Turning Iron into Copper

The recovery of copper from vitriolated waters,
from De Re Metallica, 1556, by Agricola (Georg Bauer).

In Discorso, one of the last manuscripts written by Antonio Neri before his death, he reveals several transmutation recipes. One describes turning iron into copper; it is instructive because it uses common materials that we can identify and because the chemistry is now well understood.

Take some iron sheets and lay them in vitriol water, being immersed in that, they will rust. Scrape off this rust, which will be a red powder, melt it in a crucible, and you will have perfect copper. The same effect can be had from various waters that are naturally vitriolated, because they flow through mines of vitriol, such as those of a source some distance from Leiden, and another below the fortress of Smolnik, [now in Slovakia].

Vitriol is an acidic sulfate dissolved in water, it could be made in the laboratory, but it also occurred naturally around mining operations where sulfurous minerals were present. Alchemists knew this solution as "oil of vitriol" and "spirit of vitriol." The mine that Neri references in Smolnik became famous for transmutation. As late as the eighteenth century, scientists and experimenters from around Europe made the pilgrimage to see the effect for themselves and tried to figure out what was happening. It may be a surprise to some readers, but following the above instructions will, in fact, produce copper just as Neri claimed. There is no deception or sleight of hand involved; the explanation is straightforward, but first, Neri treats us to a rare glimpse of his own reasoning on the subject:

Some estimate and not without reason, that this experiment, being used to prove the transmutation of metals, is not suitable for this purpose. They say that the vitriolated waters become such because they are already heavy with the corrosive spirits of sulfur, having passed through the copper or iron mine, these waters corrode copper in the same way aqua fortis corrodes silver. So that really the substance of the copper remains in the water, which attacks the surface of the iron, which always remains iron. However, if that were true then the iron would not get consumed, or if it were consumed it would mix with the substance of the corroded copper in the water, and if it were fused, it would remain a mixture of iron and copper. And yet in this experiment, all the iron is consumed; it is reduced by the vitriolated water into powder, […] which in the fusion is still pure copper, so there should remain no doubt that this is a true transmutation.

Given the state of chemistry at the time, Neri's reasoning is clear and rational. The iron disappears and a copper coating materializes in its place. What better evidence of transmutation could one ask for?

The key to what was actually happening is in the criticism leveled by skeptics. It turns out that they were on the right track, but neither they nor Neri had the full picture. Today, we understand it as a simple ion exchange reaction; blue vitriol water is a transparent saturated solution of copper sulfate (CuSO₄), in the presence of solid iron, the liquid dissolves the iron; copper from the vitriol is deposited in its place. The two metals, copper and iron, change places: the iron dissolves, forming green vitriol (FeSO₄) and copper is expelled from the solution. The result is a reduction in the amount of the iron, which is replaced by a proportional deposit of pure copper.

On a physical level, this chemical reaction is no different today than it was in the seventeenth century. What has changed is our interpretation of the experiment. What Neri viewed as a transformation of iron into copper, we now see as an exchange. There is, however, a deeper lesson in all this. As an alchemist, Antonio Neri was not being delusional or dishonest; he was careful, observant and applied his knowledge as best he could. This is no different from the way science works today. Both then and now, to be successful in unraveling nature’s secrets, one must become accustomed to a very uncomfortable situation: In the past, careful reasoning by brilliant thinkers has led to utterly wrong conclusions. The fact that much of our world is a mystery is unsettling; that the very process we use to understand it can be so flawed is harder to accept. Even more difficult is that the faculty we all rely on for survival—our own wits—can lead us so far astray.

For more, see Discorso sopra la Chimica: The Paracelsian Philosophy of Antonio Neri”, M.G. Grazzini / Nuncius 27 (2012)

