Oregon State UniversitySpecial Collections & Archives Research Center

“Indigo - A Story of Craft, Religion, History, Science and Culture,” Dr. Roald Hoffmann

April 19, 2012

Video: “Indigo - A Story of Craft, Religion, History, Science and Culture” 

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1:28:29 - Abstract | Biography


Faye Chadwell: Welcome to the 2012 Linus Pauling Legacy Award Lecture. My name is Feye Chadwell and I am the Donald and Delpha Campbell University Librarian and Oregon State University Press Director. The OSU libraries are really very happy and proud to be the sponsor of this award and this lecture tonight. We are also really proud that our supporters and advocates for OSU libraries and OSU press make this event possible and I want to thank you for coming out tonight. And I can assure you that we are going to have a very interesting lecture tonight based on my conversation with Dr. Hoffman at dinner. And I also want to thank you for joining us to recognize him and the legacy that was begun and has been built upon by Linus Pauling. Before we begin with the lecture, I want to introduce someone who has played an important role at Oregon State University in terms of our History of Science program and that person is Dr. Mary Jo Nye. Dr. Nye is Thomas Horning professor of humanities and professor of history emeritus at Oregon State. She came to Oregon State in 1994 and held the Horning Chair appointment until her retirement in 2008. And prior to coming to OSU, she was a faculty member at the University of Oklahoma from 1970 to 1994. Her Ph.D. in the History of Science, and she is a historian of science, is from the University of Wisconsin. She’s also held various research appointments at institutions such as the University of Pittsburgh, Rutgers University, the Institute for Advanced Study at Princeton, and the Max Planck Institute in Berlin.

Her research interests are obviously history of science but especially the history of chemistry and physics since the 18th century in Western Europe, United Kingdom, and the United States. She’s widely published and her most recent book is Michael Polanyi and His Generation: Origins of the Social Construction of Science published the University of Chicago Press. Among her many honors are also the History of Science Society’s Sarton Medal for life time scholarly achievement in 2006. Please join me in welcoming Dr. Nye. Thank You.

Mary Jo Nye: It’s very nice to see so many of you here tonight and of course tonight is not about me, it’s about our guest, Dr. Roald Hoffman. It’s a very great pleasure this evening to introduce Professor Roald Hoffman to you. Earlier this evening, Roald formally received the Linus Pauling Legacy Award, which is given every two years to distinguished individuals whose achievements are in keeping with the legacy of Linus Pauling. The Legacy Award is only the most recent in a long array of honors and awards throughout Roald’s career, perhaps the best known of which is the 1981 Nobel Prize in chemistry shared by Kenichi Fukui. In this and his chemical research of the last fifty years, Roald has played a major in using quantum mechanical theory, mathematical computation, and experimental data to explain and predict chemical properties and reactions on the basis of the arrangement and energy of electrons and molecules. Linus Pauling’s former student, William Lipscomb, was one of Roald’s mentors at Harvard, making Roald a Pauling student once removed. Together with Lipscomb calculated electronic structures for compounds of boron, one of Pauling’s own interest but they used the approach of molecular orbital theory as its called rather than Pauling’s preferred method based on the electron bond between atoms. They had great success and Roald’s subsequent research initially in collaboration with Robert B. Woodward on the electronic structure of transition states and intermediates in organic reactions lead to the Nobel award of 1981. [5:07]

The whole kingdom of organic and inorganic molecules and materials falls within the purview of Roald’s work, which has resulted in the synthesis of entirely new but predicted by him and his research groups, new molecular structures. Recent research in his research group at Cornell University still going on has focused to, on the solid state and on molecules and matters at very high pressure.

In addition to his title of Professor of Chemistry at Cornell, Roald is the Frank H.T. Rhodes Professor of Humane Letters. The two titles suggest the multiple overlapping roles of Roald’s long professional career as chemist, educator, poet, playwright, philosopher, and essayist. He is a legendary teacher who has continued throughout his career to teach regularly the first year general chemistry course at Cornell. He helped write and present the college oriented television series “The World of Chemistry” which premiered on PBS in 1990. He often can be found on Sunday evening’s, once a month at the Cornelia Street Café in Greenwich Village where he hosts readings, music, dialogs, and poetry about science and other matters. Roald is the author of chemistry textbooks and poetry, plays, and essays. His best known play, Oxygen, coauthored Carl Djerassi explores the worlds and passions of chemists past and present through the story line of the award of a retroactive Nobel Prize for the 18th century discovery of oxygen. His most recent play, Something that Belongs to You, draws upon his boyhood experiences in hiding in Nazi occupied Poland and on the struggles of survivors to forget, remember, and forgive.

Among his books and essays, the beautiful volume, Chemistry Imagined, coauthored with the artist Vivian Torrence pairs her vivid collages with short essays and poems. Tonight’s lecture offers us a sample of Roald’s extraordinary talents and his gentle wisdom as he reflects on what we can learn from the story of indigo dye about craft, religion, history, science and culture. Roald.

Roald Hoffman: Thank you for that wonderful introduction. It’s great to be associated with Linus Pauling’s name as you can imagine because he is a legendary figure in chemistry and in the theory of chemistry. The association is also important because of Pauling’s interests outside of chemistry. The particular balance of experiment and theory. He was America’s premier structural chemist as he became a great theoretical chemist and it is the authority based on that experimental work which made people listen carefully to his theory. I also take pleasure in the association that Pauling was a great expositor, teaching in the more general sense of empathy and reaching an audience was very important to him. And so it is to me. So I am very glad to be associated with this award. [9:42]

The lecture that you will hear is nothing to do with my science but it has everything to do with me. And you see where I head with this. So one thing that interests me is protochemistries. And by protochemistries I mean the chemistries which people did before there people called chemists. And we were put on this Earth to transform it. And we have to worry about that but people have been transforming things whether it’s in just cooking, or in medications, or cosmetics or cleaning agents, medicines, winning metals from their ores. All of these things were interesting and quite important technologies which people mastered and passed down before there was science. Now why are they important to me or why I think they are important in general is because somehow we have this separation of science from normal behavior. And so its important to humanize science and the chemistries that were done before there were scientists are then to me the natural bridge for that.

