Periodic Tales

by Hugh Aldersey-Williams

Born in 1834, probably the fourteenth and last child of a Siberian family, young Dmitrii was taken by his mother to St Petersburg in the hopes that at least one of her children might improve himself. Like many aspiring scientists of the day, he travelled to Germany to complete his education on a government subsidy. His kind is unfairly satirized in several novels by Turgenev. However, for a Russian chemist of any ambition this was not dilettantism but an essential way to catch up on the latest developments in the science. Upon his return to St Petersburg in 1861, Mendeleev divided his time between the university, where he soon occupied the chair in chemistry, and expeditions to remote regions of the Urals and the Caucasus, where he acted as a consultant for the government and various commercial interests on everything from cheese-making and agricultural productivity to the nascent oil industry.

  The periodic table is one of those discoveries of science that suddenly explains so much that it seems it can only have sprung fully formed from the mind of its creator as if revealed in a dream. Mendeleev obligingly concocted a myth that this was exactly how he had come by it. But in the way of these things, his story of a dream came along rather late in the day. In fact, of course, the periodic table arose as the product of long cogitation. Mendeleev struggled to find a way of making sense of the elements for students as he worked on a much-needed introductory textbook in the Russian language. He wrote out the known elements with their atomic weights and some of their chemical characteristics on sixty-three cards. Then he began to group the cards as if playing a game of patience, placing the lightest elements in a row to begin with, but mindful that certain cards, for example those representing the halogens such as chlorine and iodine, seemed to belong together. He soon found that the lightest elements of each typical kind–the lightest halogen, the lightest alkali metal, and so on–provided a template for placing their heavier cousins. This breakthrough was made in the space of a day. From there, it might simply have been a matter of inserting all the remaining elements beneath the top-row element of their group in order of increasing atomic weight. But this is to reckon without the ambiguities among the sixty-three supposedly known elements, or the number of substances then tentatively accepted as elements that would later prove in fact to be some other element or combination of elements entirely. Both of these factors made it much harder for Mendeleev to be sure he had provided the best fit for the scientific evidence. The resulting ‘Attempt at a System of the Elements, Based on Their Atomic Weight and Chemical Affinity’ finally appeared in his textbook Principles of Chemistry in 1869, and only the following year, more confidently stated, in a scientific paper. He covered his bets by including variants of the layout that are today forgotten, and though by 1871 he was calling it ‘periodic’, it was to be many decades before all the cards were properly placed into their final, familiar pattern.

  The difficulty for everybody else was that Mendeleev’s table seemed to come from nowhere. For several years there was no telling whether it was true or false. What could be ‘true’ anyway about an arrangement of symbols on paper? The Russian claimed his table could be used to predict important properties of the elements such as densities and melting points, but the fact that it did this from an entirely theoretical standpoint was merely grist to the mill for his opponents.

  However, the critics were silenced in 1875 when Paul-Emile Lecoq de Boisbaudran, entirely unaware of Mendeleev’s work, announced that he had discovered a new aluminium-like element, which he named gallium. Its atomic weight corresponded exactly to the value Mendeleev had assigned to a gap in his table directly below aluminium, and even the mode of its discovery–by identification of its characteristic spectrum–was as he had predicted. Lecoq reported a density rather lower than the Russian had estimated, but Mendeleev brazenly wrote to Lecoq suggesting he prepare a purer sample. When he did, the density very closely matched Mendeleev’s value, dramatically vindicating the Russian’s theoretical science. (Gallium’s most striking property, however, its low melting point, had been anticipated by no one–it melts in the hand, making it only the second metal, after mercury, readily observed in the liquid state.)

  The story was repeated in 1879, when Lars Nilson at Uppsala University filled the space Mendeleev had left between calcium and titanium with the discovery of scandium, and again in 1886, when Clemens Winkler at the Freiberg mining university in the ore-laden mountains on the border of Saxony and Bohemia isolated the semi-metal germanium, intermediate in the periodic table between silicon and tin, from a local mineral specimen.