Antonio Altoviti

Tomb of Antonio Altoviti
Dei Santi Apostoli Church, Florence

Of all the godparents to Antonio Neri's siblings, young Jacopo Neri's godfather was perhaps the most notable. Antonio Altoviti, the Archbishop of Florence, was a very controversial archbishop. It is an understatement to say that the relationship was tense between him and the first Grand Duke, Cosimo I de' Medici. The root source of the animosity, however, was not with Antonio Altoviti but with his father, Bindo. Bindo was a banker to four popes beginning with Paul III. He was heir to one of the largest fortunes in Italy, and an avowed enemy of the Medici. His friends included artists Raphael, Michelangelo, Cellini and Vasari. As an administrator at the Vatican, he managed the project to rebuild St. Peter's Basilica. While his wife and family continued to live in Florence, Bindo and his son spent most of their time in Rome, out of reach of the Medici. In 1555, Cosimo confiscated Bindo's Palazzo in Florence; he then made a gift of it to his youngest son, Don Giovanni Medici, who would add a laboratory and there conduct alchemy experiments. Although later reconfigured into a much larger palace, The Casino del Parione, now called the Palazzo Corsini al Parione still stands on the banks of the Arno River.

Bindo spent a fortune raising an army to oppose Cosimo in the war over Siena. Earlier, he was accused of complicity in the successful assassination plot against Cosimo's predecessor, Duke Alessandro de' Medici. He was an outspoken critic who wanted the Medici out of power permanently and he backed up his words with considerable resources. In 1548, as a poke in the eye to Cosimo, Pope Paul III appointed Bindo's son, Antonio Altoviti, as Archbishop of Florence. Cosimo retaliated by banning the new Archbishop from setting foot in the city, a prohibition that lasted for twenty years. Cosimo finally relented as part of papal negotiations that secured his new title of "Grand Duke." Antonio Altoviti was a devotee of the late great revolutionary cleric Girolamo Savonarola, decidedly not a Medici favorite. By some accounts, the high regard with which the people of Florence held the Archbishop only intensified Cosimo’s dislike. 

Nevertheless, he did ultimately gain the trust of Cosimo's inner circle; in 1567 Altoviti was involved in negotiations to bring Venetian glass workers to Tuscany. This effort would bear fruit within a couple of years. It is perhaps impossible to gain full appreciation of a man through a single anecdote, but we can get a flavor. In 1569, shortly after occupying his post for the first time, Altoviti introduced a new ritual to the Florentine Church. On Holy Thursday, the Bishop would wash the feet of twelve of the city's poor residents rather than of twelve canons (as done previously) and he would give them generous alms.  

What makes Archbishop Altoviti so interesting to Neri's story is that he had a close association with the Neri family. In fact, so close that on 13 December 1573, Altoviti became godparent to Jacopo, the first born son of Neri Neri and Dianora. It is an interesting choice for a man who would later become personal physician to Cosimo de' Medici's son, Grand Duke Ferdinando. However, Jacopo would never learn what it was like to have the Archbishop as his spiritual guide. Two weeks after his birth, on the 28th of that month, Altoviti convened a special post-Christmas meeting of regional bishops. It was during this synod that he suddenly and unexpectedly died at the age of fifty-two. Within a few years, young Jacopo would join him.

Caterina Sforza

Caterina Sforza, by Lorenzo di Credi
(now in the Museum of Forlì.)

Antonio Neri is remembered mostly for his book on glassmaking, L'Arte Vetraria. However, he considered himself first and foremost an alchemist. This interest can be traced to at least two generations before him; his father, Neri Neri, was an acclaimed physician – in fact, the personal physician to Grand Duke of Tuscany, Ferdinando I de’ Medici. Antonio's grandfather, Jacopo Neri, was a barber-surgeon. Both of these professions required an extensive knowledge of herbal distillation and other techniques which are shared by alchemists.

Antonio's benefactor, Don Antonio de' Medici, also followed a family passion for the chemical arts, in his case, traceable through an unbroken chain, to a female alchemist, his great-great-grandmother, Caterina Sforza, (c.1463–1509). After her death, over four hundred of her formulas were passed down to her son, Giovanni dalle Bande Nere, then to his son Grand Duke Cosimo I de' Medici, Grand Duke Francesco I, and finally to Don Antonio. 

She was the illegitimate daughter of the Duke of Milan, Galeazzo Maria Sforza, but was still educated at court. At age fifteen, she was married to a nephew of Pope Sixtus. The pope granted her title of Countess of Forlì and Imola. After her territory was later taken and her husband murdered (by a faction of their own people), she escaped prison and retook the two cities. In 1495, when her second husband was assassinated, she launched a campaign which gutted the families of the murderers. Her third husband was Giovanni de' Medici, and their son, named after his father would become a brilliant military strategist, like his mother. His own son, Cosimo, would later become the first "Grand Duke" of Tuscany. 

