فایل:De Re Metallica 1556 p 357AQ20 (3).TIF

English: Page 357 from De re metallica libri XII. quibus officia, instrumenta, machinae, ac omnia deni ad metallicam spectantia, non modo luculentissimè describuntur, sed et per effigies, suis locis insertas, adiunctis latinis, germanicis appellationibus ita ob oculos ponuntur, ut clarius tradi non possint. Eiusdem De animantibus subterraneis liber, ab autore recognitus: cum indicibus diversis, quicqiuid in opere tractatum est, pulchré demonstrantibus by Georgii Agricolae. Basileae : [Apud Hieron Frobenium et Nicolaum Episcopium], 1556.

Production of nitric acid

The first step in separating gold from silver is the production of nitric acid from saltpeter and vitriol, shown here. The ingredients are heated in distilling apparatus (labeled H in the illustration), which then give off a red vapor (NO2) that combines with water and oxygen in the air to form nitric acid (HNO3). The acid is collected in flasks (labeled K).