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Aurum, Gold

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AURUM.
117
another term of Punic origin. For gold alloyed with copper, a seventh part of gold and silver was ground up with the compo­sition. Theophrastus also speaks of the Chrysocolla being used as a solder, but gives no further particulars as to the mode in which it was applied.
The Roman gilder stuck the leaf-gold upon marble by means of the white of egg; for wood he had a size, " Leucophorum," made of Sinope earth, Sil, and Melinum, mixed together and suffered to ferment for twelve days. This was applied as a glue, and therefore dissolved in boiling water.
In gilding copper, quicksilver was made use of, as at present; the surface being rubbed with it, the leaf-gold was applied, and the quicksilver then driven off by the application of heat. If the leaf was single, or too thin, the surface looked pale, for which reason the workman, with a view to his profit, substituted for it the white of egg, which doubtless stood the air very satis­factorily for a certain time, at all events sufficiently long to se­cure his payment. Pliny complains that mercury was then only used in gilding silver : for bronze-work a cheap and fraudulent substitute had been universally adopted, the particulars of which however are to me unintelligible: the bronze was made red hot, then plunged in a pickle of salt, vinegar, and alum. It was now polished with sand, when its lustre proved if it were sufficiently purified. In this case it was slightly heated, and thus "tamed down" so as to receive the gold-leaf, which was fixed on it by means of a mixture of pumice, alum,8 and quick­silver. Perhaps the object was to save the quicksilver, evidently an expensive article at that time.
Strangely enough, Pliny distinguishes the Argentum Vivum, the native quicksilver found liquid and pure in the mines of other metals, from the Hydrargyrum, extracted by sublimation from the Minium, its sulphuret: although the metal is precisely the same in both cases. The greater rarity of Mercury in its native form must have given rise to this notion as to its superior quality. The Romans obtained it from the Spanish silver-mines :
8 He notes here that alum serves as well as lead iu the refining of gold.
Aurum, Gold Page of 453 Aurum, Gold
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