Harold Urey—A Personal Remembrance: Part II

By Mildred Cohn

In a previous article (CH Winter 2005/6, pp. 8–11, 48) the author described how she came to work with Harold Urey as her graduate adviser and mentor. This article recounts their later interactions, describing Urey’s character more fully along the way.

Once I finished my experimental work (as described in my previous article), I wrote up my thesis in the form of a paper to be published. I listed as authors Mildred Cohn and Harold C. Urey, and when I submitted it to Urey for his comments, his first remark was, “I see you have put my name on your paper. I’ve often wondered whether my students put my name on their papers because they think I have contributed something or because they think it will add prestige to the paper.” I looked at him and said, “A little of both,” and he was pleased with that answer. My dissertation was published in the Journal of the American Chemical Society in 1938 and is still cited today. It owes its unusual longevity to its inclusion of a method of measuring the oxygen-18 concentration of water that continues to be used to this day. Urey suggested the principle of the method to me, and I worked out the details.

I had eight figures in this paper, and each kinetic curve had seven points on it. All the points fell nicely on the curves except one, which was way out in left field. I told Urey that there must have been something wrong, and I was going to drop that point. He looked at me and said, “Do you know of anything that went wrong with that experiment?” I admitted to him that I did not. He said, “In that case, you leave the point there.” And I did so, even though according to what I then understood, a data point that deviates more than three times the average error may be dropped. But Urey did not approve, and of course it didn’t really detract from the paper at all. It taught me a lesson. You do not omit any data unless you know with certainty that the experiment was faulty.

In spite of his sophistication in matters scientific, however, Urey was most naïve about some aspects of the world. One day at afternoon tea, a daily ritual, he opened the conversation with, “When I received the Nobel Prize two years ago, I put one third of the money into the purchase of a house, another third went into life insurance, and one third I invested in the stock market. The value of my stock has doubled. Now, what have I done in the last two years to deserve another Nobel Prize?” Finding that he could make so much money without doing anything—let alone the amount of work he put into the prizewinning discovery—shocked him and struck him as undeserved. Another day at tea, he appeared exasperated because a foundation that had given him a grant to work on a specific problem now expected a report on how he had spent the money. As was his wont, he had dropped the original problem to follow a more promising lead and diverted the funds to the new project. He fumed, “Who are they to tell me what to do? They aren’t even scientists.” This attitude, brooking no interference with control of his research, foreshadowed some of the difficulties he had in war-related research under military auspices during World War II.

Urey’s political naïveté was revealed in connection with an incident involving I. I. Rabi. Urey told me that he had suggested to Rabi, a friend in the physics department, that he move to Leonia, New Jersey, where Urey and many other Columbia faculty members lived. Rabi’s response was that he preferred to remain in Manhattan among his own people; he meant his fellow Jews. Urey added, “I can understand that. If fascism comes to this country, I can conform but he cannot.” I cringed when he said that, because I knew that he could never conform, if only because of an action he had taken about a month earlier, for which I was partially responsible. I had been asked to gather signatures for a petition to Nicholas Murray Butler, the president of the university, to turn down the invitation to send a representative to the Nazi celebration of the 500th anniversary of Heidelberg University. I struggled with my conscience whether to ask Urey to sign it. I realized (as he would not) that should he sign it, publicity would follow. Finally I presented him with the petition and, without urging him to sign it, said in what I hoped was a neutral tone, “I thought you might be interested in this.” After reading it, he paused for a minute or two, then took out his pen and signed. As I had anticipated, the day after I turned the petition in, there was a banner headline “Nobel Laureate Signs Petition” in the Columbia Spectator, the undergraduate newspaper that was controlled by left-wing students. Thus Urey had unwittingly become a marked man as far as the Nazis were concerned.

