Sciencemadness Discussion Board - Ampouling volatile liquids

Ampouling volatile liquids

woelen - 18-1-2008 at 13:33

I purchased some ampoules, very much like the model, shown as 'form C' on the following website:

http://www.ls-uk.com/ampoules.htm

The ampoules I have are clear glass, 10 ml.

I also purchased a burner, which is sufficiently hot for melting the glass. I now can easily melt glass and that works fine.

I succeeded in ampouling 7 to 8 ml of thionyl chloride in one of these ampoules. I heated the top of the ampoule, while slowly turning it and keeping is more or less vertically. This causes the top to melt and to collapse, making a thick drop of glass. After some time, it is melted like a round drop, with a VERY thin channelof air in the drop (from with the ampoule), which ends a few mm before the end of the drop.

When I do the same with bromine or acetyl chloride, then I have no succes. The channel simply does not close and I think this is due to slight overpressure in the ampoule due to the heat-radiation from the flame and the handling of the ampoule with my hands. I decided to take a metal clamp and simply press the drop of glass, such that the channel is closed. This appears to be amazingly difficult, even then VERY thin (thinner than hair) channels remain and there still is a smell of bromine. If the channels really get closed, then somewhere near the top, the glass quickly blows up like a balloon and it opens up again :mad:

I already spoilt 10 ampoules on just 1 ml of bromine, and I quit ampouling the acetyl chloride altogether, it simply does not work at all (I even get a little flame from a tiny tiny hole, due to burning acetyl chloride).

What am I doing wrong? I hear from other people that they ampoule their chemicals with success,. I want to ampoule all my bromine (except 10 ml or so for direct usage) and the same with my SOCl2 and CH3COCl. In that way I can keep my chems really well. I now have 145 of these ampoules left, 25 of them are intended for the bromine, 25 of them for the SOCl2 and 25 of them for the CH3COCl.

kilowatt - 18-1-2008 at 14:02

Try keeping the filled part of the ampoule under cold water while you seal the top, to lower the vapor pressure.

Fleaker - 18-1-2008 at 15:19

If the substance need not be under inert atmosphere, you can chill whatever it is your trying to ampoule in dry ice/acetone. This will greatly reduce the vapour pressure of what you are ampouling. Also, remember to use the thinnest, hottest flame you can.

If you still have problems, maybe I can try and make a video for you or give you very specific instructions.

The_Davster - 18-1-2008 at 17:37

I ampouled 5mL or so of bromine at uni, my trick was to dip the end of the ampoule in liquid nitrogen, when the glass was molten around the channel, which caused the small channel you mention to implode in on itself, sealing the ampoule. I tried with frozen bromine and I had difficulties closing the channel. I found it important to have the bromine cooling as the channel was being sealed.

franklyn - 18-1-2008 at 19:39

I have seen this done and its all in the technique of glassforming called spindling.
Firmly clamp the end of the neck with forceps above of the point to be melted.
Turn the ampule with the fingers to twist the melting neck, narrowing the opening
until it seals. Push downward to lightly press the melted portion then slowly draw it
apart forming a very thin rod to be broken off. The end that is cut off can be re-melted
to remove sharpness.

Swany - 19-1-2008 at 14:18

Well, I have seen samples of ampouled liquid chlorine cast in acrylic. Quite frankly, that sounds awsome, if not incredibly dangerous. Has anyone else considered trying this? I have gallons of liquid nitrogen, and I am wondering how everyone else would go about trying to ampoule liquified chlorine.

Fleaker - 19-1-2008 at 22:05

That would probably be the best way. Those heavy walled quartz ampoules are available from Schott.

not_important - 19-1-2008 at 22:47

Heavy walled ampoule, or make you own from heavy walled glass tubing. Solid CO2 is plenty cold, -33.8 is all you need to liquefy chlorine; -101 freezes it which might be something to avoid. At 10 atmospheres chlorine will stay a liquid up to 35 C, to give you an idea of the pressure needed.

