Pauling’s Last Year as a Grad Student

Ava Helen and Linus Pauling, 1924.

Ava Helen and Linus Pauling, 1924.

[Part 3 of 3]

Pauling’s final year of graduate school at the California Institute of Technology, 1924-1925, was quite busy.  During this last phase of his student experience, Pauling’s primary research interests centered on hematite, corundum, and beta-alumina, though a great deal more professional and personal growth can be traced to this time in the budding young scholar’s life.

In his work on corundum and hematite, Pauling was assisted by Sterling B. Hendricks, a Texan who had received his master’s degree from Kansas State in 1924 was now in Pasadena, working on his PhD.  Hendricks became a close associate and personal friend of Pauling’s and, with their mentor Roscoe Dickinson away on a research trip, Pauling became Hendricks’ unofficial adviser. Such was Pauling’s influence that, later in life, Hendricks would come to consider himself to be “Linus’s first student.”

Together, Pauling and Hendricks worked on a theoretical paper that pieced together much of the work that they had completed over the previous year and a half. The paper was published in the Journal of the American Chemical Society (JACS) in March 1926 (nearly a year after Pauling had completed his PhD) and titled “The Prediction of the Relative Stabilities of Isosteric Isomeric Ions and Molecules.”  The paper was a milestone in that it was Pauling’s first paper devoted solely to the subject of the chemical bond.

It was not, however, the first paper that Hendricks and Pauling had co-authored. In 1925 the duo worked together to publish two sets of crystal structures: “The crystal structures of hematite and corundum” (March 1925) and “The crystal structures of sodium and potassium trinitrides and potassium cyanate, and the nature of the trinitride group” (December 1925).  During his last year of grad school, Pauling also collaborated with his friend and former roommate, Paul Emmett, on an X-ray determination of the crystal structure of barite.  Their article, which was published in JACS in April 1925, is another example of Pauling’s work that corrected previous published structures.

Peter Debye, 1926.

Peter Debye, 1926.

On top of the research that he was doing on crystal structures, Pauling also toyed with an idea in which he applied the Debye-Hückel theory, which was used to determine the energy coefficient of ions in dilute solutions. When he learned of this work, A.A. Noyes invited Peter Debye, who was based in Switzerland, to visit Caltech, in part to have him discuss his theory with Pauling. And although Pauling never published his original idea, in July 1925 Debye and Pauling did co-author a different paper, “The Inter-Ionic Attraction Theory of Ionized Solutes.  IV.  The Influence of Variation of Dielectric Constant on the Limiting Law for Small Concentrations.”  Appearing in JACS, the article was a contribution to a larger series published by the journal on the inter-ionic attraction theory of ionized solutes.


Later on in his life, Pauling developed a reputation for staying on top of the latest findings and issuing an informed opinion on a wide range of scientific topics.  This character trait was likely spurred by an experience that he had as a graduate student.

Early on in his graduate career, one of Pauling’s more influential professors, Richard C. Tolman, posed to him a question about diamagnetism. Pauling responded that diamagnetism was just a general property of matter, a lackluster reply that made clear that Pauling had not stayed current with the literature. Tolman kept questioning Pauling for more specific details until Pauling finally answered, “I don’t know.”  For this he was reprimanded by a Caltech post-doc who told him, “You are a graduate student now, and you’re supposed to know everything.” This was advice that Pauling took to heart and that made a big difference throughout his career in science.


The Paulings, 1925.

The Paulings, 1925.

Nearing the end of his graduate school tenure, Pauling read G.L. Clark’s paper on uranyl nitrate hexahydrate and, as he went, he corrected it.  This was a continuation of the critical reading habits that he had first developed at Oregon Agricultural College and had continued to hone by lantern light while working for the Oregon Highway Department the summer prior to his enrollment at Caltech. It was likewise a practice that he would continue throughout his career: closely reading papers and correcting errors, often by letting the author or publisher know what he had found.

By this time, with Roscoe Dickinson away, Pauling had taken up some of his mentor’s responsibilities in the lab and, as with Sterling Hendricks, was serving as an ad hoc advisor to several students.

Likewise, with Dickinson gone, Pauling began to develop his own techniques to aid in crystal structure determinations. A methodology that was quite different from the formal instruction that he had received, Pauling’s approach used atomic sizes and chemical behaviors to approximate reasonable structures for molecules.  After determining these possible structures, Pauling then used X-ray data to eliminate unlikely possibilities and to isolate the best possible structure for a particular substance.  As it turned out, this approach to scientific inquiry already had a name, the stochastic method, and Pauling ultimately put it to effective use across many different disciplines.


Linus Jr. and Ava Helen, 1925.

Linus Jr. and Ava Helen, 1925.

Pauling’s last year as a grad student also included big changes in his personal life.  After marrying in the summer of 1923, Ava Helen Pauling moved to Pasadena with her husband and kept house while he finished his degree. In the early years of their marriage, these duties also routinely included helping “keep house” in the laboratory, particularly by recording data and taking notes. Pauling’s research notebooks from these years are full of her handwriting, even including one note reminding Linus that she loved him.

In the midst of all his coursework and research, and as Pauling was wrapping up his last Winter term at Caltech, another big change came about when the Paulings’ first child, Linus Jr., was born on March 10, 1925.  By this time, Ava Helen was mostly excused from laboratory duty and focused her energies primarily on raising her children (ultimately there would be four) thus creating an atmosphere at home in which Linus could be as productive as possible.


Graduation day, 1925.

Graduation day, 1925.

Linus Pauling completed his PhD in chemistry in June 1925, tacking on minors in physics and mathematics as well. His dissertation, titled “The Determination with X-rays of the Structure of Crystals,” consisted of a compilation of articles that he had previously published with little more than new pagination connecting them together as a whole.

The summer after graduation, A.A. Noyes helped Pauling to secure a research fellowship that would enable him to stay at CIT and complete a research study on complex fluorides.  Pauling continued in this vein for the next eight months, during which time he began to make plans to leave Caltech to study as a post-doc at Berkeley, where he thought he might pursue a new set of experiments in G.N. Lewis’ lab, using funding from a National Research Fellowship that he had received.

Not wanting to lose Pauling to Berkeley and Lewis, Noyes managed to arrange for Pauling to remain in Pasadena in order to complete additional unfinished work on crystal structures.  Fortunately for Noyes, at the end of 1925, when the Guggenheim Fellowships were announced, Pauling was finally chosen for funding, having at last reached the program’s required minimum age.  At Noyes’s urging, Pauling resigned from his National Research Fellowship once he had received the good news from the Guggenheim Foundation. From there, Linus and Ava Helen took an important trip to Europe and ultimately returned to Caltech, their institutional home for the next thirty-six years.

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