it is hazardous to place something in liquid nitrogen and touch to yourself or put in your mouth. that object could be well below the freezing point of water, it could cause instant cell death. this would include freezing food objects or cooling alcohol beverage. as mentioned before touching an uninsulated container at liquid nitrogen temperature will freeze cells.
things have to reach their combustion point temperature before burning. things don’t burn when they are cold.
a bong of liquid nitrogen could be very hazardous. you would have a lung full of cold nitrogen gas. it could be so cold as to damage your lungs, nitrogen gas is an asphyxiation hazard at that concentration as well.
This is easy to overlook, even for someone smart enough to avoid frozen flesh. Nitrogen gas won’t directly hurt you, but if you add a bunch of it to a room, it will displace oxygen. And a lack of oxygen will make you a little stupid, then make you pass out, then kill you dead. And note how the first effects can easily lead to a) not noticing them, and b) failing to take steps to remedy the problem.
If you’re playing with it inside, make sure there are fans or other ventilation unless you’re in a very big space.
I found a distributor who will sell me some. Now I need to find someone to rent me a dewar.
Does anybody have an estimate at how long LN2 will last in an enclosed styrofoam bucket (like the ones used to hold ice in hotels)? If it will last 12 hours I might be able to get by with one of those.
it is very important to allow for pressure relief of the container. do not put into anything with a screw on top. the top must be able to come up (with the slightest flick of a finger) to relieve pressure, not necessarily come off.
you also want a container that is stable and will not tip or spill its contents easily and be insulated so you can touch it without being exposed to the cold.
i would read all the cautions people have given and take them to heart.
doing home made liquid nitrogen ice cream is a hazard. don’t ingest it until it is at normal household food freezer temperature. ingesting it before then could cause frostbite and maybe cell death in mouth, tongue and throat and would happen instantly before you could sense it.
A cell line doesn’t have warm blood pumping through it. You can definitely stick your hand in liquid N2 and pull it out without harm. I’ve done it many times. I doubt that your liquid Nitrogen was much below boiling either. If it was, your hand will change that quickly.
I would be suprised if anyone would sell you liquid nitrogen into an unapproved container. Like Chronos says, it can explode if mishandled. Even beyond simple pressure expansion, it can condense liquid oxygen. Unlike liquid Nitrogen, liquid oxygen is quite dangerous and can detonate from contact with almost anything.
I’ve used liquid nitrogen quite a bit. While it isn’t as dangerous as most people usually think, it’s certainly not “safe”. Mostly going to reiterate what other people have said.
When evaporating the stuff will expand to about 700 times it’s volume, therefore it doesn’t take much to fill an average sized room if you spill the stuff. If this does occur in an enclosed and poorly ventilated space you have much less time than you think to get out. The stuff will displace the air in your lungs just as easily as the air in your room and you can go from fine to unconscious in seconds. Fortunately it will tend to fill a room up from the bottom rather than spreading evenly, but this can cause problems if someone bends down suddenly to pick something up.
As people have said, keeping it in a sealed container will cause an explosion, the better sealed and stronger the container, the bigger the eventual bang.
These two factors are by far the biggest risks associated with the stuff and also combine to make it hard to transport safely, spilling it is bad (especially in a car) but you can’t transport it in a sealed container which increases the spillage risk!
As far as it’s freezing effects go you can treat it exactly the same way that you would with a very hot liquid with a couple of specific caveats - Firstly it is easy for the stuff to spill on other objects and cool them to the point that they can burn you.
Secondly whilst the leidenfrost effect discussed up thread does provide a degree of safety in handling, it is a very dangerous thing to rely on. The effect is caused by instant evaporation of the nitrogen, forming a cushion of gas between the droplet and the surface it has spilled on. The problem is that the effect tends to disappear abruptly once a threshold temperature has been reached. So one minute the stuff might be spilling off your hand and cooling it slowly and the next second your hand gets too cold and you are suddenly sustaining serious injury.
Being splashed on your clothing can cause problems because the fabric will quickly cool to the critical point and then get cold very fast, this cold fabric will then quickly reduce the surface temperature of your skin to the point that injury would occur. Sadly the the false sense of security caused by this effect can often cause people to be much sloppier in handling it than they would otherwise or to mess around with it, whilst unaware of the degree of risk they are taking.
As I said earlier if you treat the same way you would a very hot liquid whilst being careful not to keep it in a sealed container or use it in a confined small space you should be pretty safe.
An update just in case somebody finds this thread looking for LN2.
I was able to get a used dewar at Cambridge Scientific Products for a good price. I had to go to them, though–my phone calls were ignored. I was also lucky (I think) that they just happened to have a smallish dewar.
I found LN2 by looking up welding supplies. The best deals I found were at Spec Air Gases & Technology (the owner was very friendly) and Igo’s Welding Supply. I was able to get LN2 for less than $1/liter. Definitely check around–apparently the price will swing wildly up or down depending on how much they have on hand. One place gave me a quote of $3/liter one week and $7/liter the next week.
We made ice cream and it was very good. It took a few iterations to get the process down but we ended up with very creamy ice cream. Frozen marshmallows were a big hit too. I grabbed the opportunity to sneak in a physics lesson for my two teenage nieces and their friends.
Thanks for the suggestions and the safety tips. I felt pretty confident that nothing would go wrong.
quick question: is the reason for liquid nitrogen’s relative safeness because of it’s low thermal conductivity or because it forms an insulating layer of nitrogen gas around whatever it touches?
Chronos is right, in my experience. I have many times stuck my finger into a bowl of liquid nitrogen for several seconds, and poured and held a small handfull for a few seconds, and even taken a small mouthfull and then blown it out (to spectacular misty effect).
I’m sure that you can do yourself very nasty harm with LN2, and I consider the possibility of touching a solid object at LN2 temperatures as a very nasty threat (especially if the fingers are wet with water). But brief splashes and submersion of extremeties in the liquid does not seem to be a problem at all. It has only ever given me a whole new meaning of “how interesting, now let’s try this…”.
I’ve been playing with it a lot for the last couple of months, mostly making ice cream and sorbetto.
Safety guides say wear gloves, but I’m not so sure that’s a good idea. If the stuff soaks into or runs into your gloves, you’d be a lot worse off than if you just splashed it on your bare hand. Once while making ice cream, my girlfriend suddenly screamed and shucked her gloves as fast as she could. We were using our patented Dr. Horrible welding gloves, but they won’t help you if the stuff runs inside.
I’ve seen someone dip their hand into LN2 and splash it at us with no ill effect. I also saw someone get frostbite trying to imitate that person, so beware.
A lung-full of pure nitrogen will suck the oxygen back out of your blood. In a pure N2 environment you can be unconscious in seconds. A couple of safety documents I’ve read claim that more than half of N2-related deaths were caused by people rushing in to try to help someone else. One poor sap was standing over a vat of LN2, got a lung-full of the stuff, and then pitched forward into it. He was not missed for several hours. Mull on that.
That said, as long as there’s reasonable ventilation, and you don’t actually spill the whole dewar on the ground, there’s really nothing to worry about.
Picked up a 30L dewar for nothing on Craig’s list, but it’s rusty on the inside. Anybody know where I might take such a thing to be inspected, cleaned, and have its vacuum replenished? I’m in Silicon Valley FWIW.