Alchemy is not, per se, an actual practice of magic. Moreso it is a study of hard science and chemistry, understanding the purely corporeal nature of the ingredients used to produce an effect.
That is not to say that alchemy is entirely mundane. The combination of essences do produce often profound magical affects; Dragon Dust, love potions, and healing salves are rather well known results of the alchemical discipline.
Often called witches, alchemists use their knowledge of chemistry, and the magic essences inherent in the ingredients they use, to create items that can very closely replicate anything a mage, priest, or shaman can do. Unfortunately this comes at the cost of considerable labor, expense, and danger while producing things that those who practice magic can do, seemingly, on a whim.
Sometimes, even with exhaustive knowledge, things just don't come out as intended. Example being Pascal, one of Metamor's most notable alchemists. Her erstwhile best efforts resulted in a beaver's fur becoming a checkerboard pastiche of black and red, and other disastrous, often permanent, results. Whether or not this was an intentional result or simply the fallibility of science attempting to replicate magic, is not known.