A recent XKCD What If made me go “huh?” when it said that hazards associated with liquid nitrogen include “violent reactions with organic materials” and “severe clothing fire”. Since nitrogen is pretty inert most of the time I wondered how this could be. But the link in article to a liquid nitrogen safety page explained it:
“Because the boiling point of oxygen, 90.1K, is above that of nitrogen, oxygen can condense from the air into the liquid nitrogen. If the air over the nitrogen circulates, this liquid oxygen can build up to levels which may cause violent reactions with organic materials; even materials which are ordinarily nonflammable. For example, a severe clothing fire could result from ignition in the presence of liquid oxygen.”
Live and learn. It also mentioned the suffocation hazard, which interestingly enough io9 featured just recently, on why tossing liquid nitrogen into a pool is a bad idea:
What idiots. LN2 safety folks tell you that if you spill a large amount of LN2 in a small room there is a very good chance you won’t make it out the door.
The odd thing with nitrogen suffocation: you body panics if it cannot get rid of CO2, but not if it fails to get Oxygen.
Theo Gray includes a section on condensing liquid oxygen using liquid nitrogen in chapter 4 of his wonderful book Mad Science. It’s also on his website here:
http://graysci.com/chapter-four/flaming-oxygen-drops/
I wish I’d thought about this (or known about it) back when I had virtually unlimited access to liquid nitrogen. It would’ve been fun. As it is, telling you about the pssibility of condensing liquid oxygen wasn’t even part of the standard safety lectures I had. It’s understandable, in a way – you need an uninsulated container for the lLN, and who the heck uses anything but a Dewar flask or a styrofoam cup? (Otherwise, you get frost burns)
I remember reading a post by a Doper who put himself in the hospital when he made a mistake with liquid nitrogen. He sipped some, and forgetting that he should have immediately exhaled it in a cool but harmless plume, he swallowed it. I believe he was in intensive care for a bit.
I must say I would never have guessed. Apart from anything else, you would think that liquid oxygen would be a bit, you know, like cold to catch anything on fire.:eek:
The energy of reaction between pure oxygen and many substances is more than enough to outweigh a bit of chilliness.
And yes, if you’re splashing liquid nitrogen around, you want to make sure you have very good ventilation in the room. I used to use it a lot in the lab and I think the spec was something like 15 complete air changes per hour (and the nitrogen being used in a fume cupboard).
Liquid oxygen is wicked cool. Back in Jr High we had a guy do a demonstration with liquid oxygen. He did a few normal cryo tricks like freezing a flower and shattering it, but the one trick that stood out was when he smeared Vaseline on a little paper dish, poured some liquid oxygen on it, and hit it with a hammer. It made an impressive explosion.
One other demo I saw on TV a while back, heat a small diamond to glowing red hot, drop in in a Petri dish with a little liquid oxygen, and watch as it sizzles away to nothing but CO2 gas.
The article mentions that revellers were “coughing and hacking”. Why? I would have thought that under the circumstances they would just be calmly dropping dead.
“Don’t” is like saying, “Just say no!” You need to tell a scare story:
We were making hydrophones out of a previously mixed batch of urethane which had to be stored at extremely low temperatures (less than -100° F, IIRC), otherwise the material would beginning setting in the shape of the container.
We used a top opening freezer to store the containers material with the thermostat set to the lowest temperature. That wasn’t low enough, however–we augmented the cooling with dry ice pellets. Had to add a new batch every few days as the stuff sublimated.
As we started going through the boxes, we had to reach into the freezer deeper and deeper. As we finished with the production run, I went to get the last set of boxes at the bottom of the freezer; six inches of pellets remained at the bottom. The freezer light allowed you could to see the pool of a condensed water vapor cloud bleeding over the side of the freezer.
Without thinking, I stuck my head into a container consisting of pure CO2, and took a lung full…
Pain and panic. Think of the worst soda pop burp you’ve ever had (you know, the one that makes your nose burn?). Imagine everything burning–nose, eyes, mouth, windpipe, tongue, uvula, hell even your tooth fillings. And panic–wondering if you’re going to die because you might have giving your lungs frostbite, or if the carbonic acid destroyed my lung alveoli. I’d say this is about as close to water boarding as I’ll ever get or want. It was that bad.
Huh, I always liked taking a small, tingly whiff when scooping from the bottom of the dry ice chest.
As others have mentioned, liquid oxygen is bad news. A blue Schlenk trap (someone else’s; stupid postdoc) is the only reason I’ve made people evacuate a lab.
Another guy I worked with was following one of my preps and dipped a PTFE-stoppered glass vessel too deep into the LN2. The cold caused thePTFE to shrink sufficiently such that oxygen was able to bleed in and condense. When he removed the vessel from the cold bath, it promptly exploded in his hand.
I’ve gotten the feeling over the years that “stupid postdoc” is a common sentiment in academic labs. Personally, I’m glad I’ve never had to work much with liquid nitrogen though I did know of a cold trap or two using liquid nitrogen that blew up in undergraduate labs. I always liked watching the NMR expert doing the helium fills and his being able to tell how far along the fill was by the condensed gases that were dripping off the transfer lines at the time. I never worried until reading this thread that something might go horribly wrong during a nitrogen or helium fill and somehow set the NMR room on fire. Quench and massive release of gas, yes. Fire, no.
I’m not sure how much LO2 you end up dripping during a normal He fill. I never really thought about it. Like you, I was more concerned with a room full of not-oxygen
And stupid postdocs can serve the purpose of motivating students. “If that moron has a PhD…”
Indeed, breathing a mixture of CO2 and O2 (known as carbogen or Meduna’s mixture) will induce a state of panic, sometimes leading to a psychedelic experience.
I was making lemony concoction of gin, frozen lemonade and club soda. After pouring said ingredients into a pitcher I hoisted it up for a taste test. As my nose and mouth were in the pitcher, the breath I took before the fizzy mixture touched my lips was pure CO2 from the club soda. I very nearly passed out…and committed the unpardonable sin of spilling half a fifth of perfectly good gin on the kitchen floor.
