Sciencemadness Discussion Board

Lithium Storage problem

Shob dhillon - 28-10-2017 at 21:02

A few months ago, I decided to store around 20 grams of lithium in a flask.
I closed the lid, and after a few months, the lid was sealed shut. I tried every way I know to open sealed lids, although some other ways would be helpful.
I wasn't thinking when I put the lithium into the flask that it would react with the nitrogen. What should I do?

SWIM - 28-10-2017 at 21:17

I think this calls for a the Branz-Englert procedure.

You'll need safety glasses and ball-peen hammer....

[Edited on 29-10-2017 by SWIM]

Then go buy yourself a Schlenk flask for next time.

[Edited on 29-10-2017 by SWIM]
EDIT: Sorry, didn't realize it had xylene in there.
I think Melgar has the right idea. Heat it to whatever xylene's boillng point is at STP and you'll have equalization of pressure.

[Edited on 29-10-2017 by SWIM]

Shob dhillon - 28-10-2017 at 22:31

The problem with just smashing the flask is that the Xylene solvent is quite flammable, and if there's even a spark, I suspect that the 20 grams of Lithium will catch fire with enough energy to burn though pretty much everything, so I really don't want to have to have to break it. Also, I don't want to have to deal with the custom dummies again, last time they managed to get some Zinc powder marked as a "Dangerous goods" :mad: :mad::mad:

I didn't have any argon when I stored the lithium in the flask, so using a schlenk flask would have been pointless since Lithium reacts with nitrogen at rtp.

Melgar - 29-10-2017 at 01:53

Drill a hole in the lid, then pop it off? The lithium will have taken care of any oxygen inside the flask already, so as long as the flask stays intact, you should be just fine.

JJay - 29-10-2017 at 04:07

The xylene with the lowest flash point is o-xylene, with a flash point of 17 C. If you chill the flask in a freezer, the xylene is exceedingly unlikely to catch fire when you smash the flask (I'd be more concerned about the glass). You could smash it under oil, but that's really not necessary.

LearnedAmateur - 29-10-2017 at 05:01

As a future tip, store alkali metals under white spirit (or something with a chain length of 10-20 carbons), that's what I did with my now 25g chunk of sodium. Cheaper than mineral oil, not very volatile, and it's somewhat difficult to ignite. Remember to reflux your oil for a few minutes to get rid of as much gas as possible, and fill up the container as much as you can - leave a couple of millimetres of air at the top so it doesn't spill when opened. As an extra precaution, you could grease the mating surfaces on the container you're using, but you shouldn't need to do this.

Shob dhillon - 29-10-2017 at 10:57

Melgar: That seems to me like the most prudent course of action, but I will need to buy a suitable drill first.

JJay: I probably will do that, but the possible risk is that the flask could implode- The flask is already likely in a state of partial vacuum, thanks to the lithium reacting with all of the Oxygen and Lithium- leaving something on the order of a 1% atmosphere vacuum, but this is a brand new and hopeful strong enough flask, but I going to try and put it into a ice bath outside first, before putting into my freezer.

LearnedAmateur: I normally use Xylenes to store my alkali metals, but I should probably try to use White spirit more . However, the problem is that Lithium is the least dense of all the meals, and just floated to the top, and I deliberately used a volatile solvent in the hope that it might insulate the floating nuggets of Lithium.

I didn't have enough Xylene to fill the whole flask since I has to account for a 250 gram sample of Sodium at the same time. ;)

Melgar - 29-10-2017 at 11:12

Actually, why don't you just put the whole thing in an oil bath and heat it? Once the xylene starts to reflux, the lid will pop right off. Then just put it on loose, and let it cool off.

LearnedAmateur - 29-10-2017 at 13:11

Whoops, yes, I didn't account for the lower density since my sodium sinks in WS. Your best bet there is to use some sort of glass or Teflon support (I'm thinking glass wool) to push it under the surface and keep it submerged. That or you could store it upside-down with a tiny air bubble - the phenomenon giving you so much trouble here can be used to your advantage in decreasing the chances of a leak, but this could be dangerous and would need to be secured. I just use an old jam jar with a screw on lid since there's no neck to give me problems, it's a bit leaky (a little bit of orange gunk, NaO2?) but I've had it in there for over a year and the vast majority is still metallic.

