A taste of artefact

Qui delle divertite passioni
per miracolo tace la guerra,
qui tocca anche a noi poveri la nostra parte di ricchezza
ed è l’odore dei limoni

Eugenio Montale, I limoni

[…]Here, by some miracle, the war
of troubled passions calls a truce;
here we poor, too, receive our share of riches,
which is the fragrance of the lemons[…]

Eugenio Montale, The lemons (English translation of this poem found online).

Genova and The lemons

Take a map of the regions of Italy (or simply open an online mapping service…), and look northwest: a boomerang arches and embraces the stretch of sea in front of Corsica. This is Liguria and Genoa (Genova, in Italian), its historical and current capital, lies at the centre of this arc, like a keystone in a vault. Affluent port city in the Middle Ages and financial hub, Genoa coexisted with (but at times also fought against) Venice, the other ‘seafaring Republic’, vying for commercial predominance and for the control of trading routes in the Mediterranean. Yet, Genoa has arguably beaten its arch-rival by a naval mile in the contest of literature and music. For example, many think that the finest cantautore (singer-songwriter) of all Italian 20th-century musica d’autore (untranslatable, but literally ‘author’s music’: think of the Italian counterpart to French chanson) is a native of Genoa,  Fabrizio de André. He has even been hailed as ‘the greatest Italian poet of the last hundred years’: although this is definitely far-fetched, he did bring about a sea change in the landscape of Italian music, by writing songs about themes previously neglected, or tacitly banned, in the love-centred and somewhat soppy lyrics of contemporary singer-songwriters.

Now leave Genoa behind you and choose where to turn, right or left: take a look at the western and eastern ends of Liguria, and you will see two of the most celebrated, most influential Italian writers of the 20th century. Prose and poetry face each other: Sanremo, in the western tip, almost bordering France, is the Riviera resort where the novelist, essayist and short story writer Italo Calvino (1923-1985) spent his childhood and youth years; opposite across the sea lie the Cinque Terre (lit. ‘Five Lands’), an area of outstanding natural beauty and World Heritage Site, which greatly inspired the earlier lyrics by Eugenio Montale, born in Genoa in 1896, arguably the greatest Italian poet of the last century. Liguria is the land where mountains choose to escape their earthly nature and dive into the sea, the great salty blue beyond the shore that features in so many of Montale’s first poems; Liguria is the land where the rugged coastline can become complex and intricate, almost like a fractal, like the combinatorial or structuralist schemes informing some of Italo Calvino’s works. Invisible cities is the title of one of them: short descriptions of these “invisible cities” are arranged according to a thematic structure that follows an iterative order throughout the book. The overarching frame story of Invisible cities is Marco Polo’s fictional conversation with Kublai Khan about these cities, something clearly inspired to the 13th-century travel accounts of the real Marco Polo, The Travels of Marco Polo. A theme of Invisible cities includes “cities & memory”, and if I were to write my own account of the cities of my life, I would definitely place Genoa in this group…My invisible Genoa looks like Zora, one of Calvino’s invisible cities:

“Cities & Memory 4

Beyond six rivers and three mountain ranges rises Zora, a city that no one, having seen it, can forget. But not because, like other memorable cities, it leaves an unusual image in your recollections. Zora has the quality of remaining in your memory point by point, in its succession of streets, of houses along the streets, of doors and windows in the houses, though nothing in them possesses a special beauty of rarity. Zora’s secret lies in the way your gaze runs over patterns following one another as in a musical score where not a note can be altered or  displaced. The man who knows by heart of Zora is made, if he is unable to sleep at night, can imagine he is walking along the streets […] This city which cannot be expunged from the mind is like an armature, a honeycomb in whose cells each of us can place the things he wants to remember.[…] Between each idea and each point of the itinerary an affinity or a contrast can be established[…]”
(Italo Calvino, Invisible Cities, translated by William Weaver, Vintage Editions).

There are cities where we sense a resonance with their vibrations: we have never lived there, we do not even love them at first sight, and yet we strangely feel at home. There is usually no point in wondering why: it is just like a subliminal perception. So is Genoa for me, city and memory, and when I tread the stones of its twisted lanes I know that I am a stranger, a casual visitor to a city that maybe I do not even like; nevertheless, I feel at ease, moving effortlessly on those, in Montale’s words, frail “spiderwebs of the memory”, as if a vague reminiscence could still help me find my way. I navigate the visible city following the map of the invisible Genoa within me. On rainy days, gray skies loom large above the Ligurian Sea and you know that they are there to stay: the infamous ‘Genoa low‘ clashes against the mountains, squeezing rain onto the city from its spongy clouds. This is when I would think about Montale’s poem I limoni as I am wandering aimlessly, victim of a literary Wanderlust:

La pioggia stanca la terra, di poi; s’affolta
il tedio dell’inverno sulle case,
la luce si fa avara – amara l’anima.

The rain exhausts the earth then;
winter’s tedium weighs the houses down,
the light turns miserly-the soul bitter.

Then, as I picture myself following in Montale’s footsteps, like a Parisian flâneur in search of a flashing idea, I, too, yearn for that sudden surprise, the golden light of ripe lemons appearing all of a sudden after you turn into a narrow alleyway, the plump fruits hanging heavily from a lemon tree grown in a pot, standing in a courtyard.

Quando un giorno da un malchiuso portone
tra gli alberi di una corte
ci si mostrano i gialli dei limoni;
e il gelo del cuore si sfa,
e in petto ci scrosciano
le loro canzoni
le trombe d’oro della solarità.

Till one day through a half-shut gate
in a courtyard, there among the trees,
we can see the yellow of the lemons;
and the chill in the heart
melts, and deep in us
the golden horns of sunlight
pelt their songs.

A gate left ajar lets us catch a glimpse of the lemons, we would like to go and touch and smell the zesty fragrance of the rind. Yet, the concierge of the mansion spots us and rushes to locks us out. There we stand alone, in the torrential winter rain.

Chemistry and the invisible lemon.

Oxford is a very visible city, but lemons are rarely to be found. This is in stark contrast with Liguria, a land where citrus fruits have always flourished in the mild climate of the region, thanks to the protective embrace of the mountains. Some online sources report the whopping figure of 20-25 million lemons produced in the sole city of Sanremo in  1662. At the same time, somewhere north of the Alps, lemon trees started to be grown, too, requiring orangeries, glasshouses and conservatories: the renowned Botanic Garden of the University of Oxford still houses a couple of citrus plants in its conservatory, where they have been lovingly kept warm ‘since the 1600s’, as its website proudly states.

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Anyway, it it time for chemistry and the kitchen. Once upon a night I found myself at a friend’s place, ready to do one of my favourite things: improvisation (aka “messing up”) in the kitchen, something I seldom allow myself to do because of the imprinting of my laboratory training. A jar of ready-to-use chickpeas peeping from a shelf was too strong a temptation for us to resist: let’s make some hummus! By the way, one could try and unify the entire Mediterranean world1 (and beyond) under the name of the blessed chickpea. We set sail from the western Andalusian coasts, where espinacas con garbanzos (spinach and chickpeas) are a staple dish, we lay at anchor for a stopover at any port of the Ligurian Sea, where the whole Riviera from Nice to Pisa feasts on flatbread made from chickpea flour (known as farinata in Liguria and socca in the Nice area), and, following the ancient sailing routes, we finally reach the shore somewhere in the eastern Mediterranean, for example the port of Acre, where ships from Genoa would once dock, load cargo, and trade, and where hummus will now keep our hunger pangs at bay.

The soft chickpeas easily yielded to the blade of the blender. Then I added some sesame paste, or tahini, and went on mashing the delicious mixture, tasting it on the go. Looking scrumptious. At this point, I turned to my friend and asked her: “Could you pass me a lemon or some juice please?”. Panic. The air stood still, those silent seconds where people cross their gazes without saying a word, knowing all too well what comes next. “I’ve got no lemon juice, I’ve got no lemons”, said she. Then she pointed to a small, bright green lime: “Use that instead!”, she suggested. I could have, maybe I should have, taken the lime and squeezed it, but I could not help grasping this opportunity for some unexpected “messing up” in the kitchen. I felt like frolicking and so I turned down the offer of the alternative citrus fruit and started thinking: “OK, let’s say that the little lemon juice added to the hummus is just there to correct the flavour: I don’t expect the texture of the hummus to depend a lot on the change in pH…the texture’s more a matter of balance between thick tahini and chickpea water”. In a sense, now I think that I was following the path traced by Italo Calvino in his quote above: “Between each idea and each point of the itinerary an affinity or a contrast can be established“.

Acidity: that is what lemon juice is (almost) all about. The holy book of all food lovers2 shows that the juice is 5 % in acids (as weight/weight percentage). The main sour character is citric acid, an interesting compound that ought to deserve much more than this brief mention in a blog post about hummus. For the moment, let us just remind that it is an allowed food additive, under the EU code E 330. Malic acid comes in a far second in the acid ranking, well below 0.5% 3 . Biochemistry lovers will remember that both citric and malic acid feature in the Krebs cycle, or citric acid cycle.

Then there is a sweet note to the flavour of lemon juice, which arises from the juice sugars, having a total weight content of  3.16 %, slightly lower than that of the acids.

However, as we all know, lemon is much more than its juice: the rind of the golden fruits has a pleasant, smell, arising from some fragrant molecules: limonene and citral in the first place. If we take a look at the molecular structure, we understand the significant difference between the reactivity of these two compounds.

Limonene is a sturdy molecule that belongs to the family of terpenes. You can mistreat it to a certain extent, and it will still be fine. It is a hydrocarbon, there is not much one can do to it unless one targets the double bonds. What I have drawn here is the stereoisomer found in lemon (question for those chemists who loved organic nomenclature as undergrads: is it R or S ?).

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Citral, instead, seems poised to shortcut and curl into a comfortable 6-membered ring, with a little help from some acid, and all it takes for citral to become an aromatic molecule is some oxidiser. And beware: citral is actually a mixture of two isomers, neral and geranial, having a different smell.

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Too bad citral falls apart in harsh conditions: a lemon-scented bleach or household detergent is the hallmark of cleanliness; if only citral were not so delicate! The quest for a substitute that could be stable in acidic and/or oxidising conditions has almost acquired a legendary status in the perfumery literature. It is cited for example in The Secret of Scent by Luca Turin, a must-read for perfume lovers, and maybe the focus of a future blog post.

Back to the kitchen, how could we introduce some acidity and some lemon-like flavours in the hummus-to-be? Spicing it up with the right ingredients, that was the way to go, but what to add? Fortunately, the kitchen larder was open and lots of spices were beckoning me over: I would quickly find what I needed.

First I sprinkled the hummus with a dark-red powder having a distinctive, tart note: there was sumac, hailing from the same part of the world as hummus itself, and the combination of the two is a match made in heaven. Sumac is a very peculiar spice in that it imparts acidity thanks to its high content in…yes, here we go, malic acid. Moreover, sumac came in with an additional bonus: it also contains some limonene.

Then I opened a small bag full of a brownish powder, and I savoured the fresh smell of ground coriander, its citral notes chiming with the taste I was trying to compose. I sprinkled the hummus with some coriander, I mixed, then I added a bit of olive oil and served. In the end, the lemon-free hummus was given the thumbs up by my friend.

But can one really assemble a lemon from, er… ‘first principles’, bottom-up? Do chemistry and cooking, which are both essentially combinatorial in nature, really have something in common?4

The curse of the alchemist

Regardless of the answer to those questions, what matters here is the idea of artefact contrasted to natural. Oh, here’s another Pandora box popping open…I promise that I will keep it short and simple (look elsewhere5 for the small print), while trying to be careful as I cross this minefield.

In a nutshell, (al)chemists have often been accused of concoct counterfeits, bogus surrogates of the real stuff, their ‘crime’ straddling plain quackery and outright fraud. From the arguments of Scholastic philosophers to today’s alleged supremacy of the natural (whatever it means) over the artificial or the chemical, the perceived image of (al)chemists seems to follows, at least ostensibly, a unique thread throughout the centuries. Dante Alighieri, in his Divine Comedy, places alchemists deep down in hell,  in the Eighth Circle along with fraudsters, and more specifically in the same bolgia (a hole in the ground) as falsifiers. For the 10th-century philosopher Avicenna, alchemy is a form of deception, while the great Thomas Aquinas dismissed alchemy simply as an anomaly outside nature (‘praeternatural’). Today, the label ‘natural’ is often misused as a tacit antonym of ‘chemical’, leading to all sorts of paradoxes, chemistry as a scientific discipline being caught in the crossfire.

Yet, is the rift between the natural and the artificial still so deep? After all, the fear of some chemicals could easily coexist with an appreciation of others5, perceived as a boon to the society’s well-being. Indeed, the 2015 survey Public attitudes to chemistry in the UK by the Royal Society of Chemistry shows that people are quite pragmatic about chemicals, to say the least. Figures show that 60% of the public agree that “everything is made of chemicals” and 70% are in agreement with the statement “everything including water and oxygen can be toxic at a certain dose”. Paracelsus is alive and well, and we chemists should really take the time to sit down and reflect on our own preconceptions about the chemophobic public.

Calvino’s tarots

Calvino prematurely died 30 years ago. His legacy to Italian literature and culture is still under debate: some critics find that Calvino’s style and poetics have provided the following generations of writers with an invaluable framework; others, however, believe that his influence has ended up looming large on Italian literature, more as a magnificent hurdle to overcome than as a reference point.

At that time of his death, the writer was working on a series of lectures on literature to be delivered at Harvard. Fortunately, his notes were edited and collected in a book available in English translation, Six memos for the next millennium. Six seminars, each on a ‘value’ (and its opposite) that Calvino considered worthy of attention with an eye to 21st-century literature. Six memos for the next millennium and Invisible cities are similar in that they single out beacons, vital reference points helping us to navigate, respectively, the vast universe of literature or the everyday chaos that surrounds us. But like any map, we are free to choose if to trust and follow them or not.
At this stage, however, I would like to remember another book, The Castle of Crossed Destinies, in which Calvino crafts short stories by interpreting tarot cards randomly placed on the table. In this novel, mute characters who meet by chance in a castle or at an inn try to tell their own stories by picking, laying and arranging tarot cards; an onlooker, standing in for the writer,  watches and tries to work out what the other characters try to narrate. From this point of view, The Castle of Crossed Destinies also draws on those great works of 14th century literature, Decameron by Boccaccio and The Canterbury Tales by Chaucher, which feature a group of characters taking turns at telling stories -and turns are part and parcel of all card games.
Anyway, in one of these tales, Calvino sees the trump card of The Magician (aka The Juggler, or Le Bateleur in the French original) as a proxy for the (somewhat stereotypical) alchemist, who tells how he sold his soul to the devil. Sounds familiar?

[…]our companion was, in fact, one of those scholars who scrutinize alembics and crucibles[…]trying to wrest from Nature her secrets, and especially that of the transformation of metals[…] from his earliest youth […]he had no other passion […] save the manipulation of the elements, and for years he had waited to see the yellow king of the mineral world precipitated in the depths of his cauldron.[…] This event must have been indicated in the following card, which was the enigmatic First Arcanum, sometimes known as  The Juggler, in which some see a charlatan or magician performing his tricks […].

