Periodic Tales

by Hugh Aldersey-Williams

  Cerium is the most abundant of the rare earths, and is more plentiful than many familiar elements such as copper. It seems destined to remain widespread if largely unappreciated in our lives. The metal is used to improve the performance of cast irons, steels and aluminium alloys. Known as jeweller’s rouge, its powdered oxide is a fine abrasive used to polish gemstones and glass. In the nineteenth century, it was recognized that cerium salts were anti-emetic, and they were also incorporated into cough tinctures, anti-bacterial treatments against burns and tuberculosis–conveniently for medicines these salts also possess a characteristic sweet taste. More recently, there has been excitement at the discovery that cerium oxide added to diesel fuel greatly improves its combustion efficiency. And it is still used in illumination to brighten the powerful lights used on film sets.

  Cerium was the discovery of the greatest Swedish chemist of them all, Jöns Jacob Berzelius. Unlike some of his more bashful compatriots, he did publish his results in a timely fashion, as well as maintaining lively correspondence with his international peers and receiving chemical pilgrims at his laboratory. If he has been written out of the popular history of science, then the blame for it lies squarely with prejudices to the West.

  The mineral world was not Berzelius’s first love. Born in 1779, he came of age at a time when it was already thought the glory days of Swedish science were over. The talented apothecary Scheele was dead along with the mineral chemists Brandt and Gahn, who had identified new iron-like metals in the ores of the royal mines. So too was the world-renowned botanist Carl Linnaeus, who had dared to think that man might classify all of nature and had made a good start on the job with his binomial nomenclature for plants and animals.

  Trained as a physician, and intrigued, like many scientists of the time, by the effect of electric currents on living organisms, Berzelius wanted to know the secret of life. In order to learn this, he would first have to discredit fashionable theories of vitalism and offer a more rational explanation for animal and human physiology. One helpful step forward was to call the field ‘animal chemistry’. For a brief period at the beginning of the nineteenth century, this became a hot topic in science. An ‘Animal Chemistry Club’ formed as a special interest group of the Royal Society in London counted Davy among its regulars, with Berzelius being an active corresponding member. But the scientific problems proved largely intractable. The challenges posed by the chemistry of life nonetheless honed Berzelius’s skills as an analytical chemist, and he attracted the support of the prosperous mine owner Wilhelm Hisinger. Despite his avowed distaste for inorganic chemistry, Berzelius had little choice but to respond, like so many Swedish scientists before him, to the call of the earth.

  Berzelius was responsible for the introduction of now familiar items of laboratory equipment such as rubber tubing and filter paper but, unlike Bunsen with his burner or Davy with his miner’s safety lamp, he failed to pin his name to them. He introduced concepts and words which have since proved too useful to restrict to the scientific lexicon: ‘catalysis’ and ‘protein’ are his neologisms. He did invaluable work on the proportions in which elements and their compounds combine with one another, which underpinned the theory of atoms advanced by the English Quaker John Dalton, and for the first time gave chemistry a solid quantitative foundation. It was Berzelius too who saw the need for an abbreviated notation for the elements and invented modern chemical symbols. His system of a one-or two-letter code, often based on the element’s name in Latin, has since become iconic far beyond the discipline of chemistry. Putting together these last two ideas–the symbol for each element, and the understanding that they combine with one another in fixed proportions–led inevitably to the first chemical formulae, those concatenations of letters and numbers that mean everything to chemists and simply appear random to the rest of us. (‘Ah, H2SO4, professor!’ is Flanders and Swann’s impression of how scientists greet one another in their satirical treatment of C. P. Snow’s polemic concerning the ‘two cultures’ of the arts and sciences.)