Her chemical recipes were transcribed in 1525 by a captain in her son's army, Count Lucantonio Cuppano da Montefalco, and ultimately published as a book in 1893 (Passolini). Included are an assortment of formulas which range from cosmetics, to medical remedies, poisons and alchemical concoctions.
Researcher Jacqueline Spicer writes:

Lost among the romanticized military conquests is a thorough account [of] the project that occupied several years of her life—the manuscript of her alchemical and medical experiments and recipes titled Gli Experimenti de la Ex.ma S.r Caterina da Furlj Matre de lo inllux.mo S.r Giouanni de Medici, or Gli Experimenti. The text is an early example of what would later become the popular medical genre of "Books of Secrets", but is so early that it does not appear in most modern writing on such books. Furthermore, Gli Experimenti is unusual because it was written by a woman in an otherwise male dominated genre, and unique in that we know a great deal about the life of its author.

Among the alchemical entries are "to convert pewter into silver of the finest quality and of standard alloy," a method "for giving to bars of brass a fine golden color" and another for "for multiplying silver." Also, there are ways described  to "make iron hard," "to dissolve pearls" and "to dissolve all metals." In the medicinal category, we find "for infirm lungs, an ointment is to be made of the blood of a hen, a duck, a pig, a goose, mixed with fresh butter and white wax." This was to be applied to the chest on a fox's skin.

Sandro Botticelli, Primavera (1498)
(detail - rightmost of the three graces)

Caterina Sforza was painted many times and often depicted as the Virgin Mary, a typical trope for the nobility at the time. She may have been immortalized  by Sandro Botticelli as the rightmost of the three graces in his Primavera and as the main subject in The Birth of Venus.* Reportedly, she was the subject of ballads and sonnets, although most have been lost. She is a topic of discussion in Niccolò Machiavelli's famous treatise The Prince. 

In the end she was captured, raped and imprisoned on the orders of Pope Alexander VI, who justified her incarceration, in the Vatican's  Sant'Angelo Castle, by claiming she tried to poison him. She survived the ordeal, but after release entered the convent of the Murate nuns in Florence, and died, in 1509, at the age of forty-seven. She was buried at the convent, in the same city where her future great-great-grandson, Don Antonio, along with Antonio Neri, would perform their own alchemical experiments and help usher in the age of  modern science.

Another possibility was Simonetta Vespucci for the model of Venus.

The Glass Furnace

From "De re metallica"
Agricola (Georg Bauer) 1556.

In the seventeenth century, glass furnaces represented a pinnacle of technology. True, the ability to achieve the high temperatures required to melt glass had been around for centuries – high enough to melt gold, silver and copper as well. What made the glass furnace remarkable was its refinement. It made efficient use of its hardwood fuel and was able to maintain a controlled, even temperature long before any thermometer could measure it. In fact, Galileo was only just beginning to use glass bulbs and tubes to measure differences in ambient room temperatures.

In Florence, the construction used was typical of the time throughout Europe, called a "beehive" furnace because its shape resembled the elongated dome of a beehive. A double wall, built of fire resistant bricks, provided further insulation, trapping heat inside. Vertically, the furnace was divided into three levels, each forming a wide open chamber. The bottom space was used to build the fire, and had one or two openings to the outside, used to add wood fuel, rake the coals, or shovel out ash. The second, central level was where the pots of glass resided. A central hole or "eye" on the floor directly exposed the fire pit below. The space directly next to the eye was the hottest, and temperature could be further controlled by moving the crucibles farther away or closer to the eye. A number of openings in the wall allowed gaffers access to the glass pots, and at least one larger opening was used to place new crucibles, or rearrange the existing ones. The upper chamber was used to control the draft, and sometimes for annealing. Again, a central hole in the floor of this (top) level allowed exhaust gasses to leave the glass chamber and an opening to one side vented the exhaust.

In his book, L’Arte Vetraria, Neri is careful to stress that only dry oak or other hardwood should be used because it burns cleanly, and will not deposit ash or creosote in the glass.

The furnace should have dry wood, hard wood of oak because soft wood tinges the furnace and does no good. Stoke it steadily and continuously so that the flame is always clear, and there is never any smoke, which is very important in order to make a beautiful cristallo.

