Book VII, where (p. 220) a table is given showing the Latin and Old

German terms. Footnotes in explanation of our views as to these substances may be most easily consulted through the index. [3] _Aqua valens_, literally strong, potent, or powerful water. It will appear later, from the method of manufacture, that hydrochloric, nitric, and sulphuric acids and _aqua regia_ were more or less all produced and all included in this term. We have, therefore, used either the term _aqua valens_ or simply _aqua_ as it occurs in the text. The terms _aqua fortis_ and _aqua regia_ had come into use prior to Agricola, but he does not use them; the Alchemists used various terms, often _aqua dissolvia_. It is apparent from the uses to which this reagent was put in separating gold and silver, from the method of clarifying it with silver and from the red fumes, that Agricola could have had practical contact only with nitric acid. It is probable that he has copied part of the recipes for the compounds to be distilled from the Alchemists and from such works as the _Probierbuechlein_. In any event he could not have had experience with them all, for in some cases the necessary ingredients for making nitric acid are not all present, and therefore could be of no use for gold and silver separation. The essential ingredients for the production of this acid by distillation, were saltpetre, water, and either vitriol or alum. The other substances mentioned were unnecessary, and any speculation as to the combinations which would result, forms a useful exercise in chemistry, but of little purpose here. The first recipe would no doubt produce hydrochloric acid. [4] Agricola, in the _Interpretatio_, gives the German equivalent for the Latin _aerugo_ as _Spanschgruen_--"because it was first brought to Germany from Spain; foreigners call it _viride aeris_ (copper green)." The English "verdigris" is a corruption of _vert de grice_. Both verdigris and white lead were very ancient products, and they naturally find mention together among the ancient authors. The earliest description of the method of making is from the 3rd Century B.C., by Theophrastus, who says (101-2): "But these are works of art, as is also Ceruse (_psimythion_) to make which, lead is placed in earthen vessels over sharp vinegar, and after it has acquired some thickness of a kind of rust, which it commonly does in about ten days, they open the vessels and scrape off, as it were, a kind of foulness; they then place the lead over the vinegar again, repeating over and over again the same method of scraping it till it is wholly dissolved; what has been scraped off they then beat to powder and boil for a long time; and what at last subsides to the bottom of the vessel is the white lead.... Also in a manner somewhat resembling this, verdigris (_ios_) is made, for copper is placed over lees of wine (grape refuse?), and the rust which it acquires by this means is taken off for use. And it is by this means that the rust which appears is produced." (Based on Hill's translation.) Vitruvius (VII, 12), Dioscorides (V, 51), and Pliny (XXXIV, 26 and 54), all describe the method of making somewhat more elaborately. [5] _Amiantus_ (_Interpretatio_ gives _federwis_, _pliant_, _salamanderhar_). From Agricola's elaborate description in _De Natura Fossilium_ (p. 252) there can be no doubt that he means asbestos. This mineral was well-known to the Ancients, and is probably earliest referred to (3rd Century B.C.) by Theophrastus in the following passage (29): "There is also found in the mines of Scaptesylae a stone, in its external appearance somewhat resembling wood, on which, if oil be poured, it burns; but when the oil is burnt away, the burning of the stone ceases, as if it were in itself not liable to such accidents." There can be no doubt that Strabo (X, 1) describes the mineral: "At Carystus there is found in the earth a stone, which is combed like wool, and woven, so that napkins are made of this substance, which, when soiled, are thrown into the fire and cleaned, as in the washing of linen." It is also described by Dioscorides (V, 113) and Pliny (XIX, 4). Asbestos cloth has been found in Pre-Augustinian Roman tombs. [6] This list of four recipes is even more obscure than the previous list. If they were distilled, the first and second mixtures would not produce nitric acid, although possibly some sulphuric would result. The third might yield nitric, and the fourth _aqua regia_. In view of the water, they were certainly not used as cements, and the first and second are deficient in the vital ingredients. [7] _Distillation_, at least in crude form, is very old. Aristotle (_Meteorologica_, IV.) states that sweet water can be made by evaporating salt-water and condensing the steam. Dioscorides and Pliny both describe the production of mercury by distillation (note 58, p. 432). The Alchemists of the Alexandrian School, from the 1st to the 6th Centuries, mention forms of imperfect apparatus--an ample discussion of which may be found in Kopp, _Beitraege zur Geschichte der Chemie_, Braunschweig, 1869, p. 217. [8] It is desirable to note the contents of the residues in the retort, for it is our belief that these are the materials to which the author refers as "lees of the water which separates gold from silver," in many places in Book VII. They would be strange mixtures of sodium, potassium, aluminium sulphates, with silica, brickdust, asbestos, and various proportions of undigested vitriol, salt, saltpetre, alum, iron oxides, etc. Their effect must have been uncertain. Many old German metallurgies also refer to the _Todenkopf der Scheidwasser_, among them the _Probierbuechlein_ before Agricola, and after him Lazarus Ercker (_Beschreibung Allerfuernemsten_, etc., Prague, 1574). See also note 16, p. 234. [9] This use of silver could apply to one purpose only, that is, the elimination of minor amounts of hydrochloric from the nitric acid, the former originating no doubt from the use of salt among the ingredients. The silver was thus converted into a chloride and precipitated. This use of a small amount of silver to purify the nitric acid was made by metallurgists down to fairly recent times. Biringuccio (IV, 2) and Lazarus Ercker (p. 71) both recommend that the silver be dissolved first in a small amount of acid, and the solution poured into the newly-manufactured supply. They both recommend preserving this precipitate and its cupellation after melting with lead--which Agricola apparently overlooked. [10] In this description of parting by nitric acid, the author digresses from his main theme on pages 444 and 445, to explain a method apparently for small quantities where the silver was precipitated by copper, and to describe another cryptic method of precipitation. These subjects are referred to in notes 11 and 12 below. The method of parting set out here falls into six stages: _a_--cupellation, _b_--granulation, _c_--solution in acid, _d_--treatment of the gold residues, _e_--evaporation of the solution, _f_--reduction of the silver nitrate. For nitric acid parting, bullion must be free from impurities, which cupellation would ensure; if copper were left in, it would have the effect he mentions if we understand "the silver separated from the gold soon unites with it again," to mean that the silver unites with the copper, for the copper would go into solution and come down with the silver on evaporation. Agricola does not specifically mention the necessity of an excess of silver in this description, although he does so elsewhere, and states that the ratio must be at least three parts silver to one part gold. The first description of the solution of the silver is clear enough, but that on p. 445 is somewhat difficult to follow, for the author states that the bullion is placed in a retort with the acid, and that distillation is carried on between each additional charge of acid. So far as the arrangement of a receiver might relate to the saving of any acid that came over accidentally in the boiling, it can be understood, but to distill off much acid would soon result in the crystallization of the silver nitrate, which would greatly impede the action of subsequent acid additions, and finally the gold could not be