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Author: Subject: Liquid Nitrogen Dewars. Why so expensive?
ftirinih
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[*] posted on 3-12-2007 at 19:08
Liquid Nitrogen Dewars. Why so expensive?


I've been looking to buy a 10-30 liter dewar for liquid nitrogen. They seem to sell on ebay for about $150 at a minimum, what is driving the price so high? Who else uses these things?
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MagicJigPipe
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[*] posted on 3-12-2007 at 19:43


10-30 liters!!??? No wonder they are $150... How much would you expect to pay for just a plain jane 10-30 liter round bottom flask? I think it would be comparable.

And remember, you would have to use that 10-30 liters in a relatively short period of time. Out of curiosity, what do you need that much liquid N2 for?

And the way I understand it, there is a vacuum between the liquid area and the outside of the flask so they have to made to hold that vacuum. And since they are usually made for professional environments, they surely have to conform to stringent specifications.
[Edited on 3-12-2007 by MagicJigPipe]

[Edited on 3-12-2007 by MagicJigPipe]




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[*] posted on 3-12-2007 at 20:13


I have a 20 liter dewar and it keeps LN2 for a suprisingly long time, on the order of months. I also can get it filled for 10 USD, which is handy. Mine is an old MVE model that was donated to me. Shipping would also be an issue, and 150 USD is a good price on one of those. Ever see the new price? I was working in a lab this summer, and even the small guys were up to 100 without much difficulty. A 1 or 2 liter vacuum flask was 300 USD, sure, more complicated, but 150 is a steal. How much would it cost to fill it? That is the main issue, IMHO.
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MagicJigPipe
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[*] posted on 3-12-2007 at 20:40


I agree that $150 is a GREAT price.

I was unaware LN2 lasted that long. My short experience with it did not give the same result because I had less than a liter. Ice on top was annoying from what I remember.

I've always wondered... Does some liquid O2 condense in or around the N2 seeing as though it's boiling point is below N2s? It would be interesting to experiment with liquid O2 if it could be condensed with LN2.

Liquid H2 would be even more interesting. Seems like it would be dangerous. Or even more dangerous, a mixture of LO2 and LH2.... Sorry, I'm just rambling.

Also, a company in the US called Airgas will deliver LN2 for a decent price. They even let me rent a DEWAR. I'm not sure if that is policy for everyone because I new the guy who set it up for me. He used to deliver our gaseous N2 and compressed air when I worked in an optical lab.




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UnintentionalChaos
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[*] posted on 3-12-2007 at 20:50


Hydrogen: boiling point: 20.28 K Not happening....

Liquid Oxygen: See thread: http://www.sciencemadness.org/talk/viewthread.php?tid=5831&a...




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MagicJigPipe
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[*] posted on 3-12-2007 at 21:01


I wasn't suggesting condensing it with N2. I was just saying it's interesting to think of something that cold.... and basic.



"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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ftirinih
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[*] posted on 4-12-2007 at 16:53


I need the LN2 for cooling IR detectors, and any other science type of project I may do in my spare time. Mainly, just fiddling around in the basement.

The 10-30 liters is a guess, the larger dewars look more study. I would have to take the dewar in the car to get it filled - there is an airgas outlet nearby that I think would sell LN2 to you if you showed up with a reasonable dewar. I don't think it is very expensive.

I hear you about the price of these things new - really quite high.
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[*] posted on 12-12-2007 at 06:45


Wow, that a lot of liters! I tend not to keep any amount of chemical that large in my lab. However, I can see your point (with what you're using it for). I'll keep on the look out. I come across a great deal of used glassware in my travels.
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[*] posted on 12-12-2007 at 11:26
N2 Kills!


If you consider N2 a "chemical". :cool:

Although, I suppose in the liquid state, it really could kill.




"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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vulture
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[*] posted on 12-12-2007 at 12:46


LN2 will condense LOX out of the air and slowly replace itself with it.

