Fixatio, fixation, is the alchemical operation of rendering a volatile substance permanent and stable, preventing it from escaping as vapor when subjected to heat. In the practical language of the laboratory, to fix a substance means to transform it from a state in which it evaporates, sublimes, or escapes the vessel into a state in which it withstands fire without dissipation. Fixation is the essential counterpart to volatilization: together they constitute the alchemical mastery of the two fundamental states of matter, and the ability to fix what is volatile is presented throughout the tradition as the decisive skill of the true adept.

The concept is intimately connected to the mercury-sulphur theory that underlies much of Western alchemy. Mercury, the volatile principle, tends to flee — to evaporate, to escape, to resist containment. Sulphur, the fixed principle, tends to remain — to endure, to stabilize, to hold form. The opus requires that the volatile mercury be captured and fixed by the sulphur, and the fixed sulphur be made volatile by the mercury, until both achieve a perfect equilibrium. The Tabula Smaragdina's injunction to make the fixed volatile and the volatile fixed summarizes this fundamental operation. The Rosarium Philosophorum and the Senior Zadith both describe fixation as the restraining of the volatile, with the male principle restraining the female and preventing her flight.

In Atalanta Fugiens, fixation finds its master allegory in the frontispiece narrative of the race between Atalanta and Hippomenes. De Jong identifies the entire pursuit-and-capture motif as Maier's figure for the fixation of Mercury by Sulphur. Atalanta, the fleeing maiden, is volatile mercury — swift, elusive, impossible to capture by direct force. Hippomenes, the pursuing youth, is fixed sulphur — persistent, strategic, employing the golden apples as a means of slowing and ultimately capturing the volatile principle. The golden apples represent the catalytic agent that mediates between the fixed and volatile, enabling their union.

Emblem VII presents fixation through the image of a young bird that flies from its nest but falls back again. The text advises the reader to sublimate Mercury so often that it becomes solid and cannot evaporate through the power of fire. De Jong reads this as a depiction of the progressive fixation of the volatile through repeated sublimation — each cycle of ascent and descent renders the mercury slightly more stable until it is fully fixed. Emblem XVI extends the imagery through the winged and wingless lions: the winged lion is the volatile, mercurial, female principle; the wingless lion is the fixed, sulphurous, male principle. The two must be united, and the operation of fixation is what allows the winged to become wingless.

The comprehensive list of operations in Emblem XXXIX's discourse places fixatio as the final step: after solutio, coagulatio, sublimatio, ascensio, descensio, distillatio, and calcinatio have been completed, fixatio consummates the work. Both the volatile and the fixed are made into a solid substance, which De Jong identifies as the completion of the opus. The fixed Stone is the substance that can endure the test of fire without loss — and only a fully fixed substance has the power to transmute.

For the lay reader, fixation is the alchemical equivalent of domesticating a wild animal or setting a dye so that it will not wash out. The volatile spirit, once captured and stabilized, becomes the permanent, enduring Stone. Without fixation, the spirit would simply fly away when heated, and all the labor of dissolution and purification would evaporate with it.

Meanings Across Registers

De Jong shows that alchemical terms operate simultaneously across material, medical, spiritual, and cosmological dimensions.

Alchemical

Rendering volatile matter stable and resistant to fire; the spirit is permanently bound to the body so it can no longer escape through heating.

Medical

The stabilization of volatile symptoms and humoral imbalances; making a cure permanent rather than merely suppressing recurring disease.

Spiritual

The permanent anchoring of spiritual realization in embodied life; ensuring that transcendent insight does not evaporate when the adept returns to daily existence.

Cosmological

The principle of cosmic fixity: the immovable center around which the celestial spheres rotate, the axis mundi that grounds the turning heavens.