Used to make black gunpowder with charcoal sulfur and salt peter. That may be the only contribution I would make. Would have to think about it to decide if I have any other tidbits - most of us probably have some that we don’t even realize.
“Lord Kalvan of Otherwhen) is a good go-back-in-time story by H. Beam Piper. It’s fiction but he put a lot of thought into introducing new tech, gunpowder in particular. The “bad guys” were not using an optimum formula for their powder, Calvin had a better way and it shot better, harder, faster. So the bad guys spread the word that THEIR powder was expunged of evil spirits- but Calvin’s powder was not, and anyone using it was doomed to an unpleasant afterlife! The novel was originally called Gunpowder God