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March 1st, 2011
11:53 am - Tesla Down Under / Liquid Nitrogen
"Kids, don't try this at home" ... or anywhere else, either. I'm skimming a promising looking fun with science site when I see this: Liquid Nitrogen. Yes, the man stuck his hand into it - and why not?
 
"Where did I get the name 'Lefty' from? That's a long story ... if at first you don't succeed and all that ... where are you going?"
Oh, yes - that's why not. The author writes, following the appropriate (?) photo, which you're seeing a thumbnail of above, if you're reading this on my blog:
"I'm not sure I should show this photo but here is me (carefully) throwing all the safety precautions to the wind and putting my hand in liquid N2 (for about 0.5 secs).
When you're sticking your hand into a liquid that is just barely warmer than the surface of one of the moons of Neptune, I'm not sure that "carefully" is an adverb that you get to use. Just a thought.
The gas generation keeps a gas layer between you and the liquid and reduces the rate of freezing.
Yes, the concept is simple enough - your flesh is so much hotter than the boiling point of liquid nitrogen that the liquid will explosively evaporate on contact, briefly blowing much of the liquid away. Drop a bead of water onto a hot dry skillet and as you watch it dance, you'll see the same physical principle at work. Without having done the calculations, though, would I know offhand if the liquid N2 would be blown off one's hand quickly enough to prevent tissue damage? No. Would I care to risk my fingers on a guess, or more to the point, on the claims I just saw on the website of somebody I had never heard of before? Definitely not.
An even more enjoyable thought is this: the boiling point of liquid nitrogen is lower than the boiling point of liquid oxygen. Any container of liquid nitrogen will begin to accumulate a layer of liquid oxygen on its surface from condensation, just as moisture will collect on a glass containing a cold beverage. Owing to the greatly increased density of oxygen, post-liquification, even with the reduction in the rate of chemical activity induced by the great cold, liquid oxygen is a very potent oxidant, potent enough to have served for the burning of rocket fuel in the apollo program.
Liquid oxygen is dangerously reactive stuff, so much so that in Thermodynamics class in undergrad a standard warning was given about the explosive consequences of dropping anything made out of plastic into the stuff, producing a rapid, highly exothermic reaction in anything that can be set on fire. Great stuff to stick your skin into, right? Care to take your chances with a trip to the burn ward if you've poured out a little too much N2 and let it sit a little too long? The author continues:
Sensation is like a cold breeze and no discomfort but I am not pushing the boundaries here. Of course touching a solid,
Like, say, the walls of the container - but of course, that would never happen, because nobody ever accidentally bumps into anything, especially if he should be startled by somebody yelling "what do you think you are doing" or something like that
particularly metal, at liquid N2 temperature will give rapid severe frostbite and it might stick to you.
Or if, maybe, you were sweating a little more than you thought you were, and the sides of that container weren't as smooth as you expected them to be. Fun fact: anywhere outside of the orbit of Saturn in this system, water ice is hard enough to qualify as a rock - at temperatures that will, in places, be well above that of liquid nitrogen. Picture yourself bonded to something, your fingers immersed in that lovely fluid, maybe panicking a little as you find yourself needing to either yank yourself off and rip some flesh away in the process ... or, wait ... maybe you could wait for help that you know is coming soon. I mean, what could that do to you?
To treat warts and other skin lesions it is applied with a cotton bud and will rapidly kill tissue.
Oh, right. The skin lesions, on brief exposure, turn into something that crumbles away. The would be daredevil might very well, in a moment of panic induced misjudgment, lose his fingers.
Advice from the 'experts' for this somewhat risky stunt say not to get the liquid N2 in any crevices in your fingers or clothes as the liquid N2 gets forced in contact and freezing occurs."
Look at your own hands. What do you see a lot of, and even more of with age? Crevices. I'm not convinced, at least not on a brief reading, that the author did what he claimed with as little damage done to his person as he says, but I am convinced that this would be a fantastically stupid thing for anybody to do. This isn't "somewhat risky", this is absolutely insane, even as a half second dare, and the author gives us no sign of getting that.
I'll take a look at more as time and resources allow, but on any such page, one does have the question of how good the author will be at alerting the visitor to the possible dangers of what he is about to do. On this occasion, he has fallen distressingly short of doing just that. We would be most unwise to forget that as we read the rest of his site. |
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