Elements: a 2,000-Year Story Jennifer Rampling Traces Ideas of Material Essence and Indivisibility Before the Atom

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SCIENCE HISTORY Elements: a 2,000-year story Jennifer Rampling traces ideas of material essence and indivisibility before the atom.

ore than two millennia before Islamic and Christian natural philosophy. the periodic table was conceived, THE PERIODIC TABLE However, it sometimes fell short in terms ancient philosophers were A Nature special issue of explaining observed chemical opera- Malready grappling with the nature of ‘stuff’ go.nature.com/periodictable tions. For instance, when one substantial in the world. Are all substances reducible form is destroyed, another is created in its to the same, universal matter? If so, when world of forms, inaccessible to human sense. place; the process should be irreversible. exactly does one substance become dis- Although elemental, they were divisible, each Wine might sour into vinegar, but vinegar tinct from another? From Greece in the composed of two pairs of contrary qualities: cannot become wine again. Yet, as scholars fifth century bc to northern Europe in the hot/cold and wet/dry. Moreover, one element and metalworkers were well aware, many seventeenth century, successive attempts to shifts into another when its properties alter: operations are reversible. Pure silver can be answer these questions gave rise to a profu- thus, as coldness is replaced by heat, water recovered following its dissolution in nitric sion of coexisting concepts, from elements (cold and moist) transforms into air (hot acid, as can mercury after its transformation to principles, atoms to corpuscles — each and moist). In Aristotle’s cosmology, it is this into a red precipitate. Such effects hinted at intended to solve a specific problem, each ability to change, hard-wired into terrestrial an underlying, particulate structure of the raising new difficulties. physics, that drives the complexity and kind condemned by Aristotle. In the fourth century bc, the philosopher diversity of the elementary world. An influential compromise was developed Aristotle formulated the problem in his This model retained its prestige during the by alchemists, in response to hints in Physics: how many times can a piece of gold Middle Ages as the foundation of medieval another work by Aristotle, Meteorology. The be bisected before it ceases to be gold? He “sulfur–mercury” theory was first set down intuited that there is a level of simplicity in eighth-century Arabic alchemical writ- beyond which matter cannot be reduced ings attributed (although pseudonymously) without losing its defining character. This to Jābir ibn Hayyān. It became the domi- is the “natural minimum”: the small- nant theory of metallic generation for est particle of a substance that can another 500 years, introduced to the still be identified as being of that Latin world with the translation of substance. Any smaller, and our Arabic scientific texts during the example could no longer sup- twelfth century. WELLCOME COLLECTION. CC BY COLLECTION. WELLCOME port the bundle of properties The theory proposes two that makes gold what it is. paired principles, sulfur and Similar reasoning under- mercury. (Confusingly, these girds modern understand- do not always correspond to ing of the atom as the the elements bearing those fundamental unit of a chem- names.) The mercury princi- ical element. However, such ple is cool and moist; sulfur, analogies can be deceptive. hot and dry. Together, they Aristotle attacked the earlier combine to make the seven theory of indivisible “atoms”, core metals — gold, silver, proposed by the philosopher copper, tin, iron, lead and Democritus, as mathemati- mercury. The two principles cally impossible. Rather offer an intermediate stage than a particulate struc- of matter: composed of the ture, Aristotle suggested, all four elements, yet with quali- substances were composed ties that determine those of of matter and form. He saw metals. Iron, for instance, form as imprinted on matter, has a high melting point and which itself consists of four gives off sparks when struck, “elements”: earth, air, fire so within the theory might and water. be seen as having a high pro- portion of the hot, dry sulfur FIRST PRINCIPLES principle. Aristotle was not the first to If alchemical transmuta- conceptualize an elemen- tion offered one context for tal system: he borrowed thinking about structures of from the fifth-century-bc matter, medicine provided pre-Socratic philosopher another, particularly from the Empedocles. His elements sixteenth century. In tracts comprised a material sub- such as Opus Paramirum, the strate lying beneath the Personifications of the principles of mercury and sulfur, from the sixteenth century. Swiss medical reformer