separated from such nitrate in the way described. The explanation may be (apart from incidental evaporation when heating) that the acids used were very weak, and that by the evaporation of a certain amount of water, not only was the acid concentrated, but room was provided for the further charges. The acid in the gold wash-water, mentioned in the following paragraph, was apparently thus concentrated. The "glass" mentioned as being melted with litharge, argols, nitre, etc., was no doubt the silver nitrate. The precipitation of the silver from the solution as a chloride, by the use of salt, so generally used during the 18th and 19th Centuries, was known in Agricola's time, although he does not mention it. It is mentioned in Geber and the _Probierbuechlein_. The clarity of the latter on the subject is of some interest (p. 34a): "How to pulverise silver and again make it into silver. Take the silver and dissolve it in water with the _starckenwasser_, _aqua fort_, and when that is done, take the silver water and pour it into warm salty water, and immediately the silver settles to the bottom and becomes powder. Let it stand awhile until it has well settled, then pour away the water from it and dry the settlings, which will become a powder like ashes. Afterward one can again make it into silver. Take the powder and put it on a _test_, and add thereto the powder from the settlings from which the _aqua forte_ has been made, and add lead. Then if there is a great deal, blow on it until the lead has incorporated itself ... blow it until it _plickt_ (_blickens_). Then you will have as much silver as before." [11] The silver is apparently precipitated by the copper of the bowl. It would seem that this method was in considerable use for small amounts of silver nitrate in the 16th Century. Lazarus Ercker gives elaborate directions for this method (_Beschreibung Allerfuernemsten_, etc., Prague, 1574, p. 77). [12] We confess to a lack of understanding of this operation with leaves of lead and copper. [13] We do not understand this "appearance of black." If the nitrate came into contact with organic matter it would, of course, turn black by reduction of the silver, and sunlight would have the same effect. [14] This would be equal to from 62 to 94 parts of copper in 1,000. [15] As 144 _siliquae_ are 1 _uncia_, then 1/4 _siliqua_ in 8 _unciae_ would equal one part silver in 4,608 parts gold, or about 999.8 fine. [16] The object of this treatment with sulphur and copper is to separate a considerable portion of silver from low-grade bullion (_i.e._, silver containing some gold), in preparation for final treatment of the richer gold-silver alloy with nitric acid. Silver sulphide is created by adding sulphur, and is drawn off in a silver-copper regulus. After the first sentence, the author uses silver alone where he obviously means silver "containing some gold," and further he speaks of the "gold lump" (_massula_) where he likewise means a button containing a great deal of silver. For clarity we introduced the term "regulus" for the Latin _mistura_. The operation falls into six stages: _a_, granulation; _b_, sulphurization of the granulated bullion; _c_, melting to form a combination of the silver sulphide with copper into a regulus, an alloy of gold and silver settling out; _d_, repetition of the treatment to abstract further silver from the "lump;" _e_, refining the "lump" with nitric acid; _f_, recovery of the silver from the regulus by addition of lead, liquation and cupellation. The use of a "circle of fire" secures a low temperature that would neither volatilize the sulphur nor melt the bullion. The amount of sulphur given is equal to a ratio of 48 parts bullion and 9 parts sulphur. We are not certain about the translation of the paragraph in relation to the proportion of copper added to the granulated bullion; because in giving definite quantities of copper to be added in the contingencies of various original copper contents in the bullion, it would be expected that they were intended to produce some positive ratio of copper and silver. However, the ratio as we understand the text in various cases works out to irregular amounts, _i.e._, 48 parts of silver to 16, 12.6, 24, 20.5, 20.8, 17.8, or 18 parts of copper. In order to obtain complete separation there should be sufficient sulphur to have formed a sulphide of the copper as well as of the silver, or else some of the copper and silver would come down metallic with the "lump". The above ratio of copper added to the sulphurized silver, in the first instance would give about 18 parts of copper and 9 parts of sulphur to 48 parts of silver. The copper would require 4.5 parts of sulphur to convert it into sulphide, and the silver about 7 parts, or a total of 11.5 parts required against 9 parts furnished. It is plain, therefore, that insufficient sulphur is given. Further, the litharge would probably take up some sulphur and throw down metallic lead into the "lump". However, it is necessary that there should be some free metallics to collect the gold, and, therefore, the separation could not be complete in one operation. In any event, on the above ratios the "gold lump" from the first operation was pretty coppery, and contained some lead and probably a good deal of silver, because the copper would tend to desulphurize the latter. The "powder" of glass-galls, salt, and litharge would render the mass more liquid and assist the "gold lump" to separate out. The Roman silver _sesterce_, worth about 2-1/8 pence or 4.2 American cents, was no doubt used by Agricola merely to indicate an infinitesimal quantity. The test to be applied to the regulus by way of cupellation and parting of a sample with nitric acid, requires no explanation. The truth of the description as to determining whether the gold had settled out, by using a chalked iron rod, can only be tested by actual experiment. It is probable, however, that the sulphur in the regulus would attack the iron and make it black. The re-melting of the regulus, if some gold remains in it, with copper and "powder" without more sulphur, would provide again free metallics to gather the remaining gold, and by desulphurizing some silver this button would probably not be very pure. From the necessity for some free metallics besides the gold in the first treatment, it will be seen that a repetition of the sulphur addition and re-melting is essential gradually to enrich the "lump". Why more copper is added is not clear. In the second melting, the ratio is 48 parts of the "gold lump", 12 parts of sulphur and 12 parts copper. In this case the added copper would require about 3 parts sulphur, and if we consider the deficiency of sulphur in the first operations pertained entirely to the copper, then about 2.5 parts would be required to make good the shortage, or in other words the second addition of sulphur is sufficient. In the final parting of the "lump" it will be noticed that the author states that the silver ratio must be arranged as three of silver to one of gold. As to the recovery of the silver from the regulus, he states that 66 _librae_ of silver give 132 _librae_ of _regulus_. To this, 500 _librae_ of lead are added, and it is melted in the "second" furnace, and the litharge and hearth-lead made are re-melted in the "first" furnace, the cakes made being again treated in the "third" furnace to separate the copper and lead. The "first" is usually the blast furnace, the "second" furnace is the cupellation furnace, and the "third" the liquation furnace. It is difficult to understand this procedure. The charge sent to the cupellation furnace would contain between 3% and 5% copper, and between 3% and 5% sulphur. However, possibly the sulphur and copper could be largely abstracted in the skimmings from the cupellation furnace, these being subsequently liquated in the "third" furnace. It may be noted that two whole lines from this paragraph are omitted in the editions of _De Re Metallica_ after 1600. For historical note on sulphur separation see page 461. [17] There can be no doubt that in most instances Agricola's _stibium_ is antimony sulphide, but it does not follow that it was the mineral _stibnite_, nor have we considered it desirable to introduce the