(The tale of the alchemist, pp. 16-17)6

The second tale talking about alchemists is a much more intriguing piece, in my view: the alchemist is compared and contrasted to the figure of the knight-errant, and both of them come in with an alter ego, Doctor Faust (who else?) for the alchemist, and Perceval for the knight-errant. Put it in chemical terms, I see two resonance structures of the same molecule: the alchemist who “must (instead) free himself of all egoism […] to achieve transformations of matter“, who “tries to make his soul become as unchangeable and pure as gold” and Doctor Faust, “who inverts the alchemist’s rules, makes the soul an object of exchange” (Two tales of seeking and losing, pp. 90-91).

So, what kind of (al)chemist do you think you are?

Only now that I look back do I realise that this post has gone a long way, from Liguria through hummus to Calvino and eventually the Faustian ambitions of his alchemist. It is as if I were trying, as Marco Polo did in his travel accounts to Kublai Khan in Invisible Cities, to give an overview of the entire known world by piecing together his memories. Had he met the Faust of The Castle of Crossed Destinies, he would have agreed with him:
There is not an all, given all at once: there is a finite number of elements whose combinations are multiplied to billions of billions, and only a few of these find a form and a meaning and make their presence felt amid a meaningless, shapeless dust cloud; like the seventy-eight cards of the tarot deck in whose juxtapositions sequences of stories appear and are then immediately undone” (Two tales of seeking and losing, p. 97).

Faust, this time I have got an ace up my sleeve, too.
Such stuff, that all is made on.

Chemistry.

Footnotes

1. Neighbours are often too similar to love each other. So, there was a time when Pisa and Genoa, too, were at war. Memories of ferocious naval battles and bloodshed are still alive in the two cities. The same goes with the ongoing Israeli-Palestinian conflict. A humble suggestion: the chickpea could be the seed of durable peace… When I first wrote this footnote I was kind of joking, now I have found out that someone in Isreal has already done so: “Hummus joint gives Jewish-Arab tables 50% off“. As the newspaper writes with a witty humor, that’s chickpeace.

2. On Food & Cooking, Harold McGee, Hodder & Stoughton, 2004

3. Liu, Y., et al., History, Global Distribution, and Nutritional Importance of Citrus Fruits, in Comprehensive Reviews in Food Science and Food Safety, 2012, 11, 530–545. doi: 10.1111/j.1541-4337.2012.00201.x

4. According to a Lebanese cook who took part in a food programme on the French radio, On va déguster, replacing lemon with sumac in hummus is tantamount to blasphemy. If you speak French, you can listen to the programme, focussed on Middle Eastern cuisine from Aleppo to Tel Aviv through Lebanon.

5.Chemistry: The Impure Science, Bernadette Bensaude-Vincent and Jonathan Simon, Imperial College Press, 2012 (2nd edition).

6. All quotes from The Castle of Crossed Destinies, translated from the Italian by William Weaver, Secker & Warburg (London), 1976

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Open doors at Chemistry (2): Cupcakes on the Table

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Periodic flavours of the elements

This post is a ‘slideshow’ of pictures of the exhibition on the Periodic Table organised by the Department of Chemistry of the University of Oxford on 19th September 2015, following the public lecture of the day before. One of its highlights was an enormous knitted periodic table: a team of fourteen members of the staff of the Department first painstakingly knitted the individual square ‘patches’ housing the elements, which were then assembled, mounted on fabric and completed with plastic letters printed on a 3D printer.

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Aerial view of the knitted Periodic Table…
…and a caption putting it into the wider context

Gordon Woods, enthusiastic collector of Periodic tables and related items, provided a magnificent Ukrainian version. Securing it to the wall required the same titanic effort that, long ago, Mendeleev put into trying to make sense of the periodicity of the elements!

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A different arrangement for the same elements

The complete set of the elements, a generous loan from Max Whitby and his colleagues at http://www.periodictable.co.uk, was another leading piece of the exhibition, garnering again much attention from visitors of all age. Two metal cylinders, one made of magnesium, the other made of titanium, were tremendously useful in demonstrating the dramatic difference in weight between lighter and heavier metals.

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The hands-on table

A series of posters addressed the historical development of ideas about the periodic classification of the elements, along with the philosophical significance of the periodic system of the elements and its influence on culture and literature.

A first poster showed the timeline of the long journey from simple substances to atomic numbers. Note the accumulation of red-dot years just after the Karlsruhe Congress.

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Periodic classification of the elements from Geoffroy to Moseley

On the philosophy poster, Aristotle and Epicurus duel to establish the structure of matter and the nature of the elements; at the same time, chemistry tries to reassert its own peculiarity, dispelling the undeserved reputation of being a lesser science than physics or biology, without great ideas. Well, what about the periodic law and the chemical bonding, then? In addition, the continuous development of the ideas on the periodic classification of the elements over two centuries provides a stark contrast to the model of scientific progress proposed by philosopher of science Thomas Kuhn (quieter periods of consensus – the so-called normal science – come abruptly to an end when breakthroughs challenge the previous paradigm, marking the onset of a revolutionary phase).

Next, we explore the interface between the periodic system and literature. Starting from a brief overview of three concepts, periodicity, system and element, which feature for example in postmodern narrative, we address an interview with late Oliver Sacks, who, while terminally ill, compared the years to his life to the atomic number of the elements that he had in front of him on his desk (see the set above). Growing old is a form of nucleogenesis of heavier elements, and, alas, he stopped at 82 last month. The highlight of the poster, however, is Primo Levi’s collection of short stories Il sistema periodico (lit. The Periodic System, but translated in English as The Periodic Table). Excerpts from five stories feature on the poster, and this passage from Silver is an apt description of Primo Levi’s intentions when he set about writing and assembling his book:

I was in search of events, mine and those of others, which I wanted to put on display in a book, to see if I could convey to the layman the strong and bitter flavor of our trade, which is only a particular instance, a more strenuous version of the business of living. […] It did not seem fair to me that the world should know everything about how the doctor, prostitute, sailor, assassin, countess, ancient Roman, conspirator, and Polynesian lives and nothing about how we transformers of matter live: […] I would deliberately neglect the grand chemistry, the triumphant chemistry of colossal plants and dizzying outputs, because this is collective work and therefore anonymous. I was more interested in the stories of the solitary chemistry, unarmed and on foot, at the measure of man, which with few exceptions has been mine“.

For Levi and Sacks, elements are material symbols, stepping stones emerging from the turbulent stream of our lives, which offer us a grid to make sense of the “business of living”, allowing us to keep afloat when facing sorrowful memories, or aiding us to come to terms with our own mortality.

Primo Levi’s portrait shown on the poster is a caricature kindly provided by Italian caricaturist, humor artist and illustrator Marilena Nardi,

20150919_103632Older and newer periodic tables were displayed side-by-side: on the left, a photographic reproduction of a 1920s Periodic Table in use at the University of Turin at the time when Primo Levi was reading chemistry at that university (courtesy of the Archivio Scientifico Tecnologico dell’Università di Torino and the Centro Studi Primo Levi); on the right, a more recent, highly visual version. Which is your favourite?

20150919_104542Elemental cupcakes, arranged in the familiar sequence of periods and groups, were offered to visitors to raise funds for the Sobell House Hospice, in memory of colleague and friend Dr Kristína Csatayová.

Lastly, a few words on my personal experience as science communicator. The audience was primarily composed of Oxford alumni (after all, the exhibition was organised within the framework of the Oxford Alumni Weekend) from all walks of life, whose background was, as a consequence, extremely varied, ranging from no prior knowledge of chemistry, or a lay interest in the discipline, to a decade-long career as chemistry teacher in secondary schools. I quickly realised that I would need to brace for a volley of questions covering the entire gamut of all things periodic. At first, I found it challenging to pitch my answers at the right level, but then I sort of naturally adjusted, striking a balance between depth and breadth. In particular, it was the gist which had to be conveyed in the clearest way, and it was very helpful for me to think in terms of ‘take-home messages’, as in scientific talks. I remember this elderly lady with curious eyes and a keen interest in the poster on the historical evolution of the periodic classification of the elements, who asked me to help her to understand how the periodic system eventually morphed into the familiar arrangement. I was aware that I could never have covered the entire ground from Geoffroy to Moseley, and so I decided to compare and contrast the figures of Lavoisier and Dalton. Luckily, she had a smattering of history of chemistry, which made my task massively simpler, and, in her words, very successful.
On the other hand, I could also mention the Socratic attitude of another visitor: I let myself be dragged into a philosophical discussion on periodicity (and I am proud that I could stand my ground), which eventually led us to agree that individual elements are material simulacra: at the end of the day, what matters is the position in the periodic system, the properties associated with it, and the network of relationships creating groups and periods.

If you are an art lover, do not forget to visit the exhibition Art of the Elements at Compton Verney art gallery! A radio review was broadcast by BBC Radio 4 and is available online.

And I would like to conclude, it goes without saying, by acknowledging the entire team of volunteers who worked behind the curtains and on stage to contribute to this very successful exhibition on the Periodic Table.

Open doors at Chemistry (1): Unbolting the Periodic Stable

The nobility of Man[…] lay in making himself the conqueror of matter, and [that] I had enrolled in chemistry because I wanted to remain faithful to this nobility. That conquering matter is to understand it, and understanding matter is necessary to understanding the universe and ourselves: and that therefore Mendeleev’s Periodic Table, which just during those weeks we were laboriously learning to unravel, was poetry, loftier and more solemn than all the poetry we had swallowed down in the liceo*; and come to think of it, it even rhymed!

* liceo = Italian secondary school for students aged 14-19
Primo Levi, Iron, in The Periodic Table, translated from the Italian by Raymond Rosenthal

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The façade of the Inorganic Chemistry Laboratory, South Parks Road, Oxford

Friday 18th September 2015 marked the beginning of a series of events unfolding at the interface between chemistry and art and culminating in the exhibition Periodic Tales: Art of the Elements, which will take place at the Compton Verney Art Gallery (Warwickshire, UK) from 3rd October to 11th December. This art exhibition was launched during a special public lecture at the Inorganic Chemistry Laboratory (Department of Chemistry) of the University of Oxford, one of the first events of the 2015 Alumni Weekend of the University. On the following day, the programme continued with tours of the Department of Chemistry and a drop-in exhibition on the Periodic Table.

What follows is an insider’s account of the lecture and the exhibition, as seen through the lens of a member of the Alchemists, the outreach volunteers of the Department of Chemistry who guided the tours and contributed to organizing and staging the Saturday exhibition. If you want to see with you own eyes and relive the moment, have a look at the video/audio recordings of the Friday public lecutre, available online.

Vicious patterns and shiny reflections: the multifaceted personalities of the elements

No matter how materialistic our philosophical stance may be, we all agree that the human nature is unfathomable, a mystery still to be unravelled. Yet, one could possibly simplify this daunting challenge by trying to identify recurring patterns, repeating units that contribute to shaping who we are. The artwork Fuse (cast iron, Antony Gormley), reproduced on the poster of the public lecture Periodic Tales, can be seen at one time as a poignant reminder of this relentless quest and as the result of the recombination of elementary building blocks in the form of polyhedra. After all, weren’t the elements of ancient philosophy shaped, according to Plato, as regular solids? On the other hand, a more chemical eye could identify in Gormley’s polyhedral man the typical profile of electron microscopy images of metal nanoparticles, with their (more or less well-defined) facets and different crystal orientations.

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The poster of the public lecture “Periodic Tales”

When I arrived at the lecture theatre, the audience was flocking in, and I decided to perch onto one of the seats at the back, ready to follow Periodic Tales from this vantage point. No sooner had I taken my seat than I realised that chemical elements were already clashing in front of me, as my very 20th-century notepad-and-pen combination sat next to a sleek laptop computer. Silicon and rare earths versus oxygen, hydrogen and carbon: an apt prologue to the tales of the elements.

Three speakers took turns on the floor before the question time: Hugh Aldersey-Williams, writer and author of Periodic Tales1; Georgiana Hedesan, Wellcome Trust postdoctoral research fellow in Medical Humanities, and Peter Battle, professor of Chemistry at Oxford. The lectures were introduced by Philip Mountford, head of Inorganic Chemistry at Oxford, and Stephen Tuck, director of The Oxford Reserach Centre in the Humanities (TORCH). Periodic Tales is one of the last events of the 2014-15 series of TORCH lectures, book discussions, seminars and debates exploring the frontiers between humanities and science.

Hugh Aldersey-Williams briefly surveyed the landscape of elements and their relevance to literature, art and popular culture: as the author remarks on his website, “the elements come to us“, sometimes openly declaring their presence, while concealing themselves at times. Given my passion for the written word, I found the literary quotes particularly intriguing, in particular the following from Shakespeare’s Merchant of Venice, which, in the author’s own words, was a veritable “epiphany” for the entire project of Periodic Tales. Portia, the leading female character of the play, offers her suitors three caskets, made of gold, silver and lead, only one of which contains Portia’s portrait. He who finds it will win her hand. Aldersey-Williams explained that he regarded the caskets as material allegories of human vices and virtues, inextricably correlated with the character of the different metals (following T.S. Eliot I would say that the caskets are objective correlatives). In Shakespeare’s own verses2:

The first, of gold, who this inscription bears,
‘Who chooseth me shall gain what many men desire;’
The second, silver, which this promise carries,
‘Who chooseth me shall get as much as he deserves;’
This third, dull lead, with warning all as blunt,
‘Who chooseth me must give and hazard all he hath.’
How shall I know if I do choose the right?

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A suitor of Portia’s wondering which casket to choose

Thus, gold is the epitome of avarice, silver an invitation to trade (recalling the use of this metal as currency), while lead represents the fatalist choice, because, as the speaker remarked, lead has always been linked with fate, hazard, death and the acceptance thereof: for example, augurs could foretell the future by looking at molten lead that solidifies into bizarre shapes when cast in a bucket full of water. Lead was the material of choice for dice in the Roman world, because heavy dice fall more decisively: to have an idea, think of Caesar reportedly saying “Alea iacta est“, “The die is cast”, when crossing the Rubicon. That lead and death walk hand-in-hand can be explained by mentioning the toxicity of this metal, and this is such a pervasive topic, a powerful combination, that it keeps surfacing again and again in literature and culture: the short story dedicated to the dull metal in Primo Levi’s The Periodic System is a tale of Rodmund, a craftsman/miner of Germanic origins that roams Europe in search of (lead-containing) ores, to extract the metal which will make him rich while condemning him to fatal illness and death, the curse cast on his lineage by the daily handling of the heavy metal. Finally, lead is death by metonymy, as in bullets: Aldersey-Williams discussed an artwork by Cornelia Parker (which will be included in Art of the Elements at Compton Verney), Bullet Drawing (Crosshairs), in which the artist uses lead to trace the trajectory from cause and effect, the metal being the ‘material framework’ unifying them. Lead from a bullet was molten and cast into a net, which was then mounted on paper and distorted as if hit by the bullet.