So here are three master works from world art, the Luxor Thebes paintings in the upper left from now Egypt; in the center the Gate of Ishtar which once stood in Babylon and then through a feat of imperialism for a change not American but German found its way to Berlin and at the right you see Helenistic wall painting a period of representation or realistic art which preceded the Italian Renaissance fifteen hundred years. In all of these you see a green or a blue, that green or blue is not a product of nature which was always available by that mineral that you see at lower left which is lapis lazuli when then powdered became ultra marine. And you can see in Giotto Fresco, when you had money to use that, how beautiful that blue could be. But the blue that you see in these things in different forms is a product of human manufacture and ingenuity and comes from the Egyptians’ mastery of glass and enamel and is essentially a powdered glass frit with the usual components of glass not thrown [?] and silica and also a blue pigment related to turquoise, a copper salt of some sort. And that was a product of commerce for two thousand years and went all across the Middle East and was used and sold and it was a chemistry. It was a transformation of nature, it was not a natural product. Now when it came to dyeing textiles and the textiles of the ancient world were largely wool and linen and cotton came in rather late into this story. When it came to dyeing fabrics, that Egyptian blue was not good; you could not use the inorganic pigment. There is an art to dyeing, which some people in the audience will know more about than I do but here is an example of the earliest carpet we have, probably of Persian origin from the representation of the figures but it was found in lower Siberia, imported probably and you see third to fourth century BC. Not too many things survived, textiles don’t survive very well. Here is way on the other part of the world. So what is the blue in that textile, in that green? That’s the question. Now here is way on the other part of the world, these are the incredible textiles which have survived much better because of the climate from South America, roughly the region which is now Peru. The Moche, Wari and other pre-columbian cultures. The one at right is rather late from about 9th to 12th century AD, the one at left is a markedly modernist design and is older than that. And these have survived in remarkable ways. Way off in another part of the world, this is in a woodcut but it is of a Japanese gentleman wearing a kimono which is dyed in this blue. Very appropriate formal wear here. Again the blue here and here you see back in to Africa and the Middle East; at right in Yemen. At left you see the typical adire cloth of Nigeria of Western Africa. These are all indigo dyed fabrics and that is the blue that I want to talk to you about. It has different names in different cultures and it has various origins. [15:30]

But a little bit of history now, that blue has various forms. And the first form that I want to talk to you about is the one which is known not so much by the name blue but is known as the Royal Tyrian Purple. And it is also indigo or modifications of it. There are precious few snippets of Roman fabrics that have survived and this is a mosaic, obviously not a fabric, of the Emperor Justinian but you see the purple of the robe here. That is what I wanted to show to you. That purple was very, very precious, I’ll tell you in a while why it was so precious but it was regulated by the Romans, its manufacture was restricted geographically to certain regions, and also the wearing of it was restricted. So only the emperor or a general in full triumph could wear a full purple robe; whereas, the consuls and praetors could robes only purple in strips of it. It was very highly regulated by the Roman Empire. Meanwhile, the Hebrews wrote it into the bible, not under the name of Tyrian purple. And the passage here from Numbers begins at lower left “the Lord said to Moses as follows ‘speak to the Israelite people and instruct them to make for themselves fringes at the corners of their garments throughout the ages. Let them attach a cord of blue to the fringe at each corner.” Now what fringe are they talking about?

And it then goes on, the fringe here is the one you are likely to see in cities which have an observant Jewish population, if there are any Hasidim around, you’ll see kids running around with these fringes hanging out of their garments. It’s a poncho-like undergarment whose other manifestation is in a prayer shawl, a tallit, and here you see the strands and there you see the blue here is in a little more detail that is tied on to the end of this prayer garment, except if you watch the Hasidic kids, 99% of them, the fringes are all white, despite that one commandment which is very directly in the bible and there is a reason for it. The importance of this cord of blue is very deeply imbedded in the traditional Jewish religion and it occurs for instance; there is the bible and then there is oral law which were discussions of the rabbis called the Talmud from 500 BC to 600 AD when it was written down finally. And the Talmud is organized according to sort of chapters you could say on daily life. So there is a fifty volume work and one of the volumes is on divorce, it goes like that. The bible doesn’t tell you what to do about divorce but the Talmud tells you. And one of the first chapters is on blessings and the discussions go, it’s interesting how it looks here typographically, it’s quite remarkable. There is a central column which is older, there are commentaries; there are footnotes on footnotes on this. It’s interesting to see this even if one can not read the Hebrew. But what is the discussion that’s going on? The discussion that is going that the rabbis are discussing: when should you begin the morning prayer? Remember there is no GPS, there is no clocks, when should you begin the morning prayer (one of the three prayers that you need to say) and so the discussion goes among them and eventually one of the rabbis suggests and the others agree that begin to say the morning prayer when you can tell the blue from the white in the fringes of your garment. And that is agreed on but it just shows the importance of this, it’s also a primitive color test, you don’t see in the middle of the night the color blue without illumination. This is the only surviving piece; it’s a tiny fragment less than an inch across from a Jewish ritual fabric of this time. It’s survived in rather dramatic circumstances, it was part of what was left over after the burning of Masada the fortress where the last resisters in the war against the Romans of about 90AD committed suicide and this blue has been tested to be the same pigment. [20:49]

