Alchemy became a bad word. Alchemists were recast as frauds, charlatans, and tricksters, claiming to tell you the secret to unlimited wealth and health – for suitable payment. History is glossed over and framed from the point of view of the winners – the modern chemists. We do real chemistry! The dark magic of alchemy is merely an illusion that dissolves in the light of true science.
But reality is much more complicated. In his 2014 Dibner Library Lecture, Lawrence Principe tells a surprising story, not known to most chemists. The lecture is titled “Alchemy and Chemistry: Breaking Up and Making Up (Again and Again)”. Principe is both a chemist and a historian. He’s written the landmark book about the history of alchemy. And in my last blog post, I discussed his investigation into the phosphorescence of the Bologna Stone. Having read a number of his works, I thought I was well versed in the (hi)story of alchemy, but I gained some new insights from reading the text of his Dibner lecture.
I had thought that alchemy essentially died when modern chemistry was ushered in by Lavoisier and his contemporaries towards the end of the 18th century. But I was wrong. Alchemy’s name had been sullied, but it was still alive and kicking, biding its time quietly. The new reigning paradigm was that once you distilled substances to their most fundamental, these “elements” were fundamental. You couldn’t transmute or change one element to another. But in the 19th century there came three new developments that questioned whether indeed elements were immutable.
The first of these, thanks to Lavoisier’s insistence of very careful measurements of atomic weights, was the following observation (in Principe’s words): “the atomic weights of nearly every known element, about fifty at that time, turned out to be integral multiples of the weight of the lightest element, hydrogen. Carbon weighed exactly six hydrogens – oxygen eight, sulphur sixteen. There was no reason to expect this striking regularity… This strange outcome led William Prout (1785-1850) to propose in 1817 that all the known elements were actually condensations of hydrogen, such that hydrogen was the unique material building block of everything.”
Determining the
fundamental building block of all matter was an old philosopher’s trade going
back to the sixth century BCE. Thales thought it was water. Anaximenes thought
it was air. Heraclitus thought it was fire. Xenophanes thought it was earth. Empedocles
brought them together as the Four Elements theory, later championed by
Aristotle, and it was a fundamental building block for the early alchemists. I
tell this story on the first day of class before moving on to Lavoisier and
Dalton (he of atomic theory fame). I’ve known about Prout’s hypothesis,
but hadn’t figured out how to discuss it effectively in class; I used it once
(but students just seemed puzzled) a number of years ago but have since left it
out. I have written about pantogen.
Prout’s hypothesis had its detractors and supporters. Berzelius, who was integral to transforming the alchemical mess of elemental symbols into the standard ones we use today, was against the hypothesis. Berzelius argued that some elements, notably chlorine and copper, had masses that could not be a multiple of hydrogen. (A quick look at the periodic table will show you that most of the elements have atomic masses close to an integer value, but there are some exceptions, including chlorine and copper.) Dumas, on the other hand, was a supporter of the hypothesis because of the discovery of isomerism. As Principe says: “Isomerism implied that some unsuspected internal arrangement of their common components determined the properties of these substances, rather than merely the kind and number of atoms they contained. A similar dependence of properties on internal structure rather than on composition appeared in the phenomenon of polymorphism…”
The third observation came from the “radical theory” of organic chemistry. A notable example is ammonium (shown to contain one nitrogen and four hydrogens) which moved as a cluster (“radical”) or a unit. In particular, ammonium could substitute for the metal in a salt. Principe explains that this was “a type of substitution reaction that had long been recognized to occur among various metals, but only among metals. The implication was that ammonium was itself a metal composed of two nonmetals… that metals could be compounds after all, just so tightly bound that the means of decomposing them had simply not yet been found.”
