We Wrote a Book!

Long-time readers will have noticed that it’s been awfully quiet around here in recent months. There are many reasons for this, but one of the biggest is a project that we’re very excited to announce today, a book titled Visions of Linus Pauling that is based on a selection of our past writings! It is available for purchase in both hardback and as an e-book, and if you use the promotional code WSBOOKSSU25 you will receive 25% off your order.

Published by World Scientific and edited by Oregon State University archivist Chris Petersen, Visions of Linus Pauling consists of pieces that were originally published on the Pauling Blog, often in serial form, and compiles them for readers in a single, 396-page volume.

As the Pauling Blog consists of over 850,000 words in total, choosing content for the book project naturally required some principles of selection. Instead of taking a more rigorously biographical approach, we ultimately decided to curate material that, in our view, represented substantive contributions to the broader understanding of Pauling and his era.

In certain cases, this led us to select content that was wholly original, such as our biography of Linus Pauling’s second-eldest son, Peter, or our examination of the history of his beloved oceanside property, Deer Flat Ranch. In other instances, we chose pieces that provided a different slant on well-known stories, such as our review of Pauling’s writing process when penning The Nature of the Chemical Bond, or his experience of the run-up to and formal acceptance of the Nobel Peace Prize. At other times, we opted for content that examined pieces of the Pauling story in great depth; his battle with glomerulonephritis, for example, or his two appearances before the Senate Internal Security Subcommittee. A handful of shorter vignettes are also sprinkled throughout, many of which are meant to provoke a smile from the reader.

The book begins with a Preface that recounts the history of the Pauling Blog and the ways in which it developed as part of a larger Pauling-related program within the Oregon State University Libraries Special Collections and, later, Special Collections and Archives Research Center. Following that is a detailed biographical sketch that provides an overview of Pauling’s life for those who are newer to his story.

From there, the book’s chapters unfold in chronological order, an arrangement that allows the reader to make connections as time moves forward. One is able, for example, to gain a real sense of the undercurrents of controversy that plagued Pauling for more than a half century, as he faced criticism from groups as varied as the Soviet Academy of Sciences, the National Cancer Institute and even, during his year as president, large factions within the American Chemical Society.

Other connections are more subtle, but potentially more striking. For instance, in the early and mid-1970s, Jack Kevorkian, a medical pathologist who would eventually become internationally known for his active support and engagement with physician-assisted suicide, approached Pauling with the idea that, in Kevorkian’s words,

… prisoners condemned to death under capital punishment be allowed to submit, by their own choice, to medical experimentation under surgical anesthesia, to be induced at the set minute of execution, as a form of execution in lieu of the conventional methods prescribed by law.

Kevorkian continued,

[…] Most of us are well aware that the ultimate ‘laboratory’ for testing every medical fact, concept or device is man himself. […] In this logical and proper sequence of trial, the human subject, at the end, the ‘guinea pig,’ is, and always will be, the most difficult link to procure. […] Viewing the problem purely realistically, capital punishment, as it exists today, offers an unrivaled opportunity to break these limits. It can do this by introducing into the situation an involuntary factor without destroying the necessary safeguard of consent.

Though intrigued, Pauling ultimately declined to endorse this proposal, writing

I think that the best form of execution, if people are to be executed, is the one that causes the person the least suffering. I am not sure that this idea is compatible with your proposal.

Flash forward to the early 1990s and the book’s recounting of a cancer diagnosis that would ultimately claim Pauling’s life. Though presented with a full compliment of conventional treatment options, and continuing to take the megadoses of vitamin C that had been a mainstay for him since the 1960s, Pauling mostly chose to pursue a highly unorthodox protocol, in part because of his core belief in the advancement of science. From the final chapter of Visions of Linus Pauling,

In a letter to medical writer and cancer consultant Ralph Moss, Pauling detailed a therapy involving autologous anticancer antigen preparation, or AAAP, of which he was somewhat skeptical but nonetheless interested in pursuing. Working with friends and colleagues at Stanford Medical School to raise monoclonal antibodies against his prostate cancer cells, Pauling ultimately conducted what amounted to exploratory and self-experimental science to try and discern the potential value of AAAP. […]

By July 1992, Pauling had decided to move forward with AAAP treatment, the ultimate goal being a vaccine that would combat his own illness while also providing useful data for the science of the future. Subsequently, a 1-gram section of cancerous tumor tissue that had been surgically removed from Pauling’s body was shipped to [the AAAP treatment] lab in New York. Upon entering the operation, Pauling’s surgeon had advised him that his entire tumor should be removed, rather than a small section. Pauling refused this request, arguing that a full resection would prevent him and others from observing the effectiveness of the AAAP treatment. In other words, rather than focusing on the fact that his own life was on the line, Pauling was still operating, first and foremost, in the mode of the scientist: he was running an experiment in which he himself was a test subject, and the stakes could not have been higher.

Pauling’s choices as a nonagenarian in fading health were, of course, his alone, and were in no way ethically equivalent to those faced by prisoners sentenced to death, nor were they likely informed at all by his correspondence with Kevorkian some two decades before. But for the reader, the juxtaposition of these two stories in a single text might prove compelling, and is an example of what can be gained by engaging with this book.

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As with posts on the Pauling Blog, Visions of Linus Pauling largely avoids technical jargon and aims to be of interest to a general audience. Below is the full rundown of chapters and authors featured in the book, which also includes sourcing notes and a detailed index. We hope you’ll check it out!

