Separation of gold and silver. Historical engraving of workers separating gold and silver. Alloys of the two metals, along with acid solutions, are in glass flasks (3) on top of ovens (2). As the acid solution boils the silver dissolves in it. The resultant vapour rises into the glass covers over the flasks, where it cools, condenses into a liquid and collects in the receiver vessels (4). After all the acid solution has boiled away only gold is left in the flasks. Taken from The Laws of Art and Nature, in Knowing, Judging, Assaying, Fining, Refining and Inlarging the Bodies of Confin'd Metals (1683), John Pettus, a translation of the work by Lazarus Ercken.