precision of either of these modern terms, and have therefore retained the Latin term where the sulphide is apparently intended. The use of antimony sulphide to part silver from gold is based upon the greater affinity of silver than antimony for sulphur. Thus the silver, as in the last process, is converted into a sulphide, and is absorbed in the regulus, while the metallic antimony alloys with the gold and settles to the bottom of the pot. This process has several advantages over the sulphurization with crude sulphur; antimony is a more convenient vehicle of sulphur, for it saves the preliminary sulphurization with its attendant difficulties of volatilization of the sulphur; it also saves the granulation necessary in the former method; and the treatment of the subsequent products is simpler. However, it is possible that the sulphur-copper process was better adapted to bullion where the proportion of gold was low, because the fineness of the bullion mentioned in connection with the antimonial process was apparently much higher than the previous process. For instance, a _bes_ of gold, containing 5, 6, or 7 double _sextulae_ of silver would be .792, .750 or .708 fine. The antimonial method would have an advantage over nitric acid separation, in that high-grade bullion could be treated direct without artificial decrease of fineness required by inquartation to about .250 fine, with the consequent incidental losses of silver involved. The process in this description falls into six operations: _a_, sulphurization of the silver by melting with antimony sulphide; _b_, separation of the gold "lump" (_massula_) by jogging; _c_, re-melting the regulus (_mistura_) three or four times for recovery of further "lumps"; _d_, re-melting of the "lump" four times, with further additions of antimony sulphide; _e_, cupellation of the regulus to recover the silver; _f_, cupellation of the antimony from the "lump" to recover the gold. Percy seems to think it difficult to understand the insistence upon the addition of copper. Biringuccio (IV, 6) states, among other things, that copper makes the ingredients more liquid. The later metallurgists, however, such as Ercker, Lohneys, and Schlueter, do not mention this addition; they do mention the "swelling and frothing," and recommend that the crucible should be only partly filled. As to the copper, we suggest that it would desulphurize part of the antimony and thus free some of that metal to collect the gold. If we assume bullion of the medium fineness mentioned and containing no copper, then the proportions in the first charge would be about 36 parts gold, 12 parts silver, 41 parts sulphur, 103 parts antimony, and 9 parts copper. The silver and copper would take up 4.25 parts of sulphur, and thus free about 10.6 parts of antimony as metallics. It would thus appear that the amount of metallics provided to assist the collection of the gold was little enough, and that the copper in freeing 5.6 parts of the antimony was useful. It appears to have been necessary to have a large excess of antimony sulphide; for even with the great surplus in the first charge, the reaction was only partial, as is indicated by the necessity for repeated melting with further antimony. The later metallurgists all describe the separation of the metallic antimony from the gold as being carried out by oxidation of the antimony, induced by a jet of air into the crucible, this being continued until the mass appears limpid and no cloud forms in the surface in cooling. Agricola describes the separation of the silver from the regulus by preliminary melting with argols, glass-gall, and some lead, and subsequent cupellation of the lead-silver alloy. The statement that unless this preliminary melting is done, the cupel will absorb silver, might be consonant with an attempt at cupellation of sulphides, and it is difficult to see that much desulphurizing could take place with the above fluxes. In fact, in the later descriptions of the process, iron is used in this melting, and we are under the impression that Agricola had omitted this item for a desulphurizing reagent. At the Dresden Mint, in the methods described by Percy (Metallurgy Silver and Gold, p. 373) the gold lumps were tested for fineness, and from this the amount of gold retained in the regulus was computed. It is not clear from Agricola's account whether the test with nitric acid was applied to the regulus or to the "lumps". For historical notes see p. 461. [18] As will be shown in the historical note, this process of separating gold and silver is of great antiquity--in all probability the only process known prior to the Middle Ages, and in any event, the first one used. In general the process was performed by "cementing" the disintegrated bullion with a paste and subjecting the mass to long-continued heat at a temperature under the melting point of the bullion. The cement (_compositio_) is of two different species; in the first species saltpetre and vitriol and some aluminous or silicious medium are the essential ingredients, and through them the silver is converted into nitrate and absorbed by the mass; in the second species, common salt and the same sort of medium are the essentials, and in this case the silver is converted into a chloride. Agricola does not distinguish between these two species, for, as shown by the text, his ingredients are badly mixed. The process as here described falls into five operations: _a_, granulation of the bullion or preparation of leaves; _b_, heating alternate layers of cement and bullion in pots; _c_, washing the gold to free it of cement; _d_, melting the gold with borax or soda; _e_, treatment of the cement by way of melting with lead and cupellation to recover the silver. Investigation by Boussingault (_Ann. De Chimie_, 1833, p. 253-6), D'Elhuyar (_Bergbaukunde_, Leipzig, 1790, Vol. II, p. 200), and Percy (Metallurgy of Silver and Gold, p. 395), of the action of common salt upon silver under cementation conditions, fairly well demonstrated the reactions involved in the use of this species of cement. Certain factors are essential besides salt: _a_, the admission of air, which is possible through the porous pots used; _b_, the presence of some moisture to furnish hydrogen; _c_, the addition of alumina or silica. The first would be provided by Agricola in the use of new pots, the second possibly by use of wood fuel in a closed furnace, the third by the inclusion of brickdust. The alumina or silica at high temperatures decomposes the salt, setting free hydrochloric acid and probably also free chlorine. The result of the addition of vitriol in Agricola's ingredients is not discussed by those investigators, but inasmuch as vitriol decomposes into sulphuric acid under high temperatures, this acid would react upon the salt to free hydrochloric acid, and thus assist to overcome deficiencies in the other factors. It is possible also that sulphuric acid under such conditions would react directly upon the silver to form silver sulphates, which would be absorbed into the cement. As nitric acid is formed by vitriol and saltpetre at high temperatures, the use of these two substances as a cementing compound would produce nitric acid, which would at once attack the silver to form silver nitrate, which would be absorbed into the melted cement. In this case the brickdust probably acted merely as a vehicle for the absorption, and to lower the melting point of the mass and prevent fusion of the metal. While nitric acid will only part gold and silver when the latter is in great excess, yet when applied as fumes under cementation conditions it appears to react upon a minor ratio of silver. While the reactions of the two above species of compounds can be accounted for in a general way, the problem furnished by Agricola's statements is by no means simple, for only two of his compounds are simply salt cements, the others being salt and nitre mixtures. An inspection of these compounds produces at once a sense of confusion. Salt is present in every compound, saltpetre in all but two, vitriol in all but three. Lewis (_Traite Singulier de Metallique_, Paris, 1743, II, pp. 48-60), in discussing these processes, states that salt and saltpetre must never be used