Popular Science Monthly/Volume 45/May 1894/Ancient and Medieval Chemistry
| ANCIENT AND MEDIÆVAL CHEMISTRY. |
By M. P. E. BERTHELOT.
CHEMISTRY is a modern science, constituted hardly a century ago; but its theoretical problems were discussed and its practices put in operation during all the middle ages. The nations of antiquity were already acquainted with them, and their origin is lost in the night of primitive religions and prehistoric civilizations. I have described elsewhere the first rational attempts to explain the chemical transformations of matter, and purpose now to speak of the chemical industries of the ancient world, and their transmission to the Latins of the middle ages. The story is of interest as showing how the cultivation of the sciences has been perpetuated in the material line by the necessities of their adaptations, through the catastrophes of invasions and the ruin of civilization. Only the total extermination of populations, such as was at times practiced by the Mongols and the Tartars, could completely destroy this cultivation. But such horrors as those perpetrated by Tamerlane have been of rare occurrence.
From the most remote times man has applied chemical operations to his necessities, performing them for metallurgy, ceramics, dyeing, painting, the preservation of food, medicine, and the art of war. While gold and sometimes silver and copper existed in the native state, and required only mechanical preparation, lead, tin, iron, and often copper and silver, had to be extracted from their usual minerals by very complicated artifices. The production of alloys necessary for the fabrication of arms, money, and jewels is also an essentially chemical art. The study of the alloys used in goldsmiths' work gave rise to the prejudices and frauds of alchemy, as is proved by the testimony of an Egyptian papyrus preserved in the Leyden Museum, and of the writings of the Grecian alchemists.
The art of preparing cement, pottery, and glass likewise depends on chemical operations. The workmen who dyed cloths, clothing, and tapestries in purple or other colors, an industry practiced first in Egypt and Syria and then in all the Grecian, Roman, and Persian world, not to speak of the extreme East, employed highly developed chemical manipulations; and the cloths found on the mummies and in the sarcophagi attest their perfection. Pliny and Vitruvius describe in detail the production of colors, such as cinnabar or vermilion, minium, red chalk, indigo, black, green, and blue colors, vegetable as well as mineral, performed by painters. The chemistry of alimentation, fruitful in . resources and in frauds, was next practiced. The art was known of accomplishing at will those delicate fermentations which produce bread, wine, and beer, and which modify a large number of foods; also of falsifying wine by the addition of plaster and other ingredients. The art of healing, seeking everywhere for resources against diseases, had learned to transform and fabricate a large number of mineral and vegetable products, such as sugar of poppy, extracts of nightshades, oxide of copper, verdigris, litharge, white lead, the sulphurets of arsenic and arsenious acid; remedies and poisons were composed at the same time, for different purposes, by doctors and magicians. The manufacture of arms and of inflammatory substances—petroleum, sulphur, resins, and bitumens—had already, anciently as well as in our own time, drawn upon the talents of inventors and given rise to formidable applications, especially in the arts of sieges and marine battles, previous to the invention of the Greek fire, which was in its turn the precursor of gunpowder and of our terrible explosive matters.
This rapid review shows how far advanced in the knowledge of chemical industries the Roman world was at the moment when it went to pieces under the blows of the barbarians. But the ruin of the ancient organization came about by degrees: while high scientific study, hardly accessible to coarse minds, ceased to be encouraged, and was gradually abandoned; while the Greek philosophers, knocked about between the religious persecution of the Byzantine emperors and the indifferent disdain of the Persian sovereigns, no longer trained pupils; while the great names of Grecian physics, mathematics, and alchemy hardly passed the time of Justinian, it is still certain that the necessity of professions indispensable to human life, or sought out by sovereigns and priests, could maintain and did maintain effectively most of the chemical industries.