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Paracelsus (1493–1541) expanded the his practical experience led him to question thus served as atoms, while avoiding the sulfur–mercury dyad by adding a third whether sulfur, mercury and salt really were mathematical objection against indivisibil- principle, salt. He claimed that these “three constituents of substances, or merely products ity. A crucial caveat, however, was that they first things” underpinned all matter, not just of fire and chemical processes. could also carry properties such as size or metals. In a deeply religious culture, this triad Van Helmont’s approach influenced Robert motion, allowing Boyle and other corpuscu- conveniently corresponded to the Christian Boyle, Royal Society co-founder and advo- larians to relate the distinctive properties of trinity of Father, Son and Holy Spirit. cate of mechanism, who expressed similar materials to the “texture” of their corpuscles. Paracelsus did not propose a universal form doubts in The Sceptical Chymist (1661). Boyle Chemistry, medicine and mechanism all of matter. He argued that every substance was equated elements and principles in a purpose- contributed to solving the early modern mat- reducible to particular forms of sulfur, mer- fully loose definition, as “primitive and sim- ter problem. In the 1660s, experiment alone cury and salt. Thus, the salt of wood is not ple Bodies of which the mixt [compound] could not demonstrate the deep structures the same as the salt of gold, and might have ones are said to be composed, and into which of matter, as Boyle himself recognized. Such very different pharmacological properties. they are ultimately structures were invisible to the eye, and even The system therefore catered primarily to resolved”. On these “Chemistry, a vaunted new technology, the microscope, medical practitioners’ needs. It contrasts with grounds, he dis- medicine and failed to reveal their elementary composi- the seventeenth-century rise of mechanical qualified Paracel- mechanism all tion. Yet these challenges created scope for philosophies, which tried to account for mat sian principles as contributed to theoretical innovation, allowing natural phi- erial change in terms of the action of particles physical constitu- solving the early losophers to mix and match from a diversity governed by contact mechanics. French nat- ents of compound modern matter of models and explanations. This pluralism ural philosopher and priest Pierre Gassendi bodies. Nor did he problem.” of approach continued into the eighteenth sought to revive ancient atomism in a Chris- find experimental century. From Joseph Priestley’s work isolat- tian framework, whereas philosopher René evidence for Paracelsus’s salt. However, as a ing gases in England to Antoine Lavoisier’s Descartes proposed an entirely mechanistic keen believer in transmutation, Boyle was ingenious apparatus for weighing chemi- universe based on contiguous point particles. willing to entertain the possibility that metals cal products in France, that array yielded a In practice, a chemist might select aspects contained a ‘mercury’ and ‘sulfur’ — and, in sequence of theoretical insights and experi- from all these outwardly contradictory sys- a later work, even claimed to have extracted mental techniques that eventually allowed a tems. The Flemish physician Jan Baptist van metallic ‘mercuries’ himself. new vision of atomic structure to emerge. ■ Helmont (1580–1644) adopted some mecha- Boyle’s solution was to propose a universal nistic ideas, for instance when explaining how “catholic matter” that clumped into semi- Jennifer Rampling is assistant professor metals dissolved in mineral acids through permanent “corpuscles” (small bodies). of history at Princeton University in reduction into smaller parts. Despite criticiz- These were the smallest particles divisible by New Jersey, where she teaches the history of ing Paracelsian medicine, he was also influ- human art, so their own composition could early modern science. enced by Paracelsus’s notion of principles. Yet not be investigated. Functionally, corpuscles e-mail: [email protected] IN RETROSPECT The Periodic Table Tim Radford celebrates chemist Primo Levi’s extraordinary short-story collection.

n The Periodic Table, Primo Levi — and delights of science. moment he learnt while conducting assays scientist, poet, writer — makes chemis- His narrative briefly invokes the rise of that to conquer matter is to understand it; try a metaphor for his life. But it becomes fascism, the folly of British Prime Minister and that that knowledge — he calls it the Imore than that. Chemistry shapes his life, Neville Chamberlain at Munich, the fall of missing link between the worlds of words defines his life, in Auschwitz even saves Prague, General Francisco Franco’s conquest and of things — is in turn central to under- his life. It becomes his living. In the end, of Spanish Republican forces in Barcelona, standing the Universe. For him, the periodic chemistry becomes everything: life itself. the sustained bleakness of all-out war in the table was “poetry, loftier and more solemn When, in 1985, I reviewed Raymond 1940s, the nightmare of the concentration than all the poetry we had swallowed down Rosenthal’s translation of Levi’s collection of camps and the cruel post-war struggles to in liceo [secondary school], and come to short stories (by then a decade old), I called it survive and rebuild. think of it, it even rhymed!” gold. I wish I’d also said what I thought at the Literary references are scattered through, time: that this was a book that people would among them Thomas Mann’s The Magic ELEMENTAL STRUGGLES still be reading in 100 years. With each re- Mountain, Emile Zola’s Germinal and the Levi was born in Turin in 1919. What reading, the chapters based on memoir seem work of fellow Italian–Jewish political exile, narrative there is begins with his ances- even more perceptive, more profound. writer and physician Carlo Levi. But the try, peopled by individuals “noble, inert Western European history is embedded in narrative stubbornly returns to elemental and rare”, but poor compared with “other the work’s brief time span, from Levi’s student chemistry. He recalls in the story ‘Iron’ the illustrious Jewish communities in Italy years to the post-war recovery of Italy. Each and Europe”. The story is ‘Argon’, from the title of the very different 21 tales is the name THE PERIODIC TABLE Greek for inactive. His memories of barbe of an element at that story’s core, sustain- A Nature special issue and magne (uncles and aunts in the dialect ing the architecture of a book that delivers a go.nature.com/periodictable of his native region, Piedmont) become sharp sense of the compulsion, ambiguities a reflection on words, in Hebrew and