• Preface (Chris Petersen)
• Biographical Sketch of Linus Pauling (Chris Petersen)
• Writing The Nature of the Chemical Bond (Andy Hahn)
• Pauling’s Battle with Glomerulonephritis (Carly Dougher)
• W.H. Freeman & Co. (Dani Tellvik)
• Christmas (Linus Pauling Jr.)
• The Soviet Resonance Controversy (Miriam Lipton)
• One Year as President of the American Chemical Society (Madeleine Connolly)
• The Theory of Anesthesia (Trevor Sandgathe)
• Lloyd Jeffress (Trevor Sandgathe)
• Deer Flat Ranch (Matt McConnell)
• Stuck on a Cliff (Megan Sykes)
• The SISS Hearings (Will Clark)
• Unitarianism (Will Clark)
• An Honorary Diploma from Washington High School (Madeline Hoag)
• Receiving the Nobel Peace Prize (Andy Hahn, Jindan Chen and Michael Mehringer)
• William P. Murphy (Ben Jager)
• The National Review Lawsuit (Jessica Newgard)
• Peter Pauling (Matt McConnell)
• Patents (Olga Rodriguez-Walmisley and Trevor Sandgathe)
• Jack Kevorkian and a Twist on Capital Punishment (Chris Petersen)
• The Linus Pauling Institute of Science and Medicine (Adam LaMascus)
• A Funny Story from Andy Warhol (Chris Petersen)
• Quasicrystals (Jaren Provo)
• Pauling’s Last Years (Matt McConnell)

Linus Pauling Day, 2022

Happy Linus Pauling Day! In commemoration of Pauling’s birth 121 years ago, Dr. John Westerdahl of the Health & Longevity podcast interviewed Dr. Emily Ho, director of the Linus Pauling Institute at Oregon State University. That interview is included here, and a description of the show is below.

February 28th has been declared, Linus Pauling Day by the state of Oregon in honor of the late scientist, Dr. Linus Pauling. Today on Health & Longevity, Dr. John Westerdahl’s special guest is Dr. Emily Ho, PhD, the Director of the Linus Pauling Institute at Oregon State University. The institute is named after two time Nobel Prize winner, Dr. Linus Pauling, one of the world’s greatest scientists and humanitarians. Dr. Emily Ho discusses the institute’s research and mission, and the role of nutrition and dietary supplementation in achieving optimal health. She also discusses the institute’s free February 28th webinar on Vitamin C (learn more and register at lpi.oregonstate.edu). This program is dedicated to the life and work of Dr. Linus Pauling and features audio excerpts of Dr. Pauling discussing his concepts of science and health. Dr. Westerdahl previously served as a volunteer assistant nutritionist to Dr. Pauling.

A Resonating-Valence-Bond Theory of Metals and Intermetallic Compounds, 1949

Linus Pauling, 1949

As we have written elsewhere, Linus Pauling developed and championed the theory of resonance early on in his career. But for almost 20 years, the ways that metals might conform to the theory remained elusive. Even though he had a hunch that they too adhered to the tenets of resonance, he was not able to prove it definitively at the outset. Not until 1949, with the publication of “A Resonating-Valence-Bond Theory of Metals and Intermetallic Compounds” was he able to demonstrate that metals do resonate. 

Pauling’s interest in metals dated at least as far back as his undergraduate years at Oregon Agriculture College and continued to flourish during his graduate training at the California Institute of Technology. Later in his career, when asked to reflect on his contributions to the field of chemistry, he often spoke of his early work with metals as being important. This was especially so with his work on metals and resonance.

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“A Resonating-Valence-Bond Theory of Metals and Intermetallic Compounds,” which was published in the Proceedings of the Royal Society London, serves as an addendum of sorts to Pauling’s previous papers on the nature of the chemical bond. Even though Pauling’s theory of resonance had been well-received for several years, confusion still existed amongst chemists (including Pauling) about how the theory might apply to metals; particularly the iron-group transition metals. Pauling believed that, like other elements, resonance must be used to explain the way that these metals bond, but the specifics proved difficult to pin down.

Pauling had always aligned himself with the notion that the properties of an element were connected to the configuration of its valence electrons. For example, Pauling knew that the arrangement of valence electrons gave Carbon its stable tetrahedral properties and salts their ionic properties. Metals, however, were harder to define due to the fact that they “showed great ranges of values of their properties, such as melting and boiling point, hardness and strength, and magnetic properties.”

Pauling initially focused on magnetism, and from this work, it was determined that metals had a high ligancy of either 8 or 12. Ligancy, or the number of compounds that each metal could bond to, (often referred to as Coordination Number) is similar but still distinct from valency, and for the metals that Pauling was studying, a ligancy of 8 or 12 was higher than their valence. This discrepancy seemed to indicate that resonance could not be applied to explain how metals bonded. But Pauling still believed that resonance was the answer, and set about trying to confirm this belief.

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In his quest to understand if or how metals resonated, Pauling first needed to clarify whether or not previous thinking about metals was correct. Prior to the publication of his 1949 paper, it was believed that the d orbitals did not participate in bonding with the iron-group transition metals, such as Manganese, Iron, Cobalt, Nickel, and Copper. Using these assumptions, Pauling modeled the predicted properties of such metals and found that they would have low melting points and weak bonds. The lab work indicated otherwise however, leading Pauling to conclude that the current understanding was incorrect, and that something else had to be going on with the bonds in order to account for their physical properties.

For several years, Pauling had been unable to devise a competing theory that would explain the unique properties of metals, but he felt certain that the answer would be revealed through the application of quantum mechanics. By specifically using the wave theory of quantum mechanics, Pauling calculated that metals used 8.28 orbitals instead of the expected 9. While he was sure that the math was correct, he struggled to understand what was accounting for the missing 0.72 orbitals, and for almost nine years he worked to reconcile the discrepancy. Ultimately though, he realized that 0.72 orbitals was, in fact, the answer he was looking for; they were what gave metals their unique properties.