Proofs of various kinds can be brought up in support of these reasonings. Some are drawn from the examination of the monuments, arms, potters' and glass ware, cloths, gems and jewels, and art objects of every kind which have come down to us. Such examination furnishes, in fact, incontestable results, provided the dates of the objects are certain, and they have not suffered restoration. Respecting the date, we can not exercise too much prudence and distrust, whether we are examining buildings or objects in museums. The accounts and descriptions by contemporary historians furnish other data, but less precise, for it is better to have the object in hand than the description. They have the advantage, however, of giving us indications independent of the ulterior progress of the industry. We have a still surer and more exact class of data than the chronicles in the technical treatises and works concerning arts and trades which have come down to us, whenever those treatises have an ascertained date, even were it only the date of their copies. This source of facts is already known as to antiquity. It is not wanting as to the middle ages, although it seems to have till now escaped the erudite persons who have written the history of science, and it permits us to reconstitute that under a new form and with a new precision. By the aid of those documents I shall attempt to show, concerning myself especially with chemical industries, what knowledge, practical or theoretical, subsisted after the fall of ancient civilization, and how the traditions of the shop maintained those industries, almost without new inventions, but at least at a certain level of perfection.
The history of physical science in antiquity is very imperfectly known to us. There existed then no methodical treatise for the purpose of teaching, such as we have in the principal civilized states. Hence, except as to the medical sciences, we have only insufficient notions respecting the processes employed in the arts and trades of the ancients. The experimental method of the moderns has associated those practices into a body of doctrines, and has shown close relations between them and the theories for which they served as basis and confirmation. This method was almost unknown to the ancients, at best as a general principle of scientific learning. Their industries had little connection with theories, excepting in measures of length, surface, or volume, which were deduced immediately from geometry and in goldsmiths' receipts, which were the origin of the theories, partly real and partly imaginary, of alchemy. It has been even asked if industrial formulas were not formerly preserved by purely oral tradition and carefully held back for the initiated. Some scraps of the traditional lore may have been transcribed into the notes which have been used in the composition of Pliny's Natural History and the works of Vitruvius and Isidore de Seville, not without a considerable mixture of fables and errors. But a more thorough examination of the works that have come down to us from antiquity, a more attentive study of the manuscripts, at first neglected because they did not relate to literary or theological studies or to ordinary historical questions, permits the affirmation that they were not so. We are all the time discovering new and considerable documents which show that the processes of the ancient industrials were then, as now, inscribed in workmen's note-books or manuals intended for the use of the tradespeople, and that they were transmitted from hand to hand from the most remote times of ancient Egypt and Alexandrine Egypt, to those of the Roman Empire and the middle ages. The discovery of these note-books offers all the more interest because the use of the precious metals with civilized peoples goes back to the highest antiquity; the technique of the ancient goldsmiths and jewelers is not revealed to us all at once except by the examination of the objects that have come down to us. The earliest precise and detailed texts describing their processes are contained in an Egyptian papyrus found at Thebes, and now in the museum at Leyden.
This papyrus is in the Greek language and dates from the third century of the Christian era. In my translation of it, comparing parts of it with phrases in the works of Pliny and Vitruvius on the same subjects and with Greek alchemistic works of the fourth and fifth centuries, I have reconstituted a whole science, ancient alchemy, till now misunderstood and uncomprehended, because it was founded on a mixture of real facts, profound views on the unity of matter, and chimerical religious fancies. These practices and theories had a still larger bearing than the working of metals. The industries of the precious metals were in fact associated at that epoch with those of the dyeing of cloths, the coloring of glasses, and the imitation of precious stones, all guided by the same tinctorial ideas and executed by the same operators.
Thus alchemy and the chimerical hope of making gold were derived from the goldsmiths' artifices for coloring metals. The pretended processes of transmutation which were current during the middle ages were in their origin only tricks for preparing alloys of inferior standard—that is, for imitating and falsifying the precious metals. But, by an almost invincible attraction, the operators addicted to these practices did not hesitate to imagine that one could pass from the imitation of gold to its effective formation—especially if he had the aid of the supernatural powers, invoked by magical formulas.
