Wikipedia’s entry on alchemy:
Up to the 18th century, alchemy was considered serious science in Europe; for instance, Isaac Newton devoted a great time to the Art. Other eminent alchemists of the Western world are Roger Bacon, Saint Thomas Aquinas, Tycho Brahe, and Thomas Browne. The decline of alchemy began in the 18th century with the birth of modern chemistry, which provided more precise and reliable framework for matter transmutations and medicine, within a new grand design of the universe based on rational materialism.
Legend has it that the founder of Egyptian alchemy was the god Thoth, called Hermes-Thoth or Thrice-Great Hermes (Hermes Trismegistus) by the Greek. According to legend, he wrote what were called the forty-two Books of Knowledge, covering all fields of knowledge ? including alchemy. Hermes’s symbol was the caduceus or serpent-staff, which became one of many of alchemy’s principal symbols. The “Emerald Tablet” or Hermetica of Thrice-Greatest Hermes, which is known only through Greek and Arabic translations, is generally understood to form the basis for Western alchemical philosophy and practice, called the hermetic philosophy by its early practitioners.