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.