In its essence, Pauling breakthrough was that the extra 0.72 orbitals was not a mathematical anomaly, but instead an extra orbital, one that he called a “metallic orbital.” The metallic orbital was, according to Pauling, “required” to give metals their “characteristic properties, especially that of electronic conductivity of electricity.” In Pauling’s view, substances lacking the metallic orbital that still maintained some metallic properties, such as electric conductivity, should be classified as metalloids.

Pauling’s conceptualization of the metallic orbital allowed him to subsequently reframe his understanding of resonance. When Pauling developed the theory, it was more specifically known as synchronized resonance; a state in which all bonds resonate in the same way and valence is undisturbed by the process. Pauling realized that, in order for metals to resonate, a different kind of resonance – unsynchronized resonance – would be needed. In unsynchronized resonance, instead of all bonds resonating simultaneously, a single bond could resonate on its own. In the case of metals this happened in the metallic orbital, and it was found that unsynchronized resonating metals conferred unusual stability and high ligancy.

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Once Pauling made these connections, he was ready to publish his paper, which, first and foremost, sought to prove the existence of a metallic orbital. To do this, Pauling had to show that the existing understanding of valency was incorrect, and then to demonstrate that resonance – specifically unsynchronized resonance – could account for both the predicted and the observed properties of metals.

Using Lithium as his model element, Pauling explained that the current understanding posited a valence structure that consisted of 2s orbitals, and that this was the commonplace belief because, “the [proposed] molecular orbitals correspond to electron energies.” By using the wave function however, Pauling found that the assumed orbital structure did not correspond to observed electron energies. Specifically, he calculated that if Lithium had 2s orbitals, the predicted heat of formation would be much different than was the observed heat of formation; a calculated difference of 32.4 kcal/g. In short, the current understanding was incorrect.

Pauling’s next step was to use resonance to explain Lithium’s metallic properties, and to devise an arrangement of valence electrons that would match predicted energies with observed energies. Using the idea of unsynchronized resonance, Pauling suggested that if, instead of 2s orbitals, Lithium’s valence electrons were actually in resonance, this new arrangement could be “responsible for the difference in energy.” In other words, without resonance the electrons existed in a fixed energy state. But if the electrons were in resonance, their energy state would instead be a hybrid of all possible energy states. This circumstance, Pauling postulated, would confer lower energies to the molecule and bring predicted and observed energies into alignment. In the case of Lithium specifically, Pauling found that the valence electrons were in 2s orbitals, but also 2p orbitals. Pauling worked through different metals throughout the remainder of the paper to further support his thinking.

The theoretical work that Pauling put into this paper completed the framework for resonance. And interestingly, even though the ideas that he presented were accepted and widely used for decades, some of the math in the paper was not fully validated at the time. In fact, it wasn’t until 1984, when Pauling revisited the 0.72 orbitals, that the math was completed. By then Pauling had acknowledged that the calculations he used to get to 0.72 orbitals had been crude, and based on in part on educated guesses. But by the 1980s, many of the unknowns were known, which allowed Pauling to revisit the math with more precision and compare it to his work from the late 1940s. Using clean, contemporary data, Pauling confirmed that the new calculation was “in exact agreement with the observed value of 0.72.”

The Nature of the Intermolecular Forces Operative in Biological Processes, 1940

Linus Pauling, Max Delbrück and Max Perutz at the American Chemical Society centennial meeting, New York. April 6, 1976.

In 1940 Linus Pauling, along with colleague Max Delbrück, authored a three-page article that was published in the July issue of the journal Science. The length of the article was shorter than typical for Pauling, but what made it even more unusual was that it was not about Pauling’s findings. Instead, the piece served as a critique of a different article published earlier that year by a German scientist, Pascual Jordan.

In it, Jordan argued that when like molecules bonded, they were attracted more strongly than when dissimilar molecules bonded. Jordan believed that this stronger attraction of like molecules conferred special properties to these bonds, especially when they occurred in living cells. Pauling and Delbrück totally disagreed with this idea. Instead, the duo believed that it was a molecule’s complementary nature that conferred stability, an idea in opposition to Jordan’s concept of similarity.

In the two decades preceding these papers, chemists had come to look at their field in different ways, due mainly to advancements in quantum mechanics. This was certainly true for Pauling, who rapidly developed a reputation for using these new ideas to solve old problems. One line that he did not cross however, was the application of quantum mechanics to help “solve” topics that were already well understood and not in conflict.

For Pauling, one such instance was the basis of molecular attraction, and how that attraction created stability in a newly formed molecule. This idea, however, was something that other scientists found worth examining; Pascual Jordan in particular. Accordingly, and armed with a new set of quantum mechanical theories, Jordan set about attacking a question that others, including Pauling, believed not in need of answering.

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Pascual Jordan

Pascual Jordan was born in Germany in 1902 of Spanish lineage. Though initially interested in the arts, Jordan studied math and physics in school, completing his physics Ph.D. in 1924. His ideas at this time were novel, with no less a figure than Albert Einstein taking note of his dissertation. But Einstein did not agree with certain of the hypotheses that Jordan was putting forth, many of which used quantum mechanics to consider the photon nature of light. While Einstein felt that there wasn’t necessarily anything wrong with Jordan’s ideas, he did not agree with the logic that informed them, and wrote missives in opposition.

But others supported Jordan’s work and, soon after graduation, he began working with a circle of colleagues that included Werner Heisenberg. During this time, Jordan became one of the biggest proponents of quantum mechanics and, along with Heisenberg, helped to unlock many of its secrets. Jordan was also a member of the Nazi party, joining when Germany entered World War II and remaining so until at least the end of the war. Nonetheless, Jordan helped to develop key theories in physics and math which are foundational to the fields today.

