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Author: Subject: Sealing Ampules with Methanol content inside
Quadzumo
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[*] posted on 29-11-2013 at 01:09
Sealing Ampules with Methanol content inside


I'm looking to fill 10 ml ampules with a mixture that is mainly Methanol. That i know of, the only sealing Methods are with flame. If I go ahead and try to seal the ampules will they explode on me since the Methanol inside the ampoule is highly flammable, even tho the ampule is being heated from the outside. Is there any way?
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confused
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[*] posted on 29-11-2013 at 03:34


if you could seal the ampules under an inert atmosphere with a torch that has it's own oxygen supply, that might work.

if you could find a way to cool the methanol to below 11-12 degrees celcius you could lower the solution to below the flash point of methanol, but you'll need a way to prevent the tube from cracking due to thermal shock

or you could just use vials with screw caps on them
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dangerdog
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[*] posted on 29-11-2013 at 04:30


As confused said if you cool them down.
The normal way is cool in liquid nitrogen, add your inert gas and flame seal them.
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Pyro
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[*] posted on 29-11-2013 at 15:59


*untested procedure* how about igniting the small amount of vapor in the head space, then sealing it? that way it's under CO2, which is inert (mostly)



all above information is intellectual property of Pyro. :D
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[*] posted on 30-11-2013 at 08:17


Seal it as you would any other ampule, however, take care to fill it well below where you will be sealing. Were some of the methanol to vaporize, it won't harm you, but will render the task of finishing the seal quite tricky.
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Morgan
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[*] posted on 30-11-2013 at 13:40


I recall reading about cutting quartz tubing with CO2 lasers and wondered if it would work for sealing ampules whereupon I came across this. Sadly, cutting or fusing glass with CO2 lasers would be a luxury for most.
Sealing glass ampoules with CO2 lasers
http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-47-35-6...
http://www.synrad.com/search_apps/application_briefs/20-1.ht...
http://www.synrad.com/search_apps/application_briefs/53-3.ht...

[Edited on 30-11-2013 by Morgan]
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elementcollector1
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[*] posted on 30-11-2013 at 13:51


I remember sealing an ampoule with calcium metal turnings and kerosene inside (to preserve the calcium). The tip of the ampoule was much more brittle and resistant to pulling, and there was a black film of carbon on the tip. Probably incomplete combustion of the kerosene vapor. I would imagine the same could happen for methanol, so be wary of this.



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Morgan
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[*] posted on 30-11-2013 at 14:15


I don't think I've ever seen soot when burning methanol. The most soot I ever saw was with acetylene, where I made a blizzard of soot unintentionally.
"The mixture components represented a highly sooting fuel, toluene, and a non-sooting fuel, methanol."
http://rspa.royalsocietypublishing.org/content/435/1894/359....
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The_Davster
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[*] posted on 30-11-2013 at 17:37


Flammable =/= explosive.

All you need to make sure is that at the moment of sealing the vial pressure is lower than the surrounding air so that the molten glass gets sucked in sealing the ampule and not pushed out.

Simply heat the neck of the ampule to softening, twist and draw it out, while simultaneously dipping the MeOH side of the ampule in dry ice/acetone or LN2. Even a very good ice bath at -10 or so would work, and be more ideal than dry ice acetone as it is hard to do this without setting the acetone on fire. A piece of cardboard covering the dry ice/acetone bath with an ampule sized hole can work wonders for avoiding setting the bath on fire.
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MrHomeScientist
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[*] posted on 2-12-2013 at 07:48


A cryogenic liquid on fire? Now that's something I'd like to see.
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Morgan
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[*] posted on 2-12-2013 at 16:26


The flash point of methanol is 11 - 12 C according to Wikipedia. Acetone is -20 C . Some sites like Sigma-Aldrich say -17 C.


[Edited on 3-12-2013 by Morgan]
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