The Story of “The Nature of the Chemical Bond”: Coordinating Research & Funding

[Ed. Note: This year marks the 75th anniversary of Linus Pauling’s publication of his landmark text, The Nature of the Chemical Bond.  For the next six weeks we will take a detailed look at the creation, release and impact of a book that changed the scientific world.]

Linus Pauling’s The Nature of the Chemical Bond, first published in 1939, was the product of over two decades of diligence, sacrifice, and collaboration among a broad range of actors that included Pauling’s family, research assistants, professional colleagues and a variety of institutions. Pauling’s prefatory remarks to the book – “For a long time I have been planning to write a book on the structure of molecules and crystals and the nature of the chemical bond” – give an indication of the extent to which this was a long-term objective for Pauling, despite his being only 38 years old.

Looking back at his process, Pauling’s application for a grant from the Carnegie Institute in February 1932 provides a more detailed affirmation of his ambitions. In it, Pauling relayed how his undergraduate research in crystal structures at Oregon Agricultural College between 1917 and 1922 had laid the foundation for his current work by bringing him into contact with contemporary questions in structural chemistry. As a graduate student at Caltech, Pauling began to search for answers to those questions in the newly developing field of quantum mechanics.

In pursuit of those answers, Pauling and his wife Ava Helen, with the support of a Guggenheim Fellowship, left their one-year-old son, Linus Jr., with Ava Helen’s mother in Portland and traveled to Europe in 1926 to study quantum mechanics at its source. There, Pauling deepened his understanding and immersed himself even more by beginning to apply the new physics directly to chemical bonding.

J. Holmes Sturdivant

Upon returning to Caltech in 1927, Pauling began to seek funding so he could continue what he had begun. Let down by the National Research Fund, Pauling supported his work with funding from Caltech and the National Research Council, money which allowed him to hire a full time assistant, J. Holmes Sturdivant, who focused on x-ray crystallography and continued to work with Pauling for many years. Pauling also brought aboard Boris Podolsky for nine months to assist him with the more detailed technical components of connecting quantum mechanics to chemical bonding.

In 1932 Pauling expressed a hope that, with help from the Carnegie Institute, he could expand his work by funding more assistants and purchasing equipment like an “electric calculating machine,” a “specialized ionization spectrometer,” and a microphotometer. The Carnegie Institute was not interested. Luckily for Pauling, the Rockefeller Foundation came through with a general grant of $20,000 per year over two years, to be split between the physics and chemistry departments at Caltech. This allowed Pauling to keep Sturdivant on staff while adding George Wheland, Jack Sherman, and E. Bright Wilson, Jr. to his research team.

This scramble to secure funding and bring new people into the lab came amidst the publication of Pauling’s first four “Nature of the Chemical Bond” articles for the Journal of the American Chemical Society, proof positive that Pauling’s work was bearing fruit. Once the funding was secured and Sherman and Wheland began producing results, Pauling wrote – with Sherman and Wheland as co-authors – three more “Nature of the Chemical Bond” articles the following year, published in the newly established Journal of Chemical Physics. Wheland also worked with Pauling on a monograph discussing the application of quantum mechanics to organic molecules. Wheland finished his part of the book by 1937, but Pauling never got around to his portion: his desire to write a book length treatment of chemical bonds began, more and more, to take center stage.

Warren Weaver

In order to keep the funding coming in through the lean years of the Great Depression, Pauling was compelled to follow the lead of his patrons, the Rockefeller Foundation. Warren Weaver, Director of Natural Sciences for the foundation, told Pauling in December 1933 that the organization was “operating under severe restrictions” and that funding would go to projects “concentrated upon certain fields of fundamental quantitative biology.” That Pauling’s work had “developed to the point where it promises applications to the study of chlorophyll, haemoglobin and other substances of basic biological importance” was key to his potential receipt of continued dollars.

The commitment of Caltech’s chemistry department to continue pursuing the line of research suggested by Weaver helped Pauling to secure funding for the following year. A three-year commitment came after that, providing the Caltech group with a reliable source of support into 1938. Pauling thanked Weaver in February of that year for his direction, writing,

I am of course aware of the fact that our plans for organic chemistry not only have been developed with the aid of your continued advice but also are based on your initial suggestion and encouragement; and I can forsee that I shall be indebted to you also for the opportunity of carrying out on my own scientific work in the future to as great an extent as I have been during the past six years.