Once a finished piece of glassware is made, it must be allowed to cool slowly, over a period of many hours. This was often accomplished by building a long enclosed horizontal trough that connected to the furnace. A draft opening at the far end allowed heat from the furnace to be drawn in, and finished pieces were placed in a pan at the furnace end and then slowly pulled by a chain further and further down the trough toward the cooler end. This "annealing" process ensured the glass would not develop stresses and crack as it cooled.

Although Neri does not concern himself with the vagaries of furnace construction in the book, it is clear that he did possess considerable knowledge on the subject. Several of his unconventional methods for making pigments for glass involve taking bricks out of the furnace wall to stash chemicals for long term exposure to the heat.

Take small pieces of copper and put them inside the arches of the furnace. In that place, they will be within the walls. Leave them that way until each piece of copper is well calcined, using a simple fire.

While it is true that artisans of the early seventeenth century did not possess the same understanding of nature that we now enjoy, they did have a working knowledge that served them very well. It was backed by a theoretical framework that was quite sophisticated and was consistent with what could be observed and measured at the time. This is no different from our own modern understanding of nature: sophisticated and consistent with what we can observe and measure.

Botanical Gardens

Rudolf II as "Vertumnus"(c. 1590)
Giuseppe Arcimboldo. 

In 1543-44 new botanical gardens were founded in Pisa; L’Orto Botanico was its Italian name. It was the very first garden devoted to the research of plants. Literally within a year, similar gardens sprung up in Padua and Florence, and many other cities followed shortly thereafter. Exotic foreign species as well as important local plants were grown, studied, harvested distilled, and imbibed. These horticultural stations became centerpieces of medical programs throughout Italy, and then greater Europe. The concept of herbal (“simples”) gardens was centuries old. Almost every monastery, convent and hospital maintained a space to grow the plants they needed to transform into medicines for care of the infirmed. The grafting of fruit trees was actively practiced since before Roman times, but these new gardens were specifically planted as research spaces and run by universities. 

When Neri Neri, the father of glassmaker Antonio Neri, studied medicine at the Studio Fiorentino  in the mid 1550s, there can be no doubt he spent time at the gardens in Florence, and quite possibly at the ones in Pisa. (The Pisa gardens were moved twice before arriving at their current location in 1591). This was a period of vigorous expansion in the field of herbal medicine. Competition was fierce to obtain and study medicinal plants from around the globe. Cosimo I de’ Medici poured money into the medical school in Pisa, attracting students and faculty from around Europe. In 1554 famed botanist and physician Andrea Cesalpino took over the Pisa gardens  from his teacher, Luca Ghini, who first built them. 

In 1602, Neri was to be found working alongside Niccolò Sisti at the grand duke’s secondary glass furnace along the Arno River in Pisa. According to Neri’s own account, Pisa is where he worked on ferns as an alternative plant salt for glass and mentions many other plants with which he experimented: 

Set about making ash in the way previously described, however use the husks and stalks of broad beans after the farmhands have thrashed and shelled them. The same may be made from the ashes of cabbages, or a thorn bush that bears small fruit, called the blackberry, even from millet, rush, marsh reeds, and from many other plants that will relinquish their salt.

In a letter to Neri from his friend Emanuel Ximenes, the Antwerp based Portuguese banker expressed surprise that Neri was able to devise a fern based glass salt recipe so quickly. In all likelihood, Neri would have had access to the botanical gardens and the small adjacent laboratory located just a few blocks from the glass furnace. In the period of time the glassmaker spent there, the directorate of the gardens changed hands from Francesco Malocchi to Marco Cornacchini. Both of these men avidly pursued new botanical based cures, and corresponded internationally. 

In his Glassmaking book, L’Arte Vetraria, Neri devotes a number of recipes to making paint pigments from flower blossoms. While he could have easily obtained his stock material from any number of sources, the botanical gardens would have certainly provided a convenient cache of many different varieties.

