Chapter XXXVII: Book XI (4)

The copper flowers were no doubt cupric oxide. They were used by the Ancients for medicinal purposes. Dioscorides (V, 48) says: "Of flowers of copper, which some call the scrapings of old nails, the best is friable; it is gold-coloured when rubbed, is like millet in shape and size, is moderately bright, and somewhat astringent. It should not be mixed with copper filings, with which it is often adulterated. But this deception is easily detected, for when bitten in the teeth the filings are malleable. It (the flowers) is made when the copper fused in a furnace has run into the receptacle through the spout pertaining to it, for then the workmen engaged in this trade cleanse it from dirt and pour clear water over it in order to cool it; from this sudden condensation the copper spits and throws out the aforesaid flowers." Pliny (XXXIV, 24) says: "The flower, too, of copper (_aeris flos_) is used in medicine. This is made by fusing copper, and then removing it to another furnace, where the repeated blast makes the metal separate into small scales like millet, known as flowers. These scales also fall off when the cakes of metal are cooled in water; they become red, too, like the scales of copper known as '_lepis_,' by use of which the flowers of copper are adulterated, it being also sold for it. These are made when hammering the nails that are made from the cakes of copper. All these methods are carried on in the works of Cyprus; the difference between these substances is that the _squamae_ (copper scales) are detached from hammering the cakes, while the flower falls off spontaneously." Agricola (_De Nat. Fos._, p. 352) notes that "flowers of copper (_flos aeris_) have the same properties as 'roasted copper.'"

[27] It seems scarcely necessary to discuss in detail the complicated "flow scheme" of the various minor bye-products. They are all re-introduced into the liquation circuit, and thereby are created other bye-products of the same kind _ad infinitum_. Further notes are given on:--

Liquation thorns Note 28.
Slags " 30.
Ash-coloured copper " 29.
Concentrates " 33.
_Cadmia_ " 32.

There are no data given, either by Agricola or the later authors, which allow satisfactory calculation of the relative quantities of these products. A rough estimate from the data given in previous notes would indicate that in one liquation only about 70% of the original copper came out as refined copper, and that about 70% of the original lead would go to the cupellation furnace, _i.e._, about 30% of the original metal sent to the blast furnace would go into the "thorns," "slags," and "ash-coloured copper." The ultimate losses were very great, as given before (p. 491), they probably amounted to 25% of the silver, 9% copper, and 16% of the lead.

[28] There were the following classes of thorns:--

1st. From liquation.
2nd. From drying.
3rd. From cupellation.

In a general way, according to the later authors, they were largely lead oxide, and contained from 5% to 20% cuprous oxide. If a calculation be made backward from the products given as the result of the charge described, it would appear that in this case they must have contained at least one-fifth copper. The silver in these liquation cakes would run about 24 ozs. per ton, in the liquated lead about 36 ozs. per ton, and in the liquation thorns 24 ozs. per ton. The extraction into the liquated lead would be about 80% of the silver.

[29] The "ash-coloured copper" is a cuprous oxide, containing some 3% lead oxide; and if Agricola means they contained two _unciae_ of silver to the _centumpondium_, then they ran about 48 ozs. per ton, and would contain much more silver than the mass.

[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.

[31] See Note 16, p. 511, for discussion of yellow and _caldarium_ copper.

[32] This _cadmia_ is given in the Glossary and the German translation as _kobelt_. A discussion of this substance is given in the note on p. 112; and it is sufficient to state here that in Agricola's time the metal cobalt was unknown, and the substances designated _cadmia_ and _cobaltum_ were arsenical-cobalt-zinc minerals. A metal made from "slag" from refining, together with "base" thorns, would be very impure; for the latter, according to the paragraph on concentrates a little later on, would contain the furnace accretions, and would thus be undoubtedly zincky. It is just possible that the term _kobelt_ was used by the German smelters at this time in the sense of an epithet--"black devil" (see Note 21, p. 214).

[33] It is somewhat difficult to see exactly the meaning of base (_vile_) and precious (_preciosum_) in this connection. While "base" could mean impure, "precious" could hardly mean pure, and while "precious" could mean high value in silver, the reverse does not seem entirely _apropos_. It is possible that "bad" and "good" would be more appropriate terms.

[34] The skimmings from the molten lead in the early stages of cupellation have been discussed in Note 28, p. 539. They are probably called thorns here because of the large amount of copper in them. The lead from liquation would contain 2% to 3% of copper, and this would be largely recovered in these skimmings, although there would be some copper in the furnace bottoms--hearth-lead--and the litharge. These "thorns" are apparently fairly rich, four _unciae_ to the _centumpondium_ being equivalent to about 97 ozs. per ton, and they are only added to low-grade liquation material.

[35] _Particulis aeris tusi_. Unless this be the fine concentrates from crushing the material mentioned, we are unable to explain the expression.

[36] This operation would bring down a button of antimony under an iron matte, by de-sulphurizing the antimony. It would seem scarcely necessary to add lead before cupellation. This process is given in an assay method, in the _Probierbuechlein_ (folio 31) 50 years before _De Re Metallica_: "How to separate silver from iron: Take that silver which is in iron _plechen_ (_plachmal_), pulverize it finely, take the same iron or _plec_ one part, _spiesglasz_ (antimony sulphide) one part, leave them to melt in a crucible placed in a closed _windtofen_. When it is melted, let it cool, break the crucible, chip off the button that is in the bottom, and melt it in a crucible with as much lead. Then break the crucible, and seek from the button in the cupel, and you will find what silver it contains."