Alchemy, practiced especially in the Middle Ages, is a blend of science, magic,and religion. Its aim was to discover a substance that would transmute the more common metals into gold or silver and find a means of indefinitely prolonging human life. Although its purposes and techniques were dubious and often illusory, alchemy was in many ways the predecessor of modern science, especially the science of chemistry. The birthplace of alchemy was ancient Egypt, where, in Alexandria, it began to flourish in the Hellenistic period; simultaneously, a school of alchemy was developing in China. The writings of some of the early Greek philosophers might be considered to contain the first chemical theories; and the theory advanced in the 5th century BC by Empedocles-that all things are composed of air, earth, fire, and water-was influential in alchemy. The Roman emperor Caligula is said to have instituted experiments for producing gold from orpiment, a sulfide of arsenic, and the emperor Diocletian is said to have ordered all Egyptian works concerning the chemistry of gold and silver to be burned in order to stop such experiments. Zosimus the Theban (about AD 250-300) discovered that sulfuric acid is a solvent of metals, and he liberated oxygen from the red oxide of mercury. The fundamental concept of alchemy stemmed from the Aristotelian doctrine that all things tend to reach perfection. Because other metals were thought to be less "perfect" than gold, it was reasonable to assume that nature formed gold out of other metals deep within the earth and that with sufficient skill and diligence an artisan could duplicate this process in the workshop. Efforts toward this goal were empirical and practical at first, but by the 4th century AD, astrology, magic, and ritual had begun to gain prominence. A school of pharmacy flourished in Arabia during the caliphates of the Abbasids from 750 to 1258. The earliest known work of this school is the Summa Perfectionis (Summit of Perfection), attributed to the Arabian scientist and philosopher Geber; the work is consequently the oldest book on chemistry proper in the world and is a collection of all that was then known and believed. The Arabian alchemists worked with gold and mercury, arsenic and sulfur, and salts and acids, and they became familiar with a wide range of what are now called chemical reagents. They believed that metals are compound bodies, made up of mercury and sulfur in different proportions. Their scientific creed was the potentiality of transmutation, and their methods were mostly blind gropings; yet, in this way, they found many new substances and invented many useful processes. From the Arabs, alchemy generally found its way through Spain into
. The earliest authentic works extant on European alchemy are those of the English monk Roger Bacon and the German philosopher Albertus Magnus; both believed in the possibility of transmuting inferior metals into gold. This idea excited the imagination, and later the avarice, of many persons during the Middle Ages. They believed gold to be the perfect metal and that baser metals were more imperfect than gold. Thus, they sought to fabricate or discover a substance, the so-called philosopher's stone, so much more perfect than gold that it could be used to bring the baser metals up to the perfection of gold. Roger Bacon believed that gold dissolved in aqua regia was the elixir of life. Albertus Magnus had a great mastery of the practical chemistry of his time. The Italian Scholastic philosopher St. Thomas Aquinas, the Catalan churchman Raymond Lully, and the Benedictine monk Basil Valentine (flourished 15th century) also did much to further the progress of chemistry, although along alchemical lines, in discovering the uses of antimony, the manufacture of amalgams, and the isolation of spirits of wine, or ethyl alcohol. Important compilations of recipes and techniques in this period include The Pirotechnia (1540; trans. 1943), by the Italian metallurgist Vannoccio Biringuccio; Concerning Metals (1556; trans. 1912), by the German mineralogist Georgius Agricola; and Alchemia (1597), by Andreas Libavius, a German naturalist and chemist. Most famous of all was the 16th-century Swiss alchemist Philippus Paracelsus. Paracelsus held that the elements of compound bodies were salt, sulfur, and mercury, representing, respectively, earth, air, and water; fire he regarded as imponderable, or nonmaterial. He believed, however, in the existence of one undiscovered element common to all, of which the four elements of the ancients were merely derivative forms. This prime element of creation Paracelsus termed alkahest, and he maintained that if it were found, it would prove to be the philosopher's stone, the universal medicine, and the irresistible solvent. After Paracelsus, the alchemists of Europe became divided into two groups. One group was composed of those who earnestly devoted themselves to the scientific discovery of new compounds and reactions; these scientists were the legitimate ancestors of modern chemistry as ushered in by the work of the French chemist Antoine Lavoisier. The other group took up the visionary, metaphysical side of the older alchemy and developed it into a practice based on imposture, necromancy, and fraud, from which the prevailing notion of alchemy is derived.