In the winter of 1603-4 Neri traveled From Pisa to visit his friend in Antwerp. If he followed Ximenes suggested route, he would have passed back through his native Florence, then on to Venice where he would meet up with a caravan of merchants on their way to the Frankfort spring fair, and then on to Antwerp by river. Upon his return to Italy, seven years later, he wrote his glassmaking book, but then devoted himself fully to alchemy and medicine. In January of 1614, in what might be the very last manuscript he worked on before his death, he wrote about some recipes “copied from an old book here in Pisa.” At that time, the director of the botanical gardens was Domenico Vigna, who continued to direct the gardens on and off until 1634.

It would be interesting to know how Neri the alchemist thought about his raw materials. Did he see all the possibilities of what could be made with them? For instance, how did he approach a towering pile of May ferns, large enough to produce a hundred pounds of ash, or a giant sack of rose petals? Did he ever lean forward and breathe in the delicious musty aroma? Did he ever dig in with his hands and bury his face in an arm-load of soft, pure color? How could he not?

Homecoming

Fleur-de-lis, symbol of Florence, Italy.

In early 1611, Antonio Neri returned to Florence after visiting a good friend in Antwerp; a visit that had lasted seven years. It is not known if such a long sojourn was planned from the start, but it seems unlikely judging from correspondence leading up to the event. Neri only first met Emmanuel Ximenes (pronounced "Si-men-ez") a couple of years earlier, in 1601. The two men were introduced at the house in Florence, where Neri was living at the time, by his landlord Alamanno Bartolini and his wife Beatrice. Emmanuel was Beatrice's brother; he and Antonio quickly realized they shared a strong interest in alchemy, medicine and also glassmaking. Ximenes was a wealthy banker, probably in Florence on business, and soon he returned to Flanders, but started a correspondence with Priest Neri that would culminate in the priest's visit.

A clue to the unusual length of the stay may be found in stories that were printed long after both men were dead. In the 1840s, the distinguished historian and archaeologist Francesco Inghirami published his encyclopedic History of Tuscany, saying about Neri:

He was poor and the House Master for the Bartolini [family] of Santa Trinita. He claimed he had found the secret of making the famous philosopher's stone and it was said he had discovered it among some of his confidants. Some thugs learnt of this and attacked him at night, in order to obtain the secret by force. He shrewdly gave them a certain recipe he had in his pocket and explained the figures written on it, claiming it to be the secret oil required. But that night Neri left Florence and traveled to various parts of Europe. After the death of the two attackers, he returned to Florence.

The political situation in Flanders was tense, and had been for Neri's entire time there. The Protestant Dutch to the north were in a bloody war for independence from Spain and the Habsburg Empire. All around Antwerp cities and towns were being sacked and destroyed as troops vied for control of the territory. Catholic Antwerp became an island of calm in a sea of trouble. Battles raged around it, but the city itself was considered too valuable an asset for either side to pillage.

By the time Neri set off for home, a truce had been signed between the Dutch and Spain over the Low Countries, but it was an uneasy truce at best. Soldiers and cavaliers who had not been paid in months clogged the roadsides around Antwerp and Liege. There was unrest deep within Dutch held territory as well. In Utrecht, a popular uprising in January of 1610 threw out much of the local government over religious, social and political issues. Then in May, a Catholic fanatic assassinated King Henry IV of France. His widow, Florence's own Marie de' Medici, had been crowned in a ceremony the previous day. At Cologne, frantic negotiations were underway over the religious destiny of all Germany. By September, boatloads of English Catholic refugees were streaming into Leghorn on the Italian coast just west of Pisa. They had been expelled from Britain over the Gunpowder Plot.

What Antonio found upon his return to Florence, was a city very much familiar in outward appearance, but perhaps a bit less so on the inside. Grand Duke Ferdinando "of blessed memory" – as Neri eulogized in his glass book – had died in 1609. As a result, Prince Don Antonio de' Medici, Neri's sponsor, found himself even more marginalized from the royal family. Former landlord Alamanno Bartolini was dead, as was Giambologna, the famous sculptor. He was Neri's neighbor whose workshop and residence was directly across the narrow street from Antonio's childhood home. Neri's own family matriarch, his grandmother Maddalena, had also died within days of the grand duke, making Antonio and his siblings the elders of the Neri family.

This was the Florence to which Antonio returned, and in which he settled down to collect his notes and within a few months write the book, L'Arte Vetraria, for which he will forever be remembered: the first book ever printed that is entirely devoted to making glass.

