I was exploring different ways to make the nitration of DABT more economical, and one obvious thing to attempt was the reconcentration of the sulfuric
acid used.
After a trial run with minute amounts to make reasonably sure that no sudden decomposition ocurred when the mother liquor was heated, a larger amount
from a run was concentrated at atmospheric pressure with stirring. The process went without issue and I periodically checked the concentration of the
distillate coming over. When a concentration of 95% was reached, I stopped the procedure and allowed the flask to cool. The remarkable thing about the
experiment was that the small amounts of very fine precipitate that had passed through the filter and was thus still in the mother liquor was still
there.
I haven't absolutely determined if the solid is unchanged DNiBT (it certainly was when I began), but I find it remarkable that any organic substance
can endure several hours of boiling in 90+ % sulfuric acid.