Our aim in writing this book has been to try, through the analysis of recognised authors, to arrive at a more exact vision of what alchemy is and what its practice consists of. We cover all the points of the alchemical work, starting with the initial materials, their preparation, the operations involved in the course of the whole process, right up to the final conclusion of the alchemical work. We quote various passages from different authors, many of them unpublished in Portuguese, so that the reader can draw their own conclusions. In this way, we hope to have been able to provide a more in-depth view of what alchemy is and how it is practised, and to enable those readers who wish to delve deeper to follow in their own footsteps.