Mirror, Mirror On the Wall

Jan van Eyck
The Arnolfini Portrait (1434)

L’Arte Vetraria, Antonio Neri's 1612 book, would eventually become the glassmakers' bible throughout Europe. By 1900 it had been translated into six different languages; Italian, English, Latin, German, French, and Spanish (and in this century Japanese). Because of its seminal importance in the spread of glass technology, often overlooked are a few recipes at the back of the book, which have only a tenuous connection to the main subject.

Among these is a metallurgical formula for making convex mirrors. Neri gives instructions for producing what we would now call a "white bronze" that may be cast into a rounded form and polished to take on a highly reflective surface finish. This "spherical" form of mirror was popular throughout the Renaissance. It reflected a wide-angle view of the space in which it was hung, but at the cost of distorting the image. Nevertheless, upon looking into such a mirror, objects are still quite recognizable. 

Here is Neri's prescription:

A Mixture to Make [Mirror] Spheres:
Have 3 lbs of well-purified tin, and 1 lb of copper also purified. Melt these two metals, first the copper, then the tin. When they fuse thoroughly, throw onto them 6 oz of just singed red wine tartar, and 1½ oz of saltpeter, then ¼ oz of alum, and 2 oz of arsenic. Leave these all to vaporize, and then cast [the metal] into the form of a sphere. You will have good material, which when you burnish and polish, will look most fine. This mixture is called acciaio and is used to make spherical mirrors.

Of note is the fact that the word Neri uses for this alloy, acciaio, translates to "steel." Over the intervening four centuries, the meaning of this term has been refined so that today it denotes not simply a hard white metal, but a specific range of alloys containing iron and carbon. 

This recipe and a few others in the book show the breadth of Neri's experience in arts other than glassmaking. It is a conclusion greatly amplified by a perusal of his other manuscripts on alchemy and medicine. There is good evidence that our priest was a voracious reader, however he was also quite cautious about repeating techniques only after he had verified them personally. Besides, artisans never wrote down much of this knowledge – only passed in confidence between trusted parties – since, in a very concrete way, superior knowledge represented a competitive advantage over ones rivals. Even if Neri was in the business of divulging secrets, it is safe to assume that many of the artisans and craftsmen he interacted with were decidedly not. 

Two centuries before Neri, the beginning of the fifteenth century saw the invention of moveable type printing in Germany, but also the mastery of perspective illustration in Italy. The contribution of printing to early modern science is well documented, less obvious is the role playerd by artists and perspective illustration. Moveable type made possible the mass production of books; what did get committed to paper now stood a much better chance of survival and transmission. Perspective illustration played a more nuanced role, one that ultimately brings the convex mirror back into the discussion.

In Venice and especially in Florence (Neri's hometown), perspective drawing became the rage among artists, largely due to the Italian translation of a book entitled Deli Aspecti, or "Alhazen's Book of Optics." Suddenly, paintings were made to look three-dimensional, with a realistic sense of depth to them. The new techniques were largely kept in Italy, but interest spread across Europe. Patrons placed great value on work depicting scenes in correct perspective, and in excruciatingly accurate detail. 

Jan van Eyck
The Arnolfini Portrait (detail).

In Flanders, in 1434, Jan van Eyck produced "The Arnolfini Portrait," (above). Behind the main subjects, hanging on the wall is a convex mirror. The reflection in the mirror shows the backs of the two subjects, but also two other figures further back, one of which is thought to be the artist himself, and beyond him a strong light source. The image in the mirror is distorted exactly as one would experience in real life. 

There is growing speculation that among the secrets of "realist" (or naturalist) painters was a growing arsenal of optical tools and lenses used to map out and understand the attributes of perspective. The mirror, in the Arnolfini Portrait was a sort of boast of the artist's proficiency in recreating reality on the canvas.

The point is that here is a case where art led science into new realms. Painters started to take great pains in reproducing reality "as it is" on canvas. Soon minor experimenters like Neri and major luminaries like Galileo were taking great pains to do the same. They strove to observe nature "as it is," not as was prescribed in ancient texts, or dictated by authority. Once that process started, awareness of the world grew and there was no turning back.

Finally, it is amusing to note that in his many manuscript illustrations, Antonio Neri himself never quite mastered perspective drawing, although he did try.