Urey further revealed his ignorance of social realities on another occasion, when he came into the laboratory and said to me, “Miss Cohn, you’re a personable young woman. Why don’t you go out to the Midwest where there is no prejudice against Jews, marry a non-Jew, and forget that you are a Jew?” When I responded, “Has it ever occurred to you that maybe I don’t want to forget that I’m a Jew?” he was genuinely shocked. It was as though I had a terrible handicap, a hunchback, and he had told me how to rid myself of it so that I could stand straight to face the world and I didn’t want to. My remark must have nevertheless made an impression, because a few weeks later, when he was spending an evening with the chemistry graduate students at Princeton after a lecture, he mentioned the strange ideas of one of his Jewish graduate students. I learned of this because one of those present was the roommate of my future husband, Henry Primakoff. As I later found out, the roommate told Urey that he knew whom he was talking about. Of course by the time World War II was over, Urey was far more sophisticated about such matters. For example, he was supportive of the state of Israel and served on the Board of Governors of the Technion (the Israel Institute of Technology).

Urey was also the stereotypical absent-minded professor. Henry, while an undergraduate at Columbia, witnessed a scene in the elevator of the physics building when the no-nonsense, middle-aged Irishwoman who was the elevator operator turned to Urey and asked, “What floor do you want?” Whereupon he said, “What floor are we at?” and added, “What did I come over here for anyhow?” She greeted these remarks with a mixture of pity and disgust and kept the door open until he walked out.

And then there was the occasion when he invited all his students and postdocs to his home for dinner on a Sunday—another instance of his habitual generosity, noted in the last article—but forgot to inform his wife. When about 10 of us descended on them in Leonia, Frieda Urey looked surprised, but she took it in stride. In those days, food stores were not open on Sunday, and there were no freezers in homes. We had to be satisfied with hot dogs and fruit and cookies for dessert, which we shared with the three Urey daughters. It turned out to be a fun picnic. One of our activities was testing the Rhine cards, which were supposed to detect people with psychic powers. Urey, who kept an open mind on paranormal phenomena, had recently returned from the University of North Carolina, where he had met Joseph Rhine of Duke University. The results of our exercise were what would have been expected by chance: no one displayed any unusual powers.

The zenith of Urey’s absent-mindedness was reached in the Hopcalite affair, which occurred when I was working on the first problem that he assigned me—that of separating the carbon-12 and carbon-13 isotopes (see CH,Winter 2005/6, pp. 10–11). After some theoretical calculations, I had shown that the equilibration between carbon monoxide and carbon dioxide near room temperature should lead to the best separation. One day Urey suggested to me that a good catalyst to bring these two gases to equilibrium would be Hopcalite. Hopcalite had been developed during World War I by J. C.W. Frazer, a professor of chemistry at Johns Hopkins University, to use in gas masks to oxidize carbon monoxide. Urey told me that he would write to Frazer and ask him to send some Hopcalite. Knowing Urey’s reputation for absent-mindedness and hearing nothing further after two weeks, I stopped by his office one morning and asked, “Have you written to Professor Frazer?” “No,” he answered, “I have thought about the problem further, and I don’t think Hopcalite will work.” He then gave a very convincing explanation of why Hopcalite would not do. I went on my way and dismissed the matter from my mind. About a week later, he came into the lab and when he saw me, he said, “Oh, I forgot to write to Professor Frazer for the Hopcalite.” I was in a quandary as to how to respond to that sally. I didn’t want to embarrass him by telling him that he had satisfactorily explained that it wouldn’t work, so instead, I said, “No, I don’t think we want Hopcalite.” This statement was followed by my explanation of why it would not work, giving him exactly the reason he had given me. Shaking his head in agreement, he said, “You’re right.” At this point, his secretary popped in saying, “There’s a phone call for you.” He left for his office and returned to the lab after about 15 minutes, spied me, and said, “You must remind me to write to Professor Frazer for the Hopcalite.”

My thesis was in its final stages, and it was time for me to look for a job. Since the American Chemical Society was holding its annual meeting in Rochester, New York, in September 1937—where recruitment would be in full swing—Urey suggested that I attend and try my luck. Realizing that I could not afford the travel cost, he offered me a ride in his car. The morning he picked me up he grinned, saying, “You know what my wife said? ‘I wonder what her mother thinks of this arrangement.’” I laughed and responded, “This morning my mother said, ‘I wonder what his wife thinks of this trip.’” And we both laughed.

