Daoist alchemy is the predecessor of modern chemistry. Daoist alchemists attempted to use natural minerals and plants to produce a drug of immortality by chemical processing. They thought that they could achieve immortality by taking such drugs. Although they never realized their purpose, their observations, chemical experiments, achievements, and their instruments, equipment and methods laid a foundation for the birth of modern chemistry. So Daoist alchemy can also be called Daoist chemistry.
Daoist alchemy originated in the Daoist Elixir Cauldron sect. Li Shaojun of the Western Han dynasty refined gold with cinnabar. Liu An, the king of Huainan, once recruited magicians to refine elixirs. He himself also engaged in the practise. When organized Daoism was founded in the Eastern Han dynasty, Daoist alchemy was enriched. During the Jin and Southern and Northern dynasties, Daoist alchemy became mature in its smelting and fire techniques, as well as in theory and practice. Daoist alchemy entered a period of great prosperity in the Tang dynasty. The gentry class was engrossed with divine elixirs and golden potions in its pursuit of longevity. The Tang emperor Taizong was one of them.
Daoist alchemy in the Song lacked creativity. It was lengthy and tedious, and purposely shrouded itself in mystery, so people took it as hoax used to gain fame by deceiving the public. Daoist alchemy showed signs of decline. Daoist alchemy received some attention in the Ming Dynasty, when several emperors died because of ingesting elixirs. As Daoist alchemy could not secure longevity but benefited the corrupt and promiscuous, it finally gave way to Inner Alchemy.
Alchemists thought that if they ingested a substance which would not burn in fire, would not rot in water and would not decay in earth, they could acquire the same properties as that substance. So their bones would become strong, and they would achieve bodily longevity. " Becoming strong by taking outer substances" is the theoretical basis of Daoist alchemy.