Alchemy is more than a single thing alchemy is not about turning the silver material object into gold material object

it is a bunch of correspondences and symbols dealing with the psyche, with the spirit.

There are experiments done on material objects but these serve as observation and these observation are used upon  yourself so you can change according to your will.

Alchemists observe nature and use symbolic systems of correspondences to apply these on themselves to help overcome obstacles to evolve ones personality.

Alchemy truly belongs with spirituality and mysticism,kabbalah, archetypal astrology,tarot....and these kind of stuff.

We could argue whether there is anything "supernatural" about this or it's just psychology, but anyone practicing gets some results.

So basically while doing experiment with herbs/metals you observe nature and apply (in more complex way of course)your observations to yourself, it's is really a sort of psychological process like NLP for example.There are other benefits from the experiments of course, making tinctures out of herbs that are healthy for your body...and so on.

V.I.T.R.I.O.L

I do not believe in the urine theory a bit, but than again something so full of symbolism and double meanings is very interpretable, it's interesting nonetheless.