Note 30 — BOOK XI. (continued 2)

[Pg 541][30] There are three principal "slags" mentioned—

1st.Slag from "leading."

2nd.Slag from "drying."

3rd.Slag from refining the copper.

From the analyses quoted by various authors these ran from 52% to 85% lead oxide, 5% to 30% cuprous oxide, and considerable silica from the furnace bottoms. They were reduced in the main into liquation cakes, although Agricola mentions instances of the metal reduced from "slags" being taken directly to the "drying" furnace. Such liquation cakes would run very low in silver, and at the values given only averaged 12 ozs. per ton; therefore the liquated lead running the same value as the cakes, or less than half that of the "poor" lead mentioned in Note 17, p. 512, could not have been cupelled directly.