Alchemical Chambers and Tripod Vessels in External Alchemy 外丹术的炼丹室与炉鼎

To ensure the effective progress of alchemy, Taoist external alchemists required a wide range of equipment, such as altars, furnaces, stoves, tripods, cauldrons, pots, jars, and more. When referring to alchemical chamber tripod vessels, there are narrow and broad definitions. In the narrow sense, tripod vessels refer to the tripods and cauldrons used for refining external elixirs, as well as medicinal gold and silver. In the broader sense, alchemical chamber tripod vessels also include alchemical altars, stoves, and furnaces.

In the alchemical process, the role of the tripod is particularly prominent, as it is the vessel that holds the ingredients while being heated. In terms of material, tripods can be made of gold, silver, copper, iron, porcelain, pottery, etc. In terms of shape, tripod vessels come in various forms—such as bottles, jars, cauldrons, and basins—all of which function as tripod vessels in alchemists' experiments. In Taoism, tripods have many different names, including "匮" (cabinet), "神室" (divine chamber), and "混沌" (primordial chaos). Their structures may be cylindrical, gourd-shaped, or crucible-like.

Historically, the most commonly used tripods by external alchemists were the upper and lower tripods, which are a combination of two tripods. For example, Tao Hongjing, a renowned alchemist of the Southern and Northern Dynasties, used a two-tiered earthen cauldron, while Sun Simiao of the Tang Dynasty described a tripod made of two clay basins that could be opened and closed. The production of upper and lower tripods followed strict procedures and specifications: generally, their circumference was twelve inches, corresponding to the twelve months and the twelve hexagrams of "消息卦" (hexagrams of waxing and waning); their height was eight inches, corresponding to the eight solar terms. Fundamentally, the correspondence between tripod vessels and heaven and earth reflects ancient people's understanding of nature.

Closely associated with tripods are furnaces, the primary heating equipment in alchemical chambers, also known as "丹炉" (alchemical furnaces) or "丹灶" (alchemical stoves). Functionally, alchemical furnaces are divided into yin and yang: those heated with intense fire are called "阳炉" (yang furnaces), and those with gentle fire are called "阴炉" (yin furnaces). In form, alchemical furnaces come in various styles, such as "既济炉" (Already Crossed Furnace), "未济炉" (Not Yet Crossed Furnace), "八卦炉" (Eight Trigrams Furnace), "百眼炉" (Hundred-eyed Furnace), "偃月炉" (Crescent Moon Furnace), and "菊花炉" (Chrysanthemum Furnace). The coordination of furnaces and tripods made alchemical work possible.