Now what I forgot to tell you was that the word that’s used for blue here in Hebrew, some people forget that this was written in another language, and their word was tekhelet which is this very special word that the Talmud then goes on to explain and it’s not the usual Hebrew word for blue. So it’s a ritual blue, also the garments of the priests in the temple were specified to be of that. And that blue, as well as the Tyrian purple came from, here are the shades of it but even the shades and this is of course a contemporary fabric, in the Talmud but even by the time it’s written down, its not clear what color that blue is in terms of perception and there is a debate. Is it, a medieval commentator Rashi writes, green as leeks? But he doesn’t have the word leeks in Hebrew so he substitutes “poireau,” the French word and that’s transliterated into Hebrew. Very interesting things are going on historically and culturally but this blue and the Tyrian purple comes from a rather unusual source to us today but a historically important source and the first source of indigo that I want to talk to you about and this is a variety of snails that are found the Mediterranean. Murex is one species, imatoma [?] is another one. And they are found throughout the Mediterranean, I’ll show you some evidence of that later on.

From every place in the Mediterranean, from the most polluted part of the Port of Marseilles to the beaches in Lebanon, it is these snails are easily found. And if you break open a snail, you find a gland there. That gland has been dyed now, it usually is just as beige colored, flesh colored as the rest of it but you do have to, in normal course of events, you can try to milk the snails without killing them, most of the time you have to kill them for this. Break open the shell and extract this gland about a centimeter long, two to three millimeters wide and when you extract it and break it under the action the action of sunlight (not in the dark) and with the action of an enzyme that’s there naturally in the biological material, it turns from yellow, pus yellow to green, eventually to blue and it stains your fingers very well, better than lets say Montblanc black fountain pen ink. You can wash it out in about two or three washings but it will stain things pretty well. I’ll come back to that because that staining is not sufficient to allow it to become a commercial textile dying product and something else had to be done.

Now these snails are a veritable aggressive factory and this hypobranchial gland where the indigo is secreted from is part of their armament. These snails are carnivores, they’re cannibalistic, if they starved they perform their cannibalism and their carnivore proclivities on other snails. When the snail is threatened, the operculum closes and the snail retreats inside of course. So what this does is it has one little organ which secretes a little bit of sulfuric acid, it dabs the snail. Dabs a little bit of sulfuric acid on the calcium carbonate of the other snail, softens up the calcium carbonate, it then uses an organ it has, a proboscis like organ, the snail proceeds to bore a hole in the softened shell of the other snail and once its penetrated to the flesh of the other snail it injects a neurotoxin through the same organ to make that snail relax and then it eats it. It’s a killing machine, this snail and here is how you fish for it and this fishing was described by plenty the elder and by Aristotle in Aristotle’s Animalia in sufficient detail that you can reconstruct the fishery entirely today. You lower a chunk of meat in a basket and the snails attach themselves to it. They are, you can see, the Murex on it. [26:00]

These snails are found not only in the Mediterranean but around the world in various species, the snails that produce the blue. You can see them in the Sea of Japan, you can see down toward Indonesia and you see them around the coast of South America and the Caribbean and near Peru where those fabrics were done. And all of the pre-Columbian fabrics that I showed you before I am going to show them again. I can’t forgo the beauty of those fabrics so you will see them again. They were dyed with that snail indigo as was the Jewish ceremonial fabric and as was the Tyrian purple. It was an expensive and slow job, it took about ten thousand snails to generate one gram of the dye. And that one gram sufficed to dye about the trim of a robe and not the whole robe. And the price of this exceeded the price of gold by about a factor of ten per unit mass in ancient times and this was part of the reason why it was rigidly controlled. Everywhere you go around the Mediterranean and archeological sites, there are tons of snail shells which go back to this industry over thousands of years. Just to show its economic importance, here is a coin from the city of Tyre which is now in Southern Lebanon and what you can see of course at lower right is an anatomically pretty good picture of… there are the real snails and now we are going to see how they are portrayed over here. In this tiny little sculpture, you see a dog and a snail. What is the dog? This is the foundation myth of the city of Tyre, that Hercules’ dog, wandering along the beach found a snail, bite into it and his snout was colored purple. And what this tells you… what do you put on coins? You put the picture of the emperor, you put things which are economically important to you, perhaps something about the gods and goddesses. In this case you see here, what’s interesting is what’s on top too, but you see here that the importance of that Murex snail industry to this particular city.

Here is a pot shard with a shard with some of the traces of indigo still on it used to store it. So here are the places around the Mediterranean, the main manufactures were in the hands of the Phoenicians, along the coast of what is now Lebanon in Israel down there. I have seen the snail dumps myself, both there and I have seen them, I don’t have a pointer but I’ve seen them off the Island of Djerba and Tunisia where there is another dot there, go down to Tunisia a little bit. They are all around, these things. And now comes the sad part of the story, that trade was lost. The ability to make the ritual indigo, the tekhelet, was lost by the Hebrews by the time of the reduction of the Talmud, 600AD. It was already in decline, the trade. The Romans were losing power at that point, though of course the Eastern Empire persisted for a long time after that. But the Talmud is full of discussions which clearly showed that the trade was lost. [30:25]

The Romans lost it entirely by the time of the fall of Constantinople but of course people didn’t forget the craft in their own little ways. And the rediscover of Henri Lacaze-Duthiers in the middle of the 19th century of this dying with indigo from snails came from his observing a malty sailor who wearing a white shirt, fished out a snail from the sea and drew a [malt?] cross across his shirt. And he asked the sailor what he was doing and the sailor told him “this snail gives me blue”. And then he went on to study how this happens. You will see that it is elsewhere around the world, I already showed you this map and I can not forgo to show you two more of these incredible textiles, that both the state of perseveration but also the design which we would place squarely on the twentieth century, these fabrics go back to the period from about 200BC to Inca times which means just before the coming of Columbus. Remarkable textiles and you can find them scattered the world, they are always worth looking for. All kinds of techniques also that are interesting to see in these.