  This system of notation appears to us now both familiar and alienating. Its advent in 1811, however, was a graphic revelation. The consequences for the scientific comprehension of matter were far-reaching. In their modern laboratories, the alchemical quest now left firmly behind, Enlightenment scientists had begun to show that they could synthesize simple compounds found in nature–Lavoisier had combined the gases hydrogen and oxygen to produce only water; the exotic flammable metals that Davy had isolated could be burnt to recreate the oxides found in naturally occurring minerals. Berzelius’s system finally erased any lingering distinction between the essence of a material obtained from natural sources and the same material produced in the laboratory. Once a substance such as ammonia, say, is identified as NH3 rather than ‘spirit of hartshorn’, it is suddenly clear that it no longer matters where it has come from in order for it to be what it is.

  This would be enough to secure any chemical reputation, and yet there is more. For Berzelius was also the discoverer not only of cerium but of three more chemical elements–thorium, selenium and silicon, all elements by their nature tightly earthbound. All of these discoveries relied on his intimate involvement with mining and industry. The silicate minerals from which he eventually extracted pure silicon provide Sweden’s bedrock. He found selenium, an element related to sulphur, in the sediment of a sulphuric acid plant in which he had an investment. Thorium and cerium he isolated from unusual mineral specimens sent to him for examination. In the case of cerium, in particular, Berzelius worked closely with his patron Hisinger in Stockholm, as well as at Hisinger’s country estate, and at the mines themselves, systematically electrolysing various salts derived from the specimens, which had been obtained at one of Hisinger’s abandoned mines. Berzelius chose the name cerium, inspired by the recent discovery of the dwarf planet Ceres, and following the precedent established with uranium and Uranus a few years before.

  Although the Swedes were the first to use electrolysis in the effort to obtain new elements, they struggled to gain rightful recognition of their priority in this over Davy. When the French chemist Vauquelin learnt of this work, he commented that, if the Institut de France had known of it in time, Berzelius would have shared the Napoleon medal that it awarded to Davy.

  Berzelius may have suffered from the airbrushing of chemical history due to the later achievements of the Germans, French and British, but I felt that Swedish reserve was not helping his case. I had come to Stockholm partly in the hope that I might get a glimpse of the chemicals Berzelius had collected and labelled with his compelling new notation. I had seen these in a colour plate in an old biography–small vials with chunky glass stoppers or corks filled with dusts in pastel shades of blue, yellow, grey and soapy green, each with its identifying formula in Berzelius’s own handwriting. One container of candy pink stood out puzzlingly from the rest–few salts are really pink. The caption implied that these treasures were on display at the Berzelius Museum. But the museum no longer stands, and its contents, I am told, are held in storage crates at the Royal Swedish Academy of Sciences awaiting the day when his successors see fit once again to honour his mighty contribution to the inventory, theory and language of chemistry.

  Gadolin and Samarsky, Everymen of the Elements

  In 1788, Carl Axel Arrhenius, a Swedish army lieutenant and mineralogist (the latter interest acquired while learning how to test gunpowder in the laboratory of the Royal Mint), discovered a black, asphalt-like ore aggregated in the flesh-pink feldspar of the Ytterby mine. Arrhenius was excited by the thought that it might be a source of the dense metal tungsten, discovered a few years before. He promptly sent a specimen of it for analysis to his friend Johan Gadolin, the professor of chemistry at the university in Åbo (now Turku in Finland, then part of the Swedish empire). After a long delay, Gadolin responded with more interesting news: the lieutenant had discovered the ore of a new rare earth element. Gadolin named the ore yttria after the Ytterby mine, and worried what this late
st find might mean for chemistry as a whole. ‘It is not without great trepidation I dare speak of a new earth because they are right now becoming far too numerous,’ he wrote, ‘for it seems to me rather fatal if each of the new earths should only be found at one site or in one mineral’.

  Gadolin’s fears that the rare earths would proliferate turned out to be well founded. This one Ytterby mineral would in the end reveal not one rare earth element, but four, and their apparently exclusive association with the location of their discovery made it seem right to name each of them after it: yttrium, erbium, terbium and ytterbium. Later, Per Cleve separated the oxides of two more new metals from the same ore, and named them, more broadly, holmium after Stockholm, and thulium after the old name for Scandinavia, Thule. Meanwhile, in a different Ytterby mineral, Anders Ekeberg discovered another new element–a metal, but this time not a rare earth–tantalum. By 1879, the Ytterby mine was finally the source of seven chemical elements in a list that then totalled seventy in all.