At the meeting, I did not see much of my professor. He was busy greeting friends, talking science, the usual pastimes of a pro at such events. I stayed at the YWCA, hardly elegant accommodation, but the least expensive yet respectable that I could find. To me, it was all new and exciting but disappointing insofar as my goal for the trip. Not a single interview. I also didn’t understand why Urey had not introduced me to any prospective employers.

After five days, it was over and we were driving back to New York City. At first Urey said nothing about jobs. One incident seemed to weigh on his mind. He had been in a bar with friends when he was photographed by a reporter, and he was worried that if the photo might be published in the newspaper, his teetotaler folks in Kansas would recognize the background. Finally, he told me sadly, “Nobody wants you.” Not too surprising, since I was female and Jewish. It was the same old story. Recruiters from all the big chemical companies had been on the campus in the spring. Despite the Depression, Columbia had such an outstanding chemistry department that DuPont, Standard Oil, U.S. Rubber, and so on would each hire one graduate. Notices of the recruiters’ visits would be posted on the departmental bulletin board reading, “Mr. So and So from X company will interview all prospective Ph.D.s of this year. Male, Christian.” I was out on two counts. From the Rochester experience, it was obvious that discrimination was equally rampant in academe.

Following other futile attempts to find me a post, Urey offered me a postdoctoral position in his laboratory as a temporary solution. I accepted with alacrity. Soon thereafter David Rittenberg and Rudolf Schoenheimer from the Columbia University medical school alerted me to an opening in biochemistry. Rittenberg had preceded me as a student of Urey’s, and he and Schoenheimer were pioneering a new field, the use of isotopic tracers to study metabolism. One of the up-and-coming biochemists, Vincent du Vigneaud, from George Washington University, had appealed to them to find a postdoctoral fellow who could introduce the necessary techniques in his laboratory. And they suggested me. When he discovered that their candidate was a woman, as I later learned, he demurred. Whereupon they informed him that I was the only one in the country who was qualified, and he offered me the position.

I sought Urey’s advice, and he thought I should accept. He pointed out to me that if I stayed on at Columbia, I would always be regarded as a graduate student by the faculty, but if I went elsewhere, I would be treated as a professional. Also, he believed this new area of research held great promise. I did too. Another attraction of the field of biochemistry to me was the knowledge that there were many more women in that field than in physical chemistry. I accepted the position but was disappointed to find out when I arrived in Washington that I was the first woman du Vigneaud had ever hired.

After I had been at George Washington University a few months, Urey came to Washington and visited me in the laboratory. The medical school was old, shabby, and grimy and the stone stairs leading to my laboratory were hollowed out from the steps of hundreds of students who had used them since the building had opened. When Urey appeared in the minuscule space that had been assigned to me, he began without any preamble to tell me about his visit to Cambridge University in England, where he had been shown the dismal, dusty basement of the ancient Cavendish Laboratory where the great James Clerk Maxwell had lectured and conceived the electromagnetic theory. The take-home lesson of his story was that there was no relationship between the elegance of the physical environment or the lack thereof and scientific creativity.

When Urey attended the spring meeting of the American Physical Society in Washington in 1938, I went there to meet him. Unexpectedly I witnessed a historic encounter. As we stood chatting on the lawn of the Bureau of Standards, E. O. Lawrence of Berkeley came by. Urey introduced me to him, telling him that I was a former student of his who was using stable isotopes as tracers to investigate metabolism. He added with unaccustomed taunts that Lawrence had no radioactive isotopes that were appropriate for solving biological problems. “For hydrogen, we have deuterium, you have nothing [tritium had not yet been discovered]; carbon, we have carbon-13, you have carbon-11 with a half-life of 20 minutes; nitrogen, we have nitrogen-15, you have nothing; oxygen, we have oxygen-18, you have nothing.” Lawrence returned to Berkeley from that meeting and, as I later learned