All along, there was another source of the blue, another source of indigo. And this is in several plant species, not snails. And the map shows where these are and the one that is in the brightest blue, not the darkest but the sort of middle blue that you see here, you see it ranges across South America and the swath of the Middle of Africa and into India and that is a plant of the pea family called Indigofera. That’s the indigo plant, it’s what is connected to the name and here is a field of indigo in California. And here from the encyclopédie of Diderot and d’Alembert is the dyeing vats with plant indigo that they then made. And here is a dyeing vat in West Africa, I’ll come back to that. That plant indigo industry of making the blue, well the reason I show you this, the only place where it persists to this day pure is in Japan, where Ai indigo… And Japan is very interesting for a number of reasons. It’s not that traditional things are valued and are sufficient self-control in a homogenous society to be sure that no one substitutes chemical indigo for plant indigo. I’ll tell you why one does that in just a while, we’ll come to chemistry. But the fact that you do this, a traditional kimono must be dyed with a plant indigo leads to a premium that you are willing to pay but also the strictures of society that this is practiced. There are lots of interesting things going on here. So this is the only place in the world probably where this is done. [34:19]

Now let me stop for a moment here and talk about what this means. There is this blue, its actually slightly different, some of the blue you can get from the sea that you could not get from the plant indigo. It is the same molecule but now we come to something else. And that is that nothing in the real world is pure. The purest substances you are likely to find are in chemical laboratories. In the real world, whether it is indigo or the aroma of a good Cabernet Sauvignon which has nine hundred molecules in it, anything natural is impure. That is the workings of evolution and sure as organisms evolve and have multiple strategies for affecting something via chemicals. So in that sense the perfumers who come to concocting a perfume from six ingredients are light years behind the insect that generates a pheromone that is mixture of a great number of chemicals. Though rather interesting, when human beings started to study those pheromones of insects of course being human beings they assumed that it was one molecule. That attracted the poor males to that female. And of course any perfumer could have told them it can’t be one molecule, that it must be a mixture of molecules. But that’s another lecture. The plant differential in price between the plant indigo and the snail indigo was a factor of probably a hundred thousand to a million. People have forged for a price differential of 1.5, you can be sure and people are no better today than and no worse today than they were a thousand years ago, if there is money to be made people will try to substitute the plant indigo for the snail indigo. And so the Talmud has a large section in one book detected to what reading in retrospect looks like analytical chemistry, trying to determine if someone has put the plant indigo instead of the snail indigo because now we come in the difference between religion and science, that it should be the snail indigo that’s used in that process is important. It makes it sacred so that the substitution… well they conclude, interestingly in around 600AD that they can not determine that and so they proceed to classify this sin of the failing of substituting plant indigo for snail indigo in the category of sins, a rather limited category, which will be punished in the afterworld by God rather than by human beings. Interesting but it just shows how difficult… today it is possible to determine the difference, but then it was not. And when people analyze that little segment of clothing I showed you from Masada, they could tell that was snail indigo today by a non-destructive method. So that’s something to feel good about chemistry.

Anyway, this plant Indigo eventually became the source of a great industry. The British took it to India, it was a major source of the Indian economy in fact I think already in its waning days of that industry, Gandhi made some of his first inroads in India when he returned to India among the workers in the Indigo industry fields. All along, there was in the area that is the lightest blue here, there was still another source of the indigo. And you see where that extends, it extends even across China and the Middle East of course, all of Europe and all of Britain and into even Southern Scandinavia. And that is a plant of a totally different family, Isatis tinctoria called Woad in English, Waid in German, and Pastel in French. And this plant grows in temperate climates and it produces this blue. Here is what Caesar had to say on encountering those wild people he was in a conquest of Britain, he said, I’m not going to try my Latin, somebody else will have to, it sounds better in Latin than in English. “All Britons dye themselves with woad which makes them blue, in order that in battle their appearance be more terrible”. So that is where part of the being blue in that sense comes and you can make indigo from woad. It’s a fermentation process, just like is (I forgot to tell you) from the plant material, you chop up pieces of the plant and you ferment it in a bath for a long time and there is an enzyme that is involved. I don’t think there is light that is necessary for it but I’m not sure, somebody can correct me. [40:33]

Eventually, finally there came onto this world people called chemists. It sort of happens slowly and by the middle of the 19th century, there were chemists and you could write chemical structures. And so this is the only chemical formula you are going to see in this talk, this is the formula of dibromo-indigo. And you see the two bromines and if you replace the two bromines by hydrogens, that is ordinary indigo. And now there is the difference between the two. And the difference is that the ordinary indigo is the blue end of the range. The ordinary indigo is the blue end the range and the dibromo-indigo is the reddish, purplish end of this range. The snails are the only ones that have the dibromo-indigo. And that’s because there is a lot of bromine! There is a lot of salt, sodium chloride, there is also a good bit of sodium bromide in the sea, that is why Israel and Jordan have both bromine industries and the reddish part comes from bromo. There are still two other molecules, remember I told you nothing natural is simple that’s only the dreams of human beings that the natural is simple and pure. Its only human beings who are simple and pure and we know that we have a political election coming up, we’ll find out about that. But primarily it’s the indigo and the dibromo-indigo, there are two other molecules that are responsible for a little tunings of the color. The snails give off different amounts of the two, yield different amounts of the two, depending on the season and depending on the gender of the snail. And just to make this complicated, they change gender every few months. So these snails are fascinating, it made me want to become a biologist when I read about them.

