The "greenbelt" behind my house is plagued by lots of Western Skunk Cabbage, which is known for having calcium oxalate crystals in it which makes it
poisonous. I was thinking that it might be possible to extract oxalic acid (which could then be purified by turning it back into calcium oxalate) by
steeping the leaves in a dilute solution of hydrochloric acid to turn the calcium oxalate into oxalic acid, adding calcium chloride to the filtered
solution to precipitate out calcium oxalate while leaving most of the other contaminants in solution, and then either using the calcium oxalate or
turning it back into oxalic acid with hydrochloric acid. If needed the oxalic acid could be separated from the calcium chloride in solution by
dissolving everything in ethanol (since oxalic acid is much more soluble in ethanol than calcium chloride), or acetone, although I haven't found
whether or not oxalic acid is soluble in acetone. Yes, I know I could just go buy oxalic acid, but I like finding impractical routes to chemicals just
because I can!
[Edited on 4-16-2015 by DFliyerz]Bert - 16-4-2015 at 11:38
You might have a cheaper/easier result from sawdust and mixed alkalis.
But hey, if it looks more interesting to do a plant extraction, by all means! Please do report your results.
I'd probably do that method instead, but I don't have any potassium hydroxide! (I'm doing a small batch from potassium carbonate/calcium hydroxide,
but again; it's very small.)j_sum1 - 16-4-2015 at 15:06
Could the same be attempted with rhubarb leaves?macckone - 16-4-2015 at 20:39
There are good extractions for rhubarb, just do a Google search. Hydrochloric acid may improve the mobility of calcium oxalate but it will not
improve the oxalate solubility. The calcium oxalate is still not very soluble.j_sum1 - 16-4-2015 at 21:21
Next time I grow (or see) rhubarb, I might give this a go.Amos - 17-4-2015 at 03:36
Your procedure sounds like it would work, but I would recommend adding calcium carbonate instead of calcium chloride to re-precipitate calcium
oxalate; this will ensure neither hydrochloric acid nor oxalic acid remain in solution.
Scrolling down far enough on this page, you'll find that oxalic acid is insoluble in acetone, but it is very soluble in ethanol.