together, as he asserts that in this case _aqua regia_ would be formed and the gold dissolved. Agricola, however, apparently found no such difficulty. As to the other ingredients, apart from nitre, salt, vitriol, and brickdust, they can have been of no use. Agricola himself points out that ingredients of "metallic origin" corrupt the gold and that brickdust and common salt are sufficient. In a description of this process in the _Probierbuechlein_ (p. 58), no nitre is mentioned. This booklet does mention the recovery of the silver from the cement by amalgamation with mercury--the earliest mention of silver amalgamation. [19] While a substance which we now know to be natural zinc sulphate was known to Agricola (see note 11, p. 572), it is hardly possible that it is referred to here. If green vitriol be dehydrated and powdered, it is white. [20] The processes involved by these "other" compounds are difficult to understand, because of the lack of information given as to the method of operation. It might be thought that these were five additional recipes for cementing pastes, but an inspection of their internal composition soon dissipates any such assumption, because, apart from the lack of brickdust or some other similar necessary ingredient, they all contain more or less sulphur. After describing a preliminary treatment of the bullion by cupellation, the author says: "Then the silver is sprinkled with two _unciae_ of that powdered compound and is stirred. Afterward it is poured into another crucible ... and violently shaken. The rest is performed according to the process I have already explained." As he has already explained four or five parting processes, it is not very clear to which one this refers. In fact, the whole of this discussion reads as if he were reporting hearsay, for it lacks in every respect the infinite detail of his usual descriptions. In any event, if the powder was introduced into the molten bullion, the effect would be to form some silver sulphides in a regulus of different composition depending upon the varied ingredients of different compounds. The enriched bullion was settled out in a "lump" and treated "as I have explained," which is not clear. [21] HISTORICAL NOTE ON PARTING GOLD AND SILVER. Although the earlier Classics contain innumerable references to refining gold and silver, there is little that is tangible in them, upon which to hinge the metallurgy of parting the precious metals. It appears to us, however, that some ability to part the metals is implied in the use of the touchstone, for we fail to see what use a knowledge of the ratio of gold and silver in bullion could have been without the power to separate them. The touchstone was known to the Greeks at least as early as the 5th Century B.C. (see note 37, p. 252), and a part of Theophrastus' statement (LXXVIII.) on this subject bears repetition in this connection: "The nature of the stone which tries gold is also very wonderful, as it seems to have the same power as fire; which is also a test of that metal.... The trial by fire is by the colour and the quantity lost by it, but that of the stone is made only by rubbing," etc. This trial by fire certainly implies a parting of the metals. It has been argued from the common use of _electrum_--a gold-silver alloy--by the Ancients, that they did not know how to part the two metals or they would not have wasted gold in such a manner, but it seems to us that the very fact that _electrum_ was a positive alloy (20% gold, 80% silver), and that it was deliberately made (Pliny XXXIII, 23) and held of value for its supposed superior brilliancy to silver and the belief that goblets made of it detected poison, is sufficient answer to this. To arrive by a process of elimination, we may say that in the Middle Ages, between 1100 and 1500 A.D., there were known four methods of parting these metals: _a_, parting by solution in nitric acid; _b_, sulphurization of the silver in finely-divided bullion by heating it with sulphur, and the subsequent removal of the silver sulphide in a regulus by melting with copper, iron, or lead; _c_, melting with an excess of antimony sulphide, and the direct conversion of the silver to sulphide and its removal in a regulus; _d_, cementation of the finely-divided bullion with salt, and certain necessary collateral re-agents, and the separation of the silver by absorption into the cement as silver chloride. Inasmuch as it can be clearly established that mineral acids were unknown to the Ancients, we can eliminate that method. Further, we may say at once that there is not, so far as has yet been found, even a remote statement that could be applied to the sulphide processes. As to cementation with salt, however, we have some data at about the beginning of the Christian Era. Before entering into a more detailed discussion of the history of various processes, it may be useful, in a word, to fix in the mind of the reader our view of the first authority on various processes, and his period. (1) Separation by cementation with salt, Strabo (?) 63 B.C.-24 A.D.; Pliny 23-79 A.D. (2) Separation by sulphur, Theophilus, 1150-1200 A.D. (3) Separation by nitric acid, Geber, prior to 14th Century. (4) Separation by antimony sulphide, Basil Valentine, end 14th Century, or _Probierbuechlein_, beginning 15th Century. (5) Separation by antimony sulphide and copper, or sulphur and copper, _Probierbuechlein_, beginning 15th Century. (6) Separation by cementation with saltpetre, Agricola, 1556. (7) Separation by sulphur and iron, Schlueter, 1738. (8) Separation by sulphuric acid, D'Arcet, 1802. (9) Separation by chloride gas, Thompson, 1833. (10) Separation electrolytically, latter part 19th Century. PARTING BY CEMENTATION. The following passage from Strabo is of prime interest as the first definite statement on parting of any kind (III, 2, 8): "That when they have melted the gold and purified it by means of a kind of aluminous earth, the residue left is _electrum_. This, which contains a mixture of silver and gold, being again subjected to the fire, the silver is separated and the gold left (pure); for this metal is easily dissipated and fat, and on this account gold is most easily molten by straw, the flame of which is soft, and bearing a similarity (to the gold) causes it easily to dissolve, whereas coal, besides wasting a great deal, melts it too much, by reason of its vehemence, and carries it off (in vapour)." This statement has provoked the liveliest discussion, not only on account of the metallurgical interest and obscurity, but also because of differences of view as to its translation; we have given that of Mr. H. C. Hamilton (London, 1903). A review of this discussion will be found in Percy's Metallurgy of Gold and Silver, p. 399. That it refers to cementation at all hangs by a slender thread, but it seems more nearly this than anything else. Pliny (XXXIII, 25) is a little more ample: "(The gold) is heated with double its weight of salt and thrice its weight of _misy_, and again with two portions of salt and one of a stone which they call _schistos_. The _virus_ is drawn out when these things are burnt together in an earthen crucible, itself remaining pure and incorrupt, the remaining ash being preserved in an earthen pot and mixed with water as a lotion for _lichen_ (ring-worm) on the face." Percy (Metallurgy Silver and Gold, p. 398) rightly considers that this undoubtedly refers to the parting of silver and gold by cementation with common salt. Especially as Pliny further on states that with regard to _misy_, "In purifying gold they mix it with this substance." There can be no doubt from the explanations of Pliny and Dioscorides that _misy_ was an oxidized pyrite, mostly iron sulphate. Assuming the latter case, then all of the necessary elements of cementation, _i.e._, vitriol, salt, and an aluminous or silicious element, are present. The first entirely satisfactory evidence on parting is to be found in Theophilus (12th Century), and we quote the following from Hendrie's translation (p. 245): "Of Heating the Gold. Take gold, of whatsoever sort it may be, and beat it until thin leaves are made in breadth three fingers, and as long as you can. Then cut out pieces that are equally long