mid-14c., from Old French alchimie (14c.), alquemie (13c.), from Medieval Latin alkimia, from Arabic al-kimiya, from Greek khemeioa (found c.300 C.E. in a decree of Diocletian against "the old writings of the Egyptians"), all meaning "alchemy." Perhaps from an old name for Egypt (Khemia, literally "land of black earth," found in Plutarch), or from Greek khymatos "that which is poured out," from khein "to pour," related to khymos "juice, sap" [Klein, citing W. Muss-Arnolt, calls this folk etymology]. The word seems to have elements of both origins.
Mahn ... concludes, after an elaborate investigation, that Gr. khymeia was probably the original, being first applied to pharmaceutical chemistry, which was chiefly concerned with juices or infusions of plants; that the pursuits of the Alexandrian alchemists were a subsequent development of chemical study, and that the notoriety of these may have caused the name of the art to be popularly associated with the ancient name of Egypt. [OED]The al- is the Arabic definite article, "the." The art and the name were adopted by the Arabs from Alexandrians and thence returned to Europe via Spain. Alchemy was the "chemistry" of the Middle Ages and early modern times; since c.1600 the word has been applied distinctively to the pursuit of the transmutation of baser metals into gold, which, along with the search for the universal solvent and the panacea, were the chief occupations of early chemistry.
A medieval philosophy and early form of chemistry whose aims were the transmutation of base metals into gold, the discovery of a cure for all diseases, and the preparation of a potion that gives eternal youth. The imagined substance capable of turning other metals into gold was called the philosophers' stone.
Our Living Language : Because their goals were so unrealistic, and because they had so little success in achieving them, the practitioners of alchemy in the Middle Ages got a reputation as fakers and con artists. But this reputation is not fully deserved. While they never succeeded in turning lead into gold (one of their main goals), they did make discoveries that helped to shape modern chemistry. Alchemists invented early forms of some of the laboratory equipment used today, including beakers, crucibles, filters, and stirring rods. They also discovered and purified a number of chemical elements, including mercury, sulfur, and arsenic. And the methods they developed to separate mixtures and purify compounds by distillation and extraction are still important.
A science (no longer practiced) that sought to transform one chemical element into another through a combination of magic and primitive chemistry. Alchemy is considered to be the ancestor of modern chemistry.
Note: The search for the philosopher's stone that would change lead and other base metals into gold was part of alchemy.
Note: Today, alchemy is associated with wizards, magic, and the search for arcane knowledge.