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Historical profile A clash of symbols Two centuries ago, a Swedish developed a system of symbols that formed the basis of the modern language of . Mike Sutton finds out more ANDY MARTIN ANDY

56 | Chemistry World | November 2008 www.chemistryworld.org 1808 was not a happy year for method of naming and classifying university still taught the outdated . Its unfortunate events In short chemical substances – perhaps . (Sweden’s included a Russian invasion, heavy  Two centuries ago, resembling the biological system Academy of rejected one of military defeats and substantial Swedish chemist developed by his fellow countryman Berzelius’ earliest research papers territorial losses. Many blamed this Jöns Jacob Berzelius Linneaus (Carl von Linné, 1707–78). because it used anti-phlogistic humiliation on the incompetence developed the basis for Despite the limited resources at his terminology.) But while his seniors of King Gustav IV, and disgruntled the modern chemical disposal, Berzelius was well suited to were catching up with the last army officers deposed him early in nomenclature the task. He had come to science at revolution in chemistry, Berzelius 1809. Yet amid the troubles of 1808,  His approach was a of revolutionary change, and was already exploring new frontiers. a young Swedish professor began inspired by the Linnaean while his older contemporaries had In 1800 a project which was to have a huge system of biological much to unlearn, he started with a announced the invention of his impact on the scientific world. While nomenclature – he clean slate. (the ‘’), Sweden’s Baltic empire crumbled, invented names When Berzelius and his step- sounding what Jöns Jacob Berzelius started building for those elements that brother began teaching themselves described as ‘an alarm-bell to a new empire of the , ruled didn’t have them chemistry in the 1790s, they used a experimenters in every part of from his laboratory in .  Berzelius’ symbols German textbook which accepted ’. One of those it alerted was He dominated European chemistry were initially hated by ’s new Berzelius, who began investigating for decades, until eventually his many , including theory of . Berzelius the medical uses of authority – like King Gustav’s – was his contemporary prepared oxygen in his lodgings at while a student at Uppsala. challenged by impatient young John , and it was Uppsala, and entertained his fellow- After moving to Stockholm, he men. But although new discoveries decades before they were students by burning lodged with Wilhelm Hisinger led chemists to modify or abandon generally accepted wire in it, – a mine-owner, mineralogist and many of his theories, his system of while the chemical experimenter who had chemical symbols survived, and access to Sweden’s largest voltaic it remains the basis of chemical pile. Together they performed nomenclature today. electrochemical decompositions, Berzelius was born on 20 August and from 1803 they published papers 1779. His father, a provincial foreshadowing some of Davy’s schoolmaster, died when the boy was later achievements. Berzelius soon four years old. A few years later his recognised that electricity would SHEILA TERRY / SCIENCE PHOTO LIBRARY PHOTO SCIENCE / TERRY SHEILA mother also died, after which he was have to feature in any future brought up by relatives. He attended account of chemical reactions, high school and university but the pathway towards a intermittently, taking various jobs satisfactory theory was still to fund his studies. A scholarship unclear. enabled him to complete his One avenue had already doctorate at Uppsala in 1802, been explored by Jeremias but he continued to struggle Richter, a German scholar financially. As municipal who attempted to derive physician to the poor of general laws of chemical Stockholm he earned combination from little, and a failed business quantitative studies of partnership (for marketing specific reactions. Berzelius ) left him in mistrusted Richter’s debt. However, his prospects calculations, but felt his improved in 1807, when he ideas deserved further became Professor of consideration. However, and Pharmacy at Stockholm’s the chemical statistics on School of Surgery (where he which any such general laws had previously worked as an must be based remained a unpaid assistant). subject of controversy. While Since no satisfactory Claude Berthollet asserted Swedish chemistry textbook that elements combined with was available for his students, each other in continuously Berzelius set about writing one. variable proportions, Louis The first volume of his Lärbok Proust maintained that they i Kemien appeared in the fateful always did so in fixed ratios. For year of 1808. Later volumes (and some time, analytical techniques revised editions) followed, and were were not precise enough to translated into other languages, settle the issue – indeed, one of becoming essential reading for the challenges which Berzelius aspiring chemists everywhere. But set himself was to determine the writing this introductory work exact proportions by weight of the seems to have been an educational constituent elements in as many experience for Berzelius himself, compounds as possible. In Britain, convincing him that chemistry was undertaking a was in a state of confusion which similar task. required clarification. In particular, In 1808, Berzelius heard about he felt the need for a more helpful Jöns Jacob Berzelius, the father of modern Dalton’s new chemical atomic

