Author Topic: recycling Li salts  (Read 599 times)

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  • Guest
recycling Li salts
« on: June 03, 2003, 04:16:00 AM »
Swim has a few grams of LiI in H2O solution.  How can he make this anhydrous to use again in an epoxide rearrangement. Is it okay to heat Li Salts to dryness??


  • Guest
Probably yes. 5561. Lithium Iodide.
« Reply #1 on: June 03, 2003, 04:44:00 AM »
Probably yes.
  5561.    Lithium Iodide. 
  ILi; mol wt 133.85.  I 94.81%, Li 5.19%.  LiI.

          Trihydrate, white, deliquese granules or fused masses; becomes yellow on exposure to air, due to liberation of iodine.  mp 73 deg; mp 446 deg when anhydr.  Sol in
  about 0.5 part water or alcohol, freely in amyl alcohol or acetone.  The aq soln is neutral or slightly alkaline.  Keep tightly closed and protected from light.

          USE:  In photography.


  • Guest
Umm I wouldn't
« Reply #2 on: June 09, 2003, 05:05:00 PM »
Just dry it in a vac dessicator.


  • Guest
Other options
« Reply #3 on: June 10, 2003, 10:00:00 AM »
'Drying' in a normal vacuum dessicator will have no effect, as LiI is very hygroscopic. The only literature references I could find on making the anhydrous salt from the hydrate involved prolonged heating (2 days or so), high temperatures (around 200oC if I recall correctly), and high vacuum. This may have been slight overkill, but all the references I found were along those lines. I would suggest you chuck it after one use, assuming you're only using it in catalytic amounts (I know it isn't cheap).

The cheaper and less hygroscopic lithium perchlorate may be an alternative option, depending on what you're using it for. It can be dried under vacuum in 2 hours at 140oC, just be sure to thoroughly free it of all oxidisable impurities before heating it. See the thread

Post 422345

(Kinetic: "Friedel-Crafts acylation with LiClO4 catalyst", Novel Discourse)
and the link in my post below it, which should tell you whether you it's suitable for your purpose.


  • Guest
« Reply #4 on: June 10, 2003, 04:27:00 PM »
So that means that my dry-looking clear LiI crystals (recrystallized from 95% ethanol), dried over KOH in a desiccator is actually the trihydrate?

Can you make anhydrous Lithium Iodide through methathesis from the cheap chloride and NaI/KI in THF/MeOH or anything like that?


  • Guest
« Reply #5 on: June 11, 2003, 04:55:00 AM »
Rhod, based on the refs below, I'm pretty sure that it will be the trihydrate. A quick check on Gmelin gave the following:

For the trihydrate to the anhydrous salt:

King, F. E.; Partington, J. R.; Trans. Faraday Soc.; Vol. 23; (1927) 522 - 531 'complete dehydration on strong heating in vac. or in a stream of inert gas'

Plotnikow, W. A.; Fialkow, J. A.; Tschalij, W. P.; Z. Phys. Chem., Abt. A; Vol. 172; (1935) 304 - 313. 'dehydration on heating 4-5h in a dry H2 stream to'

Hart, A. B.; Partington, J. R.; J. Chem. Soc.; (1943) 104 - 118. 'treatment of hydrate with a warm dry stream of N2, then slow heating to melting for some hours and then heating in vac.'

For the trihydrate to the monohydrate:

Bogorodski; Zh. Russ. Fiz. - Khim. O - va., Chast Khim.; Vol. 29; (1897) 182 - 182. 'heating, pptn. at; sucking off with filter with sponge slab at (decompn. of mother lye at'

For the trihydate to the dihydrate:

Same ref. as above, 'boiling trihydrate at, crystn. on cooling to; sucking off mother lye by sponge'

Edit: For the dihydrate to the anhydrous salt:

Foosnaes, Trygve; Oeye, Harald A.; Acta Chem. Scand., Ser. A; Vol. 35; (1981) 81 - 90; English. 'drying at and 10-8atm :o  for 24 h; filtration, recrystn. from melt'

All the above reactions are carried out under solventless conditions.