Secure funding allowed Pauling to maintain a research group consisting of graduate students and post-doctoral fellows. In his preface to The Nature of the Chemical Bond, Pauling expressed his gratitude to several of these individuals, including Sherman and Sturdivant. Another, Sidney Weinbaum, earned his doctorate under Pauling and continued on afterwards, helping Pauling with quantum mechanical calculations and molecular structures.

Fred Stitt worked as research fellow with Pauling and assisted him in teaching his graduate course on the applications of quantum mechanics to chemistry – an exercise, no doubt, that helped to shape Pauling’s own thoughts on the subject, crystallizing them in preparation for the book.

Charles Coryell and Linus Pauling, 1935.

Charles Coryell and Linus Pauling, 1935.

Charles Coryell worked as a research fellow at the Caltech lab with Pauling on the topic of magnetic susceptibilities, which were central to investigating chemical bonds.  (Coryell also later helped Pauling to construct a magnet for the Caltech labs, based on one already in place at Cornell.)

Edwin H. Buchman, according to a 1985 oral history interview, was self-supporting due to royalties from his synthesis of vitamin B1. Buchman told Pauling in May 1937 that he would assist Pauling “on any problem in which an organic chemist could be useful and for which extra space could be had.”

Once assembled, Pauling’s team helped him to refine his understanding of chemical structures and bonding as the time approached when he could produce a book-length treatment on the subject.

Congratulations to Martin Karplus


We were delighted to learn last week that Martin Karplus will be one of three individuals to share the 2013 Nobel Prize for Chemistry. Karplus is among Linus Pauling’s many scientific descendants, having worked as a graduate student under Pauling in the early 1950s. A bit later, Karplus worked with Pauling and E. Bright Wilson, Jr. on an ill-fated project to publish a revised version of Pauling and Wilson’s 1935 text, Introduction to Quantum Mechanics.  We documented this story in May 2010.

In another life, the blog dabbles in oral history and it was our great good fortune to interview Dr. Karplus during a trip that he made to Corvallis just this past summer.  A few excerpts about his Pasadena experience are included below; the entire interview has been archived in our History of Science Oral History Collection (OH 17).

On choosing Caltech after finishing his undergraduate studies at Harvard...

My brother was at the Advanced Institute working with Oppenheimer and I’d decided I wanted to go west and I would either go to Caltech or Berkeley. I was admitted to both of them. And, as I said, I visited my brother and he introduced me to Oppenheimer, who had been professor both at Berkeley and Caltech and I asked him what he would do. And we talked a little bit about things and I’m not sure that he was aware that really I was going to go into biology rather than into chemistry. But he – I still remember the statement of his that Caltech was a ‘shining light in a sea of darkness,’ and he strongly recommended going to Caltech as being a smaller place where somebody like me would be able to really do what I wanted to do. So I think that was it. I mean, in those days you didn’t visit the schools or anything. So I think he was basically – well I talked with my brother about it, also, but that was sort of how I made my decision to go to Caltech and I think it was a good decision.

On taking classes from Pauling…

He was a great lecturer. But the most impressive thing was that he gave the students problems as homework problems and everyone worked very hard on them. Then it turned out that he actually didn’t know the answer to this problem and so there was a lot of discussion of this. At the time I was sort of annoyed, but afterwards realized that this was really very important, to learn the difference between doing your homework when you know that there is an answer, you can always find it, and doing research, where obviously there may be an answer somewhere but it’s not so easy to find. But that was part of his methodology.

On Pauling as a doctoral adviser…

…people built their careers on Pauling’s ideas. I still remember when I started, every morning when I would come in there would be this little yellow sheet in my mailbox, saying ‘wouldn’t it be interesting to do so-and-so?’ And at first I felt ‘okay, well Pauling wants me to look at that, I’ve got to work on it. I don’t have time to do what I’m really doing on my thesis.’ So this went on for a little while until Alex Rich and some of the other people that I talked with said ‘look, Pauling does this to everybody, he doesn’t expect you to do it. You can either throw them away or you can store them and maybe they’re ideas that you could really work out.’

