CHAP. 32.—QUICKSILVER.
There is a mineral also found in these veins of silver, which
yields a humour that is always[1] liquid, and is known as
"quicksilver."[2] It acts as a poison[3] upon everything, and
pierces vessels even, making its way through them by the
agency of its malignant properties.[4] All substances float upon
the surface of quicksilver, with the exception of gold,[5] this
being the only substance that it attracts to itself.[6] Hence
it is, that it is such an excellent refiner of gold; for, on being
briskly shaken in an earthen vessel with gold, it rejects all
the impurities that are mixed with it. When once it has thus
expelled these superfluities, there is nothing to do but to separate
it from the gold; to effect which, it is poured out upon
skins that have been well tawed, and so, exuding through them
like a sort of perspiration, it leaves the gold in a state of
purity behind.[7]
Hence it is, too, that when copper has to be gilded,[8] a coat of
quicksilver is laid beneath the gold leaf, which it retains in its
place with the greatest tenacity: in cases, however, where the
leaf is single, or very thin, the presence of the quicksilver is
detected by the paleness of the colour.[9] For this reason, persons,
when meditating a piece of fraud, have been in the habit
of substituting glair of egg for quicksilver, and then laying
upon it a coat of hydrargyros, a substance of which we shall
make further mention in the appropriate place.[10] Generally
speaking, quicksilver has not been found in any large quantities.
1. "Vomica liquoris æterni." Mercury or quicksilver becomes solidified
and assumes a crystalline texture at 40° below zero. It is found chiefly
in the state of sulphuret, which is decomposed by distillation with iron or
lime. It is also found in a native state.
2. "Argentum vivum," "living silver."
3. Ajasson thinks that this is not to be understood literally, but that
Pliny's meaning is, that mercury is a universal dissolvent.
4. "Permanans tabe dirâ."
5. The specific gravity of mercury is 13.598, that of hammered gold
19.361. Platinum is only a recent discovery.
6. "Id unum ad se trahit."
7. "The first use of quicksilver is commonly reckoned a Spanish invention,
discovered about the middle of the sixteenth century; but it
appears from Pliny, that the ancients were acquainted with amalgam and
its use, not only for separating gold and silver from earthy particles, but
also for gilding."—Beckmann, Hist. Inv., Vol. I. p. 15. Bohn's Edition.
8. See the description of the mode of gilding, given in Chapter 20 of
this Book. Beckmann has the following remarks on the present passage;
"That gold-leaf was affixed to metals by means of quicksilver, with the assistance
of heat, in the time of Pliny, we are told by himself in more passages
than one. The metal to be gilded was prepared by salts of every kind,
and rubbed with pumice-stone in order to clean it thoroughly (see Chapter
20), and to render the surface a little rough. This process is similar to
that used at present for gilding with amalgam, by means of heat, especially
as amalgamation was known to the ancients. But, to speak the truth,
Pliny says nothing of heating the metal after the gold is applied, or of
evaporating the quicksilver, but of drying the cleaned metal before the
gold is laid on. Had he not mentioned quicksilver, his gilding might
have been considered as that with gold leaf by means of heat, dorure en
feuille à feu, in which the gold is laid upon the metal after it has been
cleaned and heated, and strongly rubbed with blood-stone, or polished steel.
Felibien (Principes de l'Architecture. Paris, 1676, p. 280) was undoubtedly
right when he regretted that the process of the ancients, the excellence
of which is proved by remains of antiquity, has been lost."—Hist. Inv.
Vol. II. pp. 294, 295. Bohn's Edition.
9. Beckmann finds considerable difficulties in this description—"I acknowledge
that this passage I do not fully comprehend. It seems to say
that the quicksilver, when the gold was laid on too thin, appeared through
it, but that this might be prevented by mixing with the quicksilver the
white of an egg. The quicksilver then remained under the gold: a thing
which is impossible. When the smallest drop of quicksilver falls upon
gilding, it corrodes the noble metal, and produces an empty spot. It is,
therefore, incomprehensible to me how this could be prevented by using
the white of an egg. Did Pliny himself completely understand gilding?
Perhaps he only meant to say that many artists gave out the cold-gilding.
where the gold-leaf was laid on with the white of an egg, as gilding by
means of heat."—Hist. Inv. Vol. II. p. 295.
10. Chapter 42 of this Book. See also Chapter 20, in Note 20, to which
it has been mentioned as artificial quicksilver.