Aqua Fortis

## Aqua Fortis Aqua Fortis

**Aqua fortis** (Lat. "strong water"; nitric acid, HNO₃) is one of the most important mineral acids developed by medieval alchemists, capable of dissolving silver and most base metals (though not gold). The preparation of aqua fortis through the distillation of saltpeter (potassium nitrate) with vitriol (sulfuric acid) or alum is described in thirteenth-century Latin texts, including the *Summa Perfectionis* and works attributed to Ramon Llull and Albertus Magnus. This discovery represented a major advance in chemical technique, providing alchemists with a powerful solvent and reagent that enabled new types of operations and analyses.

Aqua fortis was used extensively in the separation of gold and silver through "parting"—dissolving silver in the acid while gold remained unaffected, allowing the two metals to be separated and recovered. This technique was fundamental to assaying and refining precious metals, and it contributed to the development of analytical chemistry. The acid was also used in the preparation of various metal salts, in etching and engraving, and in numerous alchemical experiments. The "spirit of nitre" (concentrated nitric acid) and "sweet oil of vitriol" (concentrated sulfuric acid) were among the most powerful reagents available to early modern chemists, enabling reactions and transformations impossible with traditional solvents like water, wine, or vinegar.

The corrosive power of aqua fortis and other mineral acids seemed almost miraculous to medieval practitioners, who saw in them evidence of fire's power concentrated in liquid form. The acids' ability to dissolve metals, to generate heat when mixed with water or metals, and to produce colored solutions and precipitates made them invaluable for experimental work. Modern chemistry understands nitric acid as a strong oxidizing agent whose reactions with metals produce metal nitrates and nitrogen oxides. William Newman's research has traced the development of mineral acid chemistry from its alchemical origins through its systematization in the seventeenth and eighteenth centuries, showing how techniques developed for chrysopoetic purposes contributed to the emergence of modern chemistry. The acids' symbolic significance—representing the power to dissolve and analyze, to separate the pure from the impure, to reduce complex substances to their components—made them central to both practical alchemy and alchemical allegory.

---