The author went on addressing several other elements, but I will let the curious reader set off on his/her own personal exploration of the periodic table, perhaps using Aldersey-William’s book as a primer. What matters at this point is the principle inspiring Periodic Tales: elements have a certain meaning for the chemist, but this is intertwined with countless threads from culture, history and myth creating a richly patterned fabric. Looking at every single case in the Periodic Table is like opening the lid of a set of Chinese boxes: once an element is unpacked, its multiple references to our (material and immaterial) culture will pop out, prompting us to keep on exploring.  Aldersey-William’s lecture also prompts a comment on the term element and its multiple meanings. The writer pointed out that ten elements (in modern terms) were known in antiquity (being gold, silver, carbon, sulphur, lead, tin, mercury, antimony, iron, copper and zinc), while Aristotelian elements, as discussed in On Generation and Corruption, just amounted to four (air, earth, fire and water, aether being a fifth, and most obscure, element), each one bearing a certain property (hot, cold, moist, dry) to the highest degree. If one were to stick to Mendeleev’s rigorous notion of element, an abstract entity with an experimentally accessible property (the atomic weight), it would be more appropriate to say that ten “simple substances” of elementary composition were known in the classical world. But I do not want to sound pedantic or dwell too long on this issue in this post.

If there had been an alchemist among Portia’s suitor, he would surely have chosen the gold casket: after all, transmutation of lead into the most precious metal was never accomplished, and several experimental procedures (think of the discovery and use of aqua regia, for example) eventually ended up destroying gold, rather than producing it. This is what I learned as I was listening to the second talk by Georgiana Hedesan, historian of alchemy, who focussed on alchemy as the art of making gold. However, as Hedesan warned, transmutation of base metals into gold was just one of the many goals of alchemy. Gold has attracted humans since the dawn of times for several reasons: its shine (the Proto-Indo-European root for gold means ‘glow’3), its sun-like colour, its rarity; it is a soft, easily shaped metal but at the same time it is also resistant to chemicals and it does not tarnish; it can be turned into stunningly beautiful jewellery, but this requires specialised craftsmanship, much as transmutation calls for the “dark arts” of alchemy. Here is an interesting point raised by the historian: the alchemists did not want to exploit transmutation to become rich, but they were seeking knowledge which would raise them above their contemporaries. For those interested in the history of chemistry, this sounds familiar: alchemists (and later on chemists) were regularly accused of impious, boundless hubris, trying to recreate fake reproductions (‘artifacts’) of the natural world, and in doing so defying the order created by (one or another) god4. This resonates with the opposition natural/artificial so often heard when nasty ‘chemicals’ are pitted against supposedly benign, more wholesome alternatives; in terms of reflections of this theme in literature, just think of the arrogant scientist in Mary Shelley’s Frankenstein, or the modern Prometheus. Interestingly, alchemists aimed to produce gold also because it was thought to be a panacea for good health, a proxy for eternal afterlife; even today, an relic of the alchemical era survives as (Danziger) Goldwasser, a strong liqueur containing gold flakes and dating back to the end of the 16th century, approximately the period on which Hedesan’s own scholarly interests research focus. More recently, elemental gold in the form of nanoparticles has garnered intense interest in research projects across the board seeking to develop effective drug-delivery systems or treatments for cancer. But today’s chemical research is nowhere as universal in its aims as the body of the alchemical knowledge of the 17th century, which, as Hedesan showed, could produce works such as Atalanta Fugiens (1617), which combines poetry, image and music to describe alchemical practices. Its author, Michael Maier, gives us an insight into the vastly broad scope of later alchemy in another work, De Circulo Quadrato Physico, sive de Auro (1616). It was in Maier’s times that the printing press allowed the scrutiny of alchemical practices by uninitiated but “skeptical chemists”, while also offering the inspiration for satirical comedies such as Ben Jonson’s The Alchemist 4,5.

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Gold and alchemy

Next came Peter Battle: his lifelong experience on the stages of international conferences was instrumental in delivering an engaging lecture touching on chemistry, art and aesthetics. After pointing out that chemists are mostly interested in compounds rather than elements, Battle said that he regards the latter as ‘building blocks’ and agents which introduce certain desired properties into the structures he and his group design and assemble (his research focusses on magnetic materials). This echoed a remark by the French chemist Michel Pouchard, as quoted in Chemistry: The Impure Science4: “The chemist is primarily the architect of matter as well as its mason; his scale is that of the nanometer, his bricks the hundred or so elements in Mendeleev’s periodic system, and his cement is their valency electrons“. Thus, not only are elements abstract concepts, as suggested by Mendeleev while he was working on the periodic system; they are also very practical raw materials for the wet-lab chemist, ‘bricks’ stacked to assemble structures such as this shown by Battle:

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Symmetry in chemistry

The speaker emphasised that if one looks at chemistry zooming out from the level of the single elements to those of compounds, a different type of periodicity is evident: simpler elements repeat following an ordered pattern to create an overall regular structure. One of these simple elements is the unit cell of crystals, which has its eye-catching architectural counterpart in the Atomium in Brussels, a Modernist stainless steel utopia embodying faith in technological progress as instrument of peace.  For a chemist like Battle, the Atomium is a body-centered cubic unit cell, which incidentally is that of iron, the element which Primo Levi, in one the tersest short stories of The Periodic Table, conjures up to talk about freedom, dignity and life-changing choices in a dark Europe.  Battle also stressed that chemical architectures (and the word is not randomly chosen!), from molecules to crystals, often feature symmetry elements: the structure displayed here, for example, has a horizontal symmetry plane reflecting the top half into the bottom half. This is often mirrored by landscapes, such as in the superb view of the still surface of Lake Buttermere (Lake District, UK) reflecting the mountains which rise up towards the skies from the lake shore. The solid state of matter is also characterised by simple components that are repeated periodically, giving rise to a regular shaping, and this is reminiscent of architectural features such as the recurring, imposing arches of Sweetheart Abbey. In this respect, the chemist is definitely an “architect of matter”, and not surprisingly one of the most famous chemists of all times, August Kekulé, first enrolled at the University of Giessen as an architecture undergraduate, falling for chemistry after listening to Liebig’s lectures. Mentioning Kekulé, I cannot help thinking about organic compounds and the symmetries observed in molecular orbital theory, for example in the so-called Hoffmann-Woodward rules. Roald Hoffmann himself has often reflected on the role of aesthetics in chemistry and it is an impossible task to summarise his stance in a few lines here: let us mention at this stage that Hoffmann addresses the shape of molecules and crystals at the start of his 1988 landmark paper Molecular beauty.
What is art’s own image of chemistry? Battle started by showing a painting included in the exhibition Art of the Elements, specifically The Alchemist (there we go again!), by Sir William Fettes Douglas, on loan from the Victoria & Albert Museum. Have a look at the picture and you will understand why the speaker stressed the fact that, annoyingly (at least from the chemists’ point of view), there is an intimate association between chemistry and someone looking at a round-bottomed flask. Here Battle echoes a detailed analysis by Schummer and Spector on The Visual Image of Chemistry, in which the authors maintain that “Whenever today’s chemists want to be portrayed in such a way that anybody can recognize their professional identity, they usually hold up in their hand a flask filled with some liquid that they visually inspect. This posture has become the stereotypical visual icon of chemistry in self-portraits, professional photographs, and clip-art cartoons6 . Unfortunately, it is not ideal for chemistry to be represented by this image, because, as Schummer and Spector remark, it originates from an early medical practice, uroscopy, which would eventually be associated with charlatans and their fraudulent practices. In a sense, this unflattering representation does not come as a surprise, because, at least from the point of view of philosophy of science, chemistry suffered neglect for centuries. Despite his later “conversion”, most likely following Lavoisier’s breakthroughs, a giant of philosophy like Kant was instrumental in asserting the notion of chemistry as “improper science”7. This philosophical stance may have had a fallout in the visual arts, too: Battle showed An Allegory of Chemistry, by the Austrian painter Hans Makart, which belongs to the collection of the Belvedere Palace at Vienna. An Allegory of Chemistry depicts a scantily dressed woman (euphemism!) doing…you guess…yes, right, scrutinising a laboratory vessel, and without wearing safety glasses, as Battle wittily remarked! Compare this to a related painting, Allegory of the Sciences, and you see what Kant meant by improper science: first of all, chemistry has its own painting (an undesirable privilege, in this case), and the second painting depicts a group of serious, somewhat childish-looking scholars all perusing the vastness of the cosmos with telescopes and pondering over massive tomes.

Finally, are there limits to the two-way exchange between chemistry and art? Possibly, as Battle suggested, when remarking that a chemist’s scientific background might prevent a full appreciation of the symbolic message of an artist’s artwork when the latter clashes with chemical facts. So, Gormley’s Fuse uses red iron (oxide) as a proxy for the iron-containing blood in our bodies, but, in Battle’s eyes, Fuse is primarily nothing but rust with a collection of different surface orientations (facets). This is because the chemist knows that iron in blood haem and iron in rust are fundamentally different incarnations of the same element. I find this dichotomy truly fascinating as it brings up the clash between the artist’s freedom in imbuing raw materials with any desired symbolic meaning and the outlook on the world acquired through chemical lenses, which forces the observer to take into account the molecular identity of matter beside its macroscopic qualities (i.e. colour).

Beautiful matter?

Later on, the panel of speakers took questions from the audience. The first question addressed allotropes and how they have (or not) changed our conception of the elements. This prompts us to remind Mendeleev’s philosophical stance, underpinned by the distinction between simple substances (graphite and diamond) and elements (carbon). The second question touched on the equivalence symmetry-beauty, a truly broad topic. Georgiana Hedesan pointed out that symmetry was at the heart of the alchemical thought, from the figures used (squares, circles) to the fact that, supposedly, the four elements came in identical amounts. Peter Battle remarked that, although we tend to see symmetry as neat, too much symmetry might hurt (and – I add – sometimes unexpected properties of materials indeed arise from the suppression of long-range regularities and symmetry, the so-called “defects”). All of this makes me think of Italo Calvino’s reflection on literature in his essay Exactitude in his Six Memos for the Next Millennium, in which, discussing 20th-century literature, he pitted the party of the crystal against that of the flame: “Crystal and flame: two forms of perfect beauty that we cannot tear our eyes away from, two modes of growth in time, of expenditure of the matter surrounding them, two moral symbols, two absolutes, two categories for classifying facts and ideas, styles and feelings…

Again on the issue of symmetry and beauty, we should remember that symmetry in chemistry is a deeply mathematical concept, based as it is on group theory. Hence, we can recall what the philosopher of chemistry Joachim Schummer wrote in his sweeping paper on the aesthetics of molecules: “apart from early Pythagorean views on beauty in nature, it is difficult to find any source in the whole history of western theory of art that considers mathematical symmetry the essence of beauty. Instead, we have severe criticism of that idea as well as aesthetic theories based either on the alternative concepts of proportion and harmony or on the interplay of symmetry and asymmetry in a broad sense8. Schummer’s remark is at odds with what is generally perceived as a natural relationship between between beauty and harmony of proportions, as in Palladian villas or Leonardo da Vinci’s man. As a final comment on symmetry, progress in the periodic classification of the elements took off when scientists stopped trying to force all elements in neatly symmetrical groups and periods (see for example Gmelin’s V-shaped periodic system, almost perfectly symmetrical), allowing for the existence of separate subgroups.

Finally, the audience raised the issue of the aesthetic value of scientific photography, which is becoming increasingly popular as demonstrated by the growing number of contests organised on this theme. I have always wondered what contributes to making a scientific photograph a masterpiece; in other words, which are the, so to say, ‘aesthetic criteria’ of scientific photography? Is it the technical challenge of the experiment producing a certain image? Or, rather, a purely visual appeal of the final picture? Perhaps a combination of the two? Take for example, the EPSRC Science Photo Competition 2015; applicants must submit “a jargon-free extended caption (maximum 150 words) putting the research into context. The caption must be comprehensible to the lay reader and will be taken into consideration by the judges when making their decision“. This central importance of the caption seems to mirror the fact that much contemporary art, in particular in its more conceptual forms, heavily depends on the title to ensure a complete appreciation of a certain artwork.

Ask the chemist, ask the writer

At the end of the question time, the audience streamed to the ‘Abbot’s Kitchen’, one of the oldest sections of the Inorganic Chemistry Laboratory, dating back to 1878.

The visitors could admire a complete collection of the elements of the periodic table; polonium was definitely in the limelight, because of its dark role in the assassination of Alexander Litvinenko.

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A full set of the elements of the Periodic Table

Yet, the engagement with the public has always surprises in store: as I was supervising the precious box full of elements, someone came and asked me about the current state-of-the-art in the research on lithium batteries, inspired by the chunk of silvery metal high in the top-left corner of the table.

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Lithium galore…and Swiss cheese?

In my view, improvised conversations like these are public engagement at its best because scientists do not have time to get bogged down in technical jargon and the layman can ask all sorts of questions for the sake of sheer curiosity. So, the “fourth wall” between the chemical stage and its lay audience is finally broken.

During the drinks reception I also had the pleasure of chatting with Hugh Aldersey-Williams for a short while: this was a great opportunity to find out more about what it means to be a writer. In my naivety, I was surprised to discover that a writer’s literary agent does contribute in steering the author’s pen towards this or that topic. A timely reminder of the never-ending struggle between the artist’s or the scientist’s creativity and the forces harnessing and reining it in, such as patrons’ own conception of art, and their political or strategic orientations: patronage and support of the artists have always come at a price.

The Elizabethan age and the Queen’s patronage of Shakespeare may well be history, but new characters play on the stage of the digital age, from literary agents to funding agencies and research councils.

And still we stand in front of locked caskets: which one hides our modern Portia, that coveted research grant ?

Footnotes
  1. Periodic Tales, Hugh Aldersey-Williams, Penguin Books, 2012
  2. Act II , scene 7
  3. The root being, as reported on Wikipedia, the slightly scary combination *h₂é-h₂us-o-, from which Proto-Italic *auzom which turned into Latin aurum.  ‎
  4. Chemistry: The Impure Science, Bernadette Bensaude-Vincent and Jonathan Simon, Imperial College Press, 2012 (2nd edition).
  5. Chemistryworld, August 2015: A shared secret?
  6. J. Schummer and T.I. Spector, The Visual Image of Chemistry, HYLE, 2007, 13, 3-41
  7. J. Van Brakel, Kant’s Legacy for the Philosophy of Chemistry, in D. Baird et al. (eds.), Philosophy of Chemistry, Springer, 2006
  8. J. Schummer, Aesthetics of Chemical Products, HYLE, 2003, 73-104

False Wagen

The exhaust contains principally three primary pollutants, unburned or partially burned hydrocarbons (HCs), carbon monoxide (CO) and nitrogen oxides (NOx), mostly NO, in addition to other compounds such as water, hydrogen, nitrogen, oxygen, etc. Sulphur oxides, though polluting, are normally not removed by the post-combustion treatments, since the only effective way is to reduce them to elemental sulphur, which would accumulate in the system. Accordingly, it is preferred to minimise sulphur emissions by diminishing the sulphur content in the fuel.