www.chemistryworld.org Chemistry World | November 2008 | 57 Historical profile

theory. Like Richter, Dalton was oppositely charged components. interested in chemical statistics. However, this conclusion led him to But while Richter’s work had made regard Dalton’s ‘atomic hypothesis’ little impact, Berzelius declared as being ‘attended with great that Dalton’s theory – if it proved difficulties’. correct – would be the greatest Berzelius thought that if chemical advance yet made in chemistry. The combination resulted from the Berthollet– Proust controversy had attraction between positive and highlighted the fact that some pairs negative , then two-element of elements can combine to form two compounds should be of the type or more compounds. A quantitative A + , A + 2B, A + 3B etc. He envisaged study of such compounds led Dalton a fixed number of similarly charged to his ‘law of multiple proportions’, B atoms distributed around a single stating that whenever two elements oppositely-charged A , with combine to form more than one the mutual repulsion between the

NATIONAL MUSEUM OF SCIENCE AND TECHNOLOGY, STOCKHOLM, SWEDEN STOCKHOLM, TECHNOLOGY, AND SCIENCE OF MUSEUM NATIONAL compound, the different weights of B atoms keeping them as far apart one element which combined with as possible. However, quantitative a fixed weight of the other are in a appeared to show that simple numerical proportion (often some compounds had atomic 1:1, 2:1 or 3:1). compositions of the 2A + 3B or Dalton was already convinced 3A + 4B type – structures which he – by physical rather than chemical thought must be rendered unstable evidence – that was composed by the mutual repulsion of similarly of atoms. Now, through the law of charged atoms. multiple proportions, he applied Eventually Berzelius accepted that the to chemistry. He such compounds did exist, though he regarded them as anomalies. about the atomic theory Berzelius’ table of atomic Later, his dualistic theory was more was based on his weights based on seriously shaken by the discovery electrochemical oxygen = 100 that negative could experience. In that replace positive in many crucial year of 1808, hydrocarbons, without destabilising he learned that Davy their or significantly had electrolysed changing many of their chemical molten soda and characteristics. It was not until the , yielding the 20th century that the theory previously unknown of valency confirmed that Berzelius inferred and . was on the right track – though the from the law that atoms Repeating Davy’s experiments, bonding proved to be far of each and performing further ones of his more complex than he, or his critics, had a distinctive weight own, convinced him that chemical imagined. However, we must beware and that when atoms of one element compounds were held together Berzelius’ laboratory of assessing scientists of past ages combined with those of another by electrical attraction between equipment in terms of how far their theories they did so in fixed numbers with simple ratios. However, Dalton could not determine the actual numbers of combining atoms from these ratios. He therefore assumed that these numbers were the simplest ones possible (unless there were indications to the contrary). On that basis, he proposed that the basic unit of water consisted of one atom of hydrogen plus one of oxygen. This led him, and others, to assign oxygen an atomic weight that was half the true value – an error finally laid to rest half a century later, thanks to Amadeo Avogadro and . In his publications, Dalton used graphic symbols to represent the atoms, arranging them in patterns to illustrate his ideas about their spatial relationships in compounds (see box p60). But while chemists generally welcomed Dalton’s law of multiple proportions, many had reservations about his atomic theory – and his

