Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: vmelkon on March 25, 2010, 08:47:23 PM
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What would happen if you had had one of those glass dewars made by Thermos at 20 C and you poured LN2 in it. Would it crack?
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Sometimes. Chemist generally use glass dewars for small amounts of liquid nitrogen (up to a few liters)
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Hi there I'm really interested in that question, I've a termo for coffee similar to this one:
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fwww.nautilus21.com%2Fcatalog%2Fimages%2Ftermo_lacor.jpg&hash=8d20eb90c5e814cd61cdb0271068c8adf868c341)
It's like 1,5L capacity, and I wonder if I could put LN2 into it and put it in the freezer. Would it last for 7 days or something like that? Would I've to left the termo open? (I ask because I've seen people putting LN2 into a closed bottle and puting it into a pool, and the bottle explodes).
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No idea how long it will last. You can't close it tight, gas must be able to escape.
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Ok, so if I left it a bit opened, at -20ºC in the freezer and with some kind of blanket around (leaving air ot get out) what do you think, more or less, 4-5 days?
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Safety precautions and evaporation rate data
http://www.admin.ox.ac.uk/safety/s403.shtml
http://www.bovine-elite.com/tanks.asp
http://www.chem.purdue.edu/chemsafety/chem/ln2.htm
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According too my Flinn Scientific catalog and reference, 2009
"How long can liquid nitrogen be stored in a Dewar flask? Our best estimate is that a GOOD 1000 ml Dewar flask will lose approximately 500 mL for every 24 hour period stored. The larger the Dewar Flask the slower the loss rate.
I doubt your thermos will even come close to that. The same reference also warns against over tightening causing an explosion in a standard thermos, and that it is very likely for any plastics on the thermos to crack due to the temp. decrease N2 (lq) produces.
In case you were wondering, The prices for a Dewar flask from Flinn are:1000mL 119.00
1900mL 277.
d4l (with .4L a day loss) 638.35
and 10L with .22L loss a day: 808.35.
Flinn Chemical and Biological Catalog Reference manual 2009 Pp237-238
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One more thing - I think steel termo can become so cold on the outside that it can be dangerous to touch with bare hand.
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We just bought two, 200$ 1 or 2 L Dewars, high quality, from Nalgene, and they only last 6 hours max when filled. No way you'll get 4-5 days
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I know they transport liquid nitrogen on rail cars but i have no idea on what the loss rate is during the long trips.
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I can't imagine that they loose that much. If a 10 ltr. loses .22l a day, when we get into the hundreds of liters it has to be less.
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Would insulation make any difference? Styrofoam wrapped in a space blanket in the freezer makes all the difference with dry ice, for me.
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With the temps that low, I cant imagin it making a world of difference. A Dewar flask has a vacuum between the inside and outside, NOT insulation (it attempts to stop thermal conductivity between the liquid and the rest of the world) Now, some thermoses per wikipedia use this technology (apparently the expensive Thermos brand ones) but I cant imagine the vacuum being as strong as say, a professional one.
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I think this calls for some science. Tomorrow I'm going to go buy a regular coffee thermos...fill it with liquid nitrogen, and place the cap loosely over the top. Then we shall see how long it lasts if it doesn't implode or something crazy.
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Safety precautions and evaporation rate data
http://www.admin.ox.ac.uk/safety/s403.shtml
http://www.bovine-elite.com/tanks.asp
http://www.chem.purdue.edu/chemsafety/chem/ln2.htm
What is a coldfinger?
http://www.lennox.ie/pp/Rotary_Evaporators/Coldfinger_Condenser/Rotary_Evaporator_RE302_with_Cold_Finger_Condenser_from_Stuart.html
What was that about a cryotube explosion? What does the tube look like?
http://www.chem.purdue.edu/chemsafety/chem/ln2.htm
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With the temps that low, I cant imagin it making a world of difference. A Dewar flask has a vacuum between the inside and outside, NOT insulation (it attempts to stop thermal conductivity between the liquid and the rest of the world) Now, some thermoses per wikipedia use this technology (apparently the expensive Thermos brand ones) but I cant imagine the vacuum being as strong as say, a professional one.
Good point. I have broken one and the glass thickness is 2 mm. Perhaps it doesn't have a total vaccum in it.
I'm not sure about the distance between the glass walls but I estimate less than 1 cm but perhaps this isn't important.
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I have a 4L glass dewar at home, kind of in the style of a large round bottom flask to minimize surface area. Real dewar, not improvised. When in the past I have brought LN2 home, with a styrofoam cork in the dewar, I had usable LN2 for 3 days.
I just moved, now I can post from home again :)