What Is Mercury in Alchemy?

Mercury is the most important of the three principles of the tria prima in the alchemical tradition, and the importance is practical as well as theoretical. The alchemical principle of mercury is the principle of fusibility, volatility, and the spirit, and the principle is what makes the alchemical laboratory work. Without the principle of mercury, in the alchemical framework, the metals would not melt, the liquids would not distill, and the spirit of the matter would not be separable from the body (Principe, The Secrets of Alchemy, 2013, pp. 88-100; Newman, Promethean Ambitions, 2004, pp. 91-105; Newman & Principe, Alchemy Tried in the Fire, 2002; Kahn, L’Alchimie et la Tradition, 2014; Holmyard, Alchemy, 1957, pp. 65-80). The principle is the alchemist’s first conceptual tool.

The principle and the metal

In the alchemical theory, mercury is the silvery, liquid metal known in modern chemistry and something larger at the same time. Alchemical mercury is a principle, a fundamental constituent of matter present in all substances in different proportions. The alchemists identified the principle of mercury with the qualities of fusibility, volatility, liquidity, and the spirit-like aspect of matter. The principle is the most pervasive of the three.

The principle of mercury is the receptive element in the alchemical system. It is the principle that gives matter its fluidity, its volatility, and its capacity to be shaped and formed. Where the principle of sulfur gives matter its activity, its color, and its soul, the principle of mercury gives matter its receptivity, its liquidity, and its spirit. The two principles together, with the third principle of salt (a 16th-century Paracelsian addition; the earlier Jabirian system has mercury-sulfur only), constitute all of matter (Principe, 2013, pp. 88-95). The clarification about the dating matters, because the pre-Paracelsian alchemists did not have the tria prima.

The alchemists used the term “mercury” because the ordinary substance of mercury — the silvery, liquid metal — was the most visible embodiment of the principle. The ordinary mercury is fluid, volatile (it evaporates at room temperature), dense (it is the heaviest of the common liquids), and capable of amalgamating with other metals. The alchemists saw these properties as expressions of the deeper principle that they called mercury, and the seeing is part of what made mercury the most useful of the alchemical reagents.

Mercury in the theory of metallic composition

Mercury is one of the two principles (along with sulfur) that the alchemists believed to be the immediate constituents of the metals, and the theoretical role is the one that gives mercury its central place in the alchemical theory of matter. The differences among metals are, in the alchemical theory, differences in the balance and the quality of the mercury and sulfur. Gold is the metal in which the mercury and sulfur are pure and perfectly balanced. Lead is the metal in which they are impure and unbalanced.

The alchemists developed a sophisticated account of the role of mercury in the metals. The mercury provides the metallic property of fusibility — the capacity of the metal to melt when heated. The alchemists believed that the mercury in a metal is what allows the metal to be worked, shaped, and alloyed with other metals. Without the mercury, the metal would be a lifeless, inert mass, and the alchemists were not speaking metaphorically.

The Paracelsian tradition extended the theory to include the third principle of salt, and the extension is one of the more important Paracelsian developments. The metals are made of mercury, sulfur, and salt in different proportions, and the character of each metal is determined by the balance of the three. The alchemist’s work is to adjust the balance of the three principles, purifying the impure, balancing the unbalanced, and producing the perfect metal (Principe, 2013, pp. 88-95).

Mercury in the alchemical operations

Mercury is the most important of the alchemical reagents, and the alchemists used mercury in a wide range of operations:

Amalgamation. Mercury combines with many other metals to form amalgams, and the alchemists used amalgamation to separate gold from its ores, to purify other metals, and to prepare a range of alchemical preparations.
Distillation. Mercury can be distilled, and the alchemists used the distillation of mercury to purify the metal and to obtain the “philosophical mercury,” the purified and activated form of the principle.
Calcination. Mercury can be calcined (heated in air) to produce the red oxide of mercury, and the alchemists used the calcination of mercury as a key step in the preparation of the philosopher’s stone.
Sublimation. Mercury can be sublimated (converted to a vapor and back to a solid), and the alchemists used the sublimation of mercury to produce a range of mineral preparations.

The alchemists developed a wide range of mercury compounds, including the red oxide, the yellow oxide, the corrosive sublimate (mercuric chloride), the calomel (mercurous chloride), and a long list of other preparations. Many of these compounds were used as medicines, and the Paracelsian medical system built much of its pharmacology on the mercury compounds (Newman & Principe, 2002, pp. 50-65). The pharmacology is a durable feature of the Paracelsian inheritance.

Mercury in the Paracelsian medical system

The Paracelsian medical system, examined in the cluster on Paracelsus, is built on the tria prima of mercury, sulfur, and salt, and the system is one of the more consequential medical frameworks of the early modern period. In the Paracelsian system, mercury is the principle of the spirit, the active, volatile, spirit-like aspect of the body. Diseases of the spirit are treated with mercury remedies — preparations that contain the principle of mercury in a purified and concentrated form.

