And in addition sal tostus and sal torrefactus. Sal facticius is used in distinction from rock-salt. The melted salt would apparently be salt-glass. What form the sal tostus and sal torrefactus could have we cannot say, however, but they were possibly some form of heated salt; they may have been combinations after the order of sal artificiosus (see p. [236]).
[12] "Stones which easily melt in hot furnaces and sand which is made from them" (lapides qui in ardentibus fornacibus facile liquescunt arenae ab eis resolutae). These were probably quartz in this instance, although fluorspar is also included in this same genus. For fuller discussion see note on p. [380].
[13] Tophus. (Interpretatio, Toffstein oder topstein). According to Dana (Syst. of Min., p. 678), the German topfstein was English potstone or soapstone, a magnesian silicate. It is scarcely possible, however, that this is what Agricola meant by this term, for such a substance would be highly infusible. Agricola has a good deal to say about this mineral in De Natura Fossilium (p. 189 and 313), and from these descriptions it would seem to be a tufaceous limestone of various sorts, embracing some marls, stalagmites, calcareous sinter, etc. He states: "Generally fire does not melt it, but makes it harder and breaks it into powder. Tophus is said to be a stone found in caverns, made from the dripping of stone juice solidified by cold ... sometimes it is found containing many shells, and likewise the impressions of alder leaves; our people make lime by burning it." Pliny, upon whom Agricola depends largely for his nomenclature, mentions such a substance (XXXVI, 48): "Among the multitude of stones there is tophus. It is unsuitable for [Pg 234]buildings, because it is perishable and soft. Still, however, there are some places which have no other, as Carthage, in Africa. It is eaten away by the emanations from the sea, crumbled to dust by the wind, and washed away by the rain." In fact, tophus was a wide genus among the older mineralogists, Wallerius (Meditationes Physico-Chemicae De Origine Mundi, Stockholm, 1776, p. 186), for instance, gives 22 varieties. For the purposes for which it is used we believe it was always limestone of some form.
[14] Saxum fissile album. (The Interpretatio gives the German as schifer). Agricola mentions it in Bermannus (459), in De Natura Fossilium (p. 319), but nothing definite can be derived from these references. It appears to us from its use to have been either a quartzite or a fissile limestone.
[15] Argol (Feces vini siccae,—"Dried lees of wine." Germ. trans. gives die wein heffen, although the usual German term of the period was weinstein). The lees of wine were the crude tartar or argols of commerce and modern assayers. The argols of white wine are white, while they are red from red wine. The white argol which Agricola so often specifies would have no special excellence, unless it may be that it is less easily adulterated. Agricola (De Nat. Fos., p. 344) uses the expression "Fex vini sicca called tartarum"—one of the earliest appearances of the latter term in this connection. The use of argol is very old, for Dioscorides (1st Century A.D.) not only describes argol, but also its reduction to impure potash. He says (V, 90): "The lees (tryx) are to be selected from old Italian wine; if not, from other similar wine. Lees of vinegar are much stronger. They are carefully dried and then burnt. There are some who burn them in a new earthen pot on a large fire until they are thoroughly incinerated. Others place a quantity of the lees on live coals and pursue the same method. The test as to whether it is completely burned, is that it becomes white or blue, and seems to burn the tongue when touched. The method of burning lees of vinegar is the same.... It should be used fresh, as it quickly grows stale; it should be placed in a vessel in a secluded place." Pliny (XXIII, 31) says: "Following these, come the lees of these various liquids. The lees of wine (vini faecibus) are so powerful as to be fatal to persons on descending into the vats. The test for this is to let down a lamp, which, if extinguished, indicates the peril.... Their virtues are greatly increased by the action of fire." Matthioli, commenting on this passage from Dioscorides in 1565, makes the following remark (p. 1375): "The precipitate of the wine which settles in the casks of the winery forms stone-like crusts, and is called by the works-people by the name tartarum." It will be seen above that these lees were rendered stronger by the action of fire, in which case the tartar was reduced to potassium carbonate. The weinstein of the old German metallurgists was often the material lixiviated from the incinerated tartar.
Dried lees of vinegar (siccae feces aceti; Interpretatio, die heffe des essigs). This would also be crude tartar. Pliny (XXIII, 32) says: "The lees of vinegar (faex aceti); owing to the more acrid material are more aggravating in their effects.... When combined with melanthium it heals the bites of dogs and crocodiles."
[16] Dried lees of aqua which separates gold and silver. (Siccae feces aquarum quae aurum ab argento secernunt. German translation, Der scheidwasser heffe). There is no pointed description in Agricola's works, or in any other that we can find, as to what this material was. The "separating aqua" was undoubtedly nitric acid (see p. [439], Book X). There [Pg 235]are two precipitates possible, both referred to as feces,—the first, a precipitate of silver chloride from clarifying the aqua valens, and the second, the residues left in making the acid by distillation. It is difficult to believe that silver chloride was the feces referred to in the text, because such a precipitate would be obviously misleading when used as a flux through the addition of silver to the assays, too expensive, and of no merit for this purpose. Therefore one is driven to the conclusion that the feces must have been the residues left in the retorts when nitric acid was prepared. It would have been more in keeping with his usual mode of expression, however, to have referred to this material as a residuus. The materials used for making acid varied greatly, so there is no telling what such a feces contained. A list of possibilities is given in [note 8, p. 443]. In the main, the residue would be undigested vitriol, alum, saltpetre, salt, etc., together with potassium, iron, and alum sulphates. The Probierbüchlin (p. 27) also gives this re-agent under the term Toden kopff das ist schlam oder feces auss dem scheydwasser.
[17] Recrementum vitri. (Interpretatio, Glassgallen). Formerly, when more impure materials were employed than nowadays, the surface of the mass in the first melting of glass materials was covered with salts, mostly potassium and sodium sulphates and chlorides which escaped perfect vitrification. This "slag" or "glassgallen" of Agricola was also termed sandiver.
[18] The whole of this expression is "candidus, candido." It is by no means certain that this is tin, for usually tin is given as plumbum candidum.
[Pg 236][19] Sal artificiosus. These are a sort of stock fluxes. Such mixtures are common in all old assay books, from the Probierbüchlin to later than John Cramer in 1737 (whose Latin lectures on Assaying were published in English under the title of "Elements of the Art of Assaying Metals," London, 1741). Cramer observes (p. 51) that: "Artificers compose a great many fluxes with the above-mentioned salts and with the reductive ones; nay, some use as many different fluxes as there are different ores and metals; all which, however, we think needless to describe. It is better to have explained a few of the simpler ones, which serve for all the others, and are very easily prepared, than to tire the reader with confused compositions: and this chiefly because unskilled artificers sometimes attempt to obtain with many ingredients of the same nature heaped up beyond measure, and with much labour, though not more properly and more securely, what might have been easily effected, with one only and the same ingredient, thus increasing the number, not at all the virtue of the things employed. Nevertheless, if anyone loves variety, he may, according to the proportions and cautions above prescribed, at his will chuse among the simpler kinds such as will best suit his purpose, and compose a variety of fluxes with them."