Melting point is a standard used for ID and quality assurance, also odour, colour ... crystal form ... MP alone says alot. I heard that you defat the excess acetate out of the aqueous a a certain pH. And I'm trying to remember but, if dmt-acetate is a charged molecule at pH 1.8- 2.0, then try to follow this; dmt-acetate 'looks' like this: (+)H-DMT-OOCCH3(-) or (-)CH3COO-DMT-H(+) .... with the DMT-H+ being the positively 'charged' dmt-in-acid molecule. This bonds to the negatively charged CH3COO- (acetate) molecule. At the right pH, both are floating in solution and dmt-acetate is soluble because it has a bit of both negative and positive charges on it. So start with dmt dissolved in acetic acid to get dmt-acetate and free, excess acetate. (Add acetic acid to water, then dissolve in dmt). Using just the right molar amount of acetic acid-to-dmt will make a minimum amount of 'excess' acetate to clean up. You could use too much dmt, if you exceeded the molar amount of actic acid used. To get rid of the excess, I think you have to make all the excess acetate (CH3COO-) in there become protonated and therefore uncharged and insoluble (ie add more H+ to get CH3COOH ). Acetic acid has a pKa of 4.7, so simply make the aqueous with dmt-acetate even more acid with a drop of HCL, to pH 1.8 or 2.0. ( making up numbers here folks ... it may just be pH 3 is enough..!) Then, with the aqueous at pH 1.8, adding a NP solvent like good ol' naphtha will suck out the free acetic acid but leave behind the charged dmt-acetate. Now evaporate the aqueous, and you should get dmt-acetate to scrape up. ... no..?! With dmt dissolved in acid aqueous solution, much is in our favour - the solubility of dmt is possible in water from pH of 2 to 8.5 because it has a POSITIVE charge. Acteate is CH3COO-, and is negative. When you lower pH you add 100's of times more H+'s to combine with the negative charges, like on CH3COO- to get CH3COOH. But I confess I'm just musing aloud, wandering around in my memory with my chemisty shoes on again... Also I seem to believe that some amounts of acetate and fumarate 'safe' contaminants to have in an injectable solution..? which this is because they are simple carbohydrates that your body makes and uses all the time...?