Doesn’t running heptane denatured alcohol through a decent reflux still (and thus removing the majority of the heptane) violate the spirit of the law?
You can actually request all but $1 of the excise tax on your ethanol back if you’ve got the balls to tell the feds what you’re using it for. Not sure if our accountant was up for that or not.
https://www.ttb.gov/applications/manufacturer_nonbeverage_products_packet.shtml