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Though Jordan’s legacy today is marred by his political positions, when he wrote his 1940 paper about the attraction of molecules in biological cells, he did so from a position of authority. As noted, the foundation of the paper is the idea that identical molecules are attracted to one another in a special way that does not exist for dissimilar molecules and that, because of this, the bonds formed in molecules are more stable than is the case with other bonds. Jordan’s hypothesis, if true, would have been groundbreaking and consequential for all sorts of bonds, especially those in living cells.

Understandably, the paper created a lot of commotion when it was published. Pauling, who at that point was also an authority on quantum mechanics and resonance theory, was no doubt among those surprised by Jordan’s proposition. After reading it though, he immediately saw its flaws. In it, Jordan himself admitted some doubt that resonance could work in the manner that he was suggesting, and Pauling was sure that the ideas were wrong. Wishing to publish a rejoinder, Pauling began looking for a co-author whose expertise centered around bonds in living cells, and Max Delbrück was just such a figure.

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Like Jordan, Delbrück was born in Germany in 1906. Interested in the stars, Delbrück began his studies in astrophysics, but changed directions upon meeting a physical chemist, Karl Bonhoeffer, who was eight years his elder. Fascinated by Bonhoeffer, Delbrück switched to physical chemistry in a ploy to become his friend, a tactic that ultimately worked well. The timing of the switch was also fortuitous as Delbrück entered the field at the beginning of the quantum revolution. After graduation, Delbrück studied all over Europe with scientists included Wolfgang Pauli and Niels Bohr. He eventually spent a few years at the California Institute of Technology on a Rockefeller Foundation fellowship, during which time he met Pauling and co-authored the 1940 paper. After leaving Caltech, Delbrück focused his research on bacteriophages and eventually won the 1969 Nobel Prize in Physiology or Medicine for this work. 

Even though Delbrück’s Nobel honor was nearly thirty years down the road, by 1940 he was already well-versed on the ways that living cells operated, making him a formidable writing companion. In their paper, Pauling and Delbrück argued that Jordan’s fundamental idea could not be correct because the stability of a molecule was conferred by the complementarity its components, not their similarity. By way of explanation, the duo first put forth the understanding that a stable molecule is one in which molecular distances are relatively short. This is a circumstance, they argued, that can best be achieved when complementary forces are working together, such as positive ions attracting negative ions. In other words, in a bonding pair “the two molecules must have complementary surfaces, like die and coin.” The like molecules that Jordan was advocating for were not complementary by definition; rather, they were identical, or close to it. Pauling and Delbrück acknowledged that “the case might occur in which the two complementary structures happen to be identical” but still their stability “would be due to their complementariness rather than their identity.”

Even though Pauling and Delbrück’s article was quite short, its message was clear: Jordan was plainly wrong. As they wrote, “We have reached the conclusion that the theory can not be applied in the ways indicated by him [Jordan], and his explanations of biological phenomena on this basis can not be accepted.” In short order, the scientific mainstream came to agree with their point of view, and Jordan’s ideas soon faded away.

The Nature of Interatomic Forces in Metals, 1938

Linus Pauling, ca. 1930s

“In recent years I have formed, on the basis of mainly empirical arguments, a conception of the nature of the interatomic forces in metals which has some novel features.”

­-Linus Pauling, 1938

Prior to the publication of this article, which appeared in the December 1938 issue of Physical Review, much about the interatomic forces operating in metals was either unknown, or theoretical predictions did not align properly with observed data. In publishing this paper, Linus Pauling first sought to align the incongruencies between theory and data for the transition metals, such as iron, cobalt, nickel, copper, palladium, and platinum. He was then able to correctly predict properties including “interatomic distance, characteristic temperature, hardness, compressibility, and coefficient of thermal expansion” by discarding previously held assumptions and inserting new – and correct – assumptions about transitions metals.

The most significant idea that Pauling introduced with this paper was the notion that the valence shell electrons – those in the outer shell – play a part in bonding. Previously, scientists believed that these electrons made “no significant contribution” to bond formation. Pauling was able to establish otherwise, and used this breakthrough to both align observable data with theoretical data, and make other predictions about transition metals.

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The 1938 paper was written in the wake of a revolution within the world of chemistry. A raft of new theories brought about by a widening understanding of quantum mechanics was generating intense excitement for scientists world-wide, and the tools that quantum mechanics provided for helping to “correct” previous understandings of the chemical bond were of paramount interest to many. Pauling, of course, was a leader in this area, his body of work ultimately garnering the 1954 Nobel Chemistry Prize for “research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances.”

Within this area of focus, many scientists were especially interested in exploring the ways that metals bonded because, as noted, the observed data did not match up with theory. Pauling sought to mend this gap by using quantum mechanics to look at interatomic forces in a novel way. Prior to the Physical Review paper, chemists believed that when metals bonded, their valance shell electrons played only a small role in the resulting structures. Pauling argued otherwise, and put forth an important new theory that the valence shell electrons contributed to the process through resonance, a theory that he had developed earlier in the decade and continued to champion.

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Because the crux of Pauling’s scientific intervention was to prove that valence shell electrons are involved in bonding, most of the paper is devoted to supporting this claim. The primary tool that Pauling uses to craft his argument is an analysis of temperature predictions. According to the reigning theory regarding metals and valence shell bonds, when bonding occurred, the electrons would bond in a manner that would create a moment of ferromagnetism. Specifically, it was theorized that these ferromagnetic moments would be temperature dependent, meaning that as the temperature of the metal changed, its degree of magnetism would also change in a predictable way. Experiments had shown however, that when metals bonded, their ferromagnetism remained independent of temperature.

Pauling exploited this piece of information and used it to support his theory. According to Pauling, if metals bonded through resonance, they would create ferromagnetic moments that were temperature independent, a hypothesis that correctly aligned with the observed data.

