The title ask if it's safe to throw acetone in this kind of mix.
let's say the FASA didn't show anything solid so the dude had to evaporate the initial acetone, then mix the remaining fumaric acid with sodium carbonate and some deionised water to freebase.
The idea is to pull again from there with acetone to filter out the substance of interest.
The dude did notice when adding water to the fumaric acid and sodium carbonate mix the solution was changing to an emulsion.
This eventually chilled out and dried completely.

Will the acetone be safe to add from there ?

Any help greatly appreciated.

I don't see why it would be unsafe.

However when a base and an acid are mixed they undergo what is called a nuetralization reaction. Creating a salt and water. Expect a reaction though, bases + acids do bubble/fizz(usually CO2 as a byproduct). Some can react violently(though I don't particularly think this will be the case, but be cautious). Add the base/acid slowly in a manage-able fashion in-case it were to start spilling.

Though it may be safe, you will have water containing the sodium fumarate product. I believe that particular ion, would be insoluble in acetone but my question is(not sure though). Would the water with the ion in it, also go into solution with the acetone(h20 and acetone are miscable)? I can't answer that(creating an impurity).

I don't see how it would be unsafe though.

I expect a bit of movement there then, but there will not be any more water in the sodium fumarate if you ask.

I think your fine and dandy buddy .

If your really worried about it mix a little bit of sodium carbonate and a little fumaric together then add a little acetone with no goodies in it. Just do a little test run. But I HIGHLY doubt anything spooky will happen .

Thanks.