J. Kašpar et al, Automotive catalytic converters: current status and some perspectives, Catal. Today, 2003, 77, 419, doi:10.1016/S0920-5861(02)00384-X

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For a chemist who likes cars the tailpipe is the best place to be. One day we will fill our clothes irons with water from our fuel-cell powered cars (and how soon it happens it partly depends on white coats like me…what a weighty responsibility!); for the present, the chemistry of catalytic converters is already interesting enough. So, let us take inspiration from the recent news and have a (very) quick look at it. Luckily, days in the laboratory are dotted with time-outs between experiments, which gives me a handful of snippets of time that I can devote to writing.

Recently, there has been extensive media coverage of a test-rigging scandal involving a major German car manufacturer, which has admitted to equipping its Diesel cars in the US and Europe with an illegal software to cheat during emission tests. As a car enthusiast since the ripe age of 3 (ask my parents), I have often read the road tests published in car magazines, regularly reporting a higher fuel consumption than that advertised by manufacturers in their sleek brochures. However, this is not particularly surprising, because consumption (and emission) tests are defined by standard procedures based on stationary measurements performed on a test rig. Yet, this time the car manufacturer seems to have stepped up its game: after all, when competition is cut-throat, such as in the automotive market, cutting corners is the only way to up the ante and survive, right? I have grasped a rough idea of how the system actually worked by listening to a science programme on the Italian public radio, and so I warn you that what follows is not an exhaustive (sorry for the silly pun) explanation: official enquiries have been launched to uncover the details. In a nutshell, the software running on the electronic control unit featured, along with several ‘legal’ operating modes (those options with catchy names like “sports”, “eco”, “city”) a low-nitrogen oxides (NOx) routine which activated when only two wheels were revolving (exactly as on the test rig). Under these conditions, the emissions of NOx dramatically decrease, falling below the pass threshold of the test. However, low emissions mean higher fuel consumption, and so this operating mode would never be practical while driving on the road, because low consumption is the main asset of a car, at least from the point of view of parsimonious buyers. At any rate, the whole affair will at the very least sap the consumer’s confidence in this car make, and in this case it is going to be a headlong crash from a high reputation. Cars, like friends, come in two different categories: those you go out with just to have fun, and those who you can always trust and rely on regardless of what life throws at you: German cars definitely (used to?) belong to the latter.

As a chemist, it is somewhat flattering to think that nowadays all motor vehicles are chemical reactors on four wheels, equipped as they are with catalytic converters. First of all, mind your words: catalysis is a learned combination from Ancient Greek, meaning ‘dissolution’, among other things1, and when it comes to cars we will be talking about heterogeneous catalysis, because the characters of this play belong to different phases of matter. For hetero-, have a look at a previous post on heterolysis, a word which, yes, recycles once more that Greek root that chemists like so much, λύω,  ‘I release, I set free, I unharness’. Maybe chemists unconsciously think of their discipline as a means to ‘unbind’ a Promethean power which lay locked away. A dangerous idea. More practically, when referring to things λύω means ‘I break up something into its component parts; I resolve’, which would be analysis in Lavoisier’s terms, one of the two poles of chemistry along with synthesis. Anyway, as Gerhard Ertl reminded in his 2007 Nobel Lecture, Jöns Jacob Berzelius was the first to use of the word to describe a chemical phenomenon in 1835; another ‘first’ for this pole star of chemistry rising from the north to shine over the discipline in the first decades of the 19th century, as we saw elsewhere.

For the casual (and brave!) non-scientist who might have landed on this blog by chance, catalysis is the chemists’ equivalent of the fast-forward button in old video players: a videotape has its own normal speed at which we can play it, but what if we cannot afford to wait forever and we really want to watch that particular scene of our favourite film? In this case, catalysis fast-forwards the chemical tape taking us there where we want to go, and fast. In other words, there are reactions that just will not happen unless a fast-forward agent, a catalyst, is introduced in the system, and the catalyst’s secret is its ability to engage in a special relationship with the molecules taking part in the reaction. To visualise this “physical touch”, remember that the video recorder controls the playing speed with a spindle that plugs into a socket on the videocassette, but this connection is by no means permanent, because the cassette can be ejected when we wish to. So, a catalyst must somehow bind the reagents, but unlike diamonds (while sadly similar to most romantic relationships), this bond does not last forever.

As for the type of catalysis operative in catalytic converters, heterogeneous catalysis as we said above, there are three main ingredients:

  • a solid support coated with the catalyst (think of gilding a piece of wood or baser metal)
  • gases emitted by the engine during combustion
  • energy, usually in the form of thermal energy (say: heat)

Imagine an unusual ball game: there is a wall covered with the hooky fabric of touch fastener (“Velcro”), and two players with two different sets of tennis balls, one with the same hooky fabric, the other with a (more tennis-like) hairy fabric. The players start throwing their tennis balls, aiming to bind two balls of different sets. The normal tennis balls will stick to the wall, while the “hooky” counterparts will bounce off unless they hit a hairy ball in the right way and bind to it. When a ball-ball couple (a ‘dimer’) is formed, it is either heavy enough to fall off or light enough to keep hanging onto the wall, which means that we need to go and pull it away. As you can see, the players spend some sort of energy at least once (throwing the ball), and maybe a second time (separating the ball-ball couple from the wall).

Is this just a far-fetched metaphor? Maybe, but Prof. Ertl introduces automotive catalysts in his Nobel Lecture by talking about the following reaction

2CO + O2 → 2CO2

CO and O2 bang against the catalyst (Pt or Pd), CO sticks, O2 hits hard enough for it to fall apart into two O atoms, one of which can bind to CO if it finds some of it in the surroundings, and CO2 falls off as soon as it is formed. A harmful combustion product, CO, is thus transformed into CO2, which can be regarded as harmless. In this respect, a greenhouse gas can be seen as the lesser evil, but this turns up global warming another tiny notch. Bottom line: use the bike instead if you want to go green.

A burning issue

Let’s start from the basics, which reminds me of my undergraduate course in environmental and atmospheric chemistry. It feels such a long time ago. It was the autumn term of 2004 and I was looking forward to exploring this branch of chemistry, and learning how Crutzen, Sherwood Rowland and Molina had won their Nobel Prize in 1995 by unravelling the chemical underpinnings of ozone depletion in the stratosphere … unfortunately the course turned out to be the most boring ever: the lecturer delivering the classes did his best to confuse the audience, and so we hoped that the textbook would come to our rescue. To no avail: the book itself, seemingly typed on an old typewriter, was a dry collection of reaction cycles to be learned by rote. I remember long hours spent scribbling the reaction pathways of atmospheric chemistry on a small blackboard. Funnily, the OH radical rampaging all around, reacting with this and that molecule, is one of the few concepts that has stuck into my memory: for me it was, and is, a poignant metaphor of the ultimate embodiment of life’s wear and tear. After all, “free radicals” purportedly play a key role in ageing.

Memories aside, if one wants to have a rough idea of automotive catalysts it is good to point out a few concepts to start with. Car engines burn fuel to extract energy from it; combustion is a combination of three actors (the good old “triangle”), fuel, oxidant and “heat”, or any suitable source of energy (the spark in petrol engines, for example). Combustion is just yet another chemical reaction, and like all of them, it is wise to weigh out the reactants and make sure we can control their relative proportions. That’s stoichiometry, which reads as the “measure of the elements” 2. The relative proportion of reactants which satisfies the stoichiometry of the reaction can be named stoichiometric ratio. For a simple combustion like:

CH4 + O2 → CO2 + 2H2O

the stoichiometric ratio between methane and oxygen is one molecule to one molecule. In other words, if there is a molecule of oxygen available for every molecule of methane, all fuel is expected to become CO2, while no O2 is left at the end of the reaction. (This in a real world where there are no practical issues with the actual combustion). Put too much O2, and you will end up with some of it in the combustion exhausts; on the other hand, if you are economical with O2, some CH4 will survive the combustion unscathed, or burn to incomplete stage, CO, that requires half as much oxygen:

2CH4 + O2 → 2CO + 2H2O

Similarly, one can define stoichiometric ratios for internal combustion engines. The exact values of these ratios will of course depend on the type of fuel being burned: petrol (gasoline across the Atlantic, and poetic, ephemeral essence in Francophone lands) or Diesel fuel, but the difference between the two types of fuel is not massive. A good idea is to define the air/fuel ratio with respect to the stoichiometric optimal, and call it λ: if λ > 1, there is more air than required, which is called lean mixture in car jargon, if λ < 1 there is more fuel than determined by stoichiometry, leading to a rich mixture. The parameter is not carved in stone, it keeps changing as we drive around. Roughly speaking, if we are cruising in our petrol-powered car on a motorway, λ should be slightly higher than 1, while as we want to go flat out and we put our foot down during hard acceleration λ will be less than 1 to achieve maximum power.

If we now have a look at the combustion products, for two typical engines (Table 1 in a specialised review3, here reported in a modified and shortened version):

Exhaust components and conditions Diesel engine Petrol engine
NOx 350–1000 ppm 100–4000 ppm
Unburned hydrocarbons, HC 50–330 ppm C 500–5000 ppm C
CO 300–1200 ppm 0.1–6%
O2 10–15% 0.2–2%
H2O 1.4–7% 10–12%
CO2 7% 10–13.5%
SOx 10–100 ppm 15–60 ppm
PM 65 mg/m3
λ ≈1.8 ≈1

The exhaust gases contain several nasty fellows, for example CO and NOx; the catalytic converter needs to remove them, which is quite challenging considering that exhausts look like a hotchpotch. The following plot (reproduced here by myself with low-tech tools but originally appeared as a figure in a specialised review3) shows how typical pollutants vary with respect to air/fuel ratios:

image

The classical example of an automotive catalytic converter is the so-called ‘three-way’ catalyst for petrol engines, which is a fascinating, ingenious device. Its three tasks are:

  1. convert NOx into N2 (mostly done by rhodium)
  2. convert CO into CO2 (mostly done by platinum and palladium)
  3. convert unburned fuel hydrocarbons into CO2 (mostly done by platinum and palladium)

Task 1, the conversion to N2 is in chemical terms a reduction, which can be accomplished with the proper catalyst and a reactant that could act as the reducing agent. The simplest example is H2,which steals the oxygen becoming H2O in turn. As for the actual mixture of exhaust gas leaving the combustion chamber of the engine, one has to make do with the potential reducing agents already present in this exhaust mixture. Possible candidates are CO and hydrocarbons that have escaped complete combustion:

2NO + 2CO → 2CO2 + N2

NO + HC → CO2 + N2 + H2O (not balanced)

Going back to our image of balls hooking onto a Velcro wall, NO sticks onto the catalyst, and two NO molecules nearby will engage in what they think to be a fleeting liaison. Yet, this encounter will change them forever, as they shed their useless, acidic partner oxygen to make perfectly homogeneous pair, and they fly away together, looking forward an eternal, ethereal life as N2. Oxygen is left onto the catalyst, effectively taking up space for other NO molecules to stick, split and click. Individual oxygen atoms yearn for new partners as well, and they are ready for a getaway with any oxygen-loving molecule which happens to fly past. CO is a familiar match, small and thin, similar as it is to NO in many respects; partially burned hydrocarbons are instead burly blokes with charcoal on their faces, who look forward to a life-changing metamorphosis into CO2 by abducting as many stranded oxygens as possible. In a sense, a catalyst surface is the dance floor where couples meet, flirt and swap. Is this image, seemingly taken straight from Zygmunt Bauman’s essay Liquid Love, out of place on a scientific blog? Not really…lysis (λύσις) also means ‘divorce’ in Ancient Greek.

Promiscuity aside, reactions in task 1 help to remove CO and HC, which the pollutants that are to be tackled by tasks 2 and 3, showing a synergy in catalytic conversion. However, let us also note that tasks 2 and 3 involve oxidations: antipodal reactions with respect to the NOx reduction in task 1.

CO + O2 → CO2

HC + O2 → CO2 + H2O (not balanced)

Oxidation reactions like these ideally revel in the presence of extra oxygen. So, now we understand that a catalytic converter treads a narrow line in terms of contrasting demands, and the optimisation of its three tasks at the same time is a tall order achieved by continuous fine-tuning. It is the electronic control unit that calls the shots, finding a delicate trade-off is found. Another simple plot (again reproduced here by myself with chalk and blackboard but originally appeared as a figure in a specialised review3) will show how the efficiency of pollutant removal can plummet quickly as λ moves away from 1.

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Managing oxygen is tricky also at a microscopic level, and for this reason catalytic converters also include oxides, for example CeO2 or ZrO2, which have several beneficial effects apart from physically “supporting” the catalyst; in particular, oxides can store extra oxygen when there is plenty, stockpiling a back-up supply of oxygen to keep running tasks 2 and 3 when, for example, a sudden surge in HC floods the catalytic converter as the driver goes at full throttle.

Diesel engines pose different challenges. The air/fuel ratio is higher than petrol engines, which makes it relatively straightforward to burn off CO and hydrocarbons to CO2 (functions 2 and 3 of the three-way catalyst) with a so-called Diesel Oxidation Catalyst (DOC), usually platinum on aluminium oxide (alumina). However, the DOC cannot remove the particulate matter4 produced by Diesel engines. On the other hand, more oxygen means a paucity of CO and unburned hydrocarbons in the exhaust and ready to be used to reduce NOx. This makes a traditional three-way catalyst ineffective for NOx abatement. To make matters worse, lots of oxygen means a very oxidising enviroment and, consequently, more NOx – which, as I narrated in more poetical terms in my previous post on the nitrogen cycle, forms whenever sparks fly in air.

Particulate matter and NOx have to be tackled simultaneously. There is the rub. The following excerpt from a 2011 specialised review sounds like a “writing on the wall”, and its take-home message (valid at the time of publication, but most likely still true today) is: when it comes to reducing particulate and NOx emissions of Diesel engines, striking a balance between the two is very challenging: “The performances of commercial catalytic post-treatment systems are not optimized to fulfill the forthcoming U.S.standard legislation and those that will be implemented in Europe near 2014, particularly the low limit of NOx emissions from diesel engines. The lean-burn engine is actually the most attractive solution combining low consumption and low CO2 emission, recognized for its greenhouse gas behavior. There are also apparent advantages in Europe that might explain a continuous expansion of the diesel car market related to the implementation of a favorable tax system. However, the suitability of this technology, from an environmental point of view implies the minimization of atmospheric pollutants, particularly nitric oxide emissions, which actually represent a serious drawback with no practical solution commercially available. Hence, while CO and unburned hydrocarbons can be easily removed, the simultaneous abatement of NOx and particulates from diesel exhaust gas represents an outstanding issue. The current three-way technology used near stoichiometric conditions is unable to meet upcoming regulations in Europe, United States, and Japan. The existing technical solutions […] involving an exhaust gas recirculation to get an optimal NOx/particulates compromise by controlling the recirculated gas rate or modifying the distribution channel will likely be unable to fulfill the next Euro 6 standard regulation. […] the implementation of an optimal strategy is not an easy task because a reduction of NOx induces an increase in particulate emission […] and reversibly subsequent reduction of particulate matter will induce an increase in NOx emission […]5.

