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BOOK VII.
which was not very rapid, and was more accurate for testing a large mass
than a small one. This I will explain in my commentaries. The
alchemists have shown us a way of separating silver from gold by which
neither of them is lost32.
Gold which contains silver,33 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 siciliens (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 libra3i 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 will 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. 458).
32The Alchemists (with whose works Agricola was familiar—vide preface) were the
inventors of nitric acid separation. (See note on p. 460).
33Parting gold and silver by nitric acid is more exhaustively discussed in Book X.
and notes 10, p. 443.
34The lesser weights, probably.
