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Author: Subject: Danger of adding water to NH3 + lithium solution
localbroadcast
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[*] posted on 27-5-2015 at 13:12
Danger of adding water to NH3 + lithium solution


Hello.

I was reading a reaction that uses anhydrous ammonia and lithium to produce free electrons (birch reduction)

After the main reaction takes place, it says to allow most of the ammonia to evaporate off, then to dilute the rest of the ammonia with water. This is a pretty scary thought to me, given that there is still quite possibly lithium still dissolved in the ammonia.

Is there any danger at this point of the lithium reacting with the addition of water?? Lithium would normally react with water violently if it wasn't in the ammonia... So does the fact that it is dissolved in the ammonia make it no longer reactive with water in the same way?

Thanks
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[*] posted on 27-5-2015 at 13:22


Lithium doesn't react very violently with water- it's a gentle fizz rather than the hiss and bang you get with large pieces of sodium. I'd just add the water slowly.



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[*] posted on 27-5-2015 at 13:57


Quote: Originally posted by localbroadcast  
This is a pretty scary thought to me, given that there is still quite possibly lithium still dissolved in the ammonia.

Is there any danger ...

Yes, there is always Danger, no matter what you do.

Sit at home and watch TV : a plane or meteor or part of a satellite might crash onto your house and kill you.

Add water to a solution of chemicals, well, it might explode, but at least you can control the quantity of each thing, and prepare with adequate PPE for that eventuality.

So just think of what could happen, be prepared, and then try it.

There's nothing to say that you won't get killed during the experiment by a stray bullet from a psycho on a rampage, but at least you can minimise the dangers from the Known risks.

Do a risk assessment (i.e. think about it for at least 5 mins) take appropriate care, do the experiment, see what happens.




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Loptr
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[*] posted on 27-5-2015 at 15:31


It's going to be exothermic, but a lot of reactions are exothermic.

Just make sure you aren't doing this in a bucket.
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[*] posted on 27-5-2015 at 16:34


Just forget about alkali in liquid ammonia, pretend the reaction is non-existent and nobody have ever been able to perform it.
Why? Because ammonia is flamable and toxic by itself, and after you added a reactive metal to it - it's a recipe for a disaster. And in case you somehow managed to survive this - you will have a hard time explaining to cops, which were called by neighbours, what you are doing with all this stuff.
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[*] posted on 27-5-2015 at 17:09


Ignoring byko3y ammonia is a cryogenic liquid that vaporizes and is fairly harmful to your lungs. It is unlikely to catch fire. However, he is correct in that the primary use of this reaction in a residential setting is the manufacture of illegal substances. And just having liquid ammonia and lithium is sufficient to get you arrested as a manufacturer of illicit substances in the land of the free.
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localbroadcast
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[*] posted on 27-5-2015 at 18:40


I was in no way ever considering actually doing the reaction.. I'm more of an armchair chemist.. I like to read about the stuff because it's interesting to me for some odd reason..

So as long as the addition of water is at a slow pace and the cooling of the vessel is maintained then there should be no large crack bang boom vavoom poof of smoke and shreeks of death? Good to know!
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byko3y
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[*] posted on 27-5-2015 at 21:35


About water and ammonia interaction https://www.youtube.com/watch?v=vgBe0fsPcjk
How the ammonia burns https://www.youtube.com/watch?v=n4ktAaGAyLc and this is how it explodes https://www.youtube.com/watch?v=MMtv9kWAoTs (why it happened https://www.youtube.com/watch?v=2ESemJo0XcI )
Storing liquid ammonia is pretty much the same as storing liquid propane.
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[*] posted on 28-5-2015 at 09:05


Alternatively you could use ethylenediamine or some other less volatile amine as it's safer than using liquid NH3

See woelens post...
https://www.sciencemadness.org/whisper/viewthread.php?tid=32...
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[*] posted on 28-5-2015 at 10:46


Depending on how the reaction is done (concentration, time, temp, and Fe catalyst), I believe that you can eventually convert the Li(0) and NH3 into LiNH2 (lithium amide) with the evolution of H2, and that is much less reactive than lithium with water, making LiOH and NH3 when reacted with water. I have not done that myself, but did see a Birch done years ago, and it was quite pretty.