So now we go forward, fast forward to where we were and we have this molecule. And this molecule is then, the structure is not known as such to the middle 1880s. Now here we come into another story which is interesting in the history of chemistry which is how the English discovered the first of the so called aniline dyes and that was Mauve by Perkin and how quickly the Germans ran off with that industry. So that is the story. Here are some samples of the first aniline dyes, synthetic aniline dyes. These are from the collection of the Deutsches Museum in Munich. Here is at left, you see there is actually a facsimile of a letter by 1883, Adolf von Baeyer writing to Caro at the Badische Anilin & Soda Fabrik, the big company and telling him that he’s gotten the formula of indigo and he is proposing that the company make it and they do. And within a few years, indigo is made, it’s still quite expensive. When it’s advertised, it’s rather interesting, this is an interesting story and here are some more of these incredible advertisements. The labels by which B.A.S.F is trying to sell this stuff. You notice that the labels are orientalese at its worst but part of what is going on is the same thing that goes on when the Europeans first made porcelain in 1700 to 1710, in Meissen when they finally reproduced the Chinese process of making porcelain, the designs and patterns on that porcelain were all Chinese because that’s what would sell. And that’s part of what’s going on in here, that they are selling it to the places that want to see the thing in a certain way. And you can see the range is pretty large, from South America to China in this. [45:32]

The industry grew, it became inexpensive but it was always expensive. There is one interesting thing I can give you right away, a symbol of how expensive still the indigo as a dye synthetically made was… the Chemical Heritage Foundation has in its collection a box which has a canister of indigo that came from a German submarine that ran aground after being torpedoed by the British in the period in the first world war before we entered the war. And that submarine was being used for commercial purposes to ferry indigo from Germany to sell in America. It was still expensive, it became cheaper with time. And eventually the indigo became so inexpensive. How inexpensive?

Okay this is… I must not show that, that’s an improper use of computers! Right? So let me tell you what I shouldn’t show you. I apologize to Michelangelo and to the city fathers of Florence. What I’m trying to say is that, one of America’s great gifts to civilization are blue jeans. Where would be without blue jeans? There are two to three billion pairs of blue jeans made every year, mostly in China. Each one takes one to three grams of indigo to dye. It is that indigo that gives it that beautiful color that everyone loves. Some of that is immediately washed out for fashion reasons. But still a lot remains. An estimate has been made that if indigo plants have supplied the equivalent indigo to those two to three billion pairs of jeans, those plants would cover every arable inch of the Earth ten feet high. So young people and older please be grateful for chemistry. Anyway, the fashionable young man of Florence that’s who Michelangelo depicted would surely be dressed the way I constructed over there.

Now we have most of the elements of the story. There is one element which I didn’t tell you and which allows me to introduce a bit more chemistry. And this is how does this become a dye, a good dye cause I told you that and I had this experience and the reason I could tell you is because I’ve done it myself as you will see in a moment. You put this on your hands and it stains your hands very well but it washes out and if you dye a pair blue jeans and you can be sure those Roman togas were not just simply that the snails were put on them that they were colored blue because they would wash out. And nothing has changed, you can not sell something that washes out in two launderings and the launderings were much more severe in those days then they are today. So this is a reminder, are you wondering perhaps, what the heck this molecule that I showed you is doing in several species of snails, vastly different parts the mollusk family and a fifty species of plants at least in totally different… I mean what is going on there? The question is at several levels. So first let me say that if that is a source of curiosity for you, then you are on your way to being a scientist because that’s the kind of questions we ask. [50:17]

So now the question can be asked at several levels. One is “why is that molecule there?” and the second question is “why does that organism produce a lot of it?”. So the answer to the first question is pretty obvious, look if it’s there in plants and it’s there in animals in varying species, it must be a part of some important biochemical sequence that’s in all of us. There is indigo in you. Don’t worry, no one is going to use to dye anything because you don’t produce enough of it but it’s there in every organism from E.coli on up, in Eukaryotic cells. And it’s there because it’s precursor which is half that molecule torn apart is on the way to the biosynthesis, the way things are made in the body of one important amino acid. So the chemistry is there, the precursor is there, in everything. The second question “why do these organisms produce a lot of it?”, that’s not so clear. There could be two answers, one is that it could be just an accident but that’s unlikely. Usually things with the workings of evolution there are very few accidents in this world. There probably is some utility in the snail that has been traced. So what is the utility of the precursor to this molecule? Still a question that’s under investigation, I don’t have a clear answer.

Okay now I wanted to tell you about, and here is a reference at least if you want to read some more about Royal Purple Dye: The Chemical Reconstruction of the Ancient Mediterranean Industry by a person, Patrick McGovern whom I admire a great deal. He’s an archeochemist at the University of Pennsylvania Museum and what he has done, aside from the dye investigation, he is responsible a lot of our knowledge of the first intoxicating beverages; wine, beer, and mead. And he has shown that from looking at just a few organic remains in the shards of ceramic vessels that once used to hold these things, he’s been able to identify roughly that the first intoxicating beverages were mixtures of these three kinds of beverages and mead, fermented honey, played an important role in them. So mead is very, very, very old. Patrick McGovern is great fun and this is one of his early stories. Now here, what he describes then is given here essentially in a Stockholm papyrus about two thousand years ago. So you put about a talent, some measure of woad in a tube which stands in the sun and contains not less than 15 metretes, that’s a volume and you pack it in well. Then you pore urine until the liquid rises above the woad and you let it be warmed by the sun, but on the following day you get the woad ready in a way so that you can tread around it in the sun until it becomes well moistened. And you go on to do this for three days. Some of the ancient prescriptions specify that it should be urine from men who drink and others specify that it should be from children, from infants. There are all kinds.

