| About This Archive | | DCHAS-L 2021 Index | | DCHAS-L Yearly Index | |
Check out Safety Emporium for your N95, N99, and face shield needs.
|
Previous by Date: Subject: Re: [DCHAS-L] Lan Safery position at University of Maryland Date: Monday, March 15, 2021 at 10:15:16 AM Author: pzavon**At_Symbol_Here**ROCHESTER.RR.COM |
Next by Date: Subject: Re: [DCHAS-L] Condensation of liquid oxygen in open Dewar flasks of liquid nitrogen Date: Mon, 15 Mar 2021 16:22:17 -0600 Author: Joseph DiVerdi |
I worked with SEM/EDS using an LN2 Dewar to cool the EDS detector for about 10yrs. Never seen it happen. However, this older article does anecdotally report it happening and resulting in ignition.
"ÉWe heard of an accident where ignition was due to the condensation of oxygen from room air in liquid nitrogen and subsequent elaboration of an oxygen-rich gas as the nitrogen boiled away. Because of the fire hazard, one should neither
allow liquid N2 to evaporate to drynessÉ"
J. Bastacky, T. L. Hayes, Safety in the Scanning Electron Microscope Laboratory, SCANNING Vol. 7, 255-272 (1985)
https://onlinelibrary.wiley.com/doi/pdf/10.1002/sca.4950070506
Thank you,
Yaritza Brinker
260.827.5402
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**Princeton.EDU>
On Behalf Of Daniel Kuespert
Sent: Friday, March 12, 2021 10:25 AM
To: DCHAS-L**At_Symbol_Here**Princeton.EDU
Subject: [DCHAS-L] Condensation of liquid oxygen in open Dewar flasks of liquid nitrogen
** External Email **
An interesting question occurred to me today: When you leave a Dewar flask of liquid nitrogen open to the atmosphere, such as when you're using it to cool the trap of a Schlenk apparatus, oxygen will condense in it since the boiling point
of oxygen is 90 kelvins vs 77 K for LN. How fast this happens will depend on the air-exchange into the flask, so if it's covered loosely, presumably the dynamics will slow down. Eventually, though, the flask contains liquid air, not liquid nitrogen, which
could become excessively exciting for someone who empties the flask by dumping it out somewhere near something combustible.
I've not seen any data, though, on how fast this actually happens. Has anyone ever seen data on this? If you have, please let me know. It would be useful to know how long one can really leave an open Dewar sitting around.
Regards,
Dan Kuespert
Laboratory Safety Advocate
Johns Hopkins University
Daniel Reid Kuespert, PhD, CSP
11101 Wood Elves Way
Columbia, MD 21044
410-992-9709
--- For more information about the DCHAS-L e-mail list, contact the Divisional membership chair at
membership**At_Symbol_Here**dchas.org Follow us on Twitter **At_Symbol_Here**acsdchas
The information
contained in this electronic transmission is private, confidential, the property of the sender, and intended for the use of the recipient(s),
only. If you are not the addressee, any disclosure, copying, distribution or use of this information for any purpose is strictly
prohibited. If you have received this information in error, please notify the sender,
YBrinker**At_Symbol_Here**fele.com, immediately by e-mail and then delete this message. Thank you.
[FE.EN.1]
Previous post | Top of Page | Next post