The Science of Alchemy

There is one element chemistry can never tame — the element of surprise.

The last of the magicians. That is what they would call him. And that is how he must have looked, stirring molten silver and mercury in his bubbling crucible in the dead of night. Not that he would let anyone see. It was vital that his work remained a secret, for death by murder or execution were likely fates for exposed alchemists. Only centuries after his death would the full extent of it be known. But it was just as systematic as his more famous research, and more extensive than the full works of Shakespeare. His goal was no less than the legendary philosopher’s stone, which could turn lead into gold. Many before had tried and failed, but this did not discourage him. He knew his genius was without equal. After all, he was Isaac Newton.

Newton’s scientific research lies at the foundation of physics. From the motion of planets to the creation of rainbows, he constructed rigorous scientific theories and mathematical formulae for hitherto mystical phenomena. Even poets found him inspirational; Alexander Pope memorialised him with the lines: “Nature, and Nature's laws lay hid in night; God said, Let Newton be! and all was light.” Yet it transpires that Newton was just as interested in the dark of the occult as in the light of science. While his public work adorns the pages of physics textbooks, his secret study of alchemy seems more befitting of the fantastical pages of Harry Potter.

Extract from Newton’s notes on alchemy, which in total amount to over one million words. The notes diligently describe a procedure proposed by another alchemist, Erasmus Rothmaler, just as one would record a scientific experiment.

He was not alone in his fascination with turning cheap metals into gold. Inspired by the philosophy of Aristotle, great minds chased the dream of Midas relentlessly for two millennia. Yet the advent of modern chemistry brought an end to this pursuit. To understand why, we must explore the science of the elements that make up our world. Yet remarkably once we begin this journey, we will find at its end that the dream was real along. This is the story of the real science of alchemy.

The Missing Elements

Since ancient times, philosophers have conceived of matter in terms of elements. Aristotle, whose work most influenced Western alchemy, was typical in this regard. He posited that all matter is made of different combinations of earth, air, fire and water. In this view, the only difference between lead and gold was the ratios of these elements. This meant that there was no fundamental reason why one metal could not be converted to another; all that was required was the right method for rearranging the elements.

Modern chemists, too, conceive of matter as consisting of combinations of elements. But while Aristotle allowed for just four, the modern periodic table is populated by 118 chemical elements. Aristotle’s elements are not among them. Indeed, in 1781, Henry Cavendish showed that water is not elemental but is itself a combination of two chemical elements — hydrogen and oxygen. Aristotle’s other elements were similarly found to consist of mixtures of chemical elements. On the other hand, it transpires that lead and gold — which Aristotle believed were mixtures of elements — are actually both elements themselves. It seems that Aristotle had it backwards!

The periodic table showing the chemical elements that are now known to make up all matter. While Aristotle believed that there were only four elements, we now know that there are 92 naturally occurring elements along with a number more that can be created artificially. Lead (Pb) is element number 82 and gold (Au) is element number 79.

That said, Aristotle and the alchemists were correct to believe that matter could be transformed through the rearrangement of elements. This is exactly what chemical reactions are! Hydrogen and oxygen gases can be combined to produce liquid water, which differs more profoundly from either than gold differs from lead. Indeed, the alchemists were even right that rearranging elements could transform base matter into precious materials. The cheap graphite in a pencil contains the same atoms as the diamond on a wedding ring, just in a different arrangement. With high enough temperatures and pressures, one really can be turned into the other. Indeed, today synthetic diamonds are relatively commonplace and can be much cheaper than natural diamonds.

Why can’t we make synthetic gold in the same way? The problem is that gold as an element is simply very rare. If you divided up all of the gold in the world equally, each person would only get enough to make a single coin.¹ By contrast, diamond consists of the element carbon, which is extremely common; a single tree contains the carbon needed to make billions of dollars worth of diamonds.²

This is why chemistry appeared to have proven that the alchemists’ dream was futile. The alchemists believed that gold was made of a combination of common elements, and so all that was required was to combine these ingredients in the right way. However, by the eighteenth century, scientists realised that gold was itself a very rare element that is not found in other materials. The only way to create new gold would be to transform one element into another, which is impossible by chemical processes. It certainly seemed that the alchemists' dream was dead!

Splitting the Atom

But what chemistry had ostensibly killed, physics would resuscitate! By the nineteenth century, chemists had come to understand that all matter is made of tiny particles called atoms. The defining property of an atom was that it was absolutely fixed and indivisible. Atoms, it was assumed, could not be broken nor changed. Each chemical element corresponds to a different type of atom. Therefore, it seemed self-evident that elements too must be unchangeable.