symbols. Berzelius’ initial scepticism COLLECTION SMITH FAHR EDGAR / SWEDEN STOCKHOLM, MUSEUM, BERZELIUS 58 | Chemistry World | November 2008 www.chemistryworld.org Historical profile

same initial. To iron he gave the symbol Fe, from ferrum – the ’s name in Latin. The Romans never knew metallic sodium, but SCIENCE PHOTO LIBRARY PHOTO SCIENCE they called common soda () , and from this Berzelius coined the name natrium for the element, giving its atom the symbol Na. Having organised the elements, he then tried to create a notation for compounds which revealed their chemical , as well as their constituent elements. This task proved more difficult, and Berzelius (and others) went on adjusting the system for years. At first he indicated the numbers of atoms with superscripts, so that dioxide was written SO2. Later, he tried denoting oxygen atoms by dots over the symbol of the oxidised element, representing sulfur dioxide as S¨ – though eventually, the numerical subscript version (SO2) became the standard form. At first, many chemists were not impressed by the Berzelian symbols – Dalton himself hated them. For some years even Berzelius did not use the symbols extensively in his publications, but by Dalton’s list of atomic the mid-century they were generally and molecular symbols accepted. Today, they still provide us with the tools for representing were ‘right’ or ‘wrong’ by present- own meticulous experimental results elements and compounds unknown day standards. A provocative error in the of Joseph Gay-Lussac’s to Berzelius and his contemporaries. which stimulates further enquiry law of combining volumes, Eilhard Outside the laboratory, Berzelius’ may do more for the advancement of Mitscherlich’s law of isomorphism, was relatively uneventful. He knowledge than a banal truth. and the atomic heat law of Pierre travelled widely in his later years, Berzelius’ theories – whether right Dulong and Alexis-Thérèse was honoured by foreign universities or wrong – contributed massively Petit. But his most enduring and learned societies, and continued to the evolution of chemistry as contribution was his system to take an interest in research after a discipline. This was because he of chemical notation. While his retirement in 1832. In 1835 he was continually testing them in preparing his 1808 textbook married Elizabeth Poppius (an old the laboratory, developing new he had encountered friend’s daughter), and received techniques and pieces of apparatus considerable confusion the title of Baron from the Swedish as he did so. Younger chemists over the naming of elements and monarchy. He died in 1848, four travelled from all over Europe to compounds, and he was determined decades after being elected to work under his supervision, and to do something about it. Having Sweden’s Royal Academy of Science carried his ideas and methods addressed the question in general in the eventful year of 1808. home with them. This network of terms in a French essay of 1811, he personal contacts, together with his explained his system in a series of Mike Sutton is a visiting fellow in the experimental work and his prolific articles published in a British journal School of Arts and Social publications, made him the centre of in 1813 and 1814. at Northumbria University, UK European chemistry for more than Following the precedent set by two decades. Linneaus, who assigned a definitive Further reading Berzelius and his co-workers Latin name to every and , M P Crosland, Historical Studies in the Language of Chemistry, London: Heineman, 1962 made many significant discoveries, Berzelius adopted – or invented ‘Berzelius C C Gillispie (Ed), Dictionary of Scientific including several new elements – Latin terms for the elements Biography, New York: Charles Scribner’s Sons, 1978 – , , , whenever possible. He took the adopted E M Melhado and T Frängsmyr (Eds), , and sundry first letter of this name (capitalised) – or invented – Enlightenment Science in the Romantic Era: The . He also produced the as its atomic symbol, adding a Chemistry of Berzelius in its Cultural Setting, Latin terms for Cambridge: Cambridge University Press, 1992 most reliable table of atomic weights distinguishing second letter (in J R Partington, A (volume then available, by interpreting his lower case) for elements with the the elements’ 4), London: Macmillan, 1964 60 | Chemistry World | November 2008 www.chemistryworld.org