I had a book when I was a kid that I really liked a lot. I was born in 1976 so it would have been published before the mid-80s, probably. It was about an alchemist, possibly old and doddering, who was trying to turn lead into gold. If I remember correctly it had sort of sepia-toned line drawings, and there were quite detailed illustrations and instructions on how various alchemical apparatus worked. I remember illustrations of him working with tubes and liquids and flames and such. He also needed a unicorn horn so he had to get a young maiden to help him catch one. Can’t remember the title at all.