and wide and join them together equally, and perforate through all with a fine cutting iron. Afterwards take two earthen pots proved in the fire, of such size that the gold can lie flat in them, and break a tile very small, or clay of the furnace burned and red, weigh it, powdered, into two equal parts, and add to it a third part salt for the same weight; which things being slightly sprinkled with urine, are mixed together so that they may not adhere together, but are scarcely wetted, and put a little of it upon a pot about the breadth of the gold, then a piece of the gold itself, and again the composition, and again the gold, which in the digestion is thus always covered, that gold may not be in contact with gold; and thus fill the pot to the top and cover it above with another pot, which you carefully lute round with clay, mixed and beaten, and you place it over the fire, that it may be dried. In the meantime compose a furnace from stones and clay, two feet in height, and a foot and a half in breadth, wide at the bottom, but narrow at the top, where there is an opening in the middle, in which project three long and hard stones, which may be able to sustain the flame for a long time, upon which you place the pots with the gold, and cover them with other tiles in abundance. Then supply fire and wood, and take care that a copious fire is not wanting for the space of a day and night. In the morning taking out the gold, again melt, beat and place it in the furnace as before. Again also, after a day and night, take it away and mixing a little copper with it, melt it as before, and replace it upon the furnace. And when you have taken it away a third time, wash and dry it carefully, and so weighing it, see how much is wanting, then fold it up and keep it." The next mention is by Geber, of whose date and authenticity there is great doubt, but, in any event, the work bearing his name is generally considered to be prior to the 14th, although he has been placed as early as the 8th Century. We quote from Russell's translation, pp. 17 and 224, which we have checked with the Latin edition of 1542: "Sol, or gold, is beaten into thin plates and with them and common salt very well prepared lay upon lay in a vessel of calcination which set into the furnace and calcine well for three days until the whole is subtily calcined. Then take it out, grind well and wash it with vinegar, and dry it in the sun. Afterwards grind it well with half its weight of cleansed _sal-armoniac_; then set it to be dissolved until the whole be dissolved into most clear water." Further on: "Now we will declare the way of cementing. Seeing it is known to us that cement is very necessary in the examen of perfection, we say it is compounded of inflammable things. Of this kind are, all blackening, flying, penetrating, and burned things; as is vitriol, _sal-armoniac_, _flos aeris_ (copper oxide scales) and the ancient _fictile_ stone (earthen pots), and a very small quantity, or nothing, of sulphur, and urine with like acute and penetrating things. All these are impasted with urine and spread upon thin plates of that body which you intend shall be examined by this way of probation. Then the said plates must be laid upon a grate of iron included in an earthen vessel, yet so as one touch not the other that the virtue of the fire may have free and equal access to them. Thus the whole must be kept in fire in a strong earthen vessel for the space of three days. But here great caution is required that the plates may be kept but not melt." Albertus Magnus (1205-1280) _De Mineralibus et Rebus Metallicis_, Lib. IV, describes the process as follows:--"But when gold is to be purified an earthen vessel is made like a cucurbit or dish, and upon it is placed a similar vessel; and they are luted together with the tenacious lute called by alchemists the lute of wisdom. In the upper vessel there are numerous holes by which vapour and smoke may escape; afterwards the gold in the form of short thin leaves is arranged in the vessel, the leaves being covered consecutively with a mixture obtained by mixing together soot, salt, and brick dust; and the whole is strongly heated until the gold becomes perfectly pure and the base substances with which it was mixed are consumed." It will be noted that salt is the basis of all these cement compounds. We may also add that those of Biringuccio and all other writers prior to Agricola were of the same kind, our author being the first to mention those with nitre. PARTING WITH NITRIC ACID. The first mention of nitric acid is in connection with this purpose, and, therefore, the early history of this reagent becomes the history of the process. Mineral acids of any kind were unknown to the Greeks or Romans. The works of the Alchemists and others from the 12th to the 15th Centuries, have been well searched by chemical historians for indications of knowledge of the mineral acids, and many of such suspected indications are of very doubtful order. In any event, study of the Alchemists for the roots of chemistry is fraught with the greatest difficulty, for not only is there the large ratio of fraud which characterised their operations, but there is even the much larger field of fraud which characterised the authorship and dates of writing attributed to various members of the cult. The mention of saltpetre by Roger Bacon (1214-94), and Albertus Magnus (1205-80), have caused some strain to read a knowledge of mineral acids into their works, but with doubtful result. Further, the Monk Theophilus (1150-1200) is supposed to have mentioned products which would be mineral acids, but by the most careful scrutiny of that work we have found nothing to justify such an assertion, and it is of importance to note that as Theophilus was a most accomplished gold and silver worker, his failure to mention it is at least evidence that the process was not generally known. The transcribed manuscripts and later editions of such authors are often altered to bring them "up-to-date." The first mention is in the work attributed to Geber, as stated above, of date prior to the 14th Century. The following passage from his _De Inventione Veritatis_ (Nuremberg edition, 1545, p. 182) is of interest:--"First take one _libra_ of vitriol of Cyprus and one-half _libra_ of saltpetre and one-quarter of alum of Jameni, extract the _aqua_ with the redness of the alembic--for it is very solvative--and use as in the foregoing chapters. This can be made acute if in it you dissolve a quarter of sal-ammoniac, which dissolves gold, sulphur, and silver." Distilling vitriol, saltpetre and alum would produce nitric acid. The addition of sal-ammoniac would make _aqua regia_; Geber used this solvent water--probably without being made "more acute"--to dissolve silver, and he crystallized out silver nitrate. It would not be surprising to find all the Alchemists subsequent to Geber mentioning acids. It will thus be seen that even the approximate time at which the mineral-acids were first made cannot be determined, but it was sometime previous to the 15th Century, probably not earlier than the 12th Century. Beckmann (Hist. of Inventions II, p. 508) states that it appears to have been an old tradition that acid for separating the precious metals was first used at Venice by some Germans; that they chiefly separated the gold from Spanish silver and by this means acquired great riches. Beckmann considers that the first specific description of the process seems to be in the work of William Budaeus (_De Asse_, 1516, III, p. 101), who speaks of it as new at this time. He describes the operation of one, Le Conte, at Paris, who also acquired a fortune through the method. Beckmann and others have, however, entirely overlooked the early _Probierbuechlein_. If our conclusions are correct that the first of these began to appear at about 1510, then they give the first description of inquartation. This book (see appendix) is made up of recipes, like a cook-book, and four or five different recipes are given for this purpose; of these we give one, which sufficiently indicates a knowledge of the art (p. 39): "If you would part them do it this way: Beat the silver which you suppose to contain gold, as thin as possible; cut it in