At any rate, it was not known till now how these practices and theories passed from Egypt, where they were flourishing toward the end of the Roman Empire, into the West, where we find them in full development from the thirteenth and fourteenth centuries in the writings of the Latin alchemists and in the laboratories of the goldsmiths, dyers, and makers of colored glass. Their renascence was generally attributed to translations of Arabian works made at that epoch. But, without assuming to deny the part played by the Arabian books in the renascence of the arts and sciences in the West, in the period of the Crusades, it is no less certain that a continuous tradition subsisted in the professional recollections of the arts and trades from the Roman Empire till the Carlovingian period, and later a tradition of chemical manipulations and scientific and mystical ideas. In fact, in pursuing my studies of the history of science, I have met, in the examination of the Latin works of the middle ages, certain technical manuals which were related most directly with the metallurgical treatises of the Greco-Egyptian alchemists and goldsmiths. I purpose to demonstrate here this correlation, which nobody has till now pointed out.
It is known that the receipts of therapeutics and materia medica have been preserved in a parallel way by practice, which has never ceased, in the Receptaries and other Latin treatises; these treatises, translated from the Greek during the period of the Roman Empire, and compiled in the first and second centuries, passed from hand to hand, and were copied frequently during the earlier portions of the middle ages. The transmission of the military arts and of fire-producing formulas, particularly, was carried on from the Greeks and Romans through the barbarous ages. In short, the necessity of the applications has always caused the subsistence of a certain experimental tradition of the arts of ancient civilization.
The oldest technical treatises in Latin of the middle ages on subjects in chemistry with which we are acquainted are the Formulas for Dyeing (Compositiones ad tingendo), of which we have a manuscript written toward the end of the eighth century, and the Key to Painting (Mappæ clavicula), the oldest manuscript of which is of the tenth century. The Formulas for Dyeing is not a methodical work, but a book of receipts and documents collected by a dyer for use in his art and intended to furnish him with working processes and information concerning the origin of his prime materials. It concerns such subjects as the coloring or dyeing of artificial stones for mosaic work; gilding and silvering and polishing them; making of colored glass in green, milky white, various shades of red, purple, yellow—the colors being both deep and superficial, and often brought out by the aid of simple varnishes; coloring of skins in purple, green, yellow, and various reds; dyeing of woods, bones, and horns; notices of minerals, metals, and earths used in goldsmiths' work and painting. Curious ideas are set forth on the function of the sun and of heat, peculiar to certain warm earths in the production of minerals endowed with corresponding virtues; while a cold earth produces minerals of weak quality. This reminds us of the theories of Aristotle on dry exhalation as opposed to moist exhalation in the generation of minerals—theories that made an important figure in the middle ages. The author distinguishes a feminine and light lead mineral as against a masculine and heavy mineral; a distinction like that mentioned by Pliny between male and female antimony, the male and female blue of Theophrastus, and many others. Minerals were continually likened in the chemistry of the middle ages to living beings.
We read likewise in this work of articles developed in certain operations, such as the extraction of mercury, lead, the roasting of sulphur, preparations of white lead with lead and vinegar, of verdigris with, vinegar and copper—already described by Theophrastus and Dioscorides—of cadmies, impure oxides of lead and zinc, of burned copper (aes ustum), of litharge, of orpiment, of artificial cinnabar, etc. The writer mentions a few alloys, such as bronze, white copper, and gold-colored copper—a subject often treated of by the Greek alchemists, who passed from it to the idea of transmutation. The name of bronze (brundisium) appears for the first time. While its origin has been the subject of controversy among philologists, the accompanying facts given in the text show that bronze was in the beginning an alloy made at Brundisium for the manufacture of the mirrors of which Pliny speaks. The preparation of parchment and of varnish, the fabrication of vegetable colors for the use of painters and illuminators, and their employment on walls, wood, canvas, etc., in encaustic or with isinglass, are the subjects of separate articles.
