Making Ice Cream With Liquid Nitrogen

JasonMaggini writes "Popular Science has an article on how to whip up a batch of ice cream in 30 seconds or so by using liquid nitrogen. Just the thing for those hot summer days. The article is by Theodore Gray, creator of the ultra-spiffy Periodic Table Table."

Comments

Re:Gargling

[KjetilK]

I've read one account of a person who regularly gargled with that stuff, until one day he cracked a tooth...

I've done that many times at parties. It is cool in every way you can think of... :-) My teeth are OK...

Not risk-free of course, and you don't want to get that stuff down in the stomach... :-)

I do things like firewalking (had a world record once, 165 feet, and btw, I think the current listed record is invalid), sticking the hand in molten lead, bed-of-nails, etc.

Icecream is great BTW, it's something the physics department always hands out when it tries to attract potential students...

Re:Leidenfrost

[reverseengineer]

Yes, you're right- I should have been more specific when I wrote "small quanitities." Due to the possibility of tooth damage, I'd never put more than a few milliliters into my mouth anyway. As for swallowing the stuff, I probably deserve a -1 Imprecise Use of Language for using the word "consume" when I meant more along the lines of "let it evaporate, inhale/exhale fog"(though you should also be careful with this-"DOES NOT SUPPORT LIFE" and all). As far as I can remember, I don't think I've swallowed the stuff, and if I had, it would have been a matter of a few droplets.

You're absolutely right with the whole expansion thing, though- according to some quick and dirty calculations I just did, a scant 10mL of LN2 would expand to about 7.3 liters at body temperature, which certainly might cause problems. For a comparision, the average volume of a human stomach is about 1 liter. Ouch.

I'd like to know more about the whole "it closes the entrance to your stomach" thing though. Elsewhere in this /. discussion I came acorss mention of the 2000 Darwin Awards Personal Account of a college student who required hospitalization after taking a "shot" of LN2. Now, once I again, I can see how this would be a problem- assuming he actually swallowed somewhere around 1 fluid ounce (29mL) of LN2, the end result could be over 20L of ultracold gas in his digestive tract, which would probably have a deleterious effect. In the story, though, it mentions that it's his epiglottis that keeps the gas trapped, but I'm not sure that I buy that- the epiglottis is not some sort of one-way valve- frankly, all three of the normally encountered phases of matter can return up the esophagus if the situation demands it, which becomes clear if you burp, or have occasion to pray to the porcelain deity. I don't doubt that's it's possible that LN2 could cause the digestive tract to seal up at prevent the escape of gas, but I am curious as to the mechanism of how this happens.