[7] Minium secundarium. (Interpretatio,—menning. Pb3O4). Agricola derived his Latin term from Pliny. There is great confusion in the ancient writers on the use of the word minium, for prior to the Middle Ages it was usually applied to vermilion derived from cinnabar. Vermilion was much adulterated with red-lead, even in Roman times, and finally in later centuries the name came to be appropriated to the lead product. Theophrastus (103) mentions a substitute for vermilion, but, in spite of commentators, there is no evidence that it was red-lead. The first to describe the manufacture of real red-lead was apparently Vitruvius (VII, 12), who calls it sandaraca (this name was usually applied to red arsenical sulphide), and says: "White-lead is heated in a furnace and by the force of the fire becomes red lead. This invention was the result of observation in the case of an accidental fire, and by the process a much better material is obtained than from the mines." He describes minium as the product from cinnabar. Dioscorides (V, 63), after discussing white-lead, says it may be burned until it becomes the colour of sandaracha, and is called sandyx. He also states (V, 69) that those are deceived who consider cinnabar to be the same as minium, for minium is made in Spain out of stone mixed with silver sands. Therefore he is not in agreement with Vitruvius and Pliny on the use of the term. Pliny (XXXIII, 40) says: "These barren stones (apparently lead ores barren of silver) may be recognised by their colour; it is only in the furnace that they turn red. After being roasted it is pulverized and is minium secundarium. It is known to few and is very inferior to the natural kind made from those sands we have mentioned (cinnabar). It is with this that the genuine minium is adulterated in the works of the Company." This proprietary company who held a monopoly of the Spanish quicksilver mines, "had many methods of adulterating it (minium)—a source of great plunder to the Company." Pliny also describes the making of red lead from white.
[8] Ochra plumbaria. (Interpretatio,—pleigeel; modern German,—Bleigelb). The German term indicates that this "Lead Ochre," a form of PbO, is what in the English trade is known as massicot, or masticot. This material can be a partial product from almost any cupellation where oxidation takes place below the melting point of the oxide. It may have been known to the Ancients among the various species into which they divided [Pg 233]litharge, but there is no valid reason for assigning to it any special one of their terms, so far as we can see.
[9] There are four forms of copper named as re-agents by Agricola:
| Copper filings | Aeris scobs elimata. |
| Copper scales | Aeris squamae. |
| Copper flowers | Aeris flos. |
| Roasted copper | Aes ustum. |
The first of these was no doubt finely divided copper metal; the second, third, and fourth were probably all cupric oxide. According to Agricola (De Nat. Fos., p. 352), the scales were the result of hammering the metal; the flowers came off the metal when hot bars were quenched in water, and a third kind were obtained from calcining the metal. "Both flowers (flos) and hammer-scales (squama) have the same properties as crematum copper.... The particles of flower copper are finer than scales or crematum copper." If we assume that the verb uro used in De Re Metallica is of the same import as cremo in the De Natura Fossilium, we can accept this material as being merely cupric oxide, but the aes ustum of Pliny—Agricola's usual source of technical nomenclature—is probably an artificial sulphide. Dioscorides (V, 47), who is apparently the source of Pliny's information, says:—"Of chalcos cecaumenos, the best is red, and pulverized resembles the colour of cinnabar; if it turns black, it is over-burnt. It is made from broken ship nails put into a rough earthen pot, with alternate layers of equal parts of sulphur and salt. The opening should be smeared with potter's clay and the pot put in the furnace until it is thoroughly heated," etc. Pliny (XXXIV, 23) states: "Moreover Cyprian copper is roasted in crude earthen pots with an equal amount of sulphur; the apertures of the pots are well luted, and they are kept in the furnace until the pot is thoroughly heated. Some add salt, others use alumen instead of sulphur, others add nothing, but only sprinkle it with vinegar."
[10] The reader is referred to [note 6, p. 558], for more ample discussion of the alkalis. Agricola gives in this chapter four substances of that character:
Soda (nitrum). Lye. "Ashes which wool-dyers use." "Salt made from the ashes of musk ivy."
The last three are certainly potash, probably impure. While the first might be either potash or soda, the fact that the last three are mentioned separately, together with other evidence, convinces us that by the first is intended the nitrum so generally imported into Europe from Egypt during the Middle Ages. This imported salt was certainly the natural bicarbonate, and we have, therefore, used the term "soda."
[11] In this chapter are mentioned seven kinds of common salt:
| Salt | Sal. |
| Rock salt | Sal fossilis. |
| "Made" salt | Sal facticius. |
| Refined salt | Sal purgatius. |
| Melted salt | Sal liquefactus. |