A group of formulas for gilding follow: gilding of glass, wood, skins, clothing, lead, tin, and iron; and the preparation of golden wires, processes for writing in golden letters (chrysography) on parchment, paper, glass, or marble. Then come silver foil, tin foil, and processes for reducing gold and silver to powder, in which mercury and verdigris were employed—the powder obtained by amalgamation being employed in processes for silvering and gilding. The process has played its part in political economy; for it has been used to assist the passage of gold and silver from one country to another, in spite of the prohibition of the exportation of the precious metals.
The author goes on to say: "We have described everything relative to tinctures and decorations; we have spoken of the substances which are employed in them—stones, minerals, salts, and herbs; we have shown where they are found; whence are got resins, oleoresins, and earths; what are sulphur, black water, salt waters, glue, and all the products of wild and cultivated plants, domestic and marine; beeswax, axunge, all fresh and acid waters; among woods, the pine, fir, juniper, and cypress . . . . acorns and figs. Extracts are made of all these things with a water made of fermented urine and vinegar, mixed with rain water."
These enumerations and descriptions mark the nature of the knowledge sought by the writer, and preserve the trace of ancient treatises on drugs and medicines, similar to those of Dioscorides, but more especially devoted to industry. Unfortunately, we have here hardly else than titles and summary indications, such as would figure in a dyer's scrap-book, placing one after another indications drawn from different authors. Many of the specific names found in the treatise are wanting in the most complete dictionaries. The terms salt, fresh, and acid waters, water formed of fermented urine and vinegar, deserve special notice because they point to the beginning of chemistry by moist processes. They figured in Pliny and the ancient authors, to the same purposes. The liquids are always natural ones or the results of the mixture of such, before or after spontaneous combustion. There is no mention of the active liquids obtained by distillation, which were called divine or sulphurous waters, and held an important place with the Greco-Egyptian chemists, and became the origin of our acids, alkalies, and other agents; they had not yet entered into industrial use, and are seldom met with previous to the fourteenth century.
The group of receipts transmitted by the formulas for dyeing, passed into a more extended collection called the Key to Painting, of which exist a manuscrip: of the tenth century in the library of Schlestadt and one of the twelfth century, of which an edition was published in 1847 by Mr. Way. The former manuscript is free from all Arabian influence, which has caused the interpolation of five additional articles in the second one. The work contains a treatise on the precious metals comprising now a hundred articles, about half of the original work, the other half having been lost, and a treatise on recipes for dyeing, representing principally those in the Formulas; together with sixteen articles on military ballistics and fireworks, forming a special group; articles on the hydrostatic balance and the densities of the metals; and industrial and magic recipes, added at the end of the book. The treatise on the precious metals is of great interest because of the striking analogies it presents with the Leyden Egyptian papyrus found at Thebes, and with other ancient works. Many of the recipes are literally translated from these ancient works; an identity proving indisputably the continuous preservation of alchemic practices, including transmutation, from Egypt down to the artisans of the Latin West. The theories proper, on the other hand, did not reappear in the West till toward the end of the twelfth century, after they had passed through the Syrians and the Arabs. But the knowledge of the processes themselves was never lost. This fact is demonstrated by the study of the alloys intended to imitate and falsify gold; for coloring (copper) gold-color; for fabricating gold; for making test gold; for rendering gold heavier; and for doubling gold. The recipes are filled with Greek words that betray their origin.