What a catch-22…

NOXious gases

But I feel I am beating about the bush as I promised to take inspiration from the test-rigging affair to talk about catalysis and nitrogen oxides. Here we step into my own turf, and you can read more in a previous post on the nitrogen cycle.

There are various possible strategies to reduce the amount of NOx emitted by a Diesel engine:

  • Special NOx removal catalysts able to tolerate the excess oxygen in the exhausts
  • NOx “traps”, which exploit acid/base chemistry, using oxides or carbonates such as BaCO3 as alkaline counterparts to immobilise acidic NOx as nitrate, which is released and reduced as the engine briefly operates with a rich mixture.
  • Selective Catalytic Reduction, my favourite

Selective catalytic reduction is a reincarnation of a class of reactions called comproportionations, which involve two reactants containing the same element but in two different oxidation states. Most people will remember comproportionations from general chemistry courses as outlandish chimeras standing out from the crowd of ‘normal’ reactions. As for the nitrogen cycle, think of the violent comproportionation that accounts for the explosive decomposition of ammonium nitrate. This salt is intrinsically unstable right because, in its two moieties, it combines the extreme oxidation states of nitrogen, nitrate (+5) and ammonium (−3), which liberates a powerful entropic ‘kick’ by releasing a large amount of gases in a veritable free-for-all which ends in both nitrogen atoms being triply married to each other in a multiple wedlock.

2NH4NO3→ 4H2O+ O2+ 2N2

Selective catalytic reductions are the milder (and more useful) version of this explosion. Developed for stationary sources of NOx (say, fossil-fuel power plants), they require a suitable catalyst and a nitrogen-containing molecule willing to take the lift from a lower oxidation state to the stability of ground floor. Why not ammonia, I hear you say, and so let us take ammonia on board our Diesel cars…but how? Ammonia could for instance attack and corrode the walls of a reservoir, and spill out while we are driving around in our eco-friendly (but leaky, as my favourite burette) cars.

Yet, storing ammonia is just one of the many challenges posed by automotive SCR. Running the reaction at top conversion is another tall order. When looking at the catalyst, the image of the Velcro wall and hairy tennis balls can be conjured up once more. In fact, ammonia sticks very well onto the surface of these catalysts as long as the temperature is not too high (below 473 K, as reported in a topical review); when the exhaust heats up, for example when a heavy lorry goes at full throttle, ammonia can become loose again and do business. It is exactly under these hotter conditions that SCR can occur. Implementing SCR is by no means an easy task, as it requires continuous monitoring of engine and exhaust parameters to avoid, for instance, injecting an excessive amount of ammonia that would end up being released at the tailpipe. Stoichiometry shows up again, and a NH3/NOx ratio less than 1 is often preferred for operations (after all, a short foray into rich-burn conditions could provide extra reducing agents to remove NOx leftovers). The catalyst, once more a thin layer ‘gilded’ on top of a suitable support, is vanadia (V2O5), which is a crowded nightclub where molecules flirt and hook onto each other in all possible ways 5. There is some true SCR going on, like

4NH3 + 4NO +O2 → 6H2O + 4N2

8NH3+ 6NO2 → 7N2 + 12H2O

But the latter could turn into an acid-base neutralisation leading to an old acquaintance of ours, ammonium nitrate:

2NH3+ 2NO2 →N2 + NH4NO3 + H2O

And, last but not least, there is enough oxygen for ammonia to be oxidized on its own:

4NH3 + 3O2 → 2N2 + 6H2O

Vanadium is the DJ playing the tunes for this wild night out, cycling his records between an oxidised form (V=O) that is catalytically active and a reduced one (V-OH) that consumes oxygen to bounce back to action. A complete reaction equation would then be5

NO + NH3 + V(+5)=O →  N2 + H2O + V(+4)-OH

Instead of storing a tankful of ammonia, someone had a brilliant idea that would make Friedrich Wöhler revel in his grave: take urea, instead, and hydrolyse it on board when its needed. Controlling the amount of urea, hence ammonia, injected in the exhaust would also offer another degree of freedom to adjust SCR to engine performance in real time. A concentrated urea solution is vaporised prior to the actual SCR catalyst, and Wöhler’s most beloved molecule first breaks up into ammonia and isocyanic acid5

NH2CONH2 → HNCO (gas) + NH3

In the best-case scenario, the latter acid gives off a second ammonia molecule and CO2 in a following step:

HNCO (gas) + H2O → NH3 + CO2

Things could in principle also go awry: isocyanic acid could start one of those funny and silly versions of the ‘conga line’ in which (tipsy) people line up one after the other in a moving ‘train’. This polymerization could for example lead to melamine (yes, the one that ended up in babies’ powdered milk some time ago in China), which is not great news because it could clog the catalyst (think of no space anymore for single club-goers to move on the dance floor when the snake is around). Luckily, this will not happen if a catalyst for urea hydrolysis and isocyanic acid decomposition is chosen, for example TiO2.

To sum up, the sequence of treatment stages tackling Diesel exhausts is:

  • Diesel Oxidation Catalyst
  • Urea injection and hydrolysis
  • Selective Catalytic Reduction
  • Diesel Particulate Filter

Fed up with noxious car exhausts? Too bad, you deserve some stinky sewage then, but I promise, it will be just a quick dive.

The shortcut to heaven

Miracles happen, or at least sometimes those who seem to be misfits do become famous, eventually end up in the spotlight. This is probably the case for some bacteria, which have had their fair share of fame, rising from complete obscurity to gain a certain notoriety5 in 1999, while taking researchers by surprise. Their metabolism features a reaction called anammox (anaerobic ammonium oxidation), which plays an important role in removing nitrogen species from the oceans:

NH4+ + NO2 → N2 + 2H2O.

This time, no explosive metaphor is exaggerate: these bacteria succeed in handling an anion and a cation which, as a salt, few people would like to work with for fear of explosions. Like desperate lovers imprisoned in nearby cells, nitrite and ammonium will pull all the stops to break free, flee and fly away as N2, tearing down all walls in the process. When swallowed by these bacteria, their separation ends quietly without dramatic escapes. The story of the discovery of these bacteria is fascinating and deserves a post of its own. I happen to know it because I read some of the literature when I was working for my PhD research project at Leiden University. It was my supervisor the one to point out that other Dutch researcher, part of an international team, had identified the elusive bacteria responsible for anammox reaction6. This reaction is exploited in a patented bacterial process (having the same name as the reaction) for the treatment of ammonium-rich sewage or wastewater.

It was to my great surprise that, while I was doing research as a PhD student, we observed that the same recombination between nitrite and ammonia occurs under certain conditions on some surfaces of Pt catalysts when an electrochemical potential is applied7. This time, the catalytic Velcro wall must be of a very special shape for the molecules to stick: the most external Pt atoms must be arranged as if they were located on the corners of a square, and this for the entire surface. No matter how unrelated electrochemistry is to microbiology, the overall reaction

NH3 + NO2 → N2 + H2O + OH

takes place, and, for the most curious among you, I will also mention that the ‘stuck’ (e.g. adsorbed) hairy tennis balls seem to be in this case NO and NHx. The nitrogen cycle perhaps has another surprise in store: a research group based in Québec has proposed that the very same intermediates are involved in the oxidation of NH3 to N2 on the atomically square-shaped Pt surface, and once more performed by help of an electrochemical potential8, but conceptually equivalent to the oxidation of NH3 to N2 by O2 as seen previously in the discussion of the SCR process. Is this really an universal process common to a special Pt surface, ‘anammox’ bacteria and catalysts for NOx removal from Diesel exhausts? Only time will tell, but at the moment it really seems so.

In conclusion, whatever happens in my future career as a scientist, I can already look back and feel somewhat proud, because my own investigation of the nitrogen cycle has followed Roald Hoffmann’s guiding philosophy for chemistry research: “look at hundreds of small(er) problems in chemistry, and keep in mind the connections that must be there” and you “will see the chemical universe” 9. A series of experiments part of a PhD project in electrocatalysis started unravelling a skein of yarn, pulling a thin Arianna’s thread that would lead to the world of SCR for Diesel exhausts and some puzzling bacteria. Eventually, the yarn has been rolled into a ball, and a single line connects all the dots in an elegant common pattern.

A star-studded sky waiting for curious eyes to recognise and trace more new constellations: such is the chemical universe.

Just look above you, and follow the exhausts.

Footnotes
  1. The verb καταλύω encompasses a range of meanings which look quite nasty, such as (in the order reported by this online dictionary) “I destroy”, “I dissolve” (of a political system), “I bring to an end” (of life as well). The name κατάλῠσις follows suit, meaning “dissolution” (of a political system), “disbanding” (a crew, a group of men). If I miss any meaning, forgive me: I used to know someone who had studied Ancient Greek but we are not in touch anymore.
  2. Jeremias Richter (1762-1807), starting from a Kantian perspective and following the “dynamist” approach to chemistry, tried to quantify properties such as acidity and basicity.  Stoichiometry was developed with a view to establishing a “neutralisation” law for the formation of salts (see Chemistry, the Impure Science, Bernadette Bensaude-Vincent and Jonathan Simon, Imperial College Press, 2012).
  3. J. Kašpar et al., Automotive catalytic converters: current status and some perspectives, Catal. Today, 2003, 77, 419, doi:10.1016/S0920-5861(02)00384-X
  4. Defined in J. Kašpar et al., Automotive catalytic converters: current status and some perspectives, as “the most complex of diesel emissions. Diesel particulates, as defined by most emission standards, are sampled from diluted and cooled exhaust gases. This definition includes both solids, as well as liquid material which condenses during the dilution process. The basic fractions of DPM are elemental carbon, heavy HCs derived from the fuel and lubricating oil, and hydrated sulphuric acid derived from the fuel sulphur. DPM contains a large portion of the polynuclear aromatic hydrocarbons (PAH) found in diesel exhaust. Diesel particulates contains (sic) small nuclei with diameters below 0.04 μm, which agglomerate forming particles as large as 1 μm. The non-gaseous diesel emissions are grouped into three categories: soluble organic fraction (SOF), sulphate and soot
  5. P. Granger and V. I. Parvulescu, Catalytic NOx Abatement Systems for Mobile Sources: From Three-Way to Lean Burn after-Treatment Technologies, Chem. Rev., 2011, 111, 3155–, doi: 10.1021/cr100168g
  6. M. Strous et al., Missing lithotroph identified as new planctomycete, Nature, 1999, 400, 446-, doi:10.1038/22749
  7. M. Duca et al., Selective catalytic reduction at quasi-perfect Pt(100) domains: a universal low-temperature pathway from nitrite to N2, J. Am. Chem. Soc., 2011133, 10928-, doi: 10.1021/ja203234v
  8. D.A. Finkelstein et al., Mechanistic Similarity in Catalytic N2 Production from NH3 and NO2 at Pt(100) Thin Films: Toward a Universal Catalytic Pathway for Simple N-Containing Species, and Its Application to in Situ Removal of NH3 Poisons, J. Phys. Chem. C, 2015, 118, 9860-, doi: 10.1021/acs.jpcc.5b00949
  9. As reported in Q & A Roald Hoffmann: Chemical connector, Nature, 2011, 480, 176, doi:10.1038/480179a

Karlsruhe United

The scales fell from my eyes and my doubts disappeared and they were replaced by a feeling of quiet certainty.

Lothar Meyer, co-discoverer of the periodic law, recalling the Karlsruhe Congress
(as quoted in: Periodic Table: Its Story and Its Significance, Eric R. Scerri, Oxford University Press, 2006)

Have you ever experienced the same eureka moment while getting back home from a meeting? Personally, I have often had sudden brainwaves or flashing ideas while listening to someone’s presentation, but, honestly, never have I felt so close to universal enlightenment as Lothar Meyer did in Karlsruhe in 1860. I am not as brilliant, and, besides that, the scope of my research is not as universal as the quest for a comprehensive periodic law for all the elements.

This month marks the 155th anniversary of a milestone in the history of chemistry: the International Meeting which took place at Karlsruhe from 3rd to 5th September (yes, I know, my post is a few days late…I have been awfully busy as of late). Not only is this congress extraordinary because it is the first international scientific conference ever1: this is also an example of an apparently inconclusive meeting that instead sparked an electrifying sequence of (philosophical and scientific) breakthroughs in the research of a periodic system of the elements. Like a stone thrown in a calm lake, the ripples of the Karlsruhe congress reached the shore only after a while. Scientific ideas migrate slowly: it takes time for them to come home to roost.

No formula one

Say acetic acid, and you know what it is, well, at least what it smells and tastes like. What about its formula? Nowadays it is hard even to imagine that there was a time in chemistry when a textbook could list as many as nineteen different formulae:

Kekule_acetic_acid_formulae
By A. Kekulé (edit NobbiP (Lehrbuch der Organischen Chemie, 1861) [Public domain], via Wikimedia Commons, from https://commons.wikimedia.org/wiki/File:Kekule_acetic_acid_formulae.png
To make matters worse, there were even more fundamental problems affecting mid-19th century chemistry:

  • Atomic and/or equivalent weight: Different laboratories used one or the other quantity, which led to an astounding variability in the chemical formulae of chemical substances. In other words, oxygen could weigh 8 or 16 (with respect to hydrogen). The former is the equivalent weight of oxygen in water, the latter its atomic weight. The problem partly stemmed from the fact that equivalent weights have a more immediate significance when doing experiments: they immediately show the mutual proportions of the reactants of a chemical reaction. Atomic numbers, on the other hand, depend on the determination of an empirical formula. In addition, the available values of atomic weights were often significantly inaccurate.
  • Nomenclature: ‘Atom’, ‘molecule’, ‘radical’, ‘equivalent’: there was no common guideline for the usage, and the meaning, of these terms.
  • Theories of the structure of matter. This is where the fundamental problems lay. The remarkable expansion of organic chemistry outpaced the reflection on the structure of matter. Alternative theories of matter coexisted but they were not universally applicable, being mostly suitable for a single class of compounds. For example, Berzeliuselectrochemical theory, which interpreted all chemical bonding in terms of the attraction of fragments (‘atoms’) of opposing charges, stemmed from Berzelius’ titanic work on oxides and salts to draw up an accurate table of atomic weights. It was the prestige of Berzelius’ 1818 textbook Essay on the Theory of Definite Proportions and the Chemical Influence of Electricity that thwarted the acceptance of the so-called Avogadro’s Hypothesis (1811): “equal volumes of different gases at the same temperature and pressure contain the same amount of molecules”. In fact, only apparently is this a purely stoichiometric statement: it implies the existence of diatomic gases like N2, H2, or, in other words, the possibility for an element to combine with itself. This was pure heresy for most of the chemists of the first half of the 19th century: Avogadro’s hypothesis simply did not fit in the theoretical framework of Berzelius’ theory: fragments of equal charge should simply repel.
    From the point of view of organic chemistry, the years immediately preceding the Karlsruhe Congress saw the birth of a structural theory of organic compounds based on the tetravalency of the carbon atom. It has been shown2 that the scientific milieu of chemistry was ripe for the development of this concept in the late 1850s, and that scientific research at Paris exerted a major influence on the three chemists that worked on the structural theory of organic compounds. August Kekulé, a veritable chemistry polymath with an impressively extensive background, had been a research assistant at Paris in 1851-1852; Archibald Scott Couper was working with Wurtz (yes, the same of the Wurtz reaction, an Alsatian chemist who advocated atomicity, the combination of atomic theory and valency2) in the same city when he published a paper on tetravalence in the following year, while Alexander Butlerov, the Russian chemist who, in Markovnikov’s own words “gave full value to this [Kekulé’s and Couper’s] hypothesis and developed it into the whole structural system3 also worked for five months with Wurtz at Paris in 1858.

