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Solubility of Lithium Hydroxide Monohydrate - Am I Wrong?

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rap35:

--- Quote from: wildfyr on January 02, 2022, 05:43:09 PM ---Certainly, the hydrate is fully capable of reacting with CO2 to give the carbonate.

I would think adding acid would help dissolve any carbonate though... have you done that? You'd probably notice some bubbles forming on acid addition if there was significant carbonate.

For an old bottle is entirely possible that its almost all lithium carbonate. So a new bottle is definitely the way to go.

--- End quote ---

I haven't tried adding the acid unless the LiOH has dissolved fully. I have scaled down the reaction by making the FeSO4 concentration lower to account for using less LiOH that does dissolve. I haven't tried dissolving the carbonate upon the addition of acid. I think that would introduce issues with yield and contamination? Perhaps it would be best to not have the carbonate involved at all. I guess the best route would be to use a new bottle, which may take a few weeks to arrive but I will update as soon as it's received! Thank you!

rap35:

--- Quote from: Babcock_Hall on January 02, 2022, 06:22:14 PM ---IIRC the trilithium form of phosphate is not very soluble.  Is this the white precipitate that you mentioned?  It it is possible to prepare lithium hydroxide that is free of carbonate, but it is a bit of trouble.

--- End quote ---

That's correct, the white precipitate isn't very soluble, but the issue arises prior to the formation of the precipitate. I need to add H3PO4 to a fully dissolved solution of LiOH.H2O, however, the LiOH.H2O isn't dissolving fully. The mass I'm using is much lower than the solubility value per L, so there is no reason for it not to dissolve. As Wildfyr suggested, it may potentially be carbonate CO2 contamination. 

Babcock_Hall:
One can prepare LiOH from degassed water and lithium metal.  I did this some years ago, but I don't believe that I assayed directly for carbonate.

wildfyr:
That is hella overboard for this application Babcock!

rap35:
Update: after ordering a new batch of LiOH.H2O I can confirm that the product is now entirely dissolving  :D I assume Wildyr's suggestion (CO2 contamination resulting in lithium carbonate) was the issue.

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