An alchemist, Taoist script. Used for the combination of external Dan and internal Dan. External alchemy originated from Huang, that is, smelting minerals in an alchemy furnace to make "elixir" Later, I planned to make the human body into a furnace tripod to practice the essence, which was called internal alchemy. External alchemy refers to Taoism burning alchemy medicine through various secret methods, or directly taking some Cao Zhi to touch its own yin and turn it into yang. Chen Shidao's Note: "Taoism regards refining stone as an external elixir; The dragon and tiger miscarried, and the old spit out the new one as the inner Dan. "
Alchemy is the secret recipe of refining elixir by the ancients in pursuit of "longevity". Dan refers to cinnabar or mercury sulfide, which is an inorganic compound of sulfur and mercury. Because it is red, Tao Hongjing calls it "cinnabar". Different from vegetation, cinnabar is not only incombustible, but also "the longer it is burned, the better the change." Mercury produced by cinnabar mercury is a metallic substance, but it is liquid and has metallic luster, which is different from hardware (gold, silver, copper, iron and tin).
Cinnabar was used as the main material of alchemy by ancient alchemists because of its pharmacological action and physical and chemical properties. The ancients were amazed at its roundness and volatility, so they chose other epigraphy drugs to mix with liquid mercury (mercury) according to a certain formula, and repeated reduction and oxidation experiments were carried out to extract "Jiuhuidan" or "Jiuhuidan". This is the earliest chemical reaction product of mankind.
In ancient times, it was considered as an elixir with magical effects. Shennong's Classic of Materia Medica is the earliest "materialistic" work in Qin and Han Dynasties, which classifies more than 40 kinds of drugs, such as Wujintang, Sanhuang and Shiping. They are the first, the middle and the second grade respectively, and it is pointed out that the grading standard is: "Taking medicine can make people feel safe, prolong life, ascend to heaven and become immortal ..." Among them, cinnabar was listed as the top grade of an alchemist in ancient times.
The alchemist decomposed cinnabar after heating, and then found that mercury (mercury) combined with sulfide to produce black mercury sulfide, which sublimated after heating and then returned to the original state of red mercury sulfide. In fact, smelting mercury from cinnabar and sulfurizing it to make it return to cinnabar is a chemical reduction and oxidation reaction. Ge Hong, a native of A Jin, said in "Bao Puzi Jin Zidan": "Plants and trees are burned to the ground, and cinnabar is refined into mercury, which is far from removing plants and trees, so it can make people live forever."
Therefore, the ancients regarded alchemy as a method of immortality, but there was no scientific basis to verify whether the materials and methods of alchemy were appropriate, so once the materials were mixed, even the best elixir was just a chronic poison.