To develop his argument, Pauling made specific use of the element Vanadium, which has an electron configuration of 3d³4s². Under the old model, Vanadium’s valence electrons could only interact weakly in bonding if, at most, two of the 4s² electrons were involved in a bond. This, according to Pauling, would create ferromagnetism which would decrease with increasing temperature, meaning that it was temperature dependent. On the contrary, the experimental evidence showed that Vanadium’s magnetism was temperature independent. This meant, therefore, that weak valence interaction during bonding was not possible.

Pauling’s alternative suggestion was that all of Vanadium’s valence electrons were involved in bonding through resonance; not just the two 4s² electrons, as previously believed. Further, if the valence electrons bonded through resonance, the ferromagnetism of their structure would be temperature independent, a prediction that aligned with the observed data.

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Once Pauling was able to prove that the valence electrons in Vanadium bonded through resonance, he then began to apply the concept to all transition metals. As with the previous example, Pauling continued to support the concept by comparing predicted outcomes with empirical data. And once again, when viewing the bonding through the prism of resonance, predicted outcomes of magnetic moments began to align with the empirical data.

Pauling then took it another step by repeating the exercise with interatomic distances. As demonstrated in his paper, a resonant structure would correctly predict the interatomic distances that had been observed for many bonds. Pauling also claimed that other properties, such as the “compressibility, coefficient of thermal expansion, characteristic temperature, melting point, and hardness” would likewise correctly align with experimental evidence, once resonance was used to explain valence shell bonding.

Though clearly a significant breakthrough, the assertions that Pauling made in his paper were grounded in work done by others — notably the quantum mechanical theory of ferromagnetism developed by Heisenberg, Frenkel, Bloch, Slater, et al., and Wolfgang Pauli’s theory of the temperature-independent paramagnetism of the alkali metals. And while the 1938 article acknowledges these debts, it also attempts to improve upon them.

This was especially so with the quantum mechanical theory of ferromagnetism. As we have seen, Pauling successfully applied the idea of temperature independence and ferromagnetism to support his claims, but he also found one aspect of the theory to be needlessly bothersome. As Pauling noted, in order for much of the theory to work on a mathematical level, scientists were compelled to assign positive numbers to all unpaired valence electrons. Pauling recognized that this was only necessary if it was assumed that valence electrons did not play a large role in bonding for metals. Under a resonant scenario, Pauling was able to show that the math could still work if the valence electrons were negative and that, once again, “this conclusion agrees with the observation.”

The Theoretical Prediction of the Physical Properties of Many-Electron Atoms and Ions. Mole Refraction, Diamagnetic Susceptibility, and Extension in Space, 1927

Linus and Ava Helen Pauling in Copenhagen, May 1927

[Ed Note: Today and in the three posts that will follow, we will be taking a close look at four important scientific articles published by Linus Pauling between 1927 – 1949.]

In this ambitious and hugely influential paper, Linus Pauling applied his theory of screening constants to various problems, including electric polarizability, diamagnetic susceptibility, and the sizes of ions and atoms. Pauling was fundamentally interested in pursuing this topic because of his desire to merge the new quantum mechanics – which embraced wave functions – with older ideas in order to make predictions about molecular properties like mole refraction and diamagnetic susceptibility in space.

Especially during the early phases of his career, one of Pauling’s signature rhetorical tools was to put forth a bold assumption that would serve to simplify the predictions made later on in a given article. This paper is among the best examples of that approach. In it, Pauling developed mathematical relationships that, when applied, could help the reader make generalizations about molecules. But in moving through these calculations, Pauling had to make some assumptions, oftentimes without the aid of hindsight to determine whether or not they were correct. One enduring legacy of this paper is that many of Pauling’s assumptions were indeed correct, and its findings have thus remained relevant across the decades.

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Another contributing factor to the paper’s success was that Pauling was in the right place at the right time. While working towards his PhD at Caltech, Pauling enthusiastically followed the rapid development of quantum mechanics in Europe and elsewhere. Pauling was particularly interested in the work of Arnold Somerfield in Munich and Niels Bohr in Copenhagen, and wrote to both to inquire about research opportunities. Bohr never responded but Sommerfeld did and, with his support, Pauling secured a Guggenheim Fellowship that allowed him to live and work in Europe for 19 months. During that period, he spent most of his time with Sommerfeld at the Institute of Theoretical Physics, though he did visit Bohr in Copenhagen as well as Erwin Schrödinger in Zurich.

Pauling’s residency in Europe proved auspicious, in part because Sommerfeld and his colleagues were working on uniting new ideas with old, a task not being readily pursued in the United States at the time. As they moved forward with their work, the European scientists began to solve more and more problems with quantum mechanics, cementing in Pauling’s mind the utility of the approach as a way forward.

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Gregor Wentzel (Image credit: Emilio Segre Visual Archives)

One project important to Pauling’s paper was being led by University of Leipzig physicist Gregor Wentzel. A colleague of Sommerfeld, Wentzel was seeking to apply quantum mechanics to x-rays in order to calculate the screening constants of electrons in large and complex molecules. His project had hit a snag however, in that he was unable to find agreement between the observed data and those predicted by theory. After scrutinizing his work, the young Pauling found that Wentzel had made errors in his calculations. Once Pauling had corrected these miscalculations, he found that there was in fact agreement between the observed and predicted data, which meant that Wentzel’s work was actually correct. In so doing, Pauling had confirmed the value of quantum-mechanical calculations in predicting screening constants of electrons in complex molecules.

Armed with this information, Pauling recognized that he could use these same calculations to make predictions about electron arrangement in molecules and the relative size of ions, among other properties. This led to the publication of his paper, The Theoretical Prediction of the Physical Properties of Many-Electron Atoms and Ions. Mole Refraction, Diamagnetic Susceptibility, and Extension in Space, which appeared in 1927, published by the Proceedings of the Royal Society.

