What is the most dangerous chemical you’ve handled?

Courtesy of the Periodic Table of Videos, faculty and staff at the University of Nottingham discuss the most dangerous chemicals they’ve handled:

What about you, Safety Zone readers? What do you think is most dangerous chemical you’ve handled?

Author: Jyllian Kemsley

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  1. When I was a researcher, the reagent that we were most respectful of was osmium tetroxide. Highly toxic, volatile, and apparently lipophilic. It was believed that it would osmium-plate your retina and make you blind, but that part may have been urban legend. The LD50 is very low, however, and that combined with volatility and ease of absorption is significant.

  2. 1,1′-azobis(tetrazole) (you link to my paper about this under related posts…)
    silver fulminate
    silver azidotetrazolate-2-oxide
    65% fuming sulfuric acid
    fluorine gas

  3. Nickel tetracarbonyl – I made [Ni(CO)2(diphosphine/diarsine)] complexes with this in the eighties. The lecture bottle belonged to an organic chemist famed for being gung-ho when it came to hazardous materials (he used to burn white phosphorus at the start of his lecture on Wittig chemistry, for instance), but it was noticeable that when he helped me manipulate the apparatus, his hands trembled as he opened the needle valve!

    I’ve also made and used [Ni(COD)2] in gram quantities. I’ve used elemental fluorine, and also cHNO3/cHCl/70% HClO4 mixture. I have also used OsO4, but only to dunk straight into a cHBr solution to make hexabromoosmate(IV).

  4. Gee, where to start?

    Neat trimethylaluminum, thioacetic acid, oxirane, chlorine gas, refluxing TfOH, trichloroarsine…

    Toss in a few Scheduled drugs, for good measure!

  5. tBuLi, sBuLi, nBuLi I have worked with (and titrated) all of these. I chickened out of working with osmium tetroxide because of its volatility and toxicity. It says “highly poisonous” in no less than four places on the tiny bottle. Triflic acid isn’t pleasant, especially trying to get it out of the ampule. Another dangerous mixture was NaCN in DMSO. Something about a highly poisonous compound in a solvent that dissolves through gloves and skin without trouble seems like a dangerous combination.

  6. Definitely hydrofluoric acid!

  7. Darren, osmium tetroxide (or osmic acid) used to be used as a tissue fixative. One time my mum accidentally fixed her eyes – she worked in a veterinary path lab. She got better. So not urban legend at all!

  8. Definitely Na/K alloy.

  9. Most of the prior lists seem pretty tame to me. My most dangerous chemicals list includes:

    Hydrogen selenide (H2Se)
    Tetraethylammonium cyanide [(Et4N)CN]
    Manganese heptoxide (Mn2O7) (from the dehydration of KMnO4)

    There are likely others but these sick out.

  10. Quick story – not about the chemical per se, but the way it was handled. “Back in the day” we would have to move an “A” size hydrogen cylinder through an escape trunk aboard a ship (approximately 3-4 stories vertical). Ropes, block/tackle etc. – very old school methods. It was one of a number of high-visibility, high-oversight evolutions that was performed, but not one that everyone was comfortable doing.

  11. The most correct answer is probably that I have no idea because it is bound to be something I synthesized. A lot of the materials mentioned above are dangerous, but at least have known risks.

  12. methyl fluorosulfonate (Magic Methyl)


  13. In 35 years of work, I’ve seen many of the worst, in labs and product scale. The most surprising was in my first year of lab research. I had been running sodium-in-liquid ammonia reductions. Always, when I dropped the bits of sodium into chilled (-45°C) ammonia, they dissolved rapidly and endothermically. I was doing this in a glass, 12L RBF that was sitting in a dry ice/acetone bath. One day, I noticed that each piece of sodium was making the solution hotter & the dry-ice wasn’t coping with the exotherm. I realized that a boil-over of this mixture was going to be bad news. I notified my supervisor and he alerted everyone to hold open doors as I donned safety apparel and then quickly carried the 12L flask to an cork ring laid upon the grass outdoors. I jumped back and it exploded with a 12 ft circle of fire.

    Our consultant quickly guessed what had happened. He suggested that I place a cotton filter in the tubing from the ammonia cylinder and sure enough, we caught a lot of rust coming from that cylinder. The iron oxide had reacted with the sodium. From then on, we always filtered our ammonia for experimental use and had no further problems. So be wary of quality when up-ending gas cylinders.

  14. The chemical that kills the most chemists each year is gasoline. If you assume that 0.1% of Americans are chemists, about 30 of us die every year in car accidents. Probably a third of those are during our commutes or are otherwise work related.

    Interestingly, here in Japan where I currently work, commutes are explicitly considered part of your job when it comes to safety, and traffic safety is often a topic in our safety meetings. This is precisely because it is often the most dangerous thing most people do in a given day.

  15. It’s a weird feeling to read that many of the substances with which I’ve worked on a 20 – 30 g scale are considered “most dangerous” by colleagues e.g.,: trimethylsilyl cyanide (I make my own using KCN) and hydrazine. As far as putting out other people’s fires for them is concerned, the most prominent must be t-butyl lithium.

  16. DDVP, Naled, OMAT…and that’s in the last week.

    While working in a trace metals analysis lab at a chemical plant, I used gallons of 70% perchloric acid and 49% HF per week. Oh, and I was usually alone in the lab. I was more nervous about the HF.

    When I was 17, I made chloropicrin at home. It was probably the worst idea I’ve ever had.