This presents both a SUFFOCATION and a FIRE/EXPLOSION hazard.




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[*] posted on 12-12-2007 at 16:55


I want to see this: lasting a month. Is the insulation a foot thick?
Normal 2 l dewars, professional ones (with vacuum) last over night with the lid on.
Big 50 l dewars, for storing biological samples, crystals etc are insulated heavily and are yet refilled at least once per week. Many liters of N2 are replaced every time.
A suggestion: normal foamed polystyrene boxes (styrofoam), preferably coated with some plastic on the inside to prevent N2 seeping, with a nice lid, keeps the N2 very nicely - in fact this is what we use if a proper dewar can't be found :) Not sure about hte health and safety ratings on this though :)

[Edited on 13-12-2007 by chemoleo]




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[*] posted on 12-12-2007 at 17:00


I was given a 30L dewar for liq N2 now I just have to find a place to get it filled

and the right gloves!

[Edited on 12-12-2007 by contrived]
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MagicJigPipe
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wink.gif posted on 12-12-2007 at 17:24


Maybe you should attempt synthesis of alprazolam, Vulture. Good gosh golly!



"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Fleaker
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[*] posted on 12-12-2007 at 20:13


Quote:
Originally posted by chemoleo
I want to see this: lasting a month. Is the insulation a foot thick?
Normal 2 l dewars, professional ones (with vacuum) last over night with the lid on.
Big 50 l dewars, for storing biological samples, crystals etc are insulated heavily and are yet refilled at least once per week. Many liters of N2 are replaced every time.
A suggestion: normal foamed polystyrene boxes (styrofoam), preferably coated with some plastic on the inside to prevent N2 seeping, with a nice lid, keeps the N2 very nicely - in fact this is what we use if a proper dewar can't be found :) Not sure about hte health and safety ratings on this though :)[Edited on 13-12-2007 by chemoleo]



There's so much variation with dewars. The 50L dewar I get from Linde will last 4 days tops when full. The 35L I have in the lab will hold LN2 for at least 90 days and I can say that with certainty.



[Edited on 12-12-2007 by Fleaker]




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[*] posted on 13-12-2007 at 05:19


Quote:
Originally posted by MagicJigPipe
Maybe you should attempt synthesis of alprazolam, Vulture. Good gosh golly!


Perhaps you've not heard, vaporised LN2 asphyxiation is one of the most common ways for a chemist to go. It's colourless, odourless and you don't know it's happening until you're at the pearly gates. If he was using it in his BASEMENT, which I must assume has poor ventilation, and considering that 1L LN2 might displace up to 600 L of oxygen, i.e. 2200 L of air, it presents a very real hazard. So be glib all you want, I'm sure St. Peter will appreciate it. :cool:




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[*] posted on 13-12-2007 at 20:57


Yes, this is a dangerous situation unless you have your lab set up for maximum safety. I keep any potentially dangerous chemicals in a building just outside my house and lab. Even with prime venting systems in place, I rather savor the idea of living to old age.....:o
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[*] posted on 13-12-2007 at 21:13


Yes, yes, yes... displacement of O2 and all that obvious stuff. I was speaking of it's hazards in a competent person's lab. Someone who knows what they're doing. What's so difficult about ventilation? If someone stores a liquid that they know boils rapidly at room temp and displaces O2 in a confined, non-ventilated area then I can't have much sympathy.

Other than that and it's temp it's pretty inert. Can we agree on that?

I know you guys love me and care for my safety and all but I'm not stupid. ;)

Don't take offense to this. I know you're just trying to be good sumaritans. Let's just try to do away with the condescending undertones in the future, please Vulture.




"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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[*] posted on 14-12-2007 at 00:12
syphons and gloves


I need a syphon for our dewar which is 8L, not 30L. Anyway, there's no syphon on it; just a little stopper where one would go and I know the gloves we have aren't up to a liq. gas splatter or spill. I really like having fingers. Are there any alternatives to buying the expensive lab shit for these items?