In its essence, the article used the wave mechanical feature of quantum mechanics to make predictions about molecules, an approach that emerged directly from Pauling’s exposure to European efforts to unify old ideas with new. And even though it was not the first time that Pauling had written a paper utilizing quantum mechanics, it was certainly his first publication in which he used these novel tools to make predictions about molecular properties. 

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Fundamental to these predictions were three key assumptions that Pauling put forth at the beginning of his paper. The first was that,

each electron shell within the atom is idealized as a uniform surface charge of electricity of amount-z_i e on a sphere whose radius is equal to the average value of the electron-nucleus distance of the electrons in the shell.

The second assumption stated that,

the motion of the electron under consideration is then determined by the use of the old quantum theory, the azimuthal quantum number being chosen so as to produce the closest approximation of the quantum mechanics.

And the third assumption was that,

since s_o does not depend on Z, it is evaluated for large values of Z, but expanding powers of z_i/Z and neglecting powers higher than the first, and then comparing the expansion with that of the expression containing Z-s_o in powers of s_o/Z.

Armed with these assumptions, Pauling was able to issue a collection of predictions about molecules, particularly concerning mole refraction and diamagnetic susceptibility. Prior to his doing so, chemists lacked the necessary tools for making predictions of this sort, meaning that certain chemical properties remained hazy or unknown.

This issue was particularly salient for the hydrogen atom. In the months leading up to the paper’s publication, a huge debate had emerged concerning the polarizability of hydrogen. The prevailing formula had been proven incorrect in 1926, after which time a race ensued to find a new, more suitable equation. Eventually a successor formula was developed, but it was criticized as being “a conservative Newtonian” model. Agreeing that a more robust approach was needed, Pauling set about applying quantum mechanics, and based on his three assumptions, he derived the following:

Knowing full well that the equation was based on his three assumptions, and anticipating resistance, Pauling pre-emptively argued that “it might be thought that these values of ɣ are not correct because of the fact that the electron shells actually do not consist of hydrogen-like electrons, but rather themselves of ‘penetrating electrons.'” However, “as Z [a surface harmonic] increases, the ‘penetrating orbits’ become more hydrogen-like” and therefore should be ignored because any error found would be “negligible.” Having put forth this solution to the problem of hydrogen, Pauling was then able to more broadly demonstrate the utility of his ideas.

Indeed, even though much of the work in the paper made assumptions that were oftentimes crude – such as using data from the valence shell electrons only – Pauling was able to create complex (and, as it turned out, fairly accurate) tables of polarizability of ions, diamagnetism screening constants, and mole refraction, among predictions.

It is clear that Pauling believed strongly in his paper, which he felt would “make possible the accurate prediction of the properties of any atom or ion.” And though the approach would sometimes only yield “approximate values of the physical properties of ions” based on his three assumptions, the importance of the work was not diminished as, oftentimes, directly observed data “may not exist under conditions permitting experimental investigation.”

Ava Helen Miller in Corvallis, 1921-1923

Ava Helen Miller, ca. 1922. Note annotation by Linus Pauling: “Ava Helen about when I met her.”

[Part 2 of 2]

Ava Helen Miller entered Oregon Agriculture College, now Oregon State University, as a freshman in the fall of 1921. During that first year, she met Linus Pauling, and shortly thereafter the two fell in love and became engaged. This chance meeting derailed her plans to continue her formal education, and after five terms at OAC, she left school to start her life with Pauling. But even though she spent less than two academic years in Corvallis, Ava Helen made the most of her experience.

The tenth of twelve children, Ava Helen was born in 1903 in Beavercreek, Oregon, an unincorporated area southwest of Portland. When the time came to begin considering colleges, OAC proved a natural choice because, by 1921, three of her siblings were already attending the school. These siblings were her brother Milton, a senior majoring in agriculture; another brother Clay, a junior also studying agriculture; and sister Mary, a senior in home economics. Like Mary, Ava Helen entered OAC as a home economics major. And instead of living in a women’s dormitory like most first-year students, Ava Helen lived with her siblings in a Corvallis rental home that her mother Nora also resided in.

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Though college was not an ordinary expectation for women of the era, a higher education seemed to be in the cards for Ava Helen. She had always excelled as a student, graduating from Salem High School in three years as the class president. Buoyed by her past successes, Ava Helen enrolled in a wide variety of courses during her OAC tenure, including Spanish and French, languages for which she showed a particular aptitude.

Generally speaking, her performance in college improved as she became more settled. During her first term, she received mostly Bs with a C in general chemistry and an A in English composition. Interestingly, during her second quarter, Ava Helen received her only F, which was also in English composition. That winter term was clearly challenging with respect to academics, as her grades were somewhat worse than was typical for the rest of her OAC time. (Coincidentally or not, this was also the term in which she met her future husband.) But later, her grades improved. In her last quarter, she took Child Care and received an A, perhaps a foreshadowing of her future responsibilities as a mother of four.

Chemistry was always one of her best subjects, and instructors besides the young Pauling took note of her chemistry aptitude. One of them, an organic chemistry instructor named Mr. Quigly, remarked that she was among his best students. Despite this aptitude, Ava Helen notably received a B in general chemistry during the winter term of her first year, a grade that she felt was lower than she deserved. This belief was accurate, but because the instructor for the course was her soon-to-be husband, the instructor – “boy professor” Linus Pauling – deliberately lowered her grade from an A to a B, in an effort to obfuscate any potential impropriety. This decision remained a source of good-natured ribbing between the couple for years to come.

