Handwritten manuscript containing notes for making aqua fortis, (or nitric acid), and refining silver. Includes a basic sketch of the apparatus used in the procedure. Written by John Conduitt (1688-1737), Sir Isaac Newton's (1643-1727) colleague and protégé. Conduitt was a British landowner and Whig politician. He sat in the House of Commons from 1721 to 1737 and was married to Newton's half-niece Catherine Barton (1679-1739).

In alchemy, aqua fortis (Latin for “strong water”) is nitric acid. Being highly corrosive, the solution was used in alchemy for dissolving silver and most other metals with the notable exception of gold. 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.