….And, if we’re talking about experiences, one was my qualifying oral, where Pauling asked me to discuss his theory of metals, which I knew something about. So I said innocently, ‘well, let’s start with copper,’ and I said ‘let me see, what’s the atomic number of copper?’ And so Pauling looked at me and said ‘well, you start with hydrogen and you work your way up and then you’ll get to copper.’ So, with a certain amount of fumbling, I finally did get there, but everybody was terribly amused and Pauling afterwards sort of said to me ‘now look, you’re a very bright fellow. But one thing, if you’re a chemist, you should know, is the periodic table. So that very much impressed me.

Martin Karplus and Linus Pauling, 1960s.

Martin Karplus and Linus Pauling, 1960s.

On a memorable party with the roommates…

We had a big party at the – we lived in this house in Altadena where a number of us, Sidney Bernhard, Alex Rich; Matt Meselson was involved in it too. We all lived together. I and Sidney were the cooks and the others washed the dishes and cleaned up, and we had this big party. We had often had parties and Dick Feynman would come and play the drums. And Pauling and Ava Helen came to this party.

We had a lot of snails in the garden and Pauling went out and collected them. And I thought, ‘okay, he likes snails, he’s going to go home and Ava Helen is going to cook them.’ What I discovered later when I was working – I did a lot of cooking and working in restaurants – is that it’s really a very complicated process to prepare the snails and you would have to let them sit for about a week or so until they eat up all their own slime. I never asked what they actually did with them, with this collection, but he had this big collection of snails which he took home.

On Richard Feynman…

I remember he gave a public lecture on water which was just unbelievable. He really had insights, and of course there’s this now famous quote in the Feynman lecture series, which is something like ‘everything that happens in life has to do with the wiggling and jiggling of atoms,’ and now almost everybody who works in molecular dynamics uses this quote as a sort of introduction on their importance. I talked with him a number of times about looking at larger systems and he was very encouraging. Though I must say that when I took his quantum mechanics course, it was difficult in the sense that he taught quantum mechanics from his point of view, with path integrals and such, and for people who didn’t know quantum mechanics already, it would have been very difficult. On the other hand, it was a difficult period, but it actually taught me a lot of things, which I’ve used since then.

Anyways, when he came to our parties he played the drums; he was really part of the Caltech spirit. I think most other schools you wouldn’t expect a professor like that, to come to the party with some students, say ‘look, why don’t you come up there, we’re having a big party tonight…’

Project Adrift: The Second Edition Fizzles Out

[Part 4 of 4]

The cordial disagreements over the shape of the second edition of Introduction to Quantum Mechanics began in August 1955 when Martin Karplus sent to Linus Pauling his first revision of the book. Many of the revisions that Karplus was making did not fall in line with those that Pauling and E. Bright Wilson, Jr. had in mind. Pauling and Wilson expressed their concerns to Karplus, Pauling writing that “I think that the revision that you propose is more extensive than we want” and Wilson suggesting that “I think in general I stand part way between the two of you with respect to the extent of revision necessary.”

Clearly there existed significant gaps in agreement; gaps which steadily grew into crevasses.

In October 1956, Pauling wrote to McGraw-Hill requesting that the previous agreement concerning royalties for the second edition be revised to that of an equal division among the three co-authors, as “circumstances have changed since 1935.” This was an early sign of what would soon become an apparent lack of investment in the second edition on Pauling’s part.

In November Karplus met with McGraw-Hill and agreed on a new deadline of Fall 1957 for publication in 1958. Nearly a year later, in October 1957, the deadline was extended again to the summer of 1958. In a September 1957 letter, Karplus gave some insight into the reasons for the delays:

I am very sorry that I have not been able to accomplish more on the revision. Other obligations as well as some personal problems, have prevented me from devoting as much time as I should have liked to give to the work.

As time passed, the disagreements between the co-authors and the lack of organization were becoming more and more apparent. In a letter to Karplus, Pauling’s frustration with the situation was evident

I wish that you would send me a copy of some of your material on the revision of Introduction to Quantum Mechanics…I trust that you are not changing the book completely.

In early March 1959, Karplus wrote to Pauling and offered a glimmer of hope that the end of the revisions was near, suggesting that “in terms of the present rate of progress, it is perhaps not completely unrealistic to hope that the new edition will appear in the spring of 1960.”

