Sciencemadness Discussion Board

How long can Lithium Ingots be in open air before tarnishing?

Sidmadra - 12-3-2018 at 11:05

I have several hundred grams of Lithium Ingots in a big mylar bag sealed under Argon. I wanted to vac seal the ingots in smaller bags, maybe 25-50g sizes, but I wasn't sure how best to do this to minimize reaction with atmosphere. I realize I could store it under oil, but don't want to seal with the density/floating issue.

Is this able to be done without an oxide layer forming, or is the oxide layer inevitable? If I go to sell them later, I'm not sure how/if an oxide layer would be of consequence to the buyer (or if it doesn't matter). If anyone does want to buy (or trade) some, let me know. The price would be lower than the US eBay prices. I just have too much of it to put to complete use anytime soon.

ninhydric1 - 12-3-2018 at 11:22

If you have a glovebox, you can process the lithium in an inert atmosphere, preferably under argon. I believe MrHomeScientist has a video of him ampouling lithium foil in an inert atmosphere to keep its shine.

Sidmadra - 12-3-2018 at 11:37

I don't have a glove box unfortunately. I've read that Lithium Ingots are less effected by reaction with the atmosphere, relatively speaking, when compared to foil. Lithium Foil has a much higher surface area to weight ratio than Ingots do, so I'm speculating that a glove box may be overkill for ingots. It's a good idea though.

DrP - 13-3-2018 at 04:44

Not sure if this is any good as an idea.... but what about having a flow of inert gas over the work surface for a short period of time whilst you whip the bars out, cut them and pop them back into bags that you have purged with the inert gas? Maybe if you are swift enough this could work? I wouldn't work for too long a periods to avoid suffocating though! :-)

I have never done this by the way - just speculating what might work as an alternative to a glove box or oil. I've only ever had Li/Na stored under oil.

Fulmen - 13-3-2018 at 04:58

Quote: Originally posted by Sidmadra  
Foil has a much higher surface area to weight ratio than Ingots


True, but that only applies to percentage losses. If you're worried about the surface tarnishing the shape doesn't matter, all surfaces will react at the same rate.

Sulaiman - 13-3-2018 at 06:28

Quote: Originally posted by Fulmen  
Quote: Originally posted by Sidmadra  
Foil has a much higher surface area to weight ratio than Ingots


True, but that only applies to percentage losses. If you're worried about the surface tarnishing the shape doesn't matter, all surfaces will react at the same rate.

unless the reaction is exothermic, in which case e.g. a foil will heat rapidly and react even faster.
But in the case of lithium/air, tarnishing is so fast that it makes little difference, one second is too long.

If you intend to seal in argon then work under argon,
if storing in argon with an oil coating, then work under oil,
seems logical to me.
I have no lithium - all from reading and watching, and sodium experience only.

[Edited on 13-3-2018 by Sulaiman]

happyfooddance - 13-3-2018 at 07:32

I would think that if you coated them in something inert to lithium (hexane, ether), that would give you enough time to transfer them in air without tarnishing. The vacuum would remove the solvent and you're done.

woelen - 13-3-2018 at 08:10

It only takes seconds to tarnish a piece of lithium when exposed to air. You see it tarnish when you look at it.

happyfooddance - 13-3-2018 at 08:33

Quote: Originally posted by woelen  
It only takes seconds to tarnish a piece of lithium when exposed to air. You see it tarnish when you look at it.


But if it is coated in hexane?

Sidmadra - 13-3-2018 at 10:06

It sounds like it doesn't even matter if it tarnishes, because even if someone were to get some to use, it's unlikely they would keep it completely protected seconds before their use. I imagine most people would just deal with the surface layer during their application. Do you think this is a fair assumption? The Lithium is already in the form of ~half gram ingots, so it doesn't need to be cut or anything.

For all I know the surface may already be oxidized. I never opened the lithium when I got it because I hadn't had a use for it yet, it's just been sealed in its original bag in mylar under nitrogen/argon. I just got it because it was a good deal at the time.

I think I've read somewhere that the tarnished layer on the outside does a good job protecting the inside from oxidation, so that losses should be negligible anyways.