However, by the early twentieth century, physicists were making discoveries that shattered this simple picture. Far from being indivisible, it was discovered that atoms are made of three types of particles — protons, neutrons and electrons. Electrons are relatively loosely held around the edges of atoms by electrical forces. This means that they are mobile and can be transferred between different atoms. This rearrangement of electrons is what chemical reactions are!

A simplified model of an atom showing the three types of particles that make it up. The protons (red) and neutrons (blue) are tightly held in the nucleus at the centre by the strong force, while the electrons (grey) are more loosely held around the edges by the electric force.

However, the fundamental identity of an atom is not determined by its electrons, but by its protons. The atoms of each element have different numbers of protons. Gold atoms have 79 protons while lead atoms have 82 protons. Therefore, removing three protons from a lead atom turns it into gold! However, while the electrons float around the edges with some freedom, the protons are held tightly in the dense core of the atom, called the nucleus. The nucleus is held together by the strongest and most aptly named force of nature — the strong force. The upshot of this is that turning lead into gold is possible, but only with the use of sufficiently vast quantities of energy to overcome the strongest force in the universe. That is why Newton could never achieve it with mere flames.

Fortunately, modern particle accelerators can achieve what pre-modern forges could not! Indeed, starting with Adolf Miethe in 1924, twentieth-century physicists performed a number of experiments to create gold by modifying the nuclei of atoms. These culminated in a 1980 experiment led by Glenn Seaborg which succeeded in producing stable gold from bismuth. While bismuth itself is actually even rarer than gold, the same process could be performed with lead instead. At last, after millennia of dashed dreams, alchemy was a reality!

However, this leaves one question. If Glenn Seaborg has the philosopher’s stone, why isn’t he famous as the richest man in history? The answer is that Seaborg’s method is not very economical as it produces only nanoscopic quantities of gold. Indeed, he estimated that to produce a single gram of gold (currently worth $63) would cost over thirty billion dollars. That is a very expensive way to become rich!

The Importance of Humility

If alchemy is not going to make us all rich, then what is the point of this story? It should be a humbling reminder not to be too quick to judge. It is easy to look back and laugh at Newton and his fellow alchemists. But in some ways, they were actually more correct than the chemists who succeeded them. Imagine if a time traveller were to report to a nineteenth-century chemist and a seventeenth-century alchemist that turning lead into gold is indeed possible but is prohibitively expensive. This reality would disappoint the alchemist, but be fundamentally acceptable in his worldview. By contrast, the historical chemist may well dismiss the information and mock the traveller for their incredulity in believing what science had proven to be impossible.

This chemist’s mistaken overconfidence should remind us of an important truth; in science, nothing is ever proven. When a thing is said to be scientifically impossible, this is only ever true within a model of reality. But no model is perfect, and there is always the possibility that future experiments will falsify any element of the model. The nineteenth-century chemical model of matter stipulated that atoms are unbreakable and unchangeable. Within this model, it is necessarily the case that turning lead into gold is impossible. However, once it became possible to perform experiments with higher energy, the indivisibility of atoms was falsified and a new, revised model was needed.

In this revised model, we can say that all matter is made of just three fundamental elements — protons, neutrons and electrons. Different materials, such as lead and gold, are made of different combinations of these elements. By rearranging and recombining these elements, it is possible to turn lead into gold. Put this way, Aristotle doesn’t sound quite so wrong after all! His theory encapsulated some fundamental truths; he had just identified the wrong set of elements. Similarly, Newton’s alchemy seems less like an inexplicable derangement, and more like a noble pursuit of a goal that was simply practically more difficult than it seemed. Meanwhile, while Newton’s chemist successors came to understand the chemical elements well, they could not have accounted for the discoveries of later ages. After all, there is one element chemistry can never tame — the element of surprise.

1. The total weight of gold in the world is somewhat disputed, but typical estimates are in the range of 150 to 250 million kilograms. Divided by the eight billion people in the world, this would give each person about 20 to 30 grams of gold.

2. A one-gram diamond is worth on the order $100 000. A tree’s weight is about 15% carbon. A typical tree is several hundred kilograms, so we can estimate that it contains about 50 kg of carbon. Therefore, there is enough carbon in a tree to make 50 000 one gram diamonds, at a total value of five billion dollars.