Shob dhillon - 29-10-2017 at 21:38

Melgar: Good suggestion! I admit that I didn't think of that, but there are a few problems;

Firstly,The flash point of the Xylenes is uncomfortably close to the point where I would call it a risky experiment, since all of the flash points are between 17 and 30 degrees.

Secondly, there is the risk that the lid "popping " could be too violent and crack the flask. The worst case scenario is that the Lithium spills out and catches fire on the hotplate, which would be rather bad.

I'm right now leaning towards chilling the flask, then using a drill to try and carve a hole through the plastic lid of the flask.

JJay - 30-10-2017 at 03:10

I guess it might be helpful to know how the lid fits onto the flask and what you have tried already.

Melgar - 30-10-2017 at 03:13

Quote: Originally posted by Shob dhillon  
Melgar: Good suggestion! I admit that I didn't think of that, but there are a few problems;

Firstly,The flash point of the Xylenes is uncomfortably close to the point where I would call it a risky experiment, since all of the flash points are between 17 and 30 degrees.

Secondly, there is the risk that the lid "popping " could be too violent and crack the flask. The worst case scenario is that the Lithium spills out and catches fire on the hotplate, which would be rather bad.

I'm right now leaning towards chilling the flask, then using a drill to try and carve a hole through the plastic lid of the flask.

Flash point isn't really a problem if you're heating anything except diethyl ether, with an electric heating element. What you need to do, actually, is just be watching the entire time, wearing a pair of thick gloves that you can use to handle hot things. As soon as you start to see bubbles, then attempt to take the lid off. Also, watch the lid, and see if you can see it get less concave. There should still be a negative pressure on the inside, then, but the difference won't be nearly as much, and you should be able to remove it. Also, remember that when there's xylene boiling inside the flask, there's no danger of it catching fire, because there isn't any air to react with it. Also, xylene is considerably heavier than air, so air would be unable to sink into the container and displace the xylene in a short time frame.

When you loosen the lid (I'm assuming it screws on?), just leave it on loose, turn off the heat, and allow it to cool. The condensation of the xylene could pull more air in, I suppose. I wouldn't expect it to do anything worse than slightly oxidize your lithium, but if you want to do something about it anyway, then if you have hexane or heptane, or any hydrocarbon considerably more volatile than xylene, you can add some of that to the flask before closing it. That would increase the vapor pressure on the inside, such that it would be easier to open it when it's cooled off.

If you're drilling a hole in a plastic lid, or removing the lid and letting air get in, there's essentially zero chance of starting a fire. Lithium will oxidize in air, but won't catch fire (edit: unless it's at least 300-400C initially). The oxide layer that forms limits its ability to oxidize further, and because it's a metal, it quickly conducts heat away from hot spots.

[Edited on 10/30/17 by Melgar]

LearnedAmateur - 30-10-2017 at 14:01

Since there seems to be a small misunderstanding from what I've read (not to anyone in particular), I'm just going to add in this little side note. The flash point just refers to the minimum temperature in which a chemical will catch fire with an ignition source, namely a spark because a flame will obviously bring most flammables well beyond their flash points (but remove the flame and it will self extinguish as long as the temperature hasn't increased above FP). Below this temperature, a spark will not ignite the material. On the other hand, the temperature in which a material spontaneously catches fire in air is called the autoignition point and is usually in the hundreds of degrees, which is why a flame instantly sets fire to flammable chemicals. This occurs because the molecules have sufficient energy to react with oxygen, and won't happen at STP (with some exceptions like t-butyllithium and sodium hydride, where the term pyrophoric is used).

Tl;dr, xylene isn't just going to catch fire if it's heated in a water/oil bath. It will catch fire if there is a flame or spark nearby though, but it's basic lab safety to remove ignition sources when working with most organic solvents.

[Edited on 30-10-2017 by LearnedAmateur]

Mr. Rogers - 30-10-2017 at 22:07

You can store it under regular diesel from the pump.