  Subsequent printings of Mendeleev’s Principles filled in each gap as the news came through, and the 1889 edition went so far as to print photographic portraits of Lecoq, Nilson and Winkler, lionizing them as ‘reinforcers of the periodic law’. Though now honoured by many foreign science academies, Mendeleev was nevertheless blocked from higher recognition at the St Petersburg Academy of Sciences because of concerns about his anti-imperial politics, the seeds of which had been sown in his Siberian youth when he fell in with a group of exiled Decembrists, the failed revolutionaries who tried to topple Tsar Nicholas I in 1825. Later he was forced to resign his professorship at the university. Ironically enough, he quickly found alternative employment in advisory positions to the government.

  For a while, each discovery of a new element drew an appreciative response from Mendeleev when it fitted into his grand plan. But in time, more sophisticated techniques came along that were able to reveal new elements with unforeseen properties that could not be so readily embraced. William Ramsay’s discovery of the inert gases, beginning with argon in 1894, was the first major interrogation of the periodic table after twenty-five years of successful consolidation. Mendeleev had once again observed that there were gaps, based on atomic weights, between the alkali metals and the halogens, but on this occasion the scarcely believable implication was that an entire family of elements was missing, and it was less clear how, or indeed whether, the table should be amended. The 1895 edition of his still standard textbook entered a note of scepticism about the first reports of argon and helium. There followed a tetchy correspondence between the two men, with Mendeleev at first refuting Ramsay’s claim and suggesting that his new gas argon was simply a heavy form of nitrogen. (Like the ozone form of oxygen, which contains three atoms rather than two, this putative three-atom molecule would be half as heavy again as the normal nitrogen molecule of two atoms, bringing it close to the observed weight of Ramsay’s argon.) As Ramsay added more elements of similar character, first helium, and then neon, krypton and xenon, in rapid succession, Mendeleev came round to the idea that they could after all be accommodated in his system by the simple expedient of adding a new column to the edge of the table. Astonishingly, it appears that Mendeleev’s failure to predict the inert gases after so many other successes may have been a major reason why the Nobel Committee decided not to award him the prize in chemistry when they considered the possibility in 1906.

  The discovery of the radioactive decay of elements by Marie Curie and others in Mendeleev’s declining years played further havoc with his system of chemical order. What was the point of putting elements in boxes if they could simply jump from one box to another by shedding a few subatomic particles? Mendeleev had once taken to the road in Russia in order to do battle against the spiritualism that he felt was preventing progress in the country; visiting the Curies’ laboratory in 1902, he felt he was once again dealing with the same ungovernable forces, which he scathingly called ‘spirit in matter’.

  Mendeleev has frequently been characterized as a mystic and a prophet, but this is more to do with his Siberian origins, his irascibility and his dishevelled beard than his professional record. Contemporary portraits don’t always help: one shows the chemist leaning back in his chair maniacally clutching a book to his face with both hands, a glowing cigarette held in his fingers. Mendeleev had brilliantly devised a periodic system of the elements in which he had sufficient confidence to leave gaps, but this was a sensible conjecture based on scientifi
c evidence, not prophecy. His other activities were equally grounded in rationalism–tackling spiritualism, advising on the national economy, recommending agricultural reforms. Though full of ideas, he was by nature something of a conservative and, while not accepted into institutions such as the Academy of Sciences, he still seemed like an establishment figure to others. The final seal of conventionality surely came in 1893, when he was put in charge of the newly founded national board of weights and measures.

  Shortly before becoming a professor, Mendeleev had bought a summer estate outside Moscow. Like Levin in Anna Karenina, he used the land to showcase his ideas of progressive farming. Here, his daughter Liubov’ Dmitrievna Mendeleeva met and fell in love with the young poet Alexander Blok, whose family owned a neighbouring estate. In 1903, the year of their marriage, Blok wrote admiringly to Mendeleeva of her father, who ‘knows everything that happens in the world already for a long time. He has entered into everything. Nothing is concealed from him. His knowledge is most complete.’ Blok–the author of ‘The Scythians’ and other works in which a Russian identity rooted in the wildest regions is given voice in the language of the literary avant-garde–surely responded to Mendeleev’s incongruous blend of deep Russian ancestry and immersion in the latest currents of thought in scientific Europe. After Mendeleev’s death in 1907, Blok contrasted him favourably with the cynical establishment intelligentsia for holding to an optimistic view of the country’s future. But later something snapped, and the poet, filled with revolutionary zeal, decided that his father-in-law belonged too much to the past. On 31 January 1919, he wrote in his diary: ‘Symbolic action: on the Soviet New Year I smashed Mendeleev’s desk.’

