De Re Metallica Part 29

White schist _Saxum fissile _Weisser p. 234 alb.u.m_ schifer_

Weights (see Appendix).

[2] _Crudorum_,--unbaked?

[3] This reference is not very clear. Apparently the names refer to the German terms _probier ofen_ and _windt ofen_.

[4] _Circulus_. This term does not offer a very satisfactory equivalent, as such a furnace has no distinctive name in English. It is obviously a sort of forge for fusing in crucibles.

[5] _Sp.i.s.sa_,--"Dry." This term is used in contra-distinction to _pingue_, unctuous or "fatty."

[6] _Additamenta_,--"Additions." Hence the play on words.

We have adopted "flux" because the old English equivalent for all these materials was "flux," although in modern nomenclature the term is generally restricted to those substances which, by chemical combination in the furnace, lower the melting point of some of the charge. The "additions" of Agricola, therefore, include reducing, oxidizing, sulphurizing, desulphurizing, and collecting agents as well as fluxes. A critical examination of the fluxes mentioned in the next four pages gives point to the Author's a.s.sertion that "some are of a very complicated nature." However, anyone of experience with home-taught a.s.sayers has come in contact with equally extraordinary combinations.

The four orders of "additions" enumerated are quite impossible to reconcile from a modern metallurgical point of view.

[7] _Minium secundarium_. (_Interpretatio_,--_menning_. Pb_{3}O_{4}).

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 subst.i.tute 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 a.r.s.enical 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 (x.x.xIII, 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 _ma.s.sicot_, 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 litharge, but there is no valid reason for a.s.signing 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 a.s.sume 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 s.h.i.+p 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 (x.x.xIV, 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._

And in addition _sal tostus_ and _sal torrefactus_. _Sal facticius_ is used in distinction from rock-salt. The melted salt would apparently be salt-gla.s.s. 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 liquesc.u.n.t 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 sh.e.l.ls, 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 (x.x.xVI, 48): "Among the mult.i.tude of stones there is _tophus_. It is unsuitable for 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 alb.u.m._ (_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 a.s.sayers. 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 quant.i.ty 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 pa.s.sage 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 pota.s.sium 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 scheidwa.s.ser 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 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 a.s.says, 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 pota.s.sium, iron, and alum sulphates. The _Probierbuchlin_ (p. 27) also gives this re-agent under the term _Toden kopff das ist schlam oder feces auss dem scheydwa.s.ser_.

[17] _Recrementum vitri_. (_Interpretatio_, _Gla.s.sgallen_). Formerly, when more impure materials were employed than nowadays, the surface of the ma.s.s in the first melting of gla.s.s materials was covered with salts, mostly pota.s.sium and sodium sulphates and chlorides which escaped perfect vitrification. This "slag" or "_gla.s.sgallen_" 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 _plumb.u.m candidum_.

[19] _Sal artificiosus_. These are a sort of stock fluxes. Such mixtures are common in all old a.s.say books, from the _Probierbuchlin_ to later than John Cramer in 1737 (whose Latin lectures on a.s.saying were published in English under the t.i.tle of "Elements of the Art of a.s.saying 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."

[20] This operation apparently results in a coating to prevent the deflagration of the saltpetre--in fact, it might be permitted to translate _inflammatur_ "deflagrate," instead of kindle.

[21] The results which would follow from the use of these "fluxes" would obviously depend upon the ore treated. They can all conceivably be successful. Of these, the first is the lead-gla.s.s of the German a.s.sayers--a flux much emphasized by all old authorities, including Lohneys, Ercker and Cramner, and used even yet. The "powerful flux"

would be a reducing, desulphurizing, and an acid flux. The "more powerful" would be a basic flux in which the reducing action of the argols would be largely neutralised by the nitre. The "still more powerful" would be a strongly sulphurizing basic flux, while the "most powerful" would be a still more sulphurizing flux, but it is badly mixed as to its oxidation and basic properties. (See also note 19 on _sal artificiosus_).