Going back to the Karlsruhe Congress, one can say that it coincided with the transition from the generation of Liebig and Dumas to that of Meyer (he was 30), Mendeleev (26) and Kekulé (31). Although it would be incorrect to depict the congress as an all-out rebellion of the youngsters against the old guard, the junior delegates would definitely turn out to be more receptive to the new ideas being discussed at the congress. Reportedly4, Meyer approached the congress with significant skepticism, predicting that the “idiotic church-council in Karlsruhe” would end up in the “the election of an infallible [molecular] formula-pope”. On the other hand, it is impossible to understate the role played by Kekulé (then full professor at Gent, Belgium), who, despite his relatively young age (sorry for the ‘relatively’, dear thirty-something reader like me!) , had been one of the main catalysts for the organisation of the Karlsruhe Congress5. Kekulé and Weltzien (a chemist based in Karlsruhe who would be the ‘business manager’ of the conference) went to Paris in March 1860 to meet the third organiser, Wurtz, and draw up plans for the conference together. Looking at the dates, one realises that the conference was actually called on quite a short notice, and this is all the more impressive if one considers that information and people travelled with 19th century means of transportation, the handwritten letter and the steam train.

The invitation letter was sent out in three versions, German, French and English6

Carlsruhe [sic], den 10. Juli 1860

Herrn…

Die Chemie ist auf einem Standpunkte angelangt, wo es den Unterzeichneten zweckmäßig erscheint, durch Zusammentritt einer möglichst großen Anzahl von Chemikern, welche in der Wissenschaft thätig und diese zu lehren berufen sind, eine Vereinigung über einzelne wichtige Punkte anzubahnen […]7

Gentlemen:
Chemistry has reached a state of development when to the undersigned, it seems necessary that a meeting of a great number of chemists, active in this science, who are called upon to do research and teach, be held so that a unification of a few important points shall be approached[…]8

Good old Lothar Meyer, summarises it once again for us in a note he wrote thirty years after the Karlsruhe Congress:

We now easily recognize that the argument was mainly about three things: electrochemical dualism (i.e. Berzelius’ theory), Avogadro’s Hypothesis, and the relative atomic weights of the elements. However, at the time, this was not so obvious; the most common arguments were about the formulas used to represent how chemical compounds were formed. . . . As a result, there was much confusion, every substance, even the simplest, had a series of formulas, e.g., water: H2O or HO or H2O2, mine gas (methane): CH4, C2H4 . . . . Even a simple compound such as vinegar could have enough proposed formulas to fill an entire printed page9

Meyer’s remark is important in reminding us the role of perspective when looking at the past. From the vantage point of the scientific consensus of the 21st century, it is all too easy to sneer at our chemical forefathers and point out the fallacies of some of the older theories, and their blindly stubborn rejection of Avogadro’s Hypothesis; yet, we should try and imagine how philosophically challenging it was for a chemist of that era to reconcile Berzelius’ and Avogadro’s theories. At the same time, let us not forget that even well-earned prestige, such as in Berzelius’ case, should never convince a researcher to abandon his/her skepticism, one of the four inspiring principles of scientific research, as defined by Robert Merton10:

  • Communism
  • Universalism
  • Disinterestedness
  • Organised skepticism

Bin it or read it

It is thanks to the Stanislao Cannizzaro’s mercurial speech that the Congress reaches its climax just before its end. As the conference is drawing to a close, time is running out and the delegates try to reach an agreement on chemical notation. In particular, they discuss if chemists are to revert back to the principles of Berzelius’ venerable system11, which in Cannizzaro’s view had a major shortcoming: it could not accommodate Avogadro’s hypothesis and the most recent development in chemical theory. It is at this point that, as Wurtz’s minutes of the Congress reports12, “Mr. Cannizzaro takes the floor in order to oppose the second proposition. It scarcely appears fitting or logical to him to move science back to the time of Berzelius”. Cannizzaro’s speech goes on for quite a while, or at least we are inclined to think so because of the extensive notes in Wurtz’s minutes. Moreover, we can only imagine what Cannizzaro’s stage persona looked like (Mendeleev remarks that Cannizzaro’s speeches were “heated” and “animated”8): was he waving hands extensively as Italians are often supposed to be doing all the time when they are talking? Could one hear a thick Italian accent in his French, or his German? Did he make direct eye contact with the audience? Were the listeners engaged or, rather, bored to death and already thinking about “rushing to catch that train back home”, their ongoing experiments, a doctoral thesis to correct? We will never know.

Cannizzaro’s take-home message was simple: the chemical sciences have significantly moved on since Berzelius’ times, and recent, compelling evidence supporting Avogadro’s hypothesis has been published by several groups using different experimental techniques. Therefore, the value of some of the atomic weights in Berzelius’ table must be doubled and these doubled atomic weights should be clearly rendered in notation with crossed-through symbols. Also, the simultaneous use of old and new symbolism must be discouraged to avoid all misunderstanding. Significantly, he concluded by saying: “And if we are unable to reach a complete agreement upon which to accept the basis for the new system, let us at least avoid issuing a contrary opinion that would serve no purpose, you can be sure. In effect, we can only obstruct Gerhardt’s [the newer] system from gaining advocates every day. It is already accepted by the majority of young chemists today who take the most active part in advances in science“. Reflect on this statement. The deliberations of a congress cannot stop the spreading of a novel outlook on chemical facts which is more in line with available experimental evidence. After all, as another French delegate (Boussingault) wittily remarked, “It is not chemistry that grows old, but chemists“; we should praise Boussingault for his objectivity in spite of his own age: in 1860 he was just 59.

Yet, Cannizzaro’s speech alone would probably have been much less convincing if the second Italian delegate at Karlsruhe, Angelo Pavesi, professor at the University of Pavia, had not stepped in. As recalled by Meyer1,8, Pavesi supported his friend’s speech by handing out copies of what I would call Cannizzaro’s educational pamphlet, entitled Sunto di un corso di filosofia chimica (“Sketch of a course of chemical philosophy13) and first published in Italy in 1858. Once more, how did Pavesi actually pull it off? Had he agreed with Cannizzaro to join forces and stage this combined coup de théâtre at the end of the conference? How did Pavesi stop delegates who, probably, were hurrying to Karlsruhe train station? Again, we will never know. Lots of copies must have ended up in the bin, or slipped into briefcases and forgotten there forever. However, Lothar Meyer (and certainly Dmitri Mendeleev) read the Sketch as he was travelling back to Wrocław 8 (then known as Breslau), and he was deeply impressed, hence the quote that opens this post.

Sketch of a course of chemical philosophy, it’s all in the name, those two words that immediately stir up my attention, chemistry and philosophy. But there is more: look at these lines from the first page of this pamphlet: “In order to lead my students to the conviction which I have reached myself, I wish to place them on the same path as that by which I have arrived at it –the path, that is, of the historical examination of chemical theories14. Condensed in a few words there is an entire pedagogical approach to the teaching of chemistry, and remember that Cannizzaro was lecturing on the then frontiers of chemistry, not some commonly accepted “textbook” knowledge. Here is -you will forgive the misuse of this term- a peripatetic approach: retrace your own scientific journey together with your students and let them come to the same conclusions.

No paradigm for social constructivism

A final remark. I can already hear some voices in the background saying that scientific conferences like the one at Karlsruhe are compelling evidence that “science is just social construction”: after all, these chemists actually assembled at Karlsruhe in order to decide what ‘atoms’ and ‘molecules’ are, didn’t they? Well, unfortunately I do not have time to elaborate on this very interesting topic any further, a topic that should be addressed in a post of its own. That said, let me just add a quote from the fourth Reith lecture 2010 by Martin Rees15, already cited in a previous post:

The physicist Steven Weinberg has given an apt metaphor for scientific breakthroughs. He says: “A party of mountain climbers may argue over the best path to the peak, and these arguments may be conditioned by the history and social structure of the expedition, but in the end either they find a good path to the summit or they do not, and when they get there they know it“.

Deciding on the correct use of scientific terms is one thing (by the way, nomenclature has played a paramount role in chemistry since Lavoisier’s times), discovering a law which is valid for all known (and yet to be discovered) elements is quite another cup of tea. Call it tungsten or wolfram as you wish, its place in the periodic system will remain always the same. After all, the Karlsruhe congress failed to achieve consensus, and, despite this, the shock waves generated by Cannizzaro’s paper (and speech) would shake the foundations of chemistry to rebuild this discipline on firmer ground: the periodic law.

A handshake is not a chemical bond.

Footnotes

  1. See also The Karlsruhe Congress: a Centennial Retrospect, Aaron J. Ihde, Journal of Chemical Education, 1961, 38, 83
  2. The interested reader could refer to A History of Chemistry, Bernadette Bensaude-Vincent and Isabelle Stengers, Harvard University Press, 1996
  3. As quoted in Alexander Mikhaĭlovich Butlerov, Henry M. Leicester, Journal of Chemical Education, 1940, 17, 203, doi:10.1021/ed017p203
  4. As reported in When Science Went International, Sarah Everts, Chemical & Engineering News
  5. “L’idée de provoquer une réunion internationale des chimistes appartient à M. Kekulé”, in Compte rendu des séances du congrès international des chimistes réuni à Carlsruhe, les 3, 4 et 5 septembre 1860, Charles-Adolphe Wurtz.
  6. Not surprisingly, these three languages are still today’s working languages of the European Commission, as in http://ec.europa.eu/stages/information/faq_en.htm.
  7. As reported in Der internationale Chemiker-Kongreß Karlsruhe 3.-5. September 1860 vor und hinter den Kulissen, Alfred Stock, Verlag Chemie, 1933
  8. Translation included in The Congress at Karlsruhe, Clara de Milt, Journal of Chemical Education, 195128, 421–425, doi:10.1021/ed028p421
  9. Retrieved on Thriving for Unity in Chemistry: The First International Gathering of Chemists, Michael W. Mönnich, Chemistry International, 2010, 32 . Meyer wrote this quote in the foreword to the 1891 translation of Cannizzaro’s textbook, Abriss eines Lehrganges der theoretischen Chemie. Translation by A. Miolati and edited by L. Meyer. pp. 52–58, Engelmann, Leipzig (1891).
  10. Robert K. Merton, The Normative Structure of Science, 1973. Recently, originality has been added as fifth principle before skepticism to obtain a nice acronym, CUDOS…
  11. Berzelius’ chemical notation had a major impact on chemistry: the symbols of the elements still follow Berzelius’ approach (the first letter of the Latin name of the element, or a capital letter and a lower case letter to avoid confusion), and the use of subscript numbers to indicate the proportions of elements in a certain compound (Berzelius himself used superscripts). The Swedish chemist was certainly influenced by Linnaeus’ nomenclature. Berzelius’ own symbolism incorporated conventions, now no longer used, to shorten the formulae, such as dots above the symbol of an element to indicate oxygen and a horizontal bar to indicate two atoms of a certain element. Berzelius developed his system, which eventually replaced Dalton’s notation, while he was writing a chemistry textbook in 1808. Similarly, both Lothar Meyer and Dmitri Mendeleev would include their own periodic systems in their chemistry textbooks as learning tools. For more information see A History of Chemistry, Bernadette Bensaude-Vincent and Isabelle Stengers, Harvard University Press, 1996
  12. I have not been able to retrieve the original French language version. An English translation is available online: https://web.lemoyne.edu/giunta/karlsruhe.html
  13. Available online.
  14. The original reads: “Per condurre i miei allievi al medesimo convincimento che io ho, gli ho voluto porre sulla medesima strada per la quale io ci son giunto, cioè per l’esame storico delle teorie chimiche
  15. Transcripts available online.

A day at the races

“[…]C’est le narcissisme qui vient nourrir la bête, parce que, paradoxalement, beaucoup de scientifiques vont accepter des indicateurs mal construits pour dire: «Ah, mon index h est plus élevé que celui de mon collègue qui, comme vous l’avez dit, est plutôt médiocre», parce que une des caractéristiques des chercheurs, hein, et des professeurs d’université, ce sont tous de grands individualistes avec de gros égos[…]”

“[…]This is the narcissism that feeds the beast, because, paradoxically, a lot of scientists are willing to accept poorly crafted indices to say «Hey, my h-index is higher than my colleague’s who, as you’ve said, is not that good» because one of the characteristics of researchers and university professors, say, they are all individualists with limitless egos[…]”

Yves Gingras, professor of History of Sciences at the University of Québec at Montréal, transcript at 14’00” (and my own English translation) from the radio programme L’évaluation, maladie chronique de la recherche scientifique broadcast on France Culture on 04/05/2015.

I have always been massively interested in Formula 1 (as a Ferrari fan of course), approaching the sport always from the technical viewpoint rather than the glitzy, Montecarlo-like glossy image. Put it in other words, as a young boy I used to dream of becoming a car mechanic (becoming a scientist came at a much later stage), only to service the sleek scarlet single-seaters from Maranello. Now, I do find it strange that I did not want to become a driver, but surely I was, and I am, fascinated by the drivers’ skills, their courage, and the epic narratives woven around motor racing.

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One can then easily imagine how happy I was when I could finally grab the opportunity to go and see the Saturday qualifying session of the British Grand Prix at Silverstone earlier in July. A glorious day it was, a day at the races, my ears were buzzing from the high-pitch whining of today’s F1 hybrid1 cars going through corners, while the acrid mixture of exhausts, fuel, oil, burned tyres was tickling my nostrils. Gone were the images on a TV screen: these cars were real, flashing past just across a fence, elegantly dancing through chicanes as if glued to the track by downforce.

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It was as I was watching Fernando Alonso, two-time World Champion and one of the finest, raciest drivers of the paddock, limping around in a struggling McLaren car that I started wondering: “If Alonso were a researcher, would he be fired for not delivering results as expected by the funding agency?”. The scream of the crowd rose high as local hero Lewis Hamilton sped past to grab pole position. Hip hip hooray Hamilton! “Here’s one with a quadruple h-index, at least for now”, I thought.

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Evaluation is NOT classification

Evaluation, classification, rankings, points…this is what motor racing is all about. Is it the same for scientific research? The topic of bibliometric indices, their use – and misuse – to evaluate and rank papers and researchers is a minefield, or I should say it is like racing on a wet track on slick tyres: it is so easy to spin and crash. We scientists complain about the indices, but at the same time we accept them and use them to our advantage if they can reinforce a grant application or our curriculum vitae. Ambiguity and confusion reign supreme. So I thought it was a good idea to straighten out this issue by resorting to someone else’s words. I happen to have listened to a very interesting radio programme on this subject, broadcast on the channel France Culture of the French public radio: L’évaluation, maladie chronique de la recherche scientifique. If you speak French, do take some time and listen to it. Otherwise, or if you are simply too busy, just keep on reading, and I will do a quick survey of the main points.