I'd make the chlorine, dry it, collect more than enough using dry ice, distill from that collection to the cooled ampoule by allowing the first vessel to warm up to -20. The ampoule should be narrow-tipped, reducing the effort to closed it off. Shield as much of the ampoule as possible from radiated heat using metal foil as a reflector. Leave it in a cool bath using a non-combustible liquid and dry ice, or use metal shot chilled with dry ice, or dry ice snow or finely crush it. Keep the flame pointed away from the ampoule body

You'll want the resin to cure as slow as possible consistent with getting good strength, to avoid having the curing heat the ampoule. You could cast or buy a cylinder of the matching plastic, bore a proper sized hole in it to hold the ampoule, polish the hole for transparency. That way there's a lot less resin curing, just enough to fill the remaining void around the ampoule.

dann2 - 2-8-2011 at 08:34

Just about to open a 250ml ampoule of anhydrous Stannic Chloride (SnCl4). This stuff forms clouds of HCl acid when opened (or so I believe). I only want to use a small amount.
Can I reseal the ampoule if I just break away a very small amount of the end?
I have Oxy Propane torch so heat is not a problem for me.
Will it help to put the whole thing in the freezer before opening (and resealing almost immediately).

The glass is blue/green in colour.

Thanks,
Dann2

watson.fawkes - 2-8-2011 at 11:03

Quote: Originally posted by dann2

The glass is blue/green in colour.

It's soda-lime glass, frequently used for ampules because of its lower melting point.

I don't know about resealing. Ampule blanks have necks on them that are typically used to pull vacuum, both for evacuation itself as well as provide ΔP inward to seal the neck of the ampule.

Endimion17 - 7-8-2011 at 13:48

Quote: Originally posted by dann2

Just about to open a 250ml ampoule of anhydrous Stannic Chloride (SnCl4). This stuff forms clouds of HCl acid when opened (or so I believe). I only want to use a small amount.
Can I reseal the ampoule if I just break away a very small amount of the end?
I have Oxy Propane torch so heat is not a problem for me.
Will it help to put the whole thing in the freezer before opening (and resealing almost immediately).

The glass is blue/green in colour.

Thanks,
Dann2

No, it won't help to put it in the freezer. It will make things worse.
When ampouling, you have to think about temperature difference.
When the channel at the molten top of the ampoule is just about to be closed, you need to lower the temperature a bit, so the atmosphere will collapse its walls. If the ampoule is already at the lowest temperature you can create, the gas inside can only expand, ruining your seal.

Sealing can be done by dunking the bottom of the ampoule with already molten tip, into colder water. But just for a second. If the walls collapse too much, you'll end up with a bad, imploded seal prone to cracking. It takes practice. I suggest practicing on ampoules with water or just empty ones before attempting to do something with SnCl4.

If you're sure there won't be any large pressure buildup in the ampoule, you can melt the tip of the channel, pinch it with tweezers and slowly pull inside flame, using the flame for sealing, and then flame polishing the sharp tip. But that sometimes gives thin, sensitive walls.

I had no trouble ampouling volatile liquids (even the notorious Br), but I have no experience with ampouling liquified gasses. I have some butane around so I'll try that just for practice. I believe it will be quite a challenge.

[Edited on 7-8-2011 by Endimion17]

IrC - 7-8-2011 at 15:34

For most LN2 is hard to obtain and dangerous to work with. I solved this problem the easy way. Many local grocery stores carry 5 pound blocks of dry ice. Drill a 5/8" hole (or other depending upon the diameter of your ampoules) in the block just deep enough the ampoule sits down only a third to half the depth of the wider storage area. Let it sit there a couple minutes then seal the ampoule top. I also made a round metal disc with a hole in it to set down over the wider section. Of course the center hole is drilled large enough to lift it off after sealing. This helps shield the bottom area from the thermal energy of melting the glass at the top. It also helps shield the neck from the cooler vapor of CO2 which could add to thermal differential induced cracking. A second plate which has a 3/4" hole can be used to sit on top the block of dry ice, said hole being centered on the hole you drill in the ice block. This was an afterthought about the possibility of the cooler CO2 vapor actually wafting by the area of the cooling glass seal causing it to crack.

Glass transfers heat slowly so it's all in the timing. If you wait too long temperature difference comes into play and you have trouble with cracking. Also if you drill your hole in the ice the correct diameter and depth it doubles as a handy stand to hold the ampoule while doing the work.