[22] Lead ash (_Cinis Plumbi_. Glossary, _Pleyasch_).--This was obviously, from the method of making, an artificial lead sulphide.

[23] Ashes of lead (_Nigri plumbi cinis_). This, as well as lead ash, was also an artificial lead sulphide. Such substances were highly valued by the Ancients for medicinal purposes. Dioscorides (V, 56) says: "Burned lead (_Molybdos cecaumenos_) is made in this way: Sprinkle sulphur over some very thinnest lead plates and put them into a new earthen pot, add other layers, putting sulphur between each layer until the pot is full; set it alight and stir the melted lead with an iron rod until it is entirely reduced to ashes and until none of the lead remains unburned. Then take it off, first stopping up your nose, because the fumes of burnt lead are very injurious. Or burn the lead filings in a pot with sulphur as aforesaid." Pliny (x.x.xIV., 50) gives much the same directions.

[24] Camphor (_camphora_). This was no doubt the well-known gum.

Agricola, however, believed that camphor (_De Nat. Fossilium_, p. 224) was a species of bitumen, and he devotes considerable trouble to the refutation of the statements by the Arabic authors that it was a gum. In any event, it would be a useful reducing agent.

[25] Inasmuch as orpiment and realgar are both a.r.s.enical sulphides, the use of iron "slag," if it contains enough iron, would certainly matte the sulphur and a.r.s.enic. Sulphur and a.r.s.enic are the "juices" referred to (see note 4, p. 1). It is difficult to see the object of preserving the antimony with such a sulphurizing "addition," unless it was desired to secure a regulus of antimony alone from a given antimonial ore.

[26] The lead free from silver, called _villacense_, was probably from Bleyberg, not far from Villach in Upper Austria, this locality having been for centuries celebrated for its pure lead. These mines were worked prior to, and long after, Agricola's time.

[27] This method of proportionate weights for a.s.say charges is simpler than the modern English "a.s.say ton," both because of the use of 100 units in the standard of weight (the _centumpondium_), and because of the lack of complication between the Avoirdupois and Troy scales. For instance, an ore containing a _libra_ of silver to the _centumpondium_ would contain 1/100th part, and the same ratio would obtain, no matter what the actual weight of a _centumpondium_ of the "lesser weight" might be. To follow the matter still further, an _uncia_ being 1/1,200 of a _centumpondium_, if the ore ran one "_uncia_ of the lesser weight" to the "_centumpondium_ of the lesser weight," it would also run one actual _uncia_ to the actual _centumpondium_; it being a matter of indifference what might be the actual weight of the _centumpondium_ upon which the scale of lesser weights is based. In fact Agricola's statement (p. 261) indicates that it weighed an actual _drachma_. We have, in some places, interpolated the expressions "lesser" and "greater" weights for clarity.

This is not the first mention of this scheme of lesser weights, as it appears in the _Probierbuchlein_ (1500? see Appendix B) and Biringuccio (1540). For a more complete discussion of weights and measures see Appendix C. For convenience, we repeat here the Roman scale, although, as will be seen in the Appendix, Agricola used the Latin terms in many places merely as nomenclature equivalents of the old German scale.

Ozs.

dwts.

Troy gr.

Grains. per short ton.

1 _Siliqua_ 2.87 Per _Centumpondium_ 0 3 9 6 _Siliquae_ = 1 _Scripulum_ 17.2 " " 1 0 6 4 _Scripula_ = 1 _s.e.xtula_ 68.7 " " 4 1 0 6 _s.e.xtulae_ = 1 _Uncia_ 412.2 " " 24 6 2 12 _Unciae_ = 1 _Libra_ 4946.4 " " 291 13 8 100 _Librae_ = 1 _Centumpondium_ 494640.0

However Agricola may occasionally use

16 _Unciae_ = 1 _Libra_ 6592.0 (?) 100 _Librae_ = 1 _Centumpondium_ 659200.0 (?)

Also

Oz.