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Arthur Dent

Metallic lithium and compounds

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Hi,

 

I recently acquired some metallic lithium stored in mineral oil. I was wondering about two things concerning this reactive metal...

 

1) Before using the metal to prepare a Lithium salt, I do need to remove the mineral oil on its surface (as not to contaminate my preparation). Is there a solvent I can use? Even just in air, it turns nearly black in a matter of seconds.

 

2) Just dropping the metal in water will result in creating Lithium Hydroxide, but how do I go about creating either Lithium Nitrate or chloride? I thought of just dropping very very small quantities at a time directly into Nitric acid or Hydrochloric acid, but i'm too scared about the intensity of the exothermic reaction with concentrated acids.

 

3 is there a more passive way of producing these chemicals? Can I use the LiOH to produce LiCl or LiNO3?

 

Thanks all

Robert

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I would cut the lithium up into bits using a stanley knife, drop carefully into ethanol (goggles) Add nitric or hydrochoric acid to neutral pH, and evapourate. Recrystallise if necessary.

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The mineral oil can be removed easily by washing it with hexane/petrol. However be very sure that you do it carefully incase it burns which could be rather dangerous!

 

I would advice against adding an alkali metal to acid but if u use tiny amounts and cold acid you should be ok....but only if your confident of ur ability!

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even if the lithium oxides in air wouldn't the oxide also dissolve in an acid?

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Are you sure that the reaction of lithium oxide with dilute nitric acid would be slow?

I would have expected "violent" to be a better description.

 

I'd not bother with adding a flammable solvent like ethanol.

Lithium reacts with water to produce the hydroxide. If you add the lithium slowly this is a vigorous, but not very dangerous reaction. I'd wear gloves and goggles just in case.

You might be able to remove any oily scum from the water at this point.

 

Adding dilute HCl or HNO3 to the solution of lithium hydroxide will give the salt.

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Are you sure that the reaction of lithium oxide with dilute nitric acid would be slow?

I would have expected "violent" to be a better description.

 

How does that react then? Lithium oxide is pretty stable to acid isnt it? When you add air oxidised lithium to water and it reacts, isn't that due to the fact that the total surface is not oxidised and so leaves small areas of lithium metal to react with the water?

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Adding dilute HCl or HNO3 to the solution of lithium hydroxide will give the salt.

 

Excellent, thanks!

 

I'll just gently throw little bits of lithium in water until I have a fairly concentrated LiOH solution, i'll leave it to settle so that any traces of mineral oil come up to the surface, and then add nitric acid (I guess until the solutions becomes neutral to slightly acidic). Then i'll dessicate the solution.

 

Robert

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Just a thought, do you protonate the hydroxide in the lattice to give water and then the lithium nitric acid conjugate salt? Then getting a exothermic reaction because of the stable water generation?

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With the advice above, I have just prepared the LiOH. Prepared a becher with 80 ml of distilled water and i went outside in my backyard and started dropping tiny chunks in the water (about 2mm x 2mm). It is indeed extremely exothermic, ant my first attempt resulted in the first chunk rapidly clinging to the side of the becher where it caught fire (nice red flame) and melted and cracked the Becher's side.

 

Aww, dammit, I loved that 250 ml becher... :(

 

So I emptied the content in a 500 ml becher and used a different technique of stirring the becher in a slow motion after dropping the pellets, It prevents the metal chunks from clinging to the side and prevents the hydrogen from catching on fire.

 

One interesting note is that as I was dropping pellets, they were dissolving slower and slower, until the last one that took over 90 seconds of stirring before disappearing completely.

 

The resulting solution looks very dense and slightly syrupy. Even though the metal was very blackened, it left no deposits at the bottom of the becher and it looks perfectly clear.

 

I'll let the solution cool down (It got really really hot during the process), and i'll try to add the HNO3 later. Again, I imagine that the acid and the base together will create a highly exothermic reaction, so I think I'll put the becher in a tray filled with water and ice chunks.