[Edited on 8-7-2011 by IrC]

dann2 - 7-8-2011 at 17:52

My SnCl4 ampoule has quite a large neck of about 7mm. The ampoule holds 250ml.
Perhaps I would be better just storing the stuff in an ordinary bottle (teflon top) and not bother with trying to reseal the ampoule. I would imagine that you would be battling with HCl vapours as the stuff came out of the bottle and comes into contact with moisture as you were trying to seal (cough, cough etc).
The amoule looks like something from the dark ages. It has a round bottom.
Dann2

benzylchloride1 - 18-8-2011 at 22:20

Anhydrous Stannic chloride stores well in a standard Aldrich bottle commonly used for air sensitive reagents, I also store my titanium (IV) chloride in the same type of bottle. Titanium (IV) chloride is much worse then tin (IV) chloride as far as the fuming goes.

dann2 - 19-8-2011 at 11:41

I have a bottle with a Teflon washer inside the lide which will do the job I presume.

Titanium Tetra Chloride is used for studying air flows as the fumes from in create 'smoke' trails that are visable.

SO3 also used.

Have not seen the Tin Tetra Chlorde myself, yet anyways.

Dann2

[Edited on 19-8-2011 by dann2]

Magpie - 2-10-2014 at 15:00

I had to rebottle my bromine as it had finally eaten through the seal at the cap. Before it leaks though again I decided to ampoul it. I bought 6ea 10mL Wheaton ampouls. Never having ampouled before I practiced on a water filled ampoul, one at room temperature and the other after chilling in ice-water. Both sealed easily using the "pull-sealing" method recommended on the Kimble-Chase web site. I tried Kimble's "tip-sealing" method first but the tip cracked.

Kimble methods:
http://www.kimble-chase.com/advancedwebpage.aspx?cg=1542&...

I chilled my bromine in the freezer. I then placed the ampoul in an ice bath and filled it with the chilled bromine using a pasteur pipette. Wearing full safety gear I picked up the ampoul and slowly rotated it in the MAPP gas flame of my bunsen burner. When I could see the end beginning to droop I pulled the end off to a fine point closure using needle nose pliers. The pictures below show the result.

I ruined 2 bromine ampules while attempting to close them when the glass was not hot enough. Cooling caused by air rushing into my hood due to the fan made it difficult to get the glass hot enough.

Your comments, questions, and critique are solicited.

neptunium - 3-10-2014 at 07:14

are you not affraid of the preassure building up in the ampoule when the liquid (bromine or anything) warms up again ?

i see you are using the same ampoule i had. i was very disapointed with them they are design to break (where the circle arround the top of the neck is) that is unacceptable. its already a pain to pour Bromine in it but too much force while sealing and the glass breaks.. I think a test tube and a hot enough flame would be a lot more convienent. easy to pour in and it wont break that easily.

Magpie - 3-10-2014 at 08:37

Yes, there will be some pressure build up upon warming and also the natural vapor pressure of bromine. The vapor pressure will vary according to the ambient temperature in my outdoor shed which will vary roughly from -10° to 41°C. I do wonder if the very thin glass in the vicinity of the seal will be strong enough - I'll be checking it periodically.

I had no trouble filling the ampules using a Pasteur pipette. If I would have had a hotter flame I don't think I would have had any trouble making the seal. The 1st one I sealed with the hood fan on; the 2nd one I turned the fan off to make the seal. I do need to find a hotter flame.

I have 10-20 mL of bromine left to ampule so will have to buy more ampules. I like the 10mL size as this will be convenient when I need to use the bromine. I likely won't bother trying to break the end off at the neck. I'm thinking I'll just break off the end with pliers and pour out the chilled bromine.

Magpie - 4-10-2014 at 09:40

To further my education about ampules, today I snapped off the top of one containing water. It was of course pre-scored and so snapped off very easily and cleanly. I admit that the water didn't flow out very well due to viscosity and surface tension I imagine. So I thought that I should compare the values of those properties for bromine vs water at 20°C:

absolute viscosity, cp: water 1.005; bromine 0.95
density, g/cm3: water 0.998; bromine 3.1
kinematic viscosity, cSt: water 1.007; bromine 0.307
suface tension, dynes/cm: water72.8; bromine 41.5

Based on the much lower kinematic viscosity and surface tension I'm predicting that the bromine will pour out of the ampule much easier than water.

gdflp - 4-10-2014 at 10:50

Yes, I noticed the same things using some Kimax 5ml ampoules. The significantly higher density of bromine will also most likely help it flow out since it will have more gravitational force.