small pieces and place it in 'strong' water (_starkwasser_). Put it on a mild fire till it becomes warm and throws up blisters or bubbles. Then take it and pour off the water into a copper-bowl; let it stand and cool. Then the silver settles itself round the copper bowl; let the silver dry in the copper bowl, then pour the water off and melt the silver in a crucible. Then take the gold also out of the glass _kolken_ and melt it together." Biringuccio (1540, Book VI.) describes the method, but with much less detail than Agricola. He made his acid from alum and saltpetre and calls it _lacque forti_. PARTING WITH SULPHUR. This process first appears in Theophilus (1150-1200), and in form is somewhat different from that mentioned by Agricola. We quote from Hendrie's Translation, p. 317, "How gold is separated from silver. When you have scraped the gold from silver, place this scraping in a small cup in which gold or silver is accustomed to be melted, and press a small linen cloth upon it, that nothing may by chance be abstracted from it by the wind of the bellows, and placing it before the furnace, melt it; and directly lay fragments of sulphur in it, according to the quantity of the scraping, and carefully stir it with a thin piece of charcoal until its fumes cease; and immediately pour it into an iron mould. Then gently beat it upon the anvil lest by chance some of that black may fly from it which the sulphur has burnt, because it is itself silver. For the sulphur consumes nothing of the gold, but the silver only, which it thus separates from the gold, and which you will carefully keep. Again melt this gold in the same small cup as before, and add sulphur. This being stirred and poured out, break what has become black and keep it, and do thus until the gold appear pure. Then gather together all that black, which you have carefully kept, upon the cup made from the bone and ash, and add lead, and so burn it that you may recover the silver. But if you wish to keep it for the service of niello, before you burn it add to it copper and lead, according to the measure mentioned above, and mix with sulphur." This process appears in the _Probierbuechlein_ in many forms, different recipes containing other ingredients besides sulphur, such as salt, saltpetre, sal-ammoniac, and other things more or less effective. In fact, a series of hybrid methods between absolute melting with sulphur and cementation with salt, were in use, much like those mentioned by Agricola on p. 458. PARTING WITH ANTIMONY SULPHIDE. The first mention of this process lies either in Basil Valentine's "Triumphant Chariot of Antimony" or in the first _Probierbuechlein_. The date to be assigned to the former is a matter of great doubt. It was probably written about the end of the 15th Century, but apparently published considerably later. The date of the _Probierbuechlein_ we have referred to above. The statement in the "Triumphal Chariot" is as follows (Waite's Translation, p. 117-118): "The elixir prepared in this way has the same power of penetrating and pervading the body with its purifying properties that antimony has of penetrating and purifying gold.... This much, however, I have proved beyond a possibility of doubt, that antimony not only purifies gold and frees it from foreign matter, but it also ameliorates all other metals, but it does the same for animal bodies." There are most specific descriptions of this process in the other works attributed to Valentine, but their authenticity is so very doubtful that we do not quote. The _Probierbuechlein_ gives several recipes for this process, all to the same metallurgical effect, of which we quote two: "How to separate silver from gold. Take 1 part of golden silver, 1 part of _spiesglass_, 1 part copper, 1 part lead; melt them together in a crucible. When melted pour into the crucible pounded sulphur and directly you have poured it in cover it up with soft lime so that the fumes cannot escape, and let it get cold and you will find your gold in a button. Put that same in a pot and blow on it." "How to part gold and silver by melting or fire. Take as much gold-silver as you please and granulate it; take 1 _mark_ of these grains, 1 _mark_ of powder; put them together in a crucible. Cover it with a small cover, put it in the fire, and let it slowly heat; blow on it gently until it melts; stir it all well together with a stick, pour it out into a mould, strike the mould gently with a knife so that the button may settle better, let it cool, then turn the mould over, strike off the button and twice as much _spiesglas_ as the button weighs, put them in a crucible, blow on it till it melts, then pour it again into a mould and break away the button as at first. If you want the gold to be good always add to the button twice as much _spiesglass_. It is usually good gold in three meltings. Afterward take the button, place it on a cupel, blow on it till it melts. And if it should happen that the gold is covered with a membrane, then add a very little lead, then it shines (_plickt_) and becomes clearer." Biringuccio (1540) also gives a fairly clear exposition of this method. All the old refiners varied the process by using mixtures of salt, antimony sulphide, and sulphur, in different proportions, with and without lead or copper; the net effect was the same. Later than Agricola these methods of parting bullion by converting the silver into a sulphide and carrying it off in a regulus took other forms. For instance, Schlueter (_Huette-Werken_, Braunschweig, 1738) describes a method by which, after the granulated bullion had been sulphurized by cementation with sulphur in pots, it was melted with metallic iron. Lampadius (_Grundriss Einer Allgemeinen Huettenkunde_, Goettingen, 1827) describes a treatment of the bullion, sulphurized as above, with litharge, thus creating a lead-silver regulus and a lead-silver-gold bullion which had to be repeatedly put through the same cycle. The principal object of these processes was to reduce silver bullion running low in gold to a ratio acceptable for nitric acid treatment. Before closing the note on the separation of gold and silver, we may add that with regard to the three processes largely used to-day, the separation by solution of the silver from the bullion by concentrated sulphuric acid where silver sulphate is formed, was first described by D'Arcet, Paris, in 1802; the separation by introducing chlorine gas into the molten bullion and thus forming silver chlorides was first described by Lewis Thompson in a communication to the Society of Arts, 1833, and was first applied on a large scale by F. B. Miller at the Sydney Mint in 1867-70; we do not propose to enter into the discussion as to who is the inventor of electrolytic separation. [22] There were three methods of gilding practised in the Middle Ages--the first by hammering on gold leaf; the second by laying a thin plate of gold on a thicker plate of silver, expanding both together, and fabricating the articles out of the sheets thus prepared; and the third by coating over the article with gold amalgam, and subsequently driving off the mercury by heat. Copper and iron objects were silver-plated by immersing them in molten silver after coating with sal-ammoniac or borax. Tinning was done in the same way. [23] See note 12, p. 297, for complete discussion of amalgamation. [24] These nine methods of separating gold from copper are based fundamentally upon the sulphur introduced in each case, whereby the copper is converted into sulphides and separated off as a matte. The various methods are much befogged by the introduction of extraneous ingredients, some of which serve as fluxes, while others would provide metallics in the shape of lead or antimony for collection of the gold, but others would be of no effect, except to increase the matte or slag. Inspection will show that the amount of sulphur introduced in many instances is in so large ratio that unless a good deal of volatilization took place there would be insufficient metallics to collect the gold, if it happened to be in small quantities. In a general way the auriferous button is gradually impoverished in copper until it is fit for cupellation with lead, except in one case where