The guests of the radio programme, a researcher in theoretical physics and a professor of history of sciences, brought up several points worth remembering:

  • Scientometry, the development of parameters measuring how science evolves and progresses, were developed in the 1960s with an eye to creating an analog to the economic indices and ratings created in the aftermath of the economic crash of 1929 (and this is scary enough, my personal comment). Bibliometry is a subset of scientometry, exclusively dealing with publications.
  • The 1970s saw the dawn of a massive increase in the number of scientists and in the scientific output of universities and research centres. Citations were first introduced as a practical way of cross-linking papers forming a bibliography, but the pen-and-paper approach to bibliographic searches severely impaired their use as evaluation indices. However, the same decade marked the beginning of a new era in the evaluation in the scientific research, as funding institutions in the US started wondering if it was true that those who were funded also had the largest number of citations (this is most likely a tautology: they have the largest number of citations because they are funded).
  • Eventually, citations became evaluation parameters after the 1980s and the advent of information technology let the genie out of the bottle, solving the “data crunch” that had restrained bibliometry thus far. This led to the “evaluation frenzy” that started in the late 1990s, continuing to this day, while online databases allows the so-called “wild bibliometry”.
  • The number of scientists has skyrocketed; big science and big data characterise our crowded scientific arena. Hyper-evaluation seems suitable as an additional catchword defining the current scientific era. Yet, all too often we resort to indices that measure the wrong thing, like the h-index or, that are incommensurable with one another, like the impact factors of journals.
  • The h-index is unreliable because it scales with the number of papers to the power of 0.9: it is easy to see that a scientist with a small number of papers with several citations is more likely to have written reports of broader interest, despite having a smaller h-index than another scientist with more papers receiving fewer citations.
  • Citations themselves have to be handled carefully, as reviews and articles describing experimental procedures are likely to be very highly cited, but they are not necessarily ground-breaking.
  • Journal impact factors are primarily not comparable with one another because they include self-citations to the same journal. What is worse, the misuse of impact factor has a vicious effect on journals themselves and the overall functioning of scientific publishing, in ways that are easy to understand.
  • There will always be the need to evaluate scientific articles, research proposals, and the careers of individual scientists. The least worst approach is also the oldest, the peer review, which, in the words of one of the speakers, is like democracy in being [sic] “the worst form of government, except for all the rest” 2. Peer review was first introduced at the same time as the institutionalisation of science in the 17th century, to preserve the reputation of a given scientific academy or their journals (the first was established in 1665:  Philosophical Transactions of the Royal Society). Peer review was formalised in the 1930s in the US, as exemplified by the journal Physical Review Letters.
  • In conclusion, the take-home message is: évaluer, ce n’est pas classer, “evaluation is NOT classification“.

Let me comment on this. So, in an ideal world, peer review is the best option, and it also has the advantage of preserving the social angle, the human scale of the scientific endeavour: someone will take the time to go through the scientific articles of Dr X. Y., applicant for the post of associate professor at the university of Yew Nork. This person will discuss his/her opinion on the candidate with a panel of other people, and of course they will quarrel, disagree and but hopefully come to a shared conclusion and evaluate the candidate in the most objective way. Yet, as one can easily see, a human referee can fall prey to all sorts of subconscious (let alone conscious) bias 3, although the double-blind (the evaluator and the evaluated both do not know who the other is). More simply, referees might not have time to read the applicant’s articles with due care and attention: after all, refereeing and reviewing are not the most glorious activities for a scientist, many would argue.

Here comes the number to the rescue, this (purported) epitome of rationality, objectivity, unbiased evaluation. As I mentioned in a previous post, our fascination with numbers as accurate, impartial gauges of phenomena is probably a relic of Pythagorean thought 4, or, rather, it boils down to deeply-ingrained aspects of the human mind that the Pythagorean school was the first to identify and discuss. Give us our daily numbers, churned out by an algorithm (the more arcane, the better), and we can finally feel at ease, we can finally reduce the chaotic world surrounding us to a harmonic collection of numbers. The same holds true on a larger scale: just see the massive significance acquired by economic indicators such the debt-to-GDP ratio 5. Please, do not misunderstand what I am saying: as Galileo Galilei once remarked, it is definitely true that mathematics is a powerful language that we need to learn if we are to decipher the “book of the Universe”. Indeed, mathematics, not Kabballah-like numerology: unless one is familiar with the formula (or the algorithm), or the measuring device providing a certain number, the latter becomes an empty shell, a meaningless collection of digits. No number without its unit of measurement, as my secondary school teachers used to say. So true.

In this respect, numbers are definitely double-edged swords. There is a very contemporary eagerness to classify and rank: oneself against peers, and against oneself. Take amateur athletics, for example, one of the most popular sports activities: it is all too easy to shift one’s focus from running for fun (amateur actually means he who loves something), or to become ‘fitter’ (whatever it means, fair enough), to running as yet another opportunity to show off, bolster our online avatars, and measure oneself against others. Example: I own a GPS watch with heart rate monitor. A cool gadget. I use it regularly when I go running, I have realised that it has let me train better. Yet, when I bought it I struggled to disable all ‘social’ options of the watch: it was not happy to work offline, as I forced it to. At the end of the day, I thought, there was nothing to boast about (I am not such a good runner after all), and I did not see the point in flooding social networks with my own small-scale version of a data crunch. Here is where I see a similarity with the misuse of bibliometric indices: when humans are part of a network of peers, the temptation of pinning a badge on one’s shirt, or of going around with a performance tag to be proud of, is often too irresistible, and I have the feeling that this compulsive drive to rank oneself is on the rise in our contemporary “social network society”.

Yet, evaluation is not classification. As simple as that.

A racing life?

Let us wrap it up. The overemphasis on classification in today’s academic world seems to derive from the toxic combination between a penchant for numbers and rankings deeply ingrained in our psyche and the widespread access to all sorts of bibliography indices, academic databases and search engines. As a consequence, this anxious need to rank oneself compounds the stress arising from the policies introduced in several countries to evaluate (and often, of course, to rank) the scientific “output” or “impact” of individual researchers and research groups. Sometimes, these are time-consuming, complex and arcane procedures which gobble down precious energies that could be devoted to science.

I will leave it at that to avoid getting bogged down in a critical review of evaluation policies: after all, theleakyburette is a blog on chemistry and I want this post to be just a short foray into the minefield of the evaluation of scientific research. Generally speaking, I acknowledge that scientists, like everyone else doing whatever job, artistic or sporting activity, cannot escape some evaluation, which, in my opinion, works at its best when it is conduced by competent (human) referees on small, homogeneous samples. And yes, please, do introduce the double-blind as soon as possible.

Sadly, ever-increasing competition among researchers is all too often depicted, or perceived, as a cut-throat race in which scientists go so far as to cut corners in order to be the first to cross the chequered flag. Comparisons and metaphors aside, motor racing, at least, is racing by definition and uses timings to draw up a ranking. Whichever car+driver combination completes a given amount of laps in the shortest time wins. End of the story. Does the racing metaphor really apply to the competitive world of academic research? No, it doesn’t, I strongly believe so. In spite of what we researchers feel, and in spite of the famous “publish or perish”, science is not and must not become a race. Younger academics, in particular, have the responsibility of making sure that the spirit of the scientific enquiry does not drown amidst the rough seas of ambition and the rising tide of competition, and we should be extremely wary of the misuse of bibliometric indices. Let there be a bit of competition, like a dash of salt that seasons a dish, not like a charge of saltpeter, the blast of which we addictively need to move forth: as in old firearms, it can dramatically backfire.

However, motor racing can indeed be a metaphor of scientific research, but from another point of view. Think about the countless components that make up a racing car, provided by several manufacturers6. Think about the contribution of all mechanics who work overnight to troubleshoot and set up the car, while changing tyres in the blink of an eye during the race; let’s not forget the role of race engineers who advise the driver and devise strategies. Of course, it is the driver the one who, at the end of the day, risks his/her life to drive flat out and pushes the car to the limit and secure victory; yet, the driver’s success would simply be impossible without those who lays the foundations for success. So is the researcher’s role, the prominent tip of the complex machinery of a research laboratory or university. In this context, how on Earth could a simple number account for all the work done behind the scenes by countless people, every one of them adding their own contribution, be it large or small? Any bibliometric index referring to a single researcher will incorporate all these contributions and end up being a complex convolution of them. From this point of view, the significance of the h-index should be greatly reassessed: it is a number, nothing but a number. And as a number we all should regard it.

In the end, let me just stress it once more: the scientific enquiry is a collective undertaking. It is correct to give individual scientists the credit that they deserve for their outstanding contribution to the advancement of science; however, the increasing complexity and interdisciplinary nature of today’s scientific research must warrant an increased emphasis on teams instead of the individual. Someone has remarked that the Nobel Prize should be updated and awarded to teams as well7. A long overdue update indeed. On the other hand, I once heard someone saying (I honestly do not remember when and where) that the international mobility of researchers and the competition among universities to hire the brightest minds is the contemporary counterpart of the situation in Renaissance Italy, when all sorts of princely courts, city-states and statelets would vie for the most talented artists, who, in turn, ended up moving wherever they were offered the best ‘facilities’ to create their masterpieces. Art and science: one of my favourite subjects, so much so that I myself wrote at the back of my PhD thesis that the research group is the contemporary analogue of the art workshop of the Renaissance. That said, there is a fundamental difference between artists and scientists, which Martin Rees, then President of the Royal Society and Astronomer Royal, clearly expressed in his last 2010 Reith LectureRunaway World 8. In a nutshell: the individual scientist is disposable, the individual artist is not, but his/her contribution might not last as long. In Rees’ own words 8: “Any artist’s work is individual and distinctive – but it generally doesn’t work, doesn’t last. Contrarywise, even the journeyman scientist adds a few durable bricks to the corpus of ‘public knowledge’. But our contributions as scientists lose their identity. If A didn’t discover something, in general B soon would – indeed there are many cases of near-simultaneous discovery. Not so, of course, in the arts. As another Reith Lecturer, Peter Medawar, remarked, when Wagner diverted his energies for ten years, in the middle of the Ring cycle, to compose Meistersinger and Tristan, he wasn’t worried that someone would scoop him on Götterdammerung. Even Einstein exemplifies this contrast. He made a greater imprint on 20th century science than any other individual; but had he never existed all his insights would by now have been revealed – though gradually, by several people, rather than by one great mind“.

Let us learn and savour the pleasure of assembling our cars, bit by bit; let us feel the skin-like texture of the warm rubber surface of slick tyres when they come out of the blankets. Let us take the wheel in a firm grip and secure our safety belts as we sit in the cockpit. And when we head off onto the track to race for pole position, let us not forget: “What science teaches us is not the fulfullment in the act of finding, but beauty awakened in the moments of searching9.

Footnotes

1. As of last season, F1 racing cars are equipped with a dazzling array of energy-recovery and energy-storage systems. Here the word hybrid is really to be understood in its deeper meaning: the internal combustion engine, the braking system, the turbocharger, and an electric motor all dance in unison to a tempo that can change from lap to lap to deliver either more acceleration or a higher fuel economy. The basic principle is: when it comes to energy, every little helps. For example, braking can then become a source of energy, harvested and stored, or delivered directly to the electric motor. A battery is the major energy storage device, but others can be envisaged, such as flywheels or supercapacitors. (By the way, batteries and supercapacitors are the battlefield of electrochemistry, my own discipline). The complex sequence of events taking place when the driver brakes or accelerates needs adaption in terms of driving style with respect to previous cars (up to the 2013 season). Hence the ongoing problems experienced by Räikkönen: he has been prone to spinning, which can boil down both to his driving style not matching the new car and shortcomings in the management of energy harvesting and delivery in his Ferrari. Racing geeks like me can read a full account of technicalities on this webpage.

2. Winston Churchill’s quote seems to have been: “Many forms of Government have been tried and will be tried in this world of sin and woe. No one pretends that democracy is perfect or all-wise. Indeed, it has been said that democracy is the worst form of government except all those other forms that have been tried from time to time.

3. An article appeared in Le Monde diplomatique (French edition), June 2015, Personne n’est à l’abri, (“Nobody is safe“) by Marina Maestrutti, discusses four subconscious biases contributing to the development of conspiracy theories. Scientists (and referees) should be wary of (some) them as well: conjunction fallacy (we tend to overestimate the correlation between any two distinct events), causation fallacy (we tend to prefer explanations involving clear-cut causation rather than admitting that purely random events took place), the exposure fallacy (we are heavily influenced by explanatory models or theories to which we are exposed, and we tend to construct a validation of them from available observation) and the verification fallacy (we tend to seek corroboration of theories that we hold true a priori rather than looking for evidence falsifying them).

4. Hilariously enough, the h-index is an integer, the type of number Pythagorean disciples worshipped.

5. A more scholarly discussion dealing with the veneration of numbers as tools of economic and political governance can again be found in Le Monde diplomatique (French edition): Le rêve de l’harmonie par le calcul (“The dream of harmony through computing“), Alain Supiot, February 2015. From the abstract available online, here is my own translation: “The fascination for numbers and their ordering power is ancient; it is not unique of Western cultures. The interest in their symbolic value is one of the key features of Chinese thought, and the contribution of Indian, Persian and Arabic mathematics to this discipline is well-known. Yet, it is the Western world that has continuously deepened its analysis of numbers: at first venerated idols, later on they became instruments of knowledge and then of prediction, only to be endowed with a truly legal value by means of the contemporary practice of governance through numbers.”

6. An Italian firm based in the Bergamo area (yeah!) is the leading supplier of brakes, for example (look up the name yourselves!).

7. In Scientific American.

8. Transcripts available online.

9. V. Uskoković, in Foundations of Science, 201015, 303-344

Through Griess-coloured glasses

Throughout the history and prehistory of chemistry, color played a pivotal role. Archeologists found that colored glass-like stones were made both in Egypt and Mesopotamia before 4000 BC; the earliest synthetic pigment (blue ground frit, CaO-CuO-‍4SiO4) was already produced about 2650 BC[…] The alchemical hierarchy of metals – with lead at the bottom, copper somewhere in the middle, and gold at the top – is grounded on an aesthetic hierarchy of colors (black, red, yellow), which is incidentally preserved in the German flag. It might even be said that the whole obsession with gold, before it was established as a currency by convention, was based on nothing else than on the aesthetic preference of its color and shine. It is also well known that the 19th-century success story of the chemical industry had its main source in the mass production of synthetic dyes[…] their cheap and non-fade dyes rapidly spread all over the world and changed the visual environment in such way that it is fair to speak of an aesthetic revolution.

