248 BOOK VII. 



which was not very rapid, and was more accurate for testing a large mass 

 than a smaU one. This I wiU explain in my commentaries. The 

 alchemists have shown us a way of separating silver from gold by which 

 neither of them is lost'^. 



Gold which contains silver,^' or silver which contains gold, is first rubbed 

 on the touchstone. Then a needle in which there is a similar amount of 

 gold or silver is rubbed on the same touchstone, and from the lines which are 

 produced in this way, is perceived what portion of silver there is in the gold, 

 or what portion of gold there is in the silver. Next there is added to the 

 silver which is in the gold, enough silver to make it three times as much as the 

 gold. Then lead is placed in a cupel and melted ; a little later, a small 

 amount of copper is put in it, in fact, half an uncia of it, or half an uncia and 

 a sicilicus (of the smaller weights) if the gold or silver does not contain any 

 copper. The cupel, when the lead and copper are wanting, attracts the particles 

 of gold and silver, and absorbs them. Finally, one-third of a libra of the gold, 

 and one libra^* of the silver must be placed together in the same cupel and 

 melted ; for if the gold and silver were first placed in the cupel and melted, as I 

 have already said, it absorbs particles of them, and the gold, when separated 

 from the silver, will not be found pure. These metals 'are heated until the 

 lead and the copper are consumed, and again, the same weight of each is melted 

 in the same manner in another cupel. The buttons are pounded with a 

 hammer and flattened out, and each little leaf is shaped in the form of a 

 tube, and each is put into a small glass ampulla. Over these there is poured 

 one uncia and one drachma (of the large weight) of the third quality aqua 

 valens, which I will describe in the Tenth Book. This is heated over a slow 

 fire, and small bubbles, resembling pearls in shape, will be seen to adhere 

 to the tubes. The redder the aqua appears, the better it is judged to be ; 

 when the redness has vanished, small white bubbles are seen to be resting 

 on the tubes, resembling pearls not only in shape, but also in colour. After 

 a short time the aqua is poured off and other is poured on ; when this has 

 again raised six or eight small white bubbles, it is poured off and the tubes are 

 taken out and washed four or five times with spring water ; or if they are 

 heated with the same water, when it is boiling, they wiU shine more brilliantly. 

 Then they are placed in a saucer, which is held in the hand and gradually 

 dried by the gentle heat of the fire ; afterward the saucer is placed over glowing 

 charcoal and covered with a charcoal, and a moderate blast is blown upon it 



ancient account of this affair is to be found in Vitruvius, ix, Preface. The story does not seem 

 very probable, seeing that Theophrastus, who died the year Archimedes was born, described 

 the touchstone in detail, and that it was of common knowledge among the Greeks before 

 (see note 37). In any event, there is not sufficient evidence in this story on which to build 

 the conclusion of Meyer (Hist, of Chemistry, p. 14) and others, that, inasmuch as Archimedes 

 was unable to solve the problem until his discovery of specific weights, therefore the 

 Ancients could not part gold and silver. The probability that he did not want to injure the 

 King's jewellery would show sufficient reason for his not parting these metals. It seems probable 

 that the Ancients did part gold and silver by cementation. (See note on p. 438). 



^''The Alchemists (with whose works Agricola was familiar — vide preface) were the 

 inventors of nitric acid separation. (See note on p. 460). 



^^Parting gold and silver by nitric acid is more exhaustively discussed in Book X. 

 and notes 10, p. 443. 



'*The lesser weights, probably. 