It is not a simple reaction to do properly, due to the need for anhydrous ammonia, dry ice, lithium, and the proper glassware, but it can't be too difficult if people are doing in Walmart's bathroom. I doubt that many of them do it well or safely, however. The evolution of H2 is much more likely for the explosion potential than the ammonia itself, but the ammonia is flammable itself as well. I try to stick to simple reactions like those in hot sulfuric acid and a reaction involving two different diazo compounds (someone asked me about running that one, and even I was not willing to volunteer).
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[*] posted on 7-6-2015 at 10:23


Quote: Originally posted by byko3y  
About water and ammonia interaction https://www.youtube.com/watch?v=vgBe0fsPcjk
How the ammonia burns https://www.youtube.com/watch?v=n4ktAaGAyLc and this is how it explodes https://www.youtube.com/watch?v=MMtv9kWAoTs (why it happened https://www.youtube.com/watch?v=2ESemJo0XcI )
Storing liquid ammonia is pretty much the same as storing liquid propane.


lol get a load of this guy, as dangerous as propane... I dont think so tim
I cant immediately find the activation energy or actually much data about it burning in air. The only disaster I could find out about was where a fire started next to a large ammonia tank, caused it to fail and leak large amounts of ammonia gas. It is flammable, but it must be sustained by another source of heat to continue combustion as it seems its autoignition temperature is below that of the ammonia combustion itself. Keep it away from platinum metal, high temperature sources or flames.

Lets not get scared here.

But if anyone is dealing with liquid ammonia, keep in mind the enthalpy of mixing and how it hydrolyzes, keep it away from water. The big hazard would be the ammonia gas; Ive had a wee cloud of that form once and it blinds/chokes you temporarily. Make sure you deal with it in a fume hood or outside.

The Li metal reacts to form LiN3 I think? Hydrogen gas is a hazard if the Li gets in contact with water. Pressure and flammability.




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[*] posted on 11-6-2015 at 01:08


Quote: Originally posted by localbroadcast  

So as long as the addition of water is at a slow pace and the cooling of the vessel is maintained then there should be no large crack bang boom vavoom poof of smoke and shreeks of death? Good to know!


The only time I'd be all that concerned is in the event that something flammable was used as a co-solvent or proton donor. A little ammonia may not catch fire that easily, but a flask full of THF or EtOH might. Besides, if it bothers you that much, you could always just toss in some NH4Cl to quench the reaction and scavenge any remaining electrons before boiling off the ammonia.

Quote: Originally posted by DraconicAcid  
Lithium doesn't react very violently with water- it's a gentle fizz rather than the hiss and bang you get with large pieces of sodium.


Poor lithium. It's such a shame, too. It has the lowest reduction potential and the highest hydration energy of any alkali metal, yet its reaction with water turns out to be the most pathetic of them all. If only its melting point weren't so much higher...

Molten lithium is freaking insane!

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[*] posted on 11-6-2015 at 08:27


If the goal is to quench the reaction vessel, I guess you could alternatively slowly add isopropanol to to mixture to react with the lithium to make lithium isopropoxide (I have seen this method used when sodium is solvated in liquid ammonia, as a means of safely neutralizing the final contents of the vessel).

Still, the use of water should not be a big deal at all due to reasons stated above by others.




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[*] posted on 11-6-2015 at 08:50


Apparently dropping a few ice cubes in slowly, one by one, does the trick.....................



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[*] posted on 24-6-2015 at 12:24


Use a trigger sprayer with h20 in it and half a teaspoon of naOh to help seperate the h20/base layer with the ammonium chloride impurities and lithium hydroxides . This will also help the solutions seperate
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[*] posted on 25-6-2015 at 01:57


You obviously don't know the first thing about proper nomenclature. It's not h2O, it's H2O or H2O.
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[*] posted on 25-6-2015 at 05:35


Eskarari is the guy with several PhD's in chemistry and related subjects . . . :D (for more info: see detritus)

But now let's become serious: By this I give a warning to you (Eskarari). Be precise in what you post, use proper symbols (Capital letters and small letters in formulas) and stop posting crap. I do not want anymore to see any other member of sciencemadness have a valid reason to report your posts!

[Edited on 25-6-15 by woelen]




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