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Ava Helen pursued interests outside of academics during her stint in Corvallis. She joined the school’s drama club, known as the Mask and Dagger, during her first year. The club produced several plays including larger productions like Shakespeare’s “A Midsummer Night’s Dream” and “Clarence,” a modern “light comedy” by Booth Tarkington. Near the middle of the year, Ava Helen hit the stage in a one-act offering titled “Pierro by the Light of the Moon” by Virginia Church; Ms. Miller was cast as Columbine, the second lead.

During her second year at OAC, Ava Helen also served as secretary of the Lyceum Club, which consisted of “musicians, readers, and lecturers.” The club focused on coordinating cultural events for the local community and, during Ava Helen’s year, hosted several prominent artists and musicians, including the Flonzaley String Quartet.

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A discussion of Ava Helen’s time at OAC would be remiss if it did not include mention of her romance with Linus Pauling. During the winter term of her first year, she was enrolled in a general chemistry course that was mandatory for all home economics majors. Pauling, himself a fifth-year senior at OAC, was assigned to teach the class, though he was only a few years older than the students that he was asked to teach. Shortly after their first encounter in January 1922, Ava Helen and Linus hit it off, and by the end of the school year they were engaged.

In the summer of 1922, Pauling left Oregon to begin his graduate studies at Caltech while Ava Helen continued her schooling, starting her second year at OAC. The initial plan was for Ava Helen to stay at OAC and complete her degree while Pauling worked on his Ph.D, and the pair wrote to each other nearly every day, and saw one another on breaks. But the waiting and separation proved too much, and by the end of the second quarter of her second year, in March 1923, Ava Helen dropped out of school in order to plan her wedding. In June 1923, the couple married and Ava Helen moved to Pasadena to begin a new life.

Ava Helen’s OAC

Ava Helen Miller, fall 1921

[Part 1 of 2]

Ava Helen Miller entered Oregon Agricultural College (OAC), now known as Oregon State University, in the fall of 1921. She spent a total of five quarters at the school; one quarter shy of two full academic years. And even though her experience in Corvallis was relatively short, it was a memorable period for Ava Helen, one culminating in her meeting her future husband, Linus Pauling.

During the 1921-22 school year, OAC was home to its largest student body to date – more than 7,000 enrolled for at least one quarter, and a graduating class of 3,147. (2,040 men and 1,107 women.) The freshman class was 300 students larger than had been the case the previous year and the student body included 47 international students from Bolivia, Palestine, Peru and South Africa, among other far away lands. An additional 995 out of state students pursued an OAC education, with Washington leading the way (384) followed by California (315) and Idaho (111). Within the college, Home Economics awarded the most degrees that year, tallying 889; the School of Agriculture came in a close second with 876 degrees.

Those enrolled from out of state did so despite the fact that, in the fall of 1921, OAC began charging non-residents tuition – $20 per term – for the first time. The change impacted new students only, meaning that existing out of state students could still attend for free. (Ava Helen was a resident of Oregon, so this did not affect her.) Understanding the financial burden that this decision could have on its students, the OAC Board decided that non-Oregon residents who had served in World War I could receive a 50% discount on tuition. According to the monthly OAC Alumnus, the fees were enacted to “prevent an undue influx of students from other states and at the same time [provide] additional income […] in the construction of buildings.”

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OAC’s post-war population bump coincided with shifts in the types of activities available to the college’s women students. Several clubs for women were sponsored, including those dedicated to riflery and mandolins, but new sports were an area where women were really able to broaden their horizons. OAC co-eds competed in baseball, basketball, swimming, track, tennis, archery, volleyball, and the afore-mentioned riflery; dance was also organized as part of women’s athletics.

As was the case most everywhere however, traditional men’s athletics remained far more popular across campus and the community. The most prominent sport at OAC was football and the team, affectionately known as the “gridiron squad,” was lavished with rituals and processionals prior to each game. Among the most extravagant was a feeding party where the players dined on “big juicy steaks cooked rare, toast crisp through and through, big baked potatoes that rival the prizes of the Pullman diner [a popular upscale train car from the time] – all topped off with ice-cream.” And though the men ruled the sporting world at OAC, these epic meals took place in the women’s Home Economics Tea Room, as that was clearly the place for the best food on campus.

With more people at the school, more options to choose from, and requirements that first- and second-year women sign up for P.E. credits, its no surprise that, during Ava Helen’s second year, women’s physical education courses saw more enrollees than ever before. Elective options included seasonal sports, aesthetic dancing, swimming, or apparatus work, which is similar to gymnastics. The era’s women did not play softball, but were allowed to play baseball (with other women). To help manage growing numbers, and to harken back to times when the program was much smaller, the Physical Education Club arranged weekly dinners to assist students in getting to know one another.

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Competitive speaking was another area opening up to OAC’s women. By the fall of 1921, women had three different debate teams available to them – varsity, junior varsity, and intramural. During Ava Helen’s first year, the women’s Dual Debate Team (junior varsity), competed against the University of California and was asked to address the possibility of Irish independence. Meanwhile, the varsity squad was charged with discussing: “That the principle of the closed shop should be applied to all American industries. Farming and all industries employing less than three men are excepted.”

Intramural debate tended to pit classes against one another, with a 1921 contest asking freshmen and juniors to consider federal government ownership and operation of coal mines. Other topics shed light on the culture of the state a century ago – notably, a men’s interclass competition considering whether or not “Oregon should enact a law prohibiting Orientals from acquiring land within the state.”

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By Ava Helen’s time, women had clearly emerged as a priority for OAC. Importantly, in the fall of 1922, the college finished construction of its third women’s dormitory, Margaret Snell Hall. And a year prior, OAC had welcomed it newest Dean of Women, Mary A. Rolfe.