The object for the most part is simply to make base gold, as, for instance, by preparing an alloy of gold and silver, colored with copper. The goldsmith, however, tried to make this pass for pure gold. Then manufactures of complex alloys which were made to pass for pure gold were made easier by the intervention of mercury and sulphurets of arsenic, the use of which goes back to the earliest times of the Roman Empire. Thus Pliny relates in a few lines an experiment performed by order of Caligula for fabricating gold with sulphuret of arsenic (or orpiment). There was thus a whole special chemistry, now abandoned, which was conspicuous in the practices and pretensions of the alchemists. A patent has been obtained in our own times for an alloy of copper and antimony, containing six hundredths of the latter metal, which presents most of the apparent properties of gold and is worked in the same manner. Alchemic gold belonged to a family of similar alloys. Those who made it fancied besides that some agents played the part of ferments to multiply gold and silver. Before deceiving other people they deluded themselves. Sometimes the artisan was satisfied to use a cement or superficial action, painting the surface of silver in gold or the surface of copper in silver, without modifying the metals in their thickness. This is what goldsmiths still call giving color. They would even do no more than apply to the surface of the metal a gold-colored varnish, prepared with the bile of animals or with certain resins, as is still done. From these colorings the operator, led by a mystic analogy, passed to the idea of transmutation, in the false Democritus and in the Key to Painting. The author of the last work concluded, for example, with the words, "You will thus obtain excellent gold and fit for the test." The author added further "Hide this sacred secret, which should be delivered to no one nor to any prophet." The word prophet betrays the Egyptian origin of the recipe. It refers to the Egyptian priests, who, according to a passage in Clement of Alexandria on the Hermetic books that were borne with great pomp in the processions, were called prophets.
In further proof of the Greco-Egyptam origin of goldsmiths recipes contained in the Key to Painting is the existence m the Latin collection of ten recipes—some of the elaborate ones—which are phrased in precisely the same terms in the Greek papyrus in Leyden; the former text being translated from the latter even to the detail of certain technical expressions, which are still perpetuated in the goldsmiths' manuals of the present. This does not mean that the text transcribed in the Key to Painting was originally translated from the very papyrus that we possess, which was not found till the nineteenth century at Thebes, Egypt; but the coincidence of the text proves that there existed books of secret goldsmiths' recipes transmitted from hand to hand of the tradesmen, which continued through the middle ages, and of which the Key is an example. It was firmly believed m the time of Diocletian that the Egyptians had the secret of enriching themselves by making gold and silver; and in consequence of this belief after a revolt, the emperor ordered all their books burned. Nevertheless, as we have seen, the formulas did not disappear.
The title of one of the recipes in the old table, "How to make unbreakable glass," deserves to be dwelt upon, on account of the legends and traditions that are associated with it, and which have been perpetuated down to our own time. Unbreakable glass appears to have been really discovered under Tiberius, and gave rise to a legend according to which its properties were amplified and it was made malleable. Tiberius, according to Pliny, caused the factory to be destroyed, for fear that the invention would diminish the value of gold and silver." "If it was known," wrote Petronius, "gold would become as cheap as mud." According to Dion Cassius, Tiberius slew the author. Petronius, who is repeated by other authors, says that he was decapitated, and adds that "if vessels of glass were not fragile they would be preferable to vessels of gold and silver."
These stories relate evidently to the same historical fact, reported by contemporaries, but disfigured by legend; the invention was probably suppressed for fear of its economical consequences. It is very curious to find it mentioned in the goldsmiths' recipes of the middle ages, as if the secret tradition had been preserved in the shops. Some of them claimed that glass could be made malleable and ductile and changed into a metal. A process for making glass that will not break has been discovered in our own times, and is announced unequivocally and in definite shape. In truth, malleable glass was not really in question; but even that is not a chimera. Industrial processes for beating and molding glass, based on the plasticity and malleability which it possesses at a temperature near fusion, have been described in late years. An article in the Key to Painting seems to point to a similar process. Real properties, perceived doubtless from antiquity and preserved as shop secrets, gave rise to the legend.
