4 ms·

Interesting fact about liquid nitrogen (that I learned from Dave Arnold's book, which is fantastic): liquid nitrogen is ~700x denser than gaseous nitrogen. So,

by mrjones 12y ago

Interesting fact about liquid nitrogen (that I learned from Dave Arnold's book, which is fantastic): liquid nitrogen is ~700x denser than gaseous nitrogen. So, if you vaporize a moderate amount of liquid in a contained space (e.g. spilling a dewar in a car or elevator): even if you manage to avoid touching the nitrogen itself, the gas can crowd out the oxygen and you can asphyxiate yourself. Since it's odorless and colorless, you probably wouldn't even notice. So ... if you do try this at home, be especially careful when transporting nitrogen!!

mattmaroon 12y ago
Not just transporting it, but in your kitchen too. A professional kitchen that uses it should have an oxygen monitor so they can evacuate if it goes off. Also, don't screw a lid onto anything containing it or it becomes a live grenade.
jeffwass 12y ago
>>liquid nitrogen is ~700x denser than gaseous nitrogen. One of the coolest LN2 tricks we used to do at our physics demo days took advantage of this - making bubbles the 'fun way'. Take a big pot of boiling water and add some dish soap. Wearing your protective gear, dump a few liters of LN2 into the water/soap mixture, and see it explosively create 700x its volume in bubbles! Here's someone doing something similar (he uses room-temp water, not hot, so the bubbles come out 'frozen') https://www.youtube.com/watch?v=X5ZAoHxhihU https://www.youtube.com/watch?v=X5ZAoHxhihU On your comment about displacing air - in my actual research (when we weren't making LN2 bubbles) we used alot of Liquid Helium (for reference, LN2 at 77K is about 1/4th room temperature, while LHe at 4.2K is 1/70th room temperature). We'd often have superconducting magnet running with fields up to 10T, which IIRC required nearly 100A of current in the freakishly-thin superconducting magnet wire which was submerged in the bottom of the LHe bath in the cryostat. It's possible that the magnet could 'quench' where part of it goes 'normal', immediately heating up due to the huge current, causing more of the magnet to go normal, causing more heating, which eventually boils off all the LHe, releasing HUGE quantities of He gas into the room. Even something simple like transferring LHe from the storage dewar to our cryostat, or cooling down a cryostat the first time, releases huge amount of He gas into the room. I was glad we had an oxygen meter in the lab (which I demanded our adviser buy, she didn't want to waste the money on it at first).
imurray 12y ago
This warning is spot on. "Since it's odorless and colorless, you probably wouldn't even notice." — I remember being surprised reading a haz-card for liquid nitrogen that said you could suffer serious brain damage from lack of oxygen before noticing anything odd. Humans feel we're suffocating when there's too much CO₂, not when there's too little oxygen.
deleted 12y ago
[deleted]

by mrjones 12y ago

mattmaroon 12y ago

Not just transporting it, but in your kitchen too. A professional kitchen that uses it should have an oxygen monitor so they can evacuate if it goes off. Also, don't screw a lid onto anything containing it or it becomes a live grenade.

jeffwass 12y ago

>>liquid nitrogen is ~700x denser than gaseous nitrogen. One of the coolest LN2 tricks we used to do at our physics demo days took advantage of this - making bubbles the 'fun way'. Take a big pot of boiling water and add some dish soap. Wearing your protective gear, dump a few liters of LN2 into the water/soap mixture, and see it explosively create 700x its volume in bubbles! Here's someone doing something similar (he uses room-temp water, not hot, so the bubbles come out 'frozen') https://www.youtube.com/watch?v=X5ZAoHxhihU https://www.youtube.com/watch?v=X5ZAoHxhihU On your comment about displacing air - in my actual research (when we weren't making LN2 bubbles) we used alot of Liquid Helium (for reference, LN2 at 77K is about 1/4th room temperature, while LHe at 4.2K is 1/70th room temperature). We'd often have superconducting magnet running with fields up to 10T, which IIRC required nearly 100A of current in the freakishly-thin superconducting magnet wire which was submerged in the bottom of the LHe bath in the cryostat. It's possible that the magnet could 'quench' where part of it goes 'normal', immediately heating up due to the huge current, causing more of the magnet to go normal, causing more heating, which eventually boils off all the LHe, releasing HUGE quantities of He gas into the room. Even something simple like transferring LHe from the storage dewar to our cryostat, or cooling down a cryostat the first time, releases huge amount of He gas into the room. I was glad we had an oxygen meter in the lab (which I demanded our adviser buy, she didn't want to waste the money on it at first).

imurray 12y ago

This warning is spot on. "Since it's odorless and colorless, you probably wouldn't even notice." — I remember being surprised reading a haz-card for liquid nitrogen that said you could suffer serious brain damage from lack of oxygen before noticing anything odd. Humans feel we're suffocating when there's too much CO₂, not when there's too little oxygen.

deleted 12y ago

[deleted]