Anyway, if you go to Pompeii and if you go outside what is the dyer shops you will see large flat urns like this. Those are for passersbys to deposit the next day’s chemicals in. This is what was… so urine is a natural product and a very important early industrial chemical. When its first made, I think its acid, when we first generate it but on standing in the sun for a few days it becomes basic. So actually it can serve some of the acid base functions that one needs and is that base function which is used in this because what is happening now is the following. Now I have to go into a little chemistry, the fabric is wool or linen then eventually cotton. Those are two very different molecules. Wool is protein and linen and cotton are essentially cellulose and incidentally rayon is also cellulose that is treated in a certain way. [55:10]

So when the dye… the dye is another molecule, if you want the dye not to wash out, you want it to stick to the molecules that the fibers are made out of. So it sticks for a while through various chemical forces that can bind that dimolecule. Some of you who are chemists will have noticed that it has some pieces of an amino acid like structure in it. And it can stick in some way but it turns out that if you transform this dimolecule of indigo that I showed you, if you do chemical transformation where you add two hydrogens to it which is affected by the base which the urine does or any other base, ammonia is another base you could use. There was no ammonia as such then. But their urine came close to that. If you add that base, it adds two hydrogens to the indigo molecule and the indigo molecule becomes colorless. And then in that color less form it turns out that because of something to do with ionic forces, it sticks much more strongly to either the cellulose or the protein. And then once it’s sort of integrated into the structure of the biopolymer, that’s what cellulose and the protein are, once its integrated into that biopolymer, when you next remove the two hydrogens to regenerate the blue molecule, it becomes blue again and its affixed. It’s already tied into the body of the polymer somehow. We know a good bit more than my “somehow” implies. Getting the two hydrogens off is a… I’m desperately trying not to use the words reduction and oxidation. Okay I give up. So what happens is the indigo gets reduced with two hydrogens added to it then it gets reoxidized, removing the two hydrogens and what does the oxidation? Oxygen of the air, the best oxidizing agent around. And so now I am going to show you how it’s done.

We did this in Phoenician… Phoenicians were masters of these, much better than the Hebrews and there was a lively trade. The Phoenicians in general were masters of technology, they made bronze and iron very well. Here is an archeological site now in Israel and Palestine, Taldor where the Carmel Mountains go into the sea. And there are storage bins and large dumps of shells and storage bins where the snails were kept and you can tell that the snails were kept there because they’re cannibalistic and you can see they were kept there starved while they were waiting to process the snails because the snails, you can see (I saw them) sharply drilled holes by one snail into the other. Remember that horrible story I told you? [58:57]

Alright I was doing research on a book I was doing with Shira Leibowitz Schmidt and the research was very hard to do as you can see. I wanted to see the process, we wrote about this, so I went in and I very quickly found one of the snails but we could not use it produce the blue because they are protected there so instead some young people when I was there were trying to reconstruct the trade imported some snails (this whole story is bizarre) but live snails were imported from Marseilles where there only too glad to get rid of them. And these snails were then flown to Israel and then we processed them to get the blue dye. Anyway I’m holding one of the snails and this is the book that we did. A few copies of the book are for sale, there are some copies of a few of my books for sale, others you can find at Powell’s stores. There are some poetry books and a copy of this book. The poetry I am especially interested in selling. My mother who passed away five years ago, well it took her twenty years to get over the fact that I didn’t become a real doctor. And then, when I started writing poetry, I got it all over again. She was a wonderful woman and she had a well formed idea of what was proper for a profession and what she said is that “they’re gonna fire you”. So I want you to prove my late mother wrong. What I mean by that is that it’s possible to make a living as a poet, so there are some twenty copies of my poetry books out there. The research we did for this, this is an amusing thing in a number of ways because I did this book with a coworker, Shira Leibowitz Schmidt. It was a good collaboration as you can see she is an observant woman, she wears modest clothing according, which is very much part of both Arabic and Jewish tradition. So you see this in her dress and she could not go in the water, her husband did with me because of certain rules about these things. And you can see we’re both smiling. Now we needed a picture of the authors for this book and since this book was a collaboration of two people, it was pretty much impossible to find a picture of the two of us smiling together. And we found one here so we were happy about that but we had to sensor my bare skin in this.

Here am I with these young people who are trying to revive the industry and they are trying to revive the use of the ritual blue, which was lost in 600AD. Have they got a problem. And I want you to approach a little bit the dimensions of the problem that they have. And this has to do with another part of the story. So by around 600AD, the end of the oral tradition, the Talmud gets written down, the tekhelet, the blue, the royal purple is lost from the people using it. And so its lost. So one of the sort of ritual… there were other things that were lost, observance in the temple and other things but this one somehow as often happens things that are lost in a society, rituals that are lost that can no longer be observed, they acquire a special spiritual hold. And the particular thing that got attached to loss of the blue so that you could no longer… and the only place the blue was used was in that tassel on the ritual garment and in the priest’s high robes but there was no priests any longer. So it was that blue, the loss of that blue quickly acquired a layer of belief that said the blue would come back with the messiah. And that had next thirteen hundred years of that tradition, that the loss of the blue is associated with the absence of the messiah. And now comes some young people who would, with scientists, prove conclusively that the ritual blue comes from the snail and that they can reconstruct the industry. Do you think religious people are going to adopt this? Not very easily, especially in the absence in Judaism as there is of a central religious authority. There is a Grand Rabbi of Israel but he has essentially no authority. And the authorities localized with rabbis is something that developed. And so what these young people have to do who developed this is they have to go around and community by community they have to convince the religious leaders of those communities that this is the correct ritual blue. They’re getting there, you can look at their website, but it’s a difficult task. [1:05:10]

