BOOK X.
uestions as to the methods of smelting ores and of obtaining metals I discussed in Book IX. Following this, I should explain in what manner the precious metals are parted from the base metals, or on the other hand the base metals from the precious[1]. Frequently two metals, occasionally more than two, are melted out of one ore, because in nature generally there is some amount of gold in silver and in copper, and some silver in gold, copper, lead, and iron; likewise some copper in gold, silver, lead, and iron, and some lead in silver; and lastly, some iron in copper[2]. But I will begin with gold.
Gold is parted from silver, or likewise the latter from the former, whether it be mixed by nature or by art, by means of aqua valens[3], and by powders which consist of almost the same things as this aqua. In order to preserve the sequence, I will first speak of the ingredients of which this aqua is made, then of the method of making it, then of the manner in which gold is parted from silver or silver from gold. Almost all these ingredients contain vitriol or alum, which, by themselves, but much more when joined with saltpetre, are powerful to part silver from gold. As to the other things that are added to them, they cannot individually by their own strength and nature separate those metals, but joined they are very powerful. Since there are many combinations, I will set out a few. In the first, the use of which is common and general, there is one libra of vitriol and as much salt, added to a third of a libra of spring water. The second contains two librae of vitriol, one of saltpetre, and as much spring or river water by weight as will pass away whilst the vitriol is being reduced to powder by the fire. The third consists of four librae of vitriol, two and a half librae of saltpetre, half a libra of alum, and one and a half librae of spring water. The fourth consists of two librae of vitriol, as many librae of saltpetre, one quarter of a libra of alum, and three-quarters of a libra of spring water. The fifth is composed of one libra of saltpetre, three librae of alum, half a libra of brick dust, and three-quarters of a libra of spring water. The sixth consists of four librae of vitriol, three librae of saltpetre, one of alum, one libra likewise of stones which when thrown into a fierce furnace are easily liquefied by fire of the third order, and one and a half librae of spring water. The seventh is made of two librae of vitriol, one and a half librae of saltpetre, half a libra of alum, and one libra of stones which when thrown into a glowing furnace are easily liquefied by fire of the third order, and five-sixths of a libra of spring water. The eighth is made of two librae of vitriol, the same number of librae of saltpetre, one and a half librae of alum, one libra of the lees of the aqua which parts gold from silver; and to each separate libra a sixth of urine is poured over it. The ninth contains two librae of powder of baked bricks, one libra of vitriol, likewise one libra of saltpetre, a handful of salt, and three-quarters of a libra of spring water. Only the tenth lacks vitriol and alum, but it contains three librae of saltpetre, two librae of stones which when thrown into a hot furnace are easily liquefied by fire of the third order, half a libra each of verdigris[4], of stibium, of iron scales and filings, and of asbestos[5], and one and one-sixth librae of spring water.
All the vitriol from which the aqua is usually made is first reduced to powder in the following way. It is thrown into an earthen crucible lined on the inside with litharge, and heated until it melts; then it is stirred with a copper wire, and after it has cooled it is pounded to powder. In the same manner saltpetre melted by the fire is pounded to powder when it has cooled. Some indeed place alum upon an iron plate, roast it, and make it into powder.
Although all these aquae cleanse gold concentrates or dust from impurities, yet there are certain compositions which possess singular power. The first of these consists of one libra of verdigris and three-quarters of a libra of vitriol. For each libra there is poured over it one-sixth of a libra of spring or river water, as to which, since this pertains to all these compounds, it is sufficient to have mentioned once for all. The second composition is made from one libra of each of the following, artificial orpiment, vitriol, lime, alum, ash which the dyers of wool use, one quarter of a libra of verdigris, and one and a half unciae of stibium. The third consists of three librae of vitriol, one of saltpetre, half a libra of asbestos, and half a libra of baked bricks. The fourth consists of one libra of saltpetre, one libra of alum, and half a libra of sal-ammoniac.[6]
All this preparation having been accomplished in order, and the ingredients placed in the ampulla, they are gradually heated over burning charcoal until they begin to exhale vapour and the ampulla is seen to trickle with moisture. But when this, on account of the rising of the vapour, turns red, and the aqua distils through the spout of the operculum, then one must work with the utmost care, lest the drops should fall at a quicker rate than one for every five movements of the clock or the striking of its bell, and not slower than one for every ten; for if it falls faster the glasses will be broken, and if it drops more slowly the work begun cannot be completed within the definite time, that is within the space of twenty-four hours. To prevent the first accident, part of the coals are extracted by means of an iron implement similar to pincers; and in order to prevent the second happening, small dry pieces of oak are placed upon the coals, and the substances in the ampulla are heated with a sharper fire, and the air-holes on the furnace are re-opened if need arise. As soon as the drops are being distilled, the glass ampulla which receives them is covered with a piece of linen moistened with water, in order that the powerful vapour which arises may be repelled. When the ingredients have been heated and the ampulla in which they were placed is whitened with moisture, it is heated by a fiercer fire until all the drops have been distilled[8]. After the furnace has cooled, the aqua is filtered and poured into a small glass ampulla, and into the same is put half a drachma of silver[9], which when dissolved makes the turbid aqua clear. This is poured into the ampulla containing all the rest of the aqua, and as soon as the lees have sunk to the bottom the aqua is poured off, removed, and reserved for use.