Weight - Evaporation/Recrystallization of Research Chemicals?

[Lethargy]

So having applied some thought to the problem of measuring various Research Chemicals a friend of mine proposed an idea to me and I wanted to know any opinions and or experience with this or similar ideas...

He knows that many use a process of dissolving a known weight of material in a known volume of h2o or other solvent and weighing out amounts volumetrically.

He wondered if theoretically one could then take a known volume and evaporate the solvent to recrystallize the substance, thus having a known amount of solid.

He has little chemical knowledge and thus does not know which RCs one could theoretically do this to without degrading quality, though he posited it as a form of measuring 4-ho-mipt (the fumarate salt) and the 2-c family.

He mentioned complicating factors such as the fact that some minute quantity of substance may get left on the surface used for evaporation, and when dealing with such potent substances this "minute quantity" may have a large degree of significance.

Thoughts/Experiences? As mentioned this friend specifically wondered about the possibility of this technique with substances active in the mg range and knows that alone may pose problems due to dealing with very small quantities, but would like to know of any other possible problems one could think of.