The collection bearing the name of Eraclius or Heraclius is in two parts, of different composition and date. The first part consists of two books in verse, having the character of the writing of the end of the Carlovingian epoch, or of the ninth and tenth centuries. It treats of vegetable colors, of gold leaf, of writing in letters of gold, of gilding, of painting on glass, and of the preparation of precious stones. All the recipes are of ancient origin, a little vague, and without novelty. A book in prose is more compact and precise. It was added later by a continuator, toward the twelfth century, for there is a discussion in it of the coloring of Cordovan leather, and cinnabar, which is red, is called in it azure a translation of an Arabic word, frequent in the twelfth century, which has given rise to all sorts of misconceptions and confusion with our modern azure blue. It has the stories about malleable glass; and most of the subjects were already treated in the Key to Painting.
The Picture of Different Arts of the monk Theophilus seems to he the work of an author who lived at the end of the eleventh century and beginning of the twelfth. It is more exact and detailed than the work of Eraclius, and is composed of two parts—the first devoted to painting, and the second concerning the making of objects required in worship and the construction of buildings devoted to it. It describes in detail the furnace for melting glass and the manufacture of glass, the making of painted glass and colored earthen vessels, the working of iron, the melting of gold and silver and the working of them, enamel, the fabrication of vessels used in worship—the chalice, monstrance, etc.—organs, bells, cymbals, etc. The facts are curious, for they show that the industry of glass and metals had finally concentrated around the religious edifices. But the chemical technique is the same as that of the other books, though savoring of more modern influences; it brings us directly to the thirteenth and fourteenth centuries, from which period monuments and writings multiply more rapidly down into modern times. The derivation of technical traditions from antiquity becomes less and less manifest as intermediaries multiply and the arts tend to assume an original character.
The facts I have presented deserve our attention as a whole, in view of the course and renascence of scientific traditions. Sciences begin in fact with practice. The first object is to satisfy the necessities of life and the artistic wants that awaken early in civilizable races. But this same practice at once calls out more general ideas, which appeared first among mankind in a mystic form. With the Egyptians and Babylonians the same persons were at once the priests and the men of science. Thus the chemical industries were first exercised around the temples. The Book of the Sanctuary, the Book of Hermes, and the Book of Kemi, all synonymous denominations with the Greco-Egyptian alchemists, represent the earliest manuals of those industries. It was the Greeks, as in all other scientific branches, who gave these treatises a revision freed from the old hieratic forms, and who tried to draw from them a rational theory, capable in its turn, by a similar application, of pushing the practice forward and of serving as a guide to it. But the chemical science of the Greco-Egyptians never rid itself of the errors relative to transmission—which were sustained by the theory of primal matter—or of the religious and magic formulas formerly associated in the East with every industrial operation. Yet when scientific study proper perished with Roman civilization in the West, the wants of life kept up the imperishable practice of the shops with the progress required in the time of the Greeks, and the chemical arts subsisted; while the theories, too subtile or too strong for the minds of the time, tended to disappear, or rather to return toward the ancient superstitions. In the Key to Painting, as in the Egyptian papyrus and the texts of Zosimus, are mentions of prayers to be recited during the operations; and in this way alchemy remained intimately connected with magic in the middle ages as well as in antiquity.
When civilization began to revive during the Latin middle ages, toward the thirteenth century, in the midst of a new organization, our races took up anew the taste for general ideas, and these, in the sphere of chemistry, were sustained by practices, or rather they obtained their support in the permanent problems raised by them. Thus the alchemistic theories were suddenly revived, with new vigor and development, and their progressive evolution, while improving industry, gradually eliminated the superstitions of former times. Thus was finally constituted our modern chemistry, a rational science, established on purely experimental bases. The science was therefore born in its beginning of industrial practices; it kept course with their development during the reign of ancient civilization; when science went down with civilization, practice survived and furnished science a solid ground on which it was able to achieve a new development when the times and the minds had become favorable. The historical connection of science and practice in the history of civilizations is therefore manifest. There is in it a general law of the development of the human mind.—Translated for The Popular Science Monthly from the Revue des Deux Mondes.