The most important of the mercury remedies in the Paracelsian system is mercury itself, prepared in various forms. The Paracelsian alchemists developed sophisticated procedures for purifying mercury, including repeated distillation, amalgamation with other metals, and calcination. The purified mercury was used as a treatment for a wide range of diseases, particularly syphilis and other diseases of “mercury imbalance.” The Paracelsian use of mercury was controversial, and the Galenist physicians criticized the Paracelsians for using toxic preparations, and the Paracelsian mercury treatments were often blamed for the death of patients. The Paracelsians responded that the mercury preparations, properly prepared, were safe and effective, and that the Galenist physicians were opposed to the Paracelsian system for political rather than medical reasons. The debate is worth being clear about.

Mercury in the spagyric tradition

The spagyric tradition, examined in the cluster on spagyric alchemy, is the practical application of the tria prima theory, and the spagyric tradition is where the alchemical mercury becomes a working reagent. The spagyric alchemists developed a sophisticated set of procedures for separating, purifying, and recombining the three principles in plant and mineral substances.

In the spagyric preparation of plants, the mercury is the volatile, spirit-like component that is extracted from the plant by distillation. The mercury is the “spirit” of the plant, the principle that gives the plant its life and its medicinal properties. The spagyric alchemist extracts the mercury, purifies it by repeated distillation, and recombines it with the purified sulfur and salt to produce the spagyric tincture.

The spagyric preparation of mercury is a delicate operation. The mercury is highly volatile, and the alchemist must use careful heating and cooling to avoid losing the mercury. The mercury is also highly reactive, and the alchemist must take care to protect it from contamination. The care is part of the spagyric art.

Mercury in the alchemical symbolism

Mercury is the most richly represented of the tria prima in the alchemical symbolic tradition. The most common symbols:

The caduceus, the staff of the messenger god, with its two intertwined serpents and its wings. The caduceus is the standard alchemical symbol for mercury, and it is the most recognizable of the alchemical symbols. The caduceus survived into modern medical iconography, and the survival is a piece of the alchemical inheritance.
The silvery, liquid metal itself, depicted in flasks and containers throughout the alchemical literature.
The planet Mercury, the celestial counterpart of the terrestrial mercury. The alchemists saw a close correspondence between the planet and the metal, and they used the planetary symbol ☿ interchangeably for both.
The young, androgynous figure with wings on his heels and cap, the classical depiction of the god Mercury. The figure represents the spirit, the messenger, the active principle of the alchemical work.

The cluster on alchemical symbols shows the full range of symbols associated with mercury, and the long-tail page on the color stages examines the albedo, the stage in which mercury reaches its full activation.

Mercury in the work of the magnum opus

Mercury plays a central role in the magnum opus, the great work of producing the philosopher’s stone, and the role is what makes mercury the most important of the alchemical reagents. The alchemists believed that the mercury of the metals is the active agent of the transmutation, and the work of the magnum opus is the purification and activation of the mercury of the starting material.

The role of mercury in the magnum opus is twofold. First, the mercury is the active agent that drives the work through the four color stages. Second, the mercury is the material basis of the philosopher’s stone itself. The philosopher’s stone is, in the alchemical theory, a perfected form of mercury, brought to its highest state of purity and balance.

The alchemists developed a wide range of procedures for working with the mercury in the magnum opus. The procedures included the “killing” of the mercury (the conversion of the metallic mercury into a salt or oxide), the purification of the killed mercury, the “reviving” of the killed mercury (the conversion back to the metallic form), and the “multiplying” of the mercury.

Mercury in modern chemistry and alchemy

The modern chemist knows mercury as the silvery, liquid metal with the atomic number 80. The modern chemist knows that mercury is toxic, that mercury compounds are dangerous to handle, and that mercury pollution is a serious environmental problem. The modern alchemist who works with mercury takes the toxicity seriously and uses appropriate safety precautions, and the precautions are part of the modern alchemical inheritance.

The alchemical concept of mercury is a useful complement to the modern chemical concept, and the complementarity is one of the things the modern practitioner can work with. The modern chemical concept of mercury is precise and well-defined. The alchemical concept is broader and more symbolic. The two concepts are not incompatible. They are two ways of understanding the same substance, and the modern alchemist who works with both has a richer understanding than the modern chemist who works with only one.

The alchemical legacy of mercury is also visible in the modern pharmaceutical tradition. Many of the most important drugs of the modern era — the mercurial diuretics, the mercury-based antiseptics, the mercury compounds used in dental amalgams — are descendants of the Paracelsian mercury preparations, and the descent is one of the more concrete pieces of the alchemical inheritance (Newman & Principe, 2002). The alchemists were wrong about the philosopher’s stone. They were right about mercury.