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[*] posted on 14-12-2007 at 08:00


Quote:
Originally posted by chemrox
I need a syphon for our dewar which is 8L, not 30L. Anyway, there's no syphon on it; just a little stopper where one would go and I know the gloves we have aren't up to a liq. gas splatter or spill. I really like having fingers. Are there any alternatives to buying the expensive lab shit for these items?


Based on what I see in our labs, you don't need to worry so much. LN2 doesn't have that high a specific heat, and if a bit splashes onto your skin it just flash-evaporates, not cooling your skin enough to injure it. You can even poke your finger (very briefly) into a cup of the stuff without injury.

Prolonged immersion is dangerous. Spilling it onto yourself in such a way that it's trapped against your skin is dangerous. Touching an item with higher specific heat and/or conductivity that's been in contact with LN2 is dangerous, because that can flash-freeze the top layer of your skin, leaving you stuck to the item, which means more of your skin freezes.
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MagicJigPipe
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[*] posted on 14-12-2007 at 15:55


Yes, JeffB is correct. You only need to worry about spilling large amounts or spills on certain body parts like your balls. Just don't do LN2 experiments in the nude if you value your genitalia.

Still though, it doesn't feel good even with minor spills. It's a wierd sensation actually. And also, if you put it in something other than a DEWAR and ice forms on the outside, don't touch it! It can be a lot colder than dry ice and you might get stuck to it.

On a minor note. Never spill alcohol on your sack. It burns (dehydration?). Someone told me that ... yeah.




"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think, free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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[*] posted on 15-12-2007 at 09:28


Quote:
Originally posted by MagicJigPipe

On a minor note. Never spill alcohol on your sack. It burns (dehydration?). Someone told me that ... yeah.



I'll keep that in mind :P


Main dangers with LN2 in my opinion are a.) what you chill in it, b.) spilling it on absorbent clothing. I've had frostbite before from inadvertently touching acetone that had been chilled in LN2, ouch. Also, I've almost got frostbite from spilling LN2 onto a cotton shirt. No Leidenfrost effect to protect you when it's soaked onto permeable clothing!




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[*] posted on 16-12-2007 at 06:17


I seem to remember having a debate with the safety people at work about the hazards of liquid nitrogen. There's no question that it's an asphixiant but I work in a very large, well-ventilated lab so that wouldn't matter.

The real arguments were about the stuff causing frostbite, protective gloves etc. I got 2 dewars, filled one with LN and the other with boiling water. I poured some of the LN over my bare hand then offered the other (hot water) dewar to them and asked if they were planning to write a safety procedure for handling coffee.
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[*] posted on 17-12-2007 at 01:22


Quote:
Originally posted by unionised
The real arguments were about the stuff causing frostbite, protective gloves etc. I got 2 dewars, filled one with LN and the other with boiling water. I poured some of the LN over my bare hand then offered the other (hot water) dewar to them and asked if they were planning to write a safety procedure for handling coffee.


Thats excellant unionised. :D

Our safetey people at Uni told us not to wear gloves with LN. If it spills into a glove and gets trapped then it will cause damage. As you said - if you pour it over your hand it evapourates off too quickly to do any harm. (we wore the very thick Thermal gloves when filling dewars from the tank as the nossel you had to hold get very cold).
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[*] posted on 17-12-2007 at 23:52


I'm relieved to read the above but my container won't work without a syphon so I still need to find one. The opening is too small to pour from without, I don't know what the technical word is, burping. Insulated cloth gloves would be nice.



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[*] posted on 3-12-2015 at 00:19


Quote: Originally posted by unionised  
I seem to remember having a debate with the safety people at work about the hazards of liquid nitrogen. There's no question that it's an asphixiant but I work in a very large, well-ventilated lab so that wouldn't matter.

I suppose it would be asking for disaster to store a 10L liquid nitrogen in dewar tank in the garage during the winter??

[Edited on 3-12-2015 by jamit]
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