the final stage is accomplished by amalgamation. The lore of the old refiners was much after the order of that of modern cooks--they treasured and handed down various efficacious recipes, and of those given here most can be found in identical terms in the _Probierbuechlein_, some editions of which, as mentioned before, were possibly fifty years before _De Re Metallica_. This knowledge, no doubt, accumulated over long experience; but, so far as we are aware, there is no description of sulphurizing copper for this purpose prior to the publication mentioned. [25] _Sal artificiosus_. The compound given under this name is of quite different ingredients from the stock fluxes given in Book VII under the same term. The method of preparation, no doubt, dehydrated this one; it would, however, be quite effective for its purpose of sulphurizing the copper. There is a compound given in the _Probierbuechlein_ identical with this, and it was probably Agricola's source of information. [26] Throughout the book the cupellation furnace is styled the _secunda fornax_ (Glossary, _Treibeherd_). Except in one or two cases, where there is some doubt as to whether the author may not refer to the second variety of blast furnace, we have used "cupellation furnace." Agricola's description of the actual operation of the old German cupellation is less detailed than that of such authors as Schlueter (_Huette-Werken_, Braunschweig, 1738) or Winkler (_Beschreibung der Freyberger Schmelz Huttenprozesse_, Freyberg, 1837). The operation falls into four periods. In the first period, or a short time after melting, the first scum--the _abzug_--arises. This material contains most of the copper, iron, zinc, or sulphur impurities in the lead. In the second period, at a higher temperature, and with the blast turned on, a second scum arises--the _abstrich_. This material contains most of the antimony and arsenical impurities. In the third stage the litharge comes over. At the end of this stage the silver brightens--"_blicken_"--due to insufficient litharge to cover the entire surface. Winkler gives the following average proportion of the various products from a charge of 100 _centners_:-- _Abzug_ 2 _centners_, containing 64% lead _Abstrich_ 5-1/2 " " 73% " _Herdtplei_ 21-1/2 " " 60% " Impure litharge 18 " " 85% " Litharge 66 " " 89% " --- Total 113 _centners_ He estimates the lead loss at from 8% to 15%, and gives the average silver contents of _blicksilber_ as about 90%. Many analyses of the various products may be found in Percy (Metallurgy of Lead, pp. 198-201), Schnabel and Lewis (Metallurgy, Vol. I, p. 581); but as they must vary with every charge, a repetition of them here is of little purpose. HISTORICAL NOTE ON CUPELLATION. The cupellation process is of great antiquity, and the separation of silver from lead in this manner very probably antedates the separation of gold and silver. We can be certain that the process has been used continuously for at least 2,300 years, and was only supplanted in part by Pattinson's crystallization process in 1833, and further invaded by Parks' zinc method in 1850, and during the last fifteen years further supplanted in some works by electrolytic methods. However, it yet survives as an important process. It seems to us that there is no explanation possible of the recovery of the large amounts of silver possessed from the earliest times, without assuming reduction of that metal with lead, and this necessitates cupellation. If this be the case, then cupellation was practised in 2500 B.C. The subject has been further discussed on p. 389. The first direct evidence of the process, however, is from the remains at Mt. Laurion (note 6, p. 27), where the period of greatest activity was at 500 B.C., and it was probably in use long before that time. Of literary evidences, there are the many metaphorical references to "fining silver" and "separating dross" in the Bible, such as Job (XXVIII, 1), Psalms (XII, 6, LXVI, 10), Proverbs (XVII, 3). The most certain, however, is Jeremiah (VI, 28-30): "They are all brass [_sic_] and iron; they are corrupters. The bellows are burned, the lead is consumed in the fire, the founder melteth in vain; for the wicked are not plucked away. Reprobate silver shall men call them." Jeremiah lived about 600 B.C. His contemporary Ezekiel (XXII, 18) also makes remark: "All they are brass and tin and iron and lead in the midst of the furnace; they are even the dross of the silver." Among Greek authors Theognis (6th century B.C.) and Hippocrates (5th century B.C.) are often cited as mentioning the refining of gold with lead, but we do not believe their statements will stand this construction without strain. Aristotle (Problems XXIV, 9) makes the following remark, which has been construed not only as cupellation, but also as the refining of silver in "tests." "What is the reason that boiling water does not leap out of the vessel ... silver also does this when it is purified. Hence those whose office it is in the silversmiths' shops to purify silver, derive gain by appropriation to themselves of the sweepings of silver which leap out of the melting-pot." The quotation of Diodorus Siculus from Agatharchides (2nd century B.C.) on gold refining with lead and salt in Egypt we give in note 8, p. 279. The methods quoted by Strabo (63 B.C.-24 A.D.) from Polybius (204-125 B.C.) for treating silver, which appear to involve cupellation, are given in note 8, p. 281. It is not, however, until the beginning of the Christian era that we get definite literary information, especially with regard to litharge, in Dioscorides and Pliny. The former describes many substances under the terms _scoria_, _molybdaena_, _scoria argyros_ and _lithargyros_, which are all varieties of litharge. Under the latter term he says (V, 62): "One kind is produced from a lead sand (concentrates?), which has been heated in the furnaces until completely fused; another (is made) out of silver; another from lead. The best is from Attica, the second (best) from Spain; after that the kinds made in Puteoli, in Campania, and at Baia in Sicily, for in these places it is mostly produced by burning lead plates. The best of all is that which is a bright golden colour, called _chrysitis_, that from Sicily (is called) _argyritis_, that made from silver is called _lauritis_." Pliny refers in several passages to litharge (_spuma argenti_) and to what is evidently cupellation, (XXXIII, 31): "And this the same agency of fire separates part into lead, which floats on the silver like oil on water" (XXXIV, 47). "The metal which flows liquid at the first melting is called _stannum_, the second melting is silver; that which remains in the furnace is _galena_, which is added to a third part of the ore. This being again melted, produced lead with a deduction of two-ninths." Assuming _stannum_ to be silver-lead alloy, and _galena_ to be _molybdaena_, and therefore litharge, this becomes a fairly clear statement of cupellation (see note 23, p. 392). He further states (XXXIII, 35): "There is made in the same mines what is called _spuma argenti_ (litharge). There are three varieties of it; the best, known as _chrysitis_; the second best, which is called _argyritis_; and a third kind, which is called _molybditis_. And generally all these colours are to be found in the same tubes (see p. 480). The most approved kind is that of Attica; the next, that which comes from Spain. _Chrysitis_ is the product from the ore itself; _argyritis_ is made from the silver, and _molybditis_ is the result of smelting of lead, which is done at Puteoli, and from this has its name. All three are made as the material when smelted flows from an upper crucible into a lower one. From this last it is raised with an iron bar, and is then twirled round in the flames in order to make it less heavy (made in tubes). Thus, as may be easily perceived from the name, it is in reality the _spuma_ of a boiling substance--of the future metal, in fact. It differs from slag in the same way that the scum of a liquid differs from the lees, the one being purged from the material while purifying itself, the other an excretion of the metal when purified." The works of either Theophilus (1150-1200 A.D.) or Geber (prior to the 