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BOOK VII.

which was not very rapid, and was more accurate for testing a large massthan a small one. This I will explain in my commentaries. Thealchemists have shown us a way of separating silver from gold by whichneither of them is lost 32 .

Gold which contains silver , 33 or silver which contains gold, is first rubbedon the touchstone. Then a needle in which there is a similar amount ofgold or silver is rubbed on the same touchstone, and from the lines which areproduced 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 thesilver which is in the gold, enough silver to make it three times as much as thegold. Then lead is placed in a cupel and melted; a little later, a smallamount of copper is put in it, in fact, half an uncia of it, or half an uncia anda sicilicus (of the smaller weights) if the gold or silver does not contain anycopper. The cupel, when the lead and copper are wanting, attracts the particlesof gold and silver, and absorbs them. Finally, one-third of a libra of the gold,and one libra 3i of the silver must be placed together in the same cupel andmelted; for if the gold and silver were first placed in the cupel and melted, as Ihave already said, it absorbs particles of them, and the gold, when separatedfrom the silver, will not be found pure. These metals are heated until thelead and the copper are consumed, and again, the same weight of each is meltedin the same manner in another cupel. The buttons are pounded with ahammer and flattened out, and each little leaf is shaped in the form of atube, and each is put into a small glass ampulla. Over these there is pouredone uncia and one drachma (of the large weight) of the third quality aquavalens, which I will describe in the Tenth Book. This is heated over a slowfire, and small bubbles, resembling pearls in shape, will be seen to adhereto 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 restingon the tubes, resembling pearls not only in shape, but also in colour. Aftera short time the aqua is poured off and other is poured on ; when this hasagain raised six or eight small white bubbles, it is poured off and the tubes aretaken out and washed four or five times with spring water; or if they areheated with the same water, when it is boiling, they will shine more brilliantly.Then they are placed in a saucer, which is held in the hand and graduallydried by the gentle heat of the fire; afterward the saucer is placed over glowingcharcoal 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 seemvery probable, seeing that Theophrastus, who died the year Archimedes was born, describedthe 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 buildthe conclusion of Meyer (Hist, of Chemistry, p. 14) and others, that, inasmuch as Archimedeswas unable to solve the problem until his discovery of specific weights, therefore theAncients could not part gold and silver. The probability that he did not want to injure theKing’s jewellery would show sufficient reason for his not parting these metals. It seems probablethat the Ancients did part gold and silver by cementation. (See note on p. 458).

32 The Alchemists (with whose works Agricola was familiar —vide preface) were theinventors of nitric acid separation. (See note on p. 460).

33 Parting gold and silver by nitric acid is more exhaustively discussed in Book X.and notes 10, p. 443.

3 ‘The lesser weights, probably.