Yet the publication delay continued.  When Pauling was asked to compose a recommendation for Karplus for a position opening at Tufts University in October of 1959, Pauling shed further insight into the issues plaguing the revision.

The work that Karplus has been doing in revising the book seems to me to be of the highest grade. My suggestions in the main have dealt with a simplification of what he has written. I have not found any errors, not even in judgment, except that I am afraid that he tends to be interested in the more complex aspects of the subject….I may point out that he was, I think, somewhat disturbed in his research and his revision of Introduction to Quantum Mechanics by personal difficulties.

Clearly reasons other than lack of cooperation between co-authors were causing the delays.

Two years later, in 1961, Pauling wrote to a Dr. T. Katsurai in Tokyo, who had inquired about the publication date of the new edition. In this reply, Pauling confessed of his own contributions to the slowness of the project.

Professor Wilson and I have got to the stage in life when we have many duties and less energy than formerly. Professor Karplus is hard at work, but the job is a big one, and I surmise that it will still be a year or more before it is finished.

Later that year, Pauling received a letter from a McGraw-Hill editor informing him that “Professor Karplus assured me three weeks ago that he and Professor Wilson are actively revising, and that they anticipate completion in the summer of 1962.” And yet, 1962 passed without publication.

In 1963 Pauling cut himself off from the project, in large part because of the growing press of work, especially peace work, that now defined his every waking moment.  In a letter to Karplus informing him of his decision, Pauling wrote

I feel that I should not be a co-author with you and Bright. I have decided that my many activities, combined I think, with some lack of interest in the details of modern quantum mechanics, will prevent me from making any contribution to the new book.

Wilson responded curtly to Pauling’s withdrawal, insisting that it would reflect poorly on Karplus as well as the second edition.

I was very disturbed to receive the copy of your letter of May 22 to Martin Karplus. I don’t really see how you can do this to him. After all, it was you who chose him and persuaded him to undertake the job of revising our book, a job which has turned out to be enormously more burdensome and worrying than he could possibly have realized, in good part because of his own success in research. I fear that he (and the public) will infer that you have no confidence in him and prefer the old edition even though you haven’t examined the new.

Pauling responded to his colleagues apologetically, explaining that his request to withdraw was not based on a lack of confidence in the project, but on his own inability to participate.

I[f] you and Bright are willing that I be a co-author, I would be happy to be. My conscience has been bothering me because I have not contributed anything significant to the revision. I do not like to accept anything that I do not deserve, and I have felt doubtful that I deserve to be a co-author of the new edition.

Nine years later, in 1972, Karplus sent Pauling a letter informing him that the book was near completion. But by 1974, nearly twenty years after Pauling and Wilson made their decision to publish a second edition, McGraw-Hill still had not received a manuscript. At this time, Pauling sent a final letter to Wilson and Karplus officially withdrawing as co-author.  The second edition never made it to print.

Introduction to Quantum Mechanics: A Second Edition?

Martin Karplus and Linus Pauling, 1960s.

[Part 3 of 4]

During its first eighteen years in print, Linus Pauling and E. Bright Wilson, Jr.’s Introduction to Quantum Mechanics sold over 17,000 copies.  Heartened by the success of the first edition, Pauling wrote to his co-author in November 1953,

It seems to me that the book has been successful enough to justify a second edition, and I do not think that any of the newer books takes its place.

In December, Wilson replied in agreement but with slight trepidation.

I should be quite willing to have a second edition of Introduction to Quantum Mechanics prepared if it didn’t involve too much work for me and if we could agree on the general principles which we were going to use in carrying out the revision.

Wilson’s reply in hand, Pauling wrote to their editor at McGraw-Hill, Hugh W. Handsfield, and informed him of their decision to revise the 1935 text. Handsfield replied with a deadline of winter 1956 in preparation for a publication date of January 1957.

To alleviate some of the work load, Pauling suggested that the two authors collaborate with a young Ph. D. named Martin Karplus, a former student of Pauling’s and a recent graduate of Caltech. Wilson agreed, Pauling extended the offer and Karplus accepted, if warily, noting that “though I am not certain that I am qualified for the task, I should like to attempt it.”

