in your element Green bismuth ram mohan looks at how bismuth — a remarkably harmless element among the toxic heavy metals in the periodic table — has sparked interest in areas varying from medicinal to industrial chemistry.

ismuth, the 83rd element in the many bismuth compounds are even less is also, along with graphite, one of the periodic table, has been known since toxic than table salt (sodium chloride)4! This most diamagnetic materials known — it Bancient times, but was often confused makes bismuth unique among the heavy is repelled by a magnetic field — and has with lead and tin. In 1753, Claude François metals, and has earned it the status of a found applications in magnetic levitation Geoffroy from France demonstrated that ‘green element’. For this reason, the world of (Maglev) trains, which can achieve speeds of bismuth is distinct from these elements. cosmetic and medicinal chemistry has paid over 250 mph. The word bismuth itself is derived from it particular attention. Bismuth oxychloride, More recently, bismuth and its the German word ‘wismuth’ (white mass). for example, is used to impart a silvery sheen compounds in the +3 oxidation state have Studies showed that it was used as early to cosmetics and personal care products. It is found significant applications as green Lewis as the sixteenth century by the Incas, who also marketed as BIRON powder, which acid catalysts in organic synthesis. The low mixed it with tin to prepare bismuth bronze has found applications in catheters for toxicity of bismuth salts, their for knives1. Bismuth was also the instrument diagnostic and surgical procedures ease of handling and relatively of alchemy fraud in the London Stock owing to its radio-opaque nature, low cost make bismuth Exchange — in the 1860s, a Hungarian and bismuth nitrate ox ide is used compounds more refugee named Nicholas Papaffy convinced as an antiseptic during surgery. attractive than other a large number of investors to support Perhaps the most well- corrosive Lewis his alleged method to transform bismuth known bismuth-based acids6. In addition and aluminium into silver. This led to a medicine is Peptobismol, to developing surge in the price of bismuth on the metal now a widely available applications of market, and the opening of a new company over-the-counter bismuth(iii) in Leadenhall Street (home of the London medicine in the US compounds in Metal Exchange), but by then Papaffy had for stomach disorders. organic synthesis, absconded with the rather large sum of The active ingredient we have developed some bismuth-salt- £40,000 (ref. 2). is bismuth oxide salicylate. catalysed green-chemistry experiments Bismuth is mainly found in the ores It was first concocted by a doctor in his for use in undergraduate laboratories7. bismuthinite (bismuth sulfide) and bismite home in the early twentieth century to cure Bismuth is a therefore remarkable eco- (bismuth oxide), but also occurs in its ‘cholera infantum’, an inflammatory disorder friendly metal with numerous applications elemental state, in the form of crystals with that afflicted infants suddenly, causing in everyday life. With increasing awareness an oxide layer of varying width that reflects diarrhoea, vomiting and sometimes death5. for the environment, one can expect to iridescent colours (pictured). It is commonly Although the exact mechanisms of its action see a rise in the use of green metals such obtained as a by-product in copper, lead are not well understood, it is believed that it as bismuth in applications ranging from and tin mining, and is therefore relatively lines the abdominal walls with a protective organic synthesis to engineering. ❐ inexpensive for a rare metal. coating that prevents further irritation. Frequently referred to as the heaviest Bismuth has many interesting properties RAm mOhAn is in the Department of stable isotope of any element — and for all that have led to several applications in Chemistry, Illinois Wesleyan University, practical purposes it is — bismuth-209 is industry, and it is commonly used in solders. Bloomington, Illinois 61701, USA. nonetheless slightly radioactive. This was It is one of the few substances (water being e‑mail: [email protected] first predicted by theoretical studies, then another) that expands on solidification, demonstrated in 2003 by astrophysicists in and has been used to prepare low-melting References France3, who showed that bismuth-209 has typesetting alloys that need to expand 1. Gordon, R. B. & Rutledge, J. W. Science 223, 585–586 (1984). 2. Brock, W. H. The Norton History of Chemistry 1st edn 19 an incredibly long half-life of 1.9 × 10 years to fill printing moulds. Bismuth trioxide (W. W. Norton, 1993). (the age of the universe is estimated to be is also the main ingredient in fireworks 3. Marcillac, P. D., Coron, N., Dambier, G., Leblanc, G. & about 1.4 × 109 years). called dragon’s eggs — those that produce Moalic, J.-P. Nature 422, 876–878 (2003). Despite its location amid toxic heavy a visual display before exploding with a 4. Suzuki, H. & Matano, Y. (eds) Organobismuth Chemistry metals in the periodic table, bismuth and sharp crack. Bismuth has become popular (Elsevier, 2001). its compounds are remarkably harmless — as a replacement for the highly toxic metal 5. http://www.pepto-bismol.com/ 6. Leonard, N. M., Wieland, L. C. & Mohan, R. S. Tetrahedron lead, as it has a comparable density and 58, 8373–8397 (2002). many countries now prohibit the use of 7. Roesky, H. W. & Kennepohl, D. K. (eds) Experiments in Green and lead shot for hunting water birds. Bismuth Sustainable Chemistry 50–56 (Wiley-VCH, 2009). Hg TI Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm 336 nature chemistry | VOL 2 | APRIL 2010 | www.nature.com/naturechemistry

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