14th century) are the first where adequate description of the cupel itself can be found. The uncertainty of dates renders it difficult to say which is earliest. Theophilus (Hendrie's Trans., p. 317) says: "How gold is separated from copper: But if at any time you have broken copper or silver-gilt vessels, or any other work, you can in this manner separate the gold. Take the bones of whatever animal you please, which (bones) you may have found in the street, and burn them, being cold, grind them finely, and mix with them a third part of beechwood ashes, and make cups as we have mentioned above in the purification of silver; you will dry these at the fire or in the sun. Then you carefully scrape the gold from the copper, and you will fold this scraping in lead beaten thin, and one of these cups being placed in the embers before the furnace, and now become warm, you place in this fold of lead with the scraping, and coals being heaped upon it you will blow it. And when it has become melted, in the same manner as silver is accustomed to be purified, sometimes by removing the embers and by adding lead, sometimes by re-cooking and warily blowing, you burn it until, the copper being entirely absorbed, the gold may appear pure." We quote Geber from the Nuremberg edition of 1545, p. 152: "Now we describe the method of this. Take sifted ashes or _calx_, or the powder of the burned bones of animals, or all of them mixed, or some of them; moisten with water, and press it with your hand to make the mixture firm and solid, and in the middle of this bed make a round solid crucible and sprinkle a quantity of crushed glass. Then permit it to dry. When it is dry, place into the crucible that which we have mentioned which you intend to test. On it kindle a strong fire, and blow upon the surface of the body that is being tested until it melts, which, when melted, piece after piece of lead is thrown upon it, and blow over it a strong flame. When you see it agitated and moved with strong shaking motion it is not pure. Then wait until all of the lead is exhaled. If it vanishes and does not cease its motion it is not purified. Then again throw lead and blow again until the lead separates. If it does not become quiet again, throw in lead and blow on it until it is quiet and you see it bright and clear on the surface." Cupellation is mentioned by most of the alchemists, but as a metallurgical operation on a large scale the first description is by Biringuccio in 1540. [27] In Agricola's text this is "first,"--obviously an error. [28] The Roman _sextarius_ was about a pint. [29] This sentence continues, _Ipsa vero media pars praeterea digito_, to which we are unable to attribute any meaning. [30] _Thus_, or _tus_--"incense." [31] One _centumpondium_, Roman, equals about 70.6 lbs. avoirdupois; one _centner_, old German, equals about 114.2 lbs. avoirdupois. Therefore, if German weights are meant, the maximum charge would be about 5.7 short tons; if Roman weights, about 3.5 short tons. [32] See description, p. 269. [33] _Stannum_, as a term for lead-silver alloys, is a term which Agricola (_De Natura Fossilium_, pp. 341-3) adopted from his views of Pliny. In the _Interpretatio_ and the Glossary he gives the German equivalent as _werk_, which would sufficiently identify his meaning were it not obvious from the context. There can be little doubt that Pliny uses the term for lead alloys, but it had come into general use for tin before Agricola's time. The Roman term was _plumbum candidum_, and as a result of Agricola's insistence on using it and _stannum_ in what he conceived was their original sense, he managed to give considerable confusion to mineralogic literature for a century or two. The passages from Pliny, upon which he bases his use, are (XXXIV, 47): "The metal which flows liquid at the first melting in the furnace is called _stannum_, the second melting is silver," etc. (XXXIV, 48): "When copper vessels are coated with _stannum_ they produce a less disagreeable flavour, and it prevents verdigris. It is also remarkable that the weight is not increased.... At the present day a counterfeit _stannum_ is made by adding one-third of white copper to tin. It is also made in another way, by mixing together equal parts of tin and lead; this last is called by some _argentarium_.... There is also a composition called _tertiarium_, a mixture of two parts of lead and one of tin. Its price is twenty _denarii_ per pound, and it is used for soldering pipes. Persons still more dishonest mix together equal parts of _tertiarium_ and tin, and calling the compound _argentarium_, when it is melted coat articles with it." Although this last passage probably indicates that _stannum_ was a tin compound, yet it is not inconsistent with the view that the genuine _stannum_ was silver-lead, and that the counterfeits were made as stated by Pliny. At what period the term _stannum_ was adopted for tin is uncertain. As shown by Beckmann (Hist. of Inventions II, p. 225), it is used as early as the 6th century in occasions where tin was undoubtedly meant. We may point out that this term appears continuously in the official documents relating to Cornish tin mining, beginning with the report of William de Wrotham in 1198. [34] The Latin term for litharge is _spuma argenti_, spume of silver. [35] Pliny, XXXIII, 35. This quotation is given in full in the footnote p. 466. Agricola illustrates these "tubes" of litharge on p. 481. [36] Assuming Roman weights, three _unciae_ and three _drachmae_ per _centumpondium_ would be about 82 ozs., and the second case would equal about 85 ozs. per short ton. [37] Agricola uses throughout _De Re Metallica_ the term _molybdaena_ for this substance. It is obvious from the context that he means saturated furnace bottoms--the _herdpley_ of the old German metallurgists--and, in fact, he himself gives this equivalent in the _Interpretatio_, and describes it in great detail in _De Natura Fossilium_ (p. 353). The derivatives coined one time and another from the Greek _molybdos_ for lead, and their applications, have resulted in a stream of wasted ink, to which we also must contribute. Agricola chose the word _molybdaena_ in the sense here used from his interpretation of Pliny. The statements in Pliny are a hopeless confusion of _molybdaena_ and _galena_. He says (XXXIII, 35): "There are three varieties of it (litharge)--the best-known is _chrysitis_; the second best is called _argyritis_; and a third kind is called _molybditis_.... _Molybditis_ is the result of the smelting of lead.... Some people make two kinds of litharge, which they call _scirerytis_ and _peumene_; and a third variety being _molybdaena_, will be mentioned with lead." (XXXIV, 53): "_Molybdaena_, which in another place I have called _galena_, is an ore of mixed silver and lead. It is considered better in quality the nearer it approaches to a golden colour and the less lead there is in it; it is also friable and moderately heavy. When it is boiled with oil it becomes liver-coloured, adheres to the gold and silver furnaces, and in this state it is called _metallica_." From these two passages it would seem that _molybdaena_, a variety of litharge, might quite well be hearth-lead. Further (in XXXIV, 47), he says: "The metal which flows liquid at the first melting in the furnace is called _stannum_, at the second melting is silver, that which remains in the furnace is _galena_." If we still maintain that _molybdaena_ is hearth-lead, and _galena_ is its equivalent, then this passage becomes clear enough, the second melting being cupellation. The difficulty with Pliny, however, arises from the passage (XXXIII, 31), where, speaking of silver ore, he says: "It is impossible to melt it except with lead ore, called _galena_, which is generally found next to silver veins." Agricola (_Bermannus_, p. 427, &c.), devotes a great deal of inconclusive discussion to an attempt to reconcile this conflict of Pliny, and also that of Dioscorides. The probable explanation of this conflict arises in the resemblance of cupellation furnace bottoms to lead carbonates, and the native _molybdaena_ of Dioscorides; and some of those referred to by Pliny may be this sort of lead ores. In fact, in one or two places in