Pauling, Wilson, and Karplus agreed to divide the royalties according to estimated contribution levels, allotting a quarter of both Pauling’s and Wilson’s royalties to Karplus. Having delegated a significant portion of the revision work to Karplus, Pauling did not foresee much difficulty in the development of a second edition.

Unfortunately, there emerged significant flaws in their three-way collaboration, especially that of geography. When the authors began making preparations for the revision, Karplus was in England at Oxford completing a National Science Foundation Fellowship, Pauling was in Pasadena at Caltech, and Wilson was in Massachusetts at Harvard. This distance presented obvious complications in revision efficiency, appreciably slowing down the process.

The problems, however, did not end with logistics, but extended to revision philosophy. When Pauling and Wilson asked Karplus to participate, they both made it very clear that they wished to maintain the integrity of the first edition by keeping the focus of the text on applications to chemistry for students that were less mathematically inclined.  As Bright Wilson wrote in a letter to Karplus

I think Professor Pauling agrees with me that we are very anxious to keep the book at a level which can be understood by first-year graduate students in chemistry. It has always been the great feature, in my opinion, which has made the book so successful in its first edition. My main contribution to it was to bring an adequate degree of ignorance into the authorship, and I therefore claim a lot of credit for the success of the book because I was not able to understand anything highbrow and therefore there was not very much highbrow put into it.

Their reasons for keeping the book at such a level extended beyond academic intentions. Both original authors recognized the market potential for a text on quantum mechanics applied to chemistry as there existed many quantum mechanics books available for physicists and none, other than theirs, for chemists.  Wilson summed it up succinctly

I don’t think we can hope to compete with the books designed specifically for physicists and that we should try very hard not to increase the level of difficulty because otherwise we will lose our principal attractive feature.

Karplus found such revisions difficult as he struggled to incorporate what he believed to be important while maintaining the original format developed by Pauling and Wilson. These disagreements in revision philosophy ultimately amounted to yet another considerable hurdle in the revision process.  Time passed quickly over the next year and it soon became apparent that there was no conceivable way that the co-authors were going to meet their first deadline.

Pauling and Wilson

[Part 2 of 4]

In 1926, while still in Europe completing his Guggenheim fellowship, Pauling attended history’s first full-term lecture on the new concept of wave mechanics as applied to quantum theory. This course, taught by Arnold Johannes Willhelm Sommerfeld, a renowned German theoretical physicist and a pioneer of quantum mechanics, was historically significant as the first of its kind.  Sommerfeld would later write of the classes,  “My first lectures on this theory were heard by Linus Pauling, who learned as much from them as I did myself.”

Upon returning from Europe to Caltech, Pauling used the knowledge gleaned from his Guggenheim experience to develop his own lecture series on quantum mechanics. Among those who attended these was none other than Albert Einstein who sat in on one of Pauling’s talks in 1930.

The content of this course became the foundation for Pauling’s first textbook, Introduction to Quantum Mechanics with Applications to Chemistry, which he developed with a former Ph. D. student named Edgar Bright Wilson, Jr.

E. B. Wilson, Jr., known to many as Bright, was born in Gallatin, Tennessee in 1908. After graduating from Princeton in 1930, Wilson attended Caltech and, under Pauling’s direction, received his doctorate in 1933. Wilson then became a fellow at Caltech until accepting a position at Harvard in 1934.

E. Bright Wilson, 1970.

In 1935 Wilson and Pauling published their co-authored text, which took the duo over two years to transform from Pauling’s original lecture notes.  The primary goal in writing the volume was to “produce a textbook of practical quantum mechanics for the chemist, the experimental physicist, and the beginning student of theoretical physics,” for the authors firmly believed that quantum mechanics had applications to nearly all scientific disciplines.

Cognizant of the need to guide the less mathematically adept reader “through the usually straightforward but sometimes rather complicated derivations of quantum mechanics,” Pauling and Wilson formatted their content such that it could be understood by those with mathematics training up through calculus, with some limited additional background on complex numbers, differential equations, and partial differentiation.  Pauling and Wilson wrote that

The book is particularly designed for study by men without extensive previous experience with advanced mathematics, such as chemists interested in the subject because of its chemical applications.

