Can't I just use more clean acetone to remove the excess fumaric acid?

You wash your product with a solvent it is insoluble in, such as acetone. You extract it with a solvent it is soluble in, such as water. Be sure to remove water from acetone with dehydrated MgSO4.

As 1ce said.

Washing with water wont work, it will dissolve the DMT fumarates. Unless of course you do this: https://wiki.dmt-nexus.m...on_of_Final_Purification

In that case, the water will dissolve the DMT fumarates but it wont dissolve excess fumaric acid.

You can check this thread too for more ideas on cleaning up dirty fumarates:

https://www.dmt-nexus.me...aspx?g=posts&t=28417

(I have to see if I find the pictures in my old HD since the links are dead now for some reason, they looked really nice)