  Mendeleev’s university apartment–though sadly not the laboratory that once adjoined it–is now preserved as a museum. I visited it one blistering June day, crossing the glittering Neva in a dazzle of golden domes to find myself strolling along the elegant terraced avenues of the university complex on the grid-planned Vasilevskii Island. The entire place still glowed with the sense of Peter the Great’s ambition to found a city that would rival the greatest in Europe.

  This was where Mendeleev lived for twenty-four years, from his appointment to the chair of chemistry in 1867, through the time when he worked out the periodic table and enjoyed the satisfaction of seeing his predictions of missing elements realized, to his forced retirement in 1890. The rooms were crowded with heavy armchairs and sofas and equally heavy volumes of journals. In one, a cigar-smoking portrait presided over the scene. Photographs of Mendeleev with scientists, including the discoverers of his predicted elements, and leading figures in St Petersburg lined the walls. The signatures of his visitors were illegibly inscribed on a tablecloth. There was also a desk. Was this where he had laid out his element cards, or was that on the desk that Blok demolished? The pack of cards and other documents showing Mendeleev’s workings are long lost, but his textbook survives, and so does the periodic table in it, the sequence of the elements instantly recognizable, even though the whole thing is twisted through ninety degrees, making rows into columns and columns into rows. Thus, B, C, N, O, F appears as a column on the left; Al, Si, P, S, Cl to its right. As the atomic weights increased, I noticed alignments that we would now think of as misleading–mercury grouped with copper and silver, for example, while gold was aligned with aluminium. But there were also the question marks against gaps in the sequence that were the true sign of Mendeleev’s genius.

  Seeing the familiar array of letters in cold print, it was hard to believe it had not swept all before it. I asked the museum’s curator, Igor Dmitriev, why this was. ‘There were many classifications already,’ he explained, ‘none of them taken seriously. So it is understandable that Mendeleev would have had a hard time.’

  But it was the suitcases that really stuck in my mind. Mendeleev may not have been a mystic, but he certainly had his eccentricities, and one of the oddest of them was his hobby of making leather suitcases. His apartment was cluttered with cases in varying states of completion, as well as the leather and buckles and tools used to make them. It’s tempting of course to see this curious pastime as a metaphor, as material evidence of the character of a man obsessed with packing things neatly away. But it’s neither necessary nor helpful to do this. In truth, Mendeleev could confess to his fair share of nineteenth-century science’s passion for organizing nature–he had been attentive to contemporary naturalists’ efforts to classify living species, for example. But his system for the chemical elements, the ultimate pigeonholing of nature, sprang simply from a pedagogical need to streamline the presentation of chemical knowledge rather than from rage at the disorder of the world.

  Mendelevium was the first element that had to be dragged into the world atom by atom, beginning in 1955. Even now, it has never been made in quantities visible to the eye. ‘We thought it fitting that there be an element named for the Russian chemist Dmitrii Mendeleev, who had developed the periodic table,’ wrote its discoverer, Glenn Seaborg. ‘In nearly all our experiments discovering transuranium elements, we’d depended on his method of predicting chemical properties based on the element’s position in the table.’ At the height of the Cold War, this ‘somewhat bold gesture’, as Seaborg admits, was condemned by some Americans, but was not unappreciated in top Soviet circles. The tiny amounts of mendelevium that have been made in the particle accelerators at Berkeley and elsewhere decay rapidly, and it has not been possible to make more than a start on measuring its essential properties or investigating its chemistry. One suspects that this would have bothered Dmitrii Mendeleev, the supreme theoretical chemist of his day, not one bit.