Rolfe had worked for various organizations before OAC, including the YWCA and the University of Iowa, but immediately prior to her tenure in Corvallis she had served in France as a “searcher.” In that role, she worked with other stenographers to write down wounded soldiers’ last words, which would then be conveyed to their families back home. As Dean, Rolfe believed that “My relation to young women should be that of friend,” an ideology that she upheld by creating opportunities for women and treating them as capable and inquisitive. One early example of this was her sponsoring the Oregon chapter of the Home Economics Conventions, a program “of interest to all women, whether professional home economics women, teachers, or homemakers.”

Ava Helen Miller took advantage of all that her college had to offer during a period of significant change. An exploration of her experiences at OAC will be the focus of our post next week.

Pauling’s OAC: Super Senior Year

[Ed Note: School starts today here at Oregon State University! As we have for the previous four years, we take this opportunity to look back at Linus Pauling’s undergraduate experience in Corvallis, this time documenting his “super senior” experience as a Beaver.]

The 1921-22 academic year was Linus Pauling’s fifth at Oregon Agricultural College (OAC), now known as Oregon State University. In the twelve months to come, Pauling would finish his coursework; graduate; become engaged; and move to Pasadena, California to begin his graduate studies. Needless to say, it was a year of great change for Pauling, but one that he embraced with excellence.

In the fall of 1921, seniors at OAC were welcomed back to the college through a series of “Get Acquainted” dances, which were aimed at helping them become more comfortable with their apical position in the social hierarchy. Though these dances were a running tradition at OAC, each senior class approached them in their own way. During the 1921-22 academic year the dances were themed, with one particularly memorable event, the Goof Dance, challenging participants to wear the craziest outfits they had. 

For Pauling, the start of the year marked a continuation of his effort to earn solid marks and gain entry into a good graduate program. Throughout his time at OAC, he had always applied himself, and by his senior year, those efforts were evident. As with other colleges, the OAC Beaver yearbook included basic information on all its seniors, as well as additional details documenting their participation in extracurricular organizations and clubs. These blurbs often consisted of a handful of words, but Pauling’s was, not surprisingly, several lines long.

As per OAC custom, Pauling’s entry lists his major (Chemical Engineering), his hometown (Portland), and his fraternal membership (Delta Upsilon). Other decorations included his membership in Sigma Tau, the engineering honor society into which he was inducted during his junior year and served as secretary during his final year at OAC. His participation in the Scabbard and Blade, a military honor society that he joined during his junior year, is also listed. During his senior year, Pauling served as a Captain in the Reserve Officer Training Corps, which was recognized by the yearbook as well. So too was he a member of the Chemical Engineering Association (junior year treasurer) and the Chi Epsilon civil engineering honor society (junior year president). His efforts in competitive speaking were noted as well.

Pauling’s accomplishments were likewise praised by outside organizations. One of them, the Oregon Alumni Society, heralded Pauling’s admittance into the Forum Honor Society, OAC’s most prestigious academic group. Pauling, along with sixteen other students, was admitted for his “excellence in scholarship, leadership in school activities and strength of character.” OAC President William Jasper Kerr welcomed the new members personally, a group that also included Pauling’s friend and future colleague, Paul Emmett. 

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Linus Pauling on OAC graduation day, June 1922.

As graduation day neared, Pauling was asked to deliver the senior class speech. He was a likely choice to fill this role, given his strong academic standing and his success in a junior year debate contest. But unlike past years, where speakers tended to offer fairly generic observations, Pauling’s speech was notably more pointed.

Pauling viewed the speech as an opportunity for him to position himself as a scientist, and he focused his rhetoric on contemporary world events as observed through a scientific lens. A main thrust of the talk was his belief in scientists’ duty to use their tools for good. In exploring this, he referred to the scientific developments that had advanced weaponry options, including chemical weapons, during World War I. Pauling also expressed a feeling that science was being used to create income gaps and remove humanity from workspaces, before suggesting that “the country is crying for a solution to these difficulties, and is hopefully looking to the educated man for it.” This call to action was the real point of his talk, which ended with an exhortation to his classmates that they repay OAC in the years ahead through acts of service in their communities.

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Newly arrived at Caltech, Pauling poses on the back of a student’s car.

Pauling was well-aware of the need to move beyond OAC to continue his learning, and throughout the year the decision of where to go for graduate studies weighed heavily on his mind. Always keen on a future in chemistry, Pauling stayed current on recent developments in the field and knew that there were a handful of institutions equipped to provide him with an advanced education that could keep up with the changing times.

He decided to apply to four graduate programs: Harvard University, the University of California at Berkeley, University of Illinois, and the California Institute of Technology. Of these schools, Pauling was perhaps most attracted to Berkeley because it was headed by G.N. Lewis, who had discovered that electron bonds are shared. Harvard was also enticing, in part because its program was led by Theodore Richards, who was America’s only Nobel Laureate in chemistry at the time. Richards had attended the University of Illinois for his graduate work, and this connection had helped to boost its program. Caltech, by comparison, was the smallest and newest of the possibilities in which Pauling was interested.

Pauling eventually opted for Caltech, a decision that was made, in part, because of a fortunate sequence of events. All of the universities that Pauling wanted to attend were interested in him, and Harvard offered an attractive fellowship that would cover his tuition. But shortly after receiving this offer, Caltech’s letter arrived. Like Harvard, the Pasadena school offered a full-ride fellowship, but Caltech’s package also included a $350 stipend to work as a teaching assistant in undergraduate chemistry courses. Importantly, Caltech had also accepted Pauling’s close friend, Paul Emmett, and the two would ultimately live together for their first year as graduate students. These two factors tilted the scale in Caltech’s favor, and Pauling would remain at the Institute for more than forty years.

Summer Break

Linus Pauling at the Oregon coast with his cousin Rowena, summer 1918

We’re taking a few weeks off! We’ll resume our usual posting schedule in September — please check back with us then for more from Pauling’s world.