Fixation
Zodiacal correspondence (Pernety, 1758): Gemini ♊
Fixation is the operation that renders a volatile substance stable, so that it withstands fire without subliming or evaporating away. To 'fix the volatile' was a central aim, since a fixed body was thought able to endure transformation and to fix other substances in turn. Pernety assigns the operation to Gemini. Practically it described converting fugitive materials (volatile salts, mercury preparations, arsenical 'spirits') into heat-stable solids.
Historical Development
Fixation addresses one of the defining problems of premodern chemistry: making volatile matter endure fire. A 'fixed' body was prized because it resisted destruction and was held capable of imparting stability to other substances, a decisive step on the path to a perfected medicine or Stone. The language of 'fixing the volatile' and 'volatilizing the fixed' became a shorthand for the whole transformative project.
Pernety places fixation under Gemini. Notably, fixation is not one of Ripley's twelve gates: it is among the operations Pernety's zodiacal scheme adds where Ripley had instead listed conjunction, putrefaction, cibation and exaltation. This divergence is a concrete sign that the two famous 'twelve-operation' lists are related traditions rather than a single canon.
Textual Tradition
The vocabulary of fixation pervades the corpus from the Arabic tradition through the Latin Pseudo-Geber, whose Summa perfectionis theorizes the stability of substances in corpuscular terms, and into early-modern chymistry. William Newman's edition and study of the Summa shows how carefully such operations were defined.
Modern Scholarship
Scholars note that 'fixation' maps onto real, observable changes in volatility and thermal stability, again revealing the operational substrate beneath alchemical vocabulary. They simultaneously caution against reading the eighteenth-century zodiacal scheme back into the practice of earlier centuries, where the operation existed without any fixed astrological key.