter but I’m putting this instead. I’ll have to scrub out the f-bombs (this is a family newsletter!) but I really like his descriptor over the sanitized version Tufts put out. I also appreciated how well referenced the reddit article is.