A Study of the Six-One Mud in Alchemical Scriptures
To refine external elixirs one must first build a furnace. Building the furnace is an extremely important part of alchemy, and to build a furnace one first needs Six-One Mud. This article analyzes the composition of Six-One Mud in detail. Ge Hong’s Baopuzi · Golden Elixir mentions: “Use realgar water, alum water, Rong salt, brine salt, alum, oyster shells, red halloysite, talc, and lead powder, each several tens of jin, to make Six-One Mud [for sealing].”
The main function of Six-One Mud is to seal the elixir furnace; in ancient times it was also called divine mud. But the preparation of Six-One Mud has always been kept as an alchemist’s secret, so whether what is recorded in publicly available alchemical scriptures is correct, and which version is the most correct, can no longer be verified.
The following analyzes the methods of preparing Six-One Mud recorded in common alchemical scriptures.
1. Oyster shells
In the Huangding Jiuding Shendan Jue (Secret of the Yellow Emperor’s Nine-Ding Divine Elixir), oyster shells are required to be “three hundred jin of left-looking oysters from the Eastern Sea,” clearly indicating sea oysters, so their use is very important.
Why use oyster shells? Because the main component of oyster shells is calcium carbonate CaCO3, while quicklime is calcium oxide CaO. After sea oyster shells are calcined at high temperature, CaCO3→CaO+CO2, so calcium oxide and carbon dioxide can be formed.
Therefore, oyster shells after calcination can form quicklime and serve as a coating. In addition, oyster shells contain more than 20 trace elements and 17 amino acids; if oyster shell powder is used to mix the soil, it can give the furnace water-retention, fertilizer-retention, and air-permeability properties, and can promote microbial cycling and absorption. It is better than pure quicklime and has extremely strong anti-corrosion effects.
According to research by foreign scholars, placing oyster shells into soil can greatly increase cabbage yield and can alkalize acidic soil. In addition, in concrete materials, adding 10% oyster shell powder can enhance freeze resistance and water permeability resistance, and also has anti-mold effects.
In the Taiqing Danjing, it is said that oyster shells may have been used for fineness, but without a corresponding function, so it is inferred to be useless. However, Master Sun clearly still followed the ancient method, so it is later said that there may be other better explanations—just not clear for the time being.
Looking at it today, the ancient method of using sea oyster shells has its rationale.
2. Bittern (lujian)
Crystalline substances such as magnesium chloride formed by the coagulation of brine, suitable for making refractory materials.
3. Rong salt
Also called Daqing salt (great blue salt), generally the crystal of the chloride-type halite mineral halite, usually taken from salt lakes. Its main component is calcium chloride, with strong water absorption. Another important function is that it can accelerate the solidification speed of Six-One Mud.
In addition, because bittern containing magnesium chloride is used, Rong salt (calcium chloride) can counteract magnesium poisoning.
4. Alum
According to what is stated in alchemical scriptures, the composition of alum differs by region, with the best being from Dunhuang. This should refer to yellow alum, mainly containing ferric sulfate (Fe2O3·2SO3·10H2O), of which sulfur trioxide (SO3) is 32%, iron(III) oxide (Fe2O3) 32%, and water (H2O) 36%.
Ferric sulfate has relatively good purification and bactericidal effects, and the sulfur trioxide within it is a strong oxidizing agent; at high temperatures it can oxidize sulfur, phosphorus, iron, zinc, and bromides and iodides, and can reduce toxicity.
Green alum and white alum are also sometimes used.
5. Red halloysite (chishizhi)
The main component is iron(III) oxide; however, according to Tang-dynasty red halloysite preserved in Japan, the main components should be silicon dioxide, aluminum oxide, and iron(III) oxide, and it can serve as a catalyst.
In modern times, iron oxide has often been used as a red dye. Notably, the aluminum oxide within it has high hardness, good heat resistance, and chemical inertness, making it a relatively good sealing material.
6. Talc
The main composition of talc is 3MgO·4SiO2·H2O, Al2O3, FeO/MgO. In modern industry it is used as a reinforcing and modifying filler in chemical industries such as rubber, plastics, and paint. Its characteristics include increasing product dimensional stability, increasing tensile strength, shear strength, flexural strength, and compressive strength, and reducing deformation, elongation, and coefficient of thermal expansion; it also has high whiteness, uniform particle size, and strong dispersibility.
The above six are relatively well established; one further ingredient is more doubtful, listed here.
1. Lead powder (hufen)
Questionable. Hufen is lead powder, with the composition basic lead carbonate. This one is controversial; although it has insecticidal effects, large doses can also cause poisoning in humans.
2. Realgar
Realgar is tetraarsenic tetrasulfide; when heated it forms arsenic trioxide—that is, arsenic—to which the human body is toxic. However, Chinese medicine sometimes uses arsenic as a drug, and modern science has also proven that arsenic in treating leukemia can truly achieve a “cure” effect, a major breakthrough in medicine. So this point is difficult to resolve for now.
3. Arsenopyrite (dusha)
The chemistry is FeAsS. In ancient times, arsenic trioxide was also prepared with arsenopyrite. Here it seems the same as using realgar to prepare arsenic trioxide, so either realgar or arsenopyrite could plausibly be used; the purpose is to be able to produce arsenic.
After the Song dynasty, it was basically no longer used.
4. Vinegar
Also called Huachi; most alchemical scriptures use this. Ancient alchemical scriptures often used this substance.
5. Earthworm soil
The main component is silicon dioxide, but red halloysite already contains it, which seems unreasonable in principle. However, earthworm soil also contains other components, so it may be useful. This substance was commonly used around the transition from the Han dynasties and during the Northern and Southern Dynasties.
6. Mica
Has heat-resistant effects; relatively plausible.
7. Sweet earth (gantu)
Silicate minerals such as montmorillonite, fuller’s earth, or their mixture, with a greasy feel. Slightly earthy odor, bland taste. The best quality is white, greasy to the touch, and strongly water-absorbing; relatively plausible.
Overall, the compositional structure of Six-One Mud is somewhat similar to cement, but the composition is clearly much more complex. As for the specifics, laboratory experimental research is still needed. Some scholars have discussed manufacturing Six-One Mud according to the Taiqing Danjing and studied its physical properties, obtaining a material with fairly good refractory properties. But because no attempt at refining actual elixirs was made, and because the role of oyster shells was not well understood, the preparation of Six-One Mud and its effect on enhancing alchemical results remain a mystery.