Sciencemadness Discussion Board

storage of liquid chlorine

spirocycle - 5-12-2010 at 11:31

would it be possible to store liquid chlorine in a sealed glass ampule which is sealed in a clear epoxy resin?


I imagine submerging the lower part of the ampule in a
dry ice/acetone bath, fill it with chilled liquid chlorine, and then heat the tip and seal.

the resin would have to set while chilled, too

assuming the resin would set at those low temperatures, and I could seal the ampule properly without boiling the chlorine, would it be safe?


the vapor pressure at 20 celsius is 689.01 kPa, or around 6.8 atm

http://www.atsdr.cdc.gov/mhmi/mmg172.html

would the epoxy be able to withstand this pressure?

woelen - 5-12-2010 at 11:57

It can be done, commercial samples like this are sold:

http://www.smart-elements.com/?arg=detail&element=Cl&...

Doing this yourself does not seem like an easy thing. In any case, you should use a non-flammable cooling mix for the ampoule when you want to seal the tip.

a_bab - 5-12-2010 at 12:11

I guess it would hold the pressure even in a fairly thin layer (such as 5 mm). 10 atm is no big deal; think about the plastic hoses used for air compressors rated to work at 10 and tested probably at 20: they are thin. Cast resin is really tough although brittle.

Also, when the resin cures it will put some pressure on the vial and this would "help". Glass does not have problems with such low pressures but some studies revealed that a thick tube for instance can whitstand as much as 100 atm or more for a few seconds without bursting, but the tube will start to desintegrate later. 24 hour later it will be all fractured as from a bad tamper in water.


In any case I have seen lots of such samples, so it's working. Don't forget the liquid xenone ampoule, where you can actually witness the supercritical transition.
I'd use prefferably LN to chill the chlorine and a thick tube, but dry ice/acetone ought to work. You also have to train your hand a bit before attempting chlorine with some milder stuff such as bromine.

Another interesting fact I just remembered was the discovery of the heat absorbtion during the vaporisation, as a scientist intentionally snapped a sealed glass tube containig liquid chlorine and water at more then 10 atm (obtained from heating chlorine hydrate crystals in a closed tube) and besides a nasty cut he also got a frostbite.

garage chemist - 5-12-2010 at 15:46

I have made a few ampoules of liquid chlorine out of ordinary 7mm OD glass tubing in the past.
When made correctly, the ampoules will resist the vapor pressure of the chlorine at 20°C without problems.
The emphasis being on "made correctly". Tens of ampoules have either exploded or slowly leaked their chlorine while warming up until I had the technique down on correctly sealing them.

I found liquid nitrogen to be suitable, but only with some precautions. The chlorine freezes to a solid in the cooled ampoule. If continuously immersed in LN2, the solid chlorine will block the gas inlet tube and either your chlorine generator or the H2SO4 washing bottle will eject its stopper.
Only periodically immerse the ampoule in LN2 so that some liquid chlorine is always below the inlet tube.
If your chlorine is moist, the inlet tube will block instantly. Use a good H2SO4 washing bottle with sintered glass bubbler.

You have to make premade ampoules with thin pulled-out neck that can be sealed more easily than the glass tubing itself.
Then cool them, and introduce the chlorine through the thin neck using a thin pipette as inlet tube, which is inserted down to nearly the bottom of the ampoule, and then slowly pulled out with the speed that chlorine is condensing.
When the desired quantity has accumulated, pull out the inlet tube, freeze the whole chlorine solid and flame-seal the ampoule at its thin neck.
Don't cool further after all the chlorine has frozen, as there is the danger of aerial oxygen condensing in the ampoule if it is completely brought down to LN2 temperature- this would make the ampoule violently explode in your hands immediately after taking it out of the LN2 due to the pressure rise accompanying the evaporation of LOX.

spirocycle - 5-12-2010 at 16:03

well I do intend to try it out with bromine first, so I will get some practice there
I do not have access to liquid nitrogen though, and I do not have any means to get the chlorine cold enough to freeze.



DCM/dry ice would be a suitable cooling liquid, right?
no real risk of fire, and the solvent wouldnt really be lost in the process

garage chemist - 5-12-2010 at 16:19

I found dry ice cooling mixtures unsuitable. The vapor pressure of chlorine is too high at those temperatures- when trying to seal the ampoule, the glass always blows up into a bubble, and it's impossible to flame-seal glass when the inner pressure is above atmospheric.

Get some LN2 for this task. It's more available than you think, even if the internet doesn't turn up any suppliers near you.
For starters, every university has its supply of LN2. Also, all large technical gas distributors have huge tanks of LN2, LOX and liquid Ar on site.

spirocycle - 5-12-2010 at 16:21

also, if a little over half a gram of dry ice were placed in a 2mL ampule, sealed, resin'd, and warmed up you may be able to see the phase transition to supercritical fluid.

i wonder if a couple inches of epoxy could withstand >150 atm

spirocycle - 5-12-2010 at 17:46

Quote: Originally posted by garage chemist  
I found dry ice cooling mixtures unsuitable. The vapor pressure of chlorine is too high at those temperatures- when trying to seal the ampoule, the glass always blows up into a bubble, and it's impossible to flame-seal glass when the inner pressure is above atmospheric.

Get some LN2 for this task. It's more available than you think, even if the internet doesn't turn up any suppliers near you.
For starters, every university has its supply of LN2. Also, all large technical gas distributors have huge tanks of LN2, LOX and liquid Ar on site.


so the process would be:
seal while cooled with LN2, then set in resin.
or should I try to set in the resin while still cooled with LN2?
would that even work?
I'd imagine some cooling would be necessary because the setting is usually exothermic.
I definitely wouldn't want a roomful of chlorine gas