Those were some fun (and really hard) chemical puzzles! I actually love that there's minimal guidance on how to make components, because it means, like a true scientist, you have to experiment to figure out the rules. And the characters and story add a lot to this game; their small boost of emotional investment gave me the perseverance to push forward.
Others have already mentioned an undo button. Something else that would be neat is a growing catalog of names and "recipes" as they are discovered, I guess kind of like in Doodle God back in the day.