So there we are, sitting in a Phoenician… pit full of shells around and on a propane stove or whatever it is we have that stuff which is yellow, not because its urine, its yellow because when you cut out a hundred glands, it gets messy and smelly if you ever go into a dyers market in some country where this is still done for instance in Fez in Morocco you can see this is still a profession that is full of smells and chemistry. And we put in the glands that we cut out and they turned colorless or at least yellow and then as you take it, just as you take it out of that beaker, before your eyes it turns blue. You can see, the color is not too good, but you can the end of it is blue as I am taking this wool out of this beaker. Now what I want you to think about here is I want you to think about something that is more precious than gold per gram, a lot of these glands (ten thousand of them a gram), and its blue. And then someone, two thousand years ago put that valuable carved out glands, as messy as they are, a lot of work and blue as they are, and puts them into urine. And he or she is hoping that, knowing, hoping, some mixture of that that when they take it out it come back to the blue. A little bit like gold into aqua regia and then back out again. But what does it take? One of the things that it takes is faith. The faith here is in the craftsmanship, maybe there is a religious [tinge?] to it because this whole thing is part of a religious ritual and Mircea Eliade has written beautifully about the way ritual and chemistry get mixed up in metallurgy and alchemy. But what I also think that when, as a scientist, as I do this, as I take this out and see that turn blue before my eyes… Do I believe my chemistry? Yes I believe my chemistry but I think there is something more than that, there is aside from an act of faith now into the science that goes on that will turn back blue, there is just a spiritual moment from seeing that blue come out blue before your eyes. That’s the end of my story. [1:08:32]

Larry Landis: Questions?

Audience Member (1): I just wanted you to know that you are most welcome and that the Portland Hand Weavers Guild is all here.

Roald Hoffman: Oh, good. They know more about this than I do

Audience Member (1): We are weavers and dyers and we all start fermentation vats early in the summer until our husbands complain about the smell. Then we have to get rid of it.

Roald Hoffman: Thank you, the next slide I have is in fact one of great books which is Dominique Cardon’s Natural Dyes book which is just full of history as well as chemistry and prescriptions and I would recommend to people. There are many stories like these, I have another lecture on cochineal. [1:10:04]

Audience Member (2): Let’s have it now.

Roald Hoffman: No, not now. Thanks for the dyers, I really appreciate that. Any other questions? Yes back there.

Audience Member (3): Could you comment briefly on the effect of indigo on the slave trade.

Roald Hoffman: I don’t know anything about that. Could you say something? Were they brought over in part to do? Because there is indigo in South Carolina, certainly, that I know there were indigo plantations and in the Caribbean probably and you think that played an economic part in bringing over…

Audience Member (3): I read a little bit about it, not a lot.

Roald Hoffman: I don’t know a lot about it but it’s not unreasonable given the economic value of the indigo at that time. I can’t see because of the light here, just stand up. Yes, thank you.

Audience Member (4): First off I was trained on your book many, many years ago so don’t feel too bad. But my question really is, as you watched your career, gone through your career at what point did you begin broadening out from what is very, very difficult theoretical chemistry to bigger cultural issues?

Roald Hoffman: Did people hear the question? So that’s an interesting story, so the beginning is that everything began in college. And that was at Columbia and me, and a large of it is owed to a core curriculum, contemporary civilizations and humanities courses which had an incredible influence on me. So I began as a pre-med, still being a good boy and it about one year of college, it was not easy. I was an only child until I was about seventeen and the pressures on an immigrant child to become a doctor given the kind of family background. So it was Jewish immigrants from Eastern Europe, the same pressures are working on a child of your local Korean grocer. It’s the same story for Asian American kids at Cornell, I know because part of my work is how to tell them to tell their parents they don’t want to be doctors. I don’t have anything against doctors, sorry. No I’m joking but my first year of college was enough to convince me that I didn’t want to be a doctor. But then what to do? And the courses in science, as it happened, were boring. The only things I had that kept me going in science was summer research experiences, which are very important for many people, for me at Brookhaven and the National Institute of Standards in Washington at that time. They showed me what research was like. Meanwhile, the world was opening up in humanities and it was these courses, the core courses and then a poetry course with Mark Van Doren and a course in Japanese literature with Donald Keene, a Shakespeare course with Andrew [Schaap?]. These things and the poetry course, the Mark Van Doren course, in those days you couldn’t teach writing poetry in college. Mark Van Doren couldn’t do that, he taught us how to read a poem, if you wanted to learn how to write a poem you had to go to night school. Things have changed. The world opened up in all of these fields, I still remember the world opening up and the poetry through Mark Van Doren’s reading with us of Wallace Steven’s Sunday Morning. You can see how an 18-19 year old young person would be influenced by these things. So it began then and then I kept reading. The worst time from a point of view, so I didn’t have enough courage to tell my parents that I wanted really to study history of art, that would have been too much. So I became a chemist and I didn’t really decide on being a chemist until halfway through a Ph.D. in chemistry. Really, I am not a good example of being a scientist from childhood. [1:15:17]