Joachim Schummer, Aesthetics of Chemical Products – Materials, Models, Molecules, in Hyle, 9, 2003, 76-77

Chemistry, as Schummer reminds us, is first and foremost a sensual experience, and I rejoice whenever there is a chance to run an experiment involving brightly coloured materials. So, when I started my exploration of simple inorganic nitrogen molecules, I did not have many reasons to cheer up: in fact, I thought that NO2 was the only coloured animal to be found in this bestiary1, and not a particularly pleasant one. During my PhD, the custom of cleaning glassware in boiling sulphonitric mixture2 meant that my nose became adept at picking up the distinctive pungent note of NO2 scratching its way into my nostrils like a clawed paw. An orange haze sometimes hovered above the boiling acid mixture, in particular when it was freshly made, or when it was rich in nitric acid (or when it was accidentally overheated). I often stood in awe, feeling safe on the other side of the closed sash of a fumehood as I kept staring at the orange vapours drifting upwards like flames rising from a liquid inferno. After a few months in the lab, I realised that I was able to detect NO2 effortlessly in the exhaust gases puffing out of the Diesel engine of buses, and I developed a vicious habit: as I was cycling behind an accelerating bus, I used to suck in a deep breath, only to wait for that acrid gas to hurt my nose. Possibly, it was a subconscious way of remaining constantly alert to the presence of this very toxic molecule: the nose is a fairly good detector, although it becomes saturated on a very short timescale.

Little did I know that I would have to wait a few extra years to quench my thirst for coloured molecules, and that would involve tearing a page from the inorganic nitrogen family album to dip it into organic chemistry, like a forgotten photographic film brought to life by a developing bath. That torn page reads nitrite.

So here I was, a researcher in an Oxford laboratory, and I was faced with this problem: how to detect and quantify micromolar (µM) levels of nitrite in solution. “Ion chromatography? Yes, why not…if only I could get hold of a column and the right detector before my fellowship ends! No, I can’t bide my time, I need something now”. Suddenly, a name emerged from a dusty drawer, from long-forgotten files of my undergraduate years: diazo coupling.

It was the spring of 2004, a season born of a cold March, when a late snowfall unexpectedly hit Milano on the 10th of that month. I was young and hopeful, energised by that carefree attitude of the twenty-somethings, and feeling worried only about the end of term exams. Chemistry was somewhat more coloured back then, although the dull ochre solid in my round-bottomed flask was the blatant evidence of a multistep organic synthesis gone wrong, a step of which involved using an ice-cold acidic sodium nitrite solution. Where was the bright orange dye3 that I was promised, the first really useful molecule I had ever made? A dripping pipette, the pH shifts, and the final colour is wrong. Matter, the unpredictable foe of every chemist, had got the upper hand once more, and the ugly brownish paste even ended up smearing my cotton sweatshirt. Luckily, this dye does not feature affinity for cellulose fibres, and it disappeared after the first wash, leaving behind only a bizarre whitish halo, as if the dye had bleached the original colour. I still own that tattered sweatshirt, a humbling memento of the inevitable failures inherent to the chemist’s trade.

Fast forward to 2014, and that multicolour drawer brimming with azo dyes was open again; it was nitrite that worked its magic, in the presence of an aryl amine, and so I thought that there must have been some commercially-available reactant for the spectrophotometric determination of nitrite. After skimming through the catalogues of chemical suppliers, I came across what I needed, the modern reincarnation of a time-honoured chemical assay: the Griess test.

Peter Griess

On a typical procrastination spree, I went on to read some vintage papers4 by and on Peter Griess5 (1829 -1888). It was hard work (euphemism!), my German being rusty at best, or most likely completely pulverised into disconnected syntagms, and encroached by Dutch (no offence taken on either bank of the Rhine!). What a pity: one might rightfully claim that German is the most chemical language, not only because of some of its structures do remind me of chemical connectivity, but also considering the massive contribution of German chemists to the development of modern chemistry and chemical industry in the 19th century. While working my way through these publications, I came to appreciate the enormous impact made by Peter Griess on the development of organic chemistry, and I realised with astonishment that nobody, during my organic chemistry undergraduate classes, had ever mentioned his name. Every chemist knows Kekulé, but maybe not his contemporary Griess, the first to report on the preparation of aryldiazonium salts (in 1858)6, a reaction that paved the way for the development of synthetic dyes, and a veritable “rainbow revolution”, along with Perkin’s synthesis of mauveine in 1856. Griess’s original description of the diazonium salt prepared from picramic acid,

picramicacid

goes like this, in Hofmann’s translation6: “On passing a current of nitrous acid into an alcoholic solution of picramic acid […] the red liquid assumes at once a yellow colour, and furnishes rapidly a copious deposit of yellow crystals. […] The new body7, for which I propose the provisional name diazodinitrophenol, is soluble in alcohol and ether, and crystallizes from the former solvent in magnificent golden-yellow plates, which detonate on heating. […] on ebullition with water it appears to undergo decomposition; alkalis induce at once a copious evolution of gas […] the gas evolved consisting, according to a minute examination, of perfectly pure nitrogen“.

In addition, my foray into the life of Peter Griess let me peep behind the scenes of his scientific career…


Marburg is surrounded by gorgeous wooded hills, an idyllic setting ideal for a relaxing afternoon stroll away from the hustle and bustle of downtown academic life. Two gentlemen in their forties, walking stick in one hand, the other fiddling with the chain of the pocket-watch hanging from their vests, are chatting in a low voice while following an uphill path at a leisurely pace. The summer strides above them in the arched, cloudless sky.

– I wish I could keep him here, dear August – said one of the two gentlemen – you should really know how gifted this bloke is. He works flat out, he’s got intuition, and he’s committed. I’ve seen him in the lab these months, handling these diazo bodies, nasty stuff, he’s got practical skills, he’s curious, and hungry for knowledge. He could churn out paper after paper, and become a leading scientist in the field, were it not…

– Were it not for…

– Well…his father, his family, they’ve got no money to support him. His father, I don’t know, must be some sort of penniless farmer, a rustic peasant, whatever, he’s hard up. He can’t afford to pay for his son’s career anymore. That’s too bad for Peter, he’s already achieved so much despite his father’s pressure to find a permanent job and to settle down. But now, well, Peter’s got to find the means to keep himself afloat on his own. So I wish I could keep him in my lab, oh, if only I had funding for a research fellowship, then I’d tailor the vacancy on Peter! But no, and not even in the foreseeable future, nothing, nothing at all for him. I can’t hire anyone else, August. I’m worried Peter might end up following his father’s advice and quit academia.

August stops walking and looks straight into his friends’ eyes with a snug gaze, he knows what is next.

-Take him to London with you, to your lab, find a position for him, you won’t be disappointed! Let him work, give him freedom and equipment, and you’ll see what he can do in a couple of months!

Indeed. August is taken aback by his friend’s enthusiasm for this unknown young chemist, but he expected to hear this. He pauses and breathes deeply, while tweaking his moustache with his left hand. Then, trying to look as impassible as ever, he gently taps on his friend’s shoulder with the handle of his walking stick and says:

– Hermann, come on, come on, it’s not so easy! You know my lab in London is packed full as well. Yes, there’s lots of money for research in England these days…finally fat years after the lean ones…but when it comes to staff, there’s no vacancy at all! I’ve brought the most talented youngsters over from Germany, and I’ve already got my dream team…not even the my former supervisor at Giessen8 can boast such a research group. I wonder where could your Peter…

– Ehm… Griess

– Yes, I wonder where your Peter Griess would fit in this picture at all!

– Right, right, I see what you mean August, but let me try and convince you. I’ve got a printout of his latest communication, it’s a stunning piece of work, all new stuff, new reactions he’s stumbled upon and studied with the utmost commitment and passion. Read it tonight before going to bed, and sleep over it. And also, Peter will be in the lab tomorrow morning, very early. I’ve got to teach at 9, but why don’t you come with me, I’ll introduce you to him, and the two of you can have a quick chat. He’s going to show you what he’s working on, he won’t let you down. Please, August!

August is used to Hermann’s sanguine temper, and he does not feel like upsetting him. At any rate, why not taking this opportunity to read a freshly-printed paper and to talk about cutting-edge chemistry with his friend? August will think about this Peter Griess later on. But anyway, he had better be really good…

The two friends turn back, and walk home as the sun is setting.


Even today, how many professors’ chats like this9 can make or break the career of a young scientist? The year was 1858, but it seems like yesterday. Eventually, Griess impressed Hofmann and left (Hermann) Kolbe’s laboratory to join Hofmann’s group at London. This group was a scientific powerhouse, and Hofmann modelled it on his former supervisor’s laboratory at Giessen. Hofmann’s management of his own research group was simply astonishing, and thanks to his young talented coworkers “the London school stayed abreast of the latest chemical thinking on the Continent, and with their help the school became for a while the most productive organic chemical laboratory in the world after Giessen10. In a fruitful exchange between academia and industry, most of the young researchers left within three years, when “Hofmann got them better paying jobs, usually with British chemical firms.10. So did Peter Griess, who joined a brewery in 1862, in an early example of the typical scenario of the “young talented researcher leaving academia to get a (better-paid), steady job in the private sector and settle down”. A career shift from explosive diazonium salts to pale ale, and the relocation from London to Burton-upon-Trent: these must have been quite challenging times for Griess, who, to make matters worse, was not really proficient in English 6.

Griess’s test

I should stop beating about the bush, let us go back to the lab. The classical Griess test involves a two-step reaction:

The first time I carried out this simple test, the bright colour filled me with such joy that I wrote a smiley in my laboratory journal (who on Earth has ever said that laboratory journals should be impersonal, devoid of emotions?). I kept staring at the lively pink solution dancing in the plastic tube…

20150528_155242

…and I could not help thinking that lonely nitrite had finally found love in the twin embrace of the sulphanilic and napthilic moieties, the happy, colourful ending of nitrite’s tale. No sooner had I thought this than I started humming a well-known tune:

…Quand il me prend dans ses bras
il me parle tout bas
je vois la vie en rose…

(Edith Piaf, La vie en rose)

This “pink” (or, as my student used to say, “purple”), is nothing but a charming illusion created by the brain and its optical sensor, the eye. As far as light is concerned, wavelengths (symbol: λ) replace perception, and a suitable instrument (spectrophotometer) can record the following absorption spectrum for the azo dye obtained as a result of the Griess test. The peak maximum corresponds to λmax = 540 nm

18

I shall resist the temptation of boasting that my eye, like my nose, is also highly trained at recognising the faintest pinkish hue in very diluted samples. Honestly, I have been able to detect the colour unambiguously only at nitrite concentrations between 2.5 and 5 µM (not too bad!), when the measured absorbance ranges between 0.06 and 0.11 (for a 1 cm light path).

If you think that you have seen such ‘fluorescent’ pink in the lab before, you are probably right: Griess pink looks stunningly similar to the colour of a solution of another, but completely unrelated, dye, Rhodamine B.

rhodamineb

Its absorption spectrum in ethanol shows a λmax at 542.8 nm, almost bang on, just a bit redder. I first met this dye during research on soft matter when I was an Erasmus student in 2006…but this is another story, another blog post.

Let’s go back to diazo dyes and nitrite. Since I wanted to determine the concentration of the analyte in my samples, I moved on to record the absorbance as a function of nitrite concentration, fitting the data with a linear fit routine to obtain a calibration “curve”. Then I sat down and stopped for a while, looking at the plot, and I somehow felt like a rambler who is about to set off on a long walk well-equipped with a detailed map. There is something reassuring about these straight lines shooting upwards from the interception of the Cartesian axes and cutting through the neatly arranged experimental points like the trajectory of a crossbow bolt piercing through a line of apples. Calibration curves trace a path, carving out an ordered, knowable space from the untidy, bewildering world that surrounds us. This treasure island affords quantifiable information, while all around rough seas, the messy business of life, threaten to wreck our frail boat. Instead, a calibration curve is a safe haven where one can lie at anchor and fathom the depth of the sea from a vantage point. There is yet another interesting aspect: calibration curves associate an observable phenomenon or quantity with a number (plus experimental error), and here I see a clear connection with the Pythagorean philosophical stance, which sought Nature’s harmony in the realm of numbers and proportions. Could calibration curves possibly be unconscious reincarnations of Pythagorean thought?

Griess’s grief

The unpredictable twists and turns of life do bend our trajectory from the linear path charted by calibration curves.

In 1869, a few years after moving to Burton-on-Trent, Peter Griess married Louisa Anna Mason, the daughter of the most renowned medical doctor in Burton. Tying the knot, settling down, starting his own family: we can only speculate what all of this could mean to this forty-year-old chemist in the second half of the 19th century. A dream coming true? The accomplishment of the bourgeois life path expected of all respectable men? The make-or-break attempt to try and integrate, once and for all, in the English lifestyle that Griess found so foreign to him?

Several letters provide a glimpse into Griess’s family life: he comes across as a caring husband and father. His wife soon fell seriously ill, eventually being unable to leave the house, and she was even bedridden for months. Griess “lovingly devoted to her all of his free time”, and “his ill wife was the focus of his loving care for years”4. Despite the joy from his sons’ achievements, Griess was filled with a deep longing for his homeland11, but his wife’s illness and the upbringing of his children prevented him from travelling back to Germany as often as he would have wished to. In particular, he had to turn down a tantalising job offered by his friend Heinrich Caro, by then a major figure at BASF.

Sadly, rarely can we resort to a calibration curve to find our bearings, as the experience of life is all too often an imperfect reaction, like that brownish dye I made in 2004. Seldom is there a colourful nemesis for nitrite.

Footnotes

1. To be honest, sodium nitrite is a (sickly) pale yellow crystalline solid, but nothing impressive enough.
2. A mixture of concentrated sulphuric acid and nitric acid. Yes, sulphuric, I like writing it the old way, it looks more ‘alchemical’.
3. I think it was a dye of the “Acid Orange” family, but I cannot recall its exact name.
4. See the bibliography at the bottom of the Wikipedia page on Peter Griess. In particular, Bopp, A., v. Hofmann, A. W. and Fischer, E., Zur Erinnerung an Peter Griess Ber. Dtsch. Chem. Ges., 189124: 1006–1078, makes for a very engaging read, full of first-hand insight into Griess, the chemist and the man.
5. Yes yes yes, I know, the purists are right. It ought to be written *Grieß*. I don’t feel like scaring the non-German reader this time…keep it simple.
6. Available in English as a report to the Proceedings of the Royal Society of London, translated by Griess’s mentor August Wilhelm von Hofmann: On New Nitrogenous Derivatives of the Phenyl- and Benzoyl-Series, Proc. R. Soc. Lond. 1857-1859 9, 594-597. Hoffmann was working at the Royal College of Chemistry at that time and shortly afterwards he offered Griess a position at his laboratory in London.
7. Körper in the German original. Body, as referred to a substance, is literally correct, although it might look a bit weird nowadays.
8. Justus von Liebig’s chemical laboratory was based at the University of Giessen (yes, purists, another ß gone)
9. The original German “transcript” of this chat, and the follow-up, can be found on pages 1023-1026 Zur Erinnerung an Peter Griess
10. William Henry Perkin, too, was working under Hofmann’s supervision at the Royal College of Chemistry when he serendipitously synthesised mauveine. More information in John J. Beer,  A. W. Hofmann and the founding of the Royal College of Chemistry, in J. Chem. Educ., 1960, 37, p 248.
11. “Die Sehnsucht nach der alten Heimat hat Peter Griess nie ganz verlassen“, R. Wizinger-Aust, Peter Griess und seine Zeit, Angew. Chem. , 1958, 7, p 199