  The Liquid Mirror

  In Jean Cocteau’s 1949 film Orphée, Orpheus enters the underworld in pursuit of Eurydice by passing through a mirror of mercury. The scene is a masterly cinematic sleight of hand. Orpheus, played by a Grecian-coiffed Jean Marais, is led to a large dressing mirror. He dons latex gloves–a magical preparatory ritual that doesn’t entirely disguise the fact that Cocteau, the renowned avant-garde artist, seems to have had a thoroughly modern concern for health and safety. ‘With these gloves, you will be able to pass through the mirror like water’, Orpheus’ guide explains. ‘First the hands.’ Doubtfully, Orpheus does as he is told and puts his palms to the reflective surface, and is met by its resistance–it’s just a mirror. ‘Il s’agit de croire’, he is advised: you must believe. Then we see his fingers in close-up pushing through the barrier, its surface set aquiver by the fateful action. The film cuts to an overhead shot. With the liquid mirror surface now hidden from our view, Orpheus and his guide disappear through the portal.

  It is axiomatic that we cannot know the underworld until we ourselves leave the world, and for this reason Cocteau sought for his divide between the two a total optical barrier that was nevertheless physically penetrable. The set-up is said to have required a reservoir of half a tonne of mercury. This seems excessive until one remembers that this metal is so dense that lead will float on its surface. A pool of this weight the size of a full-length mirror would be not much more than a centimetre deep. It is of course not possible to arrange for such a pool to stand upright, so Cocteau had to turn his camera to produce the illusion of a vertical mirror for the brief scene where Orpheus’ hands pass through the barrier. And it is not possible, or safe, for whole bodies to be immersed in mercury, hence the subsequent cutaway to overhead.

  The artist might have used milk or paint to achieve some of the necessary effect, but mercury was well chosen as the only liquid able to provide a perfect reflection. The material also offered a serendipitous bonus. In an interview, Cocteau later explained: ‘In mercury the hands disappear, and the gesture is accompanied by a kind of shiver, whereas water would have produced ripples and circles of waves. On top of that, mercury has resistance.’ In this single action, then, are made visible signs of Orpheus’ trepidation, of his fright and of the effort of will he must summon in order to abandon life. Furthermore, the unfamiliar, almost unnatural, quality o
f the mercury hints nicely at uncertainties to come in the supernatural world.

  Known for perhaps 5,000 years, mercury has always been celebrated for its unique confluence of liquid and metallic properties, even if this made it no easier for people to find a use for the stuff. For a material that is clearly special, yet also rather useless, there is one obvious application, and that is in sacred rites. Cocteau’s employment of mercury as the gateway to another world is merely a modern twist in a long and universal tale.

  The first emperor of China, Qin Shi Huang, who unified the country in 221 BCE, is said by legend to lie buried beneath a rugged verdant mound near Xi’an in the Shaanxi Province of northern China. The historian Sima Qian, writing a century after the emperor’s death, describes a vast bronze-lined chamber, its ceiling jewelled to represent the heavens, containing a fantastic model of the emperor’s palace, his capital city Xianyang lying around it, and his entire empire beyond. Through the model landscape are said to run channels of mercury representing the hundred great rivers of China. Although it is not easy to see how it could be done, Sima writes of mechanisms to pump the heavy liquid round, maintaining a continuous flow that symbolizes the eternal lifeblood of the emperor. It is likely, what’s more, that Qin’s blood actually did contain mercury at the time of his death as he is thought to have swallowed mercury pills in the hope of obtaining immortality.

  It was in this region of China in 1974 that archaeologists began to uncover the now famous Terracotta Army, hundreds of life-size earthenware figures, soldiers first, then later musicians, athletes and bureaucrats, providing extraordinary details of life at the beginning of the Qin Dynasty. The location of the find was soon matched with descriptions of the landscape in Sima’s history, and from this it was surmised that a particular eminence a kilometre off to the west might hide the emperor’s tomb. Subsequent excavations have revealed that the pits containing the Terracotta Army were just part of a large underground complex around this feature, but the mound itself has not yet been broached for fear that it may not be possible to preserve its contents–not least its fabulous mercury rivers–if they are disturbed. However, scientists have carried out various non-destructive tests at the site, including chemical analysis of soil samples. These have revealed levels of mercury well above the normal in the immediate vicinity of the burial mound. In Sima’s account, the model empire is carefully oriented underground to correspond with the real geography, and it has been found that some of highest concentrations of mercury align with some of China’s coastal seas and the vast sweep of the lower Yangtze River.