 

Should I use the pure HNO3 (42 BE) and pour it drop by drop or should I dilute it 50% with distilled water?

 

Robert

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I think one would also have to consider the formation of Lithium Nitride when doing these reactions also. Lithium metal reacts with atmospheric nitrogen, so the product you get will have some Lithium Nitride mixed in. (Can't recall off the top of my head how Lithium Nitride reacts with water, even if it does). It's just something to take into account when doing your calculations.

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Thanks jdurg, I'll take this into account, although Lithium Nitride decomposes instantly when in contact with water and generates ammonia gas: Li3N + 3 H2O → 3 LiOH (aq) + NH3.

 

Been busy for the past few days so I never got to the final step of turning the LiOH into a nitrate. I'll do that during the weekend. My thoughts were to dilute my HNO3 with water so that the reaction isn't too intense, and add a small surplus of acid so that all of my LiOH turns into LiNO3. I want to have relatively pure stuff to work with.

 

Robert

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Finally took the time to "complete" my experiment of producing Lithium Nitrate. I had left my batch of Lithium Hydroxide in a dessicating bag and it did the job as flakes of solid LiOH were already forming on the surface of the liquid.

 

So I put the becher containing the LiOH in a bath of ice water... better be safe than sorry, the production of LiOH was extremely exothermic so I want to make sure my solutions don't explode im my face!

cool_lioh.jpg

So here's the becher in ice water. It contains 50 ml of very saturated LiOH solution.

 

So I prepared a solution of 50% concentrated Nitric Acid (42 BE) with distilled water. always being careful and wearing goggles and rubber gloves.

hno3_50pc.jpg

 

I very gently poured the solution with a pipette and it effervesced pretty intensely and the becher became warm. After it stopped effervescing, I let things sit for 10 min. and poured the contents of the becher in an erlenmeyer.

 

Now for the bad stuff...

lino3sln.jpg

The solution as you see is a clear, very light peach color, so I guess there were impurities in my Lithium. :( It's a shame because my LiOH looked perfectly clear and colorless.

 

And the other thing, I may have been a bit too enthusiastic in my addition of the acid (I added 100 ml of the 50% solution) so a litmus paper test indicated a ph of 2.5... aargh!

 

Is there a way to neutralize the Nitric acid without adding further impurities to the solution? I know I should prepare another batch of LiOH and just add until I get a more neutral PH, but then again, I'm afraid I don't know if a pure solution of LiNO3 is more towards the neutral or towards the acidic side of the PH scale.

 

Any suggestions would be appreciated.

 

Robert


Merged post follows:

Consecutive posts merged

UPDATE!!!

 

An odd thing happened. I decided to put the erlenmayer filled with the LiNO3 solution in a bain marie on my hotplate (the erlenmayer in a pan full of water on the hotplate at low). I let it boil for 1/2 hour, right up until there was no water left in the pan.

 

To my surprise, the contents has barely evaporated 3 or 4 ml (from 150 to 147 maybe) but the stranger thing is now my LiNO3 solution is absolutely perfectly clear and completely transparent! The "peach" color has completely disappeared!

 

I can only figure that I boiled-off some of the impurities in the solution. So the next step will be to figure the PH of a perfectly pure solution of LiNO3 with all of the nitric acid neutralized, then i'll just dessicate the solution until I get clear LiNO3 crystals.

 

Robert

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Based on the fact that your initial solution had a low pH of 2.5, and the light peach color of it, I would guess that due to all the HNO3 you had added to the solution there were some nitrogen oxides in there (They are a brownish color) in a very low concentration that boiled out of solution when you put it on the hotplate. At least, that's the logical assumption one could make based on the information you've given.

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Thanks jdurg, that's what I figured. :) I'll let the solution slowly decant in my dessication bag. Now I read in the LiNO3 MSDS that this substance in its crystal form may explode if submitted to a shock! :( Is there any precautions I should take when the material is completely dry? or should I leave it a bit hydrated/deliquescent?

- Robert

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