It's interesting, because I thought the solubility of the hydrate would be far lower than that of the any of the hydrates. With lithium perchlorate I don't think the trihydrate can be used as a catalyst in organic solutions because it won't dissolve; the anhydrous form dissolves to make a 5M solution in ether whereas less than a gram of the trihydrate dissolves in 100g ether.

Maybe you could check the solubilities of your LiI vs. commercial anhydrous LiI, or check if the mass of your recrystallised LiI decreases after subjecting it to one of the methods above. That way, we'll know whether they really are overkill - I'd be happy to be wrong on this one!

Edit: The closest thing I can find to the metathesis is in:

Gnessin, I. D.; Dorossinski, L. S.; Khim.-farm. Promyshlennost' (russ.); 5; (1934) 30 - 32; C. II; 1935; 1914.

However, the use of iron (II) iodide makes it impractical as this is even more expensive than LiI. If you're interested, it's the reaction of lithium carbonate with FeI2 in water, then drying over sulfuric acid and storing in darkness. This produces the trihydrate.

More interesting ways to make LiI.3H2O:

King, F. E.; Partington, J. R.; Trans. Faraday Soc.; Vol. 23; (1927) 522 - 531. 'formation by neutralization of Li2CO3 with HI soln.; no solvent given'

Troost; Ann. Chim. Phys.; Vol. 51; (1857) 128 - 128. 'soln. of Li2CO3 in HI, various conditions;'

It would seem there is no direct way to make the anhydrous LiI salt; all methods go via the trihydrate intermediate. Still, it'd be much cheaper to make the trihydrate with HI/lithium carbonate, and then drying it. Anhydrous LiI is rather expensive.

BTW Rhodium, it seems that LiI is happy to crystallise with almost any solvent; it crystallises with 4 moles of ethanol, so you may have inadvertantly produced LiI.4EtOH during recrystallisation. These being 'colourless plates', according to Turner; Bisset; J. Chem. Soc.; Vol. 105; (1914) 1784 - 1784.; it mentions that they are stable below 10oC but doesn't say what happens above that.


  • Guest
« Reply #6 on: June 12, 2003, 11:52:00 AM »
Yup, as good as insoluble in ether. Dang.

I need to try the NaI/LiCl metathesis though, I think Ritter once mumbled that would work...


  • Guest
drying it dissolved in alc/acetone?
« Reply #7 on: July 24, 2003, 08:11:00 AM »
I might be way off here, but what about dissolving it in IPA or acetone and drying it?


  • Guest
« Reply #8 on: July 24, 2003, 11:20:00 AM »
those solvents will remove all of the water except any water that is part of the compounds 'water of hydration'.  any water still acting as a solvent will be gone after a wash or two, but the bonded water will stay.


  • Guest
Umm I never got it to work
« Reply #9 on: December 16, 2003, 08:51:00 PM »
Hello rhodium.. Remember a while back I asked you for your suggested method of making this salt?? And you told me to dissolve certain quantities fo each salt in a minimum ammount of meoh and filter teh precipitate and remove solvent...

Well I never got a precipitate even after refluxing for a day. That was after trying to get it to dissolve first.  But knowing me I got the ammounts backwards working from memory or something and you or someone else should try it to confirm this as I trust ritters words. Just turned out to me that an 88% yield from xylene/10% acid on warm bath several hours is much preffered.

 Instead I ended up making it from HI and lithium carbonate....And was unaware to the detail of it having to be anhydrous and used it right out of a vac dessicator after only one partial recrystalization..

I read a method a while back that was for making the anhydrous form by fusing elemental iodine with lithium carbonate or chlroide in a molten state. I believe it was a patent or something. Don't remember, just remember LiI didn't work for shit as it was much too much work and thermal/biphasic acid rearrangement was much preferred with higher yields.