Ive been FASAing some xylene from a BLAB tek using xylene as the np solvent. Been going slowly, adding a few pipettes a day and leaving to settle. Getting a bit worried now though as Ive added plenty of FASA and still clouds form with each addition. Thought Id try adding FASA to some clean xylene to compare, and that caused clouding too!

My acetone had been dried with baked epsom salts and kept in a sealed container before and after saturating with fumaric acid. The xylene was also dried and kept sealed. Anyway, I think Ill keep adding FASA for a bit longer, then decant, dry the crystals and think about how to remove the excess fumaric acid.

Pictures show the clouding caused by first addition of FASA, crystals settling out and the total mass of crystals on the bottom after a week of adding and settling.

Work out how much FASA a 2% yield from your source material would correspond to. If you've already added that much FASA, consider stopping. It's not so difficult to separate the fumarate from excess fumaric acid so don't worry too much.

Example: 100 g starting material x 2% = 2 g freebase (ambitious but possible!)

molar mass of DMT, C12H16N2, = 188 g/mol

molar mass of fumaric acid, C4H4O4, = 116 g/mol

2 equivalents of DMT react with 1 equivalent of fumaric acid, so 2 x 188 = 376 g DMT react with 116 g fumaric acid.

Therefore, in the case of 100 g @ 2%, 2 g of DMT react with (2/376) x 116 = 0.61702127659574468085, i.e. about 617 mg of fumaric acid. This is about the same amount of fumaric acid as will dissolve in 100 mL acetone, so the rest of the maths is exceedingly simple!

Thanks for doing the maths. I was thinking its a 2:1 ratio, but forgot about molar masses (been 30 years since I did them in school). Convenient how it works out to be the amount needed to saturate 100ml. Ill carry on adding FASA till Ive used 250ml (for 250g starting material) and then decant, dry, weigh and report back.

Quick update: eventually got to the point where adding FASA didnt produce more clouding. Left to settle, decanted and dried. Massive yield, around 7 grams fumarate from 250 g mhrb! Assumed some fumaric acid contamination, and still some xylene smell, so tried recrystallisation using minimal H2O. This took ages to evaporate and no crystals forming, so lost patience and used heat and a fan, resulting in rock hard clear reddish candy stuck to the plate. This scraped up to a tan powder. Still tastes a bit sour.

Dont want to use loads of acetone to wash it, but I noticed Downwardsfromzero recommends IPA/ethanol recrystallisation in another thread. Would methanol work? Im assuming fumaric acid stays in the solution and fumarates crystalise without having to evap all the alcohol(?). I just freebased 1.5g, hoping to get about a gram of freebase, but only got 600mg, so must have been some fumaric acid in there.

Anyway, heres some pics:

First photo; Decanted fumarates after xylene evaporation, some clumps of white, fine, hair-like crystals can be seen.

Second photo; Hard candy after water recrystalisation.

Third photo; Candy after scraping/chopping up.