You could think of alchemy as the practical side of Hermetic theory.

Alchemy is nothing less than the study of the generation of material reality. In essence, the old adepts were after the secrets of creation itself. And they found them.

They accomplished their goals in the lab by reducing material to its elements and re-combining them to purify them as far as it is possible in material reality. That's simplifying it a bit, but that is really what alchemy is.

All of the psycho-spiritual stuff came long after the old adepts wrote their famous tracts. It was modern people, around the time of the occult revival, who twisted the theory of alchemy to fit into their psycho-spiritual worldview. The truth is, they didn't understand alchemy but became enamored of it's mystique. They found that they could get other people to listen to them by pretended to know what the old texts were talking about. They did not.

Some may have sincerely deluded themselves that they did, and some cynically chose to re-package whatever superficial understanding they may have had, in woo-woo spiritual terms, in order to extract gold from rubes. That sort of thing goes on to this day.

Spirituality and alchemy are intimately conjoined, but not in the way Jung et al thought/think. They are conjoined because the old boys understood that material reality is generated from spirit, and all of their practical experiments were made by observing nature and attempting to replicate the natural processes of creation in their labs and other works.

All of the metaphors in the old texts are about actual, practical, chemical materials or processes that they observed in their labs, their flasks and their experiments. For example, their use of planetary names correspond to certain metals and/or principles in the Work.

People who doubt that alchemy's roots are in fact practical, chemical processes should read the old texts to find out for themselves. In the many known, authentic texts, there is no mention of the kind of spiritual stuff Jung spouted. In those texts, the only mention of spirituality are exhortations to readers to pray, love God, and ask God for help.

The old adepts are universally viewed as being wise and learned. The were the original Natural Philosophers, which is the term used to describe 'scientist' before that term was coined. So why would we doubt that such wise and learned people spent their lives in practical lab work if what they were doing was only spiritual in nature? How does putting stuff into flasks to dissolve and coagulate it have anything to do with a purely spiritual practice? It doesn't, but some people insist on making that stretch. In so doing, they miss the mark completely.

So, why did the old boys use metaphors at all then? Because the information they learned is secret. It is kept from the uninitiated for a very good reason, which is, the same reason you wouldn't give a loaded weapon to a child. Yet the old boys wished to leave a trail for those who had the patience, forbearance, intelligence and spiritual maturity to follow.

There is a spiritual practice followed by Gnostics in conjunction with practical work. It is even more secret than the operations and true materials used in practical alchemy. Anything found freely about this online should be viewed with skepticism. Even known, authentic works by accepted masters such as Manly P Hall are deliberately incomplete.

Gnostic say this 'inner work' is necessary to succeed in one's exterior practice. They are right, and they are wrong. What is necessary is for the person to be at a place in their development where they are no longer a 'child', spiritually speaking. Gnostic practice is but one way to get there.