In completing the text, the authors acknowledged a number of mentors and colleagues – many of them Caltech contemporaries – for their contributions to both the authors’ own personal knowledge and to the field of quantum mechanics: Arnold Sommerfeld, Edward U. Condon, Howard Percy Robertson, Richard C. Tolman, Philip M. Morse, Leslie E. Sutton, George W. Wheland, Lawrence O. Brockway, Jack Sherman and Sidney Weinbaum. And last, but certainly not least, the authors acknowledged their wives, Emily Buckingham Wilson and Ava Helen Pauling.

In the years following publication, Wilson built a career as a highly successful chemist and an esteemed member of the scientific community. In 1949 Wilson too received a Guggenheim Fellowship, with another to follow in 1970. And in 1975 Wilson was awarded the prestigious National Medal of Science for physical sciences, just one year after Pauling.

Pauling the Educator

Linus Pauling in lecture, 1960s.

Linus Pauling in lecture, 1960s.

…[T]o awaken an interest in chemistry in students we mustn’t make the courses consist entirely of explanations, forgetting to mention what there is to be explained.”
– Linus Pauling. Letter to A. A. Noyes. November 18, 1930.

Linus Pauling began his teaching career in 1919, as an undergraduate sophomore, when Oregon Agricultural College offered him an assistant teaching position. After completing his graduate work at Caltech, Pauling dove into the role of educator as a fulltime professor.

Pauling believed that every student should approach chemistry with a sense of wonder and anticipation — he wanted his students to be excited and engaged. Pauling was not one to drone on in a hot classroom while his pupils dozed in their seats. Instead, he was always moving, gesturing and talking, a veritable flurry of activity at the front of the room. His lectures were filled with demonstrations, drawings, and models.

At a recent conference hosted by Oregon State University, one of the speakers, Nobel laureate Dr. Dudley Herschbach, told a story of Pauling’s in-class exploits. Dr. Herschbach explained,

“[T]here’s a classic [demonstration] always done in freshman chemistry – you have a bowl of water, you throw a chunk of sodium in, with some phenolphthalein so it changes colors as things go around and it reacts to produce a base. Well, Linus would do that, and then he’d get very excited about it and say “Isn’t this wonderful, it’s giving off hydrogen,” and all this, and then he’d say “What if we did it with gasoline!” He’d run down here, and all the students would be moving out of the way because the guy looks crazy because he’s so excited. He pours some gasoline in, steps back, and throws off the sodium chunk. Nothing happens. It was his way of making sure they appreciated one of the wonders of chemistry, that is, the business [of] how different things are.”

During his career at Caltech, Pauling’s freshman lectures became famous. While giving a presentation, if something caught his attention, he would explore the problem, following it through its different disciplines, tracing out theories and methods as he went. These seeming digressions often served to teach his students much more than any standard chemistry lecture could.

Indeed, Pauling was both interesting and entertaining, blessed with both an expansive knowledge base and a quick wit. Thomas Hager, a Pauling biographer, writes,

“Together with a spontaneity, vigor, and excitement, there was an ever-present sense of humor, and what a great many people have called ‘showmanship.’ Some have called one aspect of it ‘classroom calisthenics’ – leaps from the classroom floor to a sitting position on the lecture desk with legs dangling, or parallel bar exercises with one hand on the chalk tray and the other on the lecture podium, the body swinging back and forth while the lecture was going on at the same time.”

Despite his advanced abilities and deep understanding of multiple scientific disciplines, Pauling chose to spend much of his career teaching freshman chemistry. He was dedicated to bringing fresh minds into the field. By igniting a passion for the subject, or at least sparking an interest in young students, he knew he would be able to benefit both his pupils and the sciences.

Included among his students are:

Jerry Donohue – Aided James Watson and Francis Crick in their discover y of DNA’s structure.

Martin Karplus – Known for the creation of the Karplus equation.

Matthew Meselson – Responsible, in collaboration, for discovering how DNA replicates, recombines, and is repaired in cells.

E. Bright Wilson, Jr. – Notable advances in the fields of quantum mechanics and spectroscopy.

To learn more about Linus Pauling’s influence as an educator, please visit the website “Linus Pauling and the Nature of the Chemical Bond: A Documentary History.”