I was still at Harvard in graduate school in chemistry, I wasn’t sure about things. And I went to the Soviet Union for a year in 1960-61, after two years of graduate school. Part of that going there was still trying to prolong the decision about being a chemist. When I came back I knew I wanted to be a chemist and I found the field to my liking and I did well in it. I kept on reading, probably the worst time for keeping up with these other interests was around the time when I was, let’s say around 30 to 35. Because the work was going extremely well, science is both demanding and addictive, both. And I was forming a family. There were all these other pulls which are quite natural in that period and with that I still kept on reading and eventually I came back and I started writing poetry at age 40 or so. And that’s a long time now, 35 years ago almost and I started writing essays 25 years ago or so and the plays just about 10 or 12. So these things came in, but a little different from let’s say Carl Sagan or other people because sometimes you see a progression to popularizing science to other forms of writing. For me it was first the science and then the poetry and the two were separate. It took me seven years to get a poem published, I probably should have taken a course but I was ashamed to, I could have taken it at a local community college of course it would have provided structure, it would provided structured criticism. I didn’t do that. I just sent them in and I got rejection slips with no answers. Well mind you, there was one thing from science that was clear was that I felt the urge to publish. But that’s so obvious, that’s so obvious. If you think about what poems you like, how did you find out about them. They were published. Of course there is a world of difference between therapy and poetry. You know, poetry can be therapeutic to the poet but most therapy is not poetry. So is difference. So as to why plays and poetry but the plays also goes back to something in college and that is, these are just moments, but there was a production at Barnard across the street from Columbia of Lorca’s Blood Wedding and what I didn’t know was that Barnard was teaching one of Lorca’s relatives. Lorca had a connection to Columbia by having visited there at some point spent a year but that production was not only noticed, I wandered into it by chance but later I saw writing about that production. It was something special and I’ve never forgotten that production to this day. So there are little things a poem that Mark Van Doren reads, Blood Wedding, but it all goes back to college. So there is a moral here, don’t complain about distribution requirements. The world just may open up to you as it did to me. Thanks for asking the question.

Audience Member (5): Any advice to aspiring chemists.

Roald Hoffman: Yes, well I think it’s very hard to predict what areas of chemistry will be interesting or not, I would say continue to be curious and to follow your own instincts on what is interesting or important at some point. The world of chemistry will continue to be, first of all chemistry has got no problems, it’s got an economic basis which is the most important thing and it’s going to continue to be important. But there are interesting battles out there in chemistry between, for instance in my own field of theoretical chemistry, similar to other fields of science, there is now a kind of struggle between simulation and understanding. As the computers get so good that it can simulate something but who understands what the numbers are that they give. So there is an interesting struggle there, there are other things. I think chemistry will continue to be alive just have faith in what you do, it sounds like a puff answer but I’ve found it useful for myself.

Audience Member (6): I remember Richard Feynman once said that chemistry could reduced from physics. What is the difference between…

Roald Hoffman: Well I don’t know if he said it but I don’t agree with him. So part of what I’ve done… I think you planted this question… part of what I’ve been doing is trying to defeat that reductionist viewpoint and to give chemists the confidence especially in their interactions with physicists to not believe that. So now here is what I believe, I think that view and again I’m not sure if this is Feynman’s, but that view is a classical reductionist approach. Reductionists in a sense who should we blame for it? Should we blame the French. ... But anyway, reductionist is meaning that there is hierarchy of sciences like physics, chemistry, biology, social sciences and so on. And that understanding is to be defined in terms of reducing from chemistry to physics, from biology to chemistry. Reductionism I don’t think works as a practical thing and I think also, I’ll tell you an alternative to it. I also think it has no good philosophical basis for it. What I think is true is that there are several ways of understanding and one of them is, I like to call, horizontal and the other vertical. So vertical understanding is the reductionist way that we’ve just mentioned, but horizontal understanding is a little harder to grasp on to but I’ll give you an example in a moment. But horizontal understanding to me means understanding something in terms of concepts that are of equal level of complexity to the concept that you are trying to understand. In one sense, language for instance, that sounds almost circular but it’s not. It’s not circular thinking. Language is very much like that, if you look up in a dictionary the word dog, it’ll say quadraped of the genus such and such and you look up those words in an English dictionary and in about six looks up you are going to close the circle, those words are defined in other words. Plus the world outside but that doesn’t go into a dictionary. That deeply circular nature of language does not prevent you from sending the fire engine to the fire and give the directions exactly. Nor does it prevent you from writing great poetry in that deeply circular language. I would say for instance, I can give the example another way. If I get a line in an anonymous letter and there is a line, it’s a line from a poem by John Donne, “Love is a growing or full constant light and his first moment afternoon is night”. Knowing the sequence of neurons firing in John Donne’s mind when he wrote that and the beautiful intricacy of the biochemical actions behind that firing of neurons. In the mind of John Donne or the mind of the person who sent me that, then my mind as I read it, that will get you a lot of Nobel prizes that knowledge, but has nothing to do with understanding that poem, absolutely nothing. That poem is understood horizontally in terms of the complexities of the English language and the psychology of the actions involved. Okay if you admit for that going to the humanities, to the sciences, I tell you that in even two supposedly hard sciences as close to each other as chemistry and physics are, that a lot of the concepts of chemistry are to be understood horizontally and not by being reduced to physics. I am talking about concepts like aromaticity, acid base, reduction oxidation which I used here, substituent effects, steric effects, these are ideas which very well formed concepts that are useful in the making of new molecules which is the stuff of chemistry and synthesis. And yet you try to reduce them to physics and their interest and their significance wilts at the edges, goes away. So I think reductionism doesn’t work for a number of reasons and we should be in chemistry in our time when we see we take so much pleasure in biological actions being understood on a chemical level, we should be careful. It’s a seductive ground that all of biology can be reduced to chemistry. We’re beginning to see that it isn’t so simple, that one gene doesn’t determine one function, that it’s a very complex interplay and I think the understanding that will evolve will be a kind of a holistic understanding which will evolve in the complexity of the actions interacting with each other. [1:27:14]


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