Threading through Principe’s lecture is the story of an individual I had never heard of: Cyprien-Theodore Tiffereau (1819-1909), later known as “the alchemist of the 19th century”. Alchemy wasn’t dead, but it had gone underground. Principe argues that, in France, shortly after its premier scientific academy was founded, political figures and administrators forbade members of the academy from studying the transmutation of metals, characterizing such activity as both futile and fraudulent. However, according to Principe: “The Academie’s chymists, however, acted the way all academics should towards administrators. They ignore them.” Principe provides several examples leading up to the late 18th century when alchemy peters out with the theories of Lavoisier and Dalton.
Tiffereau is an interesting character. He goes to Mexico to learn more about making daguerreotypes (forerunners to photography), but what’s he’s really interested in is metals and their ores, and the possibility of transmutation. Principe writes that in 1846, “he achieved a result that would inspire (or haunt) him for the rest of his days. After exposing nitric acid to strong sunlight for several days, he poured it over filings of a silver-copper alloy and left the mixture in the sun. A portion of the filings dissolved. He then boiled the mixture to dryness and added more acid. Upon repetitions of the process, the initially greenish-black residue grew increasingly lighter in color, and finally turned a brilliant metallic yellow. His tests (and those done by others later) showed the yellow material to be gold.” He was successful three times. The ores he obtained came from mining operations where gold was also found. Tiffereau’s explanation builds off Prout’s hypothesis: He thinks that copper is converted to silver by incorporating oxygen, and then in turn, the silver is converted into gold. Nitric acid acts as an oxidizer.
The Mexican-American war forces Tiffereau to return to France. But he is not able to replicate his experiments, and he beseeches the Academie for funds (and help) to do so. And thanks to the work of Dumas, they seemed at least open to the possibility, although ultimately no help was forthcoming. Tiffereau thought the problem might be the weaker sunlight in France compared to Mexico. A similar argument was made by John William Draper (who became the first president of the American Chemical Society). Draper made a claim that he had succeeded in converting silver into something with similar properties to gold when he did his experiments in America, but they failed in the weaker sunlight of England. These arguments might sound spurious to us today, but I’m now more circumspect given that the difference in light can lead to very significant differences in the wide world of biology that I’ve been learning from The Optics of Life.
By the late 19th century, alchemy and the transmutation of metals had fallen out of favor again. Principe argues that this was because “the occultist revival and its radical interpretation of alchemy… had now made the subject more distasteful, even embarrassing, to scientists. Many occultists set themselves in explicit opposition to the scientific establishment, decrying chemistry as mechanical and lifeless and chemists as blind… In the context of the occult revival, it was now alchemy’s turn to spurn chemistry.” Meanwhile, Tiffereau shoulders on, now thinking that the missing link could be the (recently discovered) nitrogen-fixing bacteria present in the soil and the ore. He called them “mineral microbes”.
But in the 20th century, the twin discoveries of radioactivity and the internal structure of the atom would revive transmutation. With more modern apparatus that could alter the composition of the atomic nucleus (usually with neutron bombardment), scientists would successfully convert platinum or mercury into gold. (Platinum and mercury are the left and right neighbors of gold on the periodic table.) Chemistry classes all over the world now teach that elements are uniquely defined by the number of protons in the nucleus (known as the atomic number). Hydrogen’s atomic number is 1 and its most common isotope only has a single proton in its nucleus. In a way, one might say Prout’s hypothesis has been revived – different elements can be formed by adding protons or hydrogen nuclei. However, the energies required to effect this transformation are huge, and most of what we call chemistry – involving the movement and transfer of valence electrons far outside the nucleus – takes place at more accessible lower energies.
Principe says in his conclusion: “The successive making-up and breaking-up of alchemy and chemistry underscores the commonality of goals and practices expressed by the word chymistry when speaking of the early modern period. The desire to understand and control matter and its transformations lies at the heart of both alchemy and chemistry… The story also underscores how difficult it really has been (and remains) to understand the microstructure – indeed the very nature itself – of matter, a realm forever beyond the limits of human sense perception.”
This blog post is just a small excerpt from a wealth of interesting information provided by Principe in its lecture. Do an internet search and read it in full for yourself!
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