464

BOOK X.

Finally, the gold is taken out of this and quenched, and if there is ablackish colour settled in it, it is melted with a little of the chrysocollawhich the Moors call borax ; if too pale, it is melted with stibium, andacquires its own golden-yellow colour. There are some who take out themolten copper with an iron ladle and pour it into another crucible, whoseaperture is sealed up with lute, and they place it over glowing charcoal,and when they have thrown in the powders of which I have spoken, theystir the whole mass rapidly with an iron rod, and thus separate the goldfrom the copper ; the former settles at the bottom of the crucible, the latterfloats on the top. Then the aperture of the crucible is opened with thered-hot tongs, and the copper runs out. The gold which remains is re-heatedwith stibium, and when this is exhaled the gold is heated for the third timein a cupel with a fourth part of lead, and then quenched.

The fourth method is to melt one and a third librae of the copperwith a sixth of a libra of lead, and to pour it into another crucible smeared onthe inside with tallow or gypsum; and to this is added a powder consisting ofhalf an uncia each of prepared sulphur, verdigris, and saltpetre, and an unciaand a half of sal coctus. The fifth method consists of placing in a crucibleone libra of the copper and two librae of granulated lead, with one and a halfunciae of sal-artificiosus ; they are at first heated over a gentle fire and thenover a fiercer one. The sixth method consists in heating together a bes ofthe copper and one-sixth of a libra each of sulphur, salt, and stibium. Theseventh method consists of heating together a bes of the copper and one-sixtheach of iron scales and filings, salt, stibium, and glass-galls. The eighthmethod consists of heating together one libra of the copper, one and a halflibrae of sulphur, half a libra of verdigris, and a libra of refined salt. Theninth method consists of placing in one libra of the molten copper asmuch pounded sulphur, not exposed to the fire, and of stirring it rapidlywith an iron rod ; the lump is ground to powder, into which quicksilveris poured, and this attracts to itself the gold.

Gilded copper articles are moistened with water and placed on the fire,and when they are glowing they are quenched with cold water, and the goldis scraped off with a brass rod. By these practical methods gold is separatedfrom copper.

Either copper or lead is separated from silver by the methods which Iwill now explain . 26 This is carried on in a building near by the works, orin the works in which the gold or silver ores or alloys are smelted. Themiddle wall of such a building is twenty-one feet long and fifteen feet high, andfrom this a front wall is distant fifteen feet toward the river ; the rear wall

26 Throughout the book the cupellation furnace is styled the secunda fornax (Glossary,Treibeherd). Except in one or two cases, where there is some doubt as to whether the authormay not refer to the second variety of blast furnace, we have used “ cupellation furnace.”Agricola’s description of the actual operation of the old German cupellation is less detailedthan that of such authors as Schliiter (Hutte-Werken, Braunschweig, 1738) or Winkler (Besch-reibimg der Freyberger Schmelz Huttenprozesse, Freyberg, 1837). The operation falls into fourperiods. In the first period, or a short time after melting, the first scum—the abzug —arises.This material contains most of the copper, iron, zinc, or sulphur impurities in the lead.In the second period, at a higher temperature, and with the blast turned on, a second scum