  The mineral from which Gadolin obtained his yttria, called ytterbite to begin with, was soon renamed gadolinite in his honour. However, this was not to be his only or his greatest claim to scientific immortality. For later, the element gadolinium was, with samarium, the first to be named, not after a figure in mythology, nor after some Greek neologism based on its chemical behaviour, nor even after the place where it was found, but after a real person. Samarium was discovered in 1879, and named for a Russian mining engineer, Vasili Samarsky. Gadolinium was identified the following year.

  It was not until 1944 that a new element was again named after a person. That was curium. Other new arrivals followed this honorific convention during the 1950s, including einsteinium, fermium, mendelevium and nobelium. All these elements esteem scientific figures already much esteemed for their achievements. You might think these elements are all rather remote from daily experience. At any rate, they seem much less familiar than the figures for whom they are named. With gadolinium and samarium, it’s surely the other way around: their discoverers are even more obscure than they are. Although you may not have heard of these two metals, they are both more abundant than tin and are found in every modern home. Gadolinium is used in magnetic recording discs and tape, while the miniaturized loudspeakers of personal stereos depend on highly magnetic alloys of samarium. Who, then, were Gadolin and Samarsky, this pair who sound like a Milwaukee firm of attorneys? And who was it that wished to praise them by rendering tribute in this uniquely enduring form?

  Johan Gadolin was born in Åbo in 1760 into a family that included two bishops of the city. Deviating slightly from the custom among clerical families of gentrifying one’s name into a Latin form (like Linnaeus), Johan’s grandfather had taken the name Gadolin, meaning great, from the Hebrew. Gadolinium would thus become the only element with its etymological root in Hebrew. His investigation of the black mineral sent by Arrhenius was the nearest Gadolin came to discovering an element. In 1827, his collection of minerals was lost when fire destroyed Åbo and its university; yttrium metal was finally isolated by others the following year. Gadolin lived into his ninety-third year, long enough to savour the honour of having the mineral gadolinite named after him though not long enough to see the arrival of gadolinium.

  Vasili Evgrafovich Samarsky-Bykhovets rose to the rank of colonel in the Russian Corps of Mining Engineers. Stationed in the southern Ural mountains in 1847, he noticed an unfamiliar friable mineral the colour of burnt caramel, which he was curious enough to have sent to Berlin for expert assessment, where a German mineralogist confirmed its novelty and recommended the name samarskite, following the convention in the field; samarium duly followed. Little more seems to be known about Samarsky, who made no further contribution to science.

  Compared with the Curies, or with pioneers such as Berzelius or Lavoisier or Davy, seemingly destined never to feature in the periodic table, Gadolin’s and Samarsky’s contributions seem minimal. Why were these two so favoured? If their achievements are not recommendation enough, we must turn for our answer to the later investigators of the elements that came to be called samarium and gadolinium.

  In 1879, Paul-Emile Lecoq de Boisbaudran, the wealthy son of a Cognac distillery owner, extracted certain salts of a rare earth element thought to be didymium from a sample of Urals samarskite. When he combined the salt solution with another reagent, he found that it did not produce the single precipitate he expected, but formed a sediment with two distinct phases. ‘Didymium’ was not an element at all, but a complicated mixture of unknown rare earths. Separating the two residues, he was able to show that one of them was a compound of a new element, which he named samarium. The following year Jean Charles Galissard de Marignac in Geneva, working with a different specimen of the ‘didymium’ mineral, isolated another new rare earth oxide. Lecoq confirmed de Marignac’s discovery and suggested the name gadolinium for this new element. (Then, five years later, Carl Auer finished ‘didymium’ off for good by showing that it contained two further true elements, neodymium and praseodymium.)

  So it was Lecoq who was responsible for shooting these relative nonentities to stardom in the periodic table. What was his motive? As we have seen, the last quarter of the nineteenth century was the zenith of European nationalism. Should he not have named samarium instead after France or Paris, where he worked, and gadolinium after Geneva or Switzerland, where his friend Marignac was based? In fact, he was probably wise not to try, for he had already shot his bolt in this direction, and done so in spectacularly controversial fashion.

  Lecoq had made his first contribution to the periodic table in 1875 when he isolated a new element from zinc ore. He presented a specimen of it to the French Academy of Sciences and named it gallium in honour of France. The trouble began a couple of years later when suspicions were raised that the naming was not quite the patriotic gesture it seemed, but was in fact Lecoq’s sly way of naming his discovery after himself–though the Latin for France might be Gallia, the Latin for coq was also gallus. The controversy was such that Lecoq was obliged to deny that he had chosen the name in self-homage. The episode would have been painfully fresh in his mind as he worked on the didymium minerals.

  After the embarrassment of gallium, it is possible that Lecoq simply wished to play it safe. And nothing was safer than following the accepted naming of the source minerals as closely as he could, replacing the -ite suffix of the geologist with the-ium of the chemist. It seems that he chose samarium because it was obtained from samarskite and gadolinium because it was obtained from gadolinite with no more ado. If so, it is chemistry’s loss. Many more minerals are named after geologists than elements after chemists, and not only because the list of minerals is long compared with the list of chemical elements. Mineralogists have a long and fine tradition of naming minerals after pioneers in their field, a practice which self-deprecating chemists have by and large been loath to emulate. As a consequence, many chemists who never got their name attached to an element nevertheless have a mineral named in their honour. Among these, cleveite, tennantite and wollastonite honour chemists who discovered elements. Gadolinium and samarium are two rare examples of the favour being returned. Gadolinium must stand as the memorial for all the chemists who have struggled to free a new element from its mineral source, and samarium for all the mineralogists who spotted that unusual mineral in the first place, chipped it from the native rock and brought it to the attention of the world. Neither Gadolin nor Samarsky are the greatest representatives that might have been chosen for this duty: they are the everymen of the elements.

  Ytterby Gruva

  Hearing the stories of the rare earths, I felt I was beginning to understand more deeply where the elements came from. Of course, I knew that in their totality they came from the earth, the sea and the sky. I wanted to penetrate beyond this obvious syllogism–everything is made of elements, so the elements are found everywhere–and identify a kind of locus classicus for these fundamental ingredients of all matter. After all, they are univ
ersal only in a sense. True, everything is made of elements, yet the pure elements themselves seem oddly elusive, almost always locked away in inscrutable minerals and compounds. Searching for the elements in nature was like raiding a bakery and finding plenty of cakes and buns but no sign of the flour and sugar from which they were made. You do not find nuggets of aluminium or rivers of mercury when you go for a walk in the country. Still, I thought, there must be places where the aura of the elements could be felt.

  It was time to visit a mine. I did not want to go to the Great Copper Mountain at Falun, the vast mining centre celebrated by E. T. A. Hoffmann, founded in the thirteenth century and still in commercial operation as recently as 1992. Nor did I want to go to Hisinger’s mines in nearby Västmanland. Berzelius and Hisinger had discovered cerium from ores dug there, but they had been searching for Gadolin’s yttria, the ore that took its name from the village of Ytterby, whose little mine gave the world not only yttrium but six other elements besides. I wanted to go to this most prolific source of the elements.

  Ytterby is the site of what is said to be the oldest feldspar and quartz mine in Sweden. It lies on the island of Resarö, one of an infinity of rocky islands east of Stockholm where Sweden disintegrates into the Baltic Sea. In the early eighteenth century, the feldspar quarried here went for making porcelain in Swedish Pomerania, while the unusually pure quartz was sent to Britain for making glass. But to the element collector, it was only when men examined the impurities that impeded these operations that the mine revealed its real treasure.