This is a historical article. For current information, see Nitric acid

] ] In alchemy, aqua fortis (Latin for "strong water") is nitric acid (HNO₃). Being highly corrosive, the solution was used in alchemy for dissolving silver and most other metals with the notable exception of gold, which can be dissolved using aqua regia or "regal water". Aqua fortis was prepared by mixing either sand, alum, or vitriol, or the last two together, with saltpeter, then distilling it by a hot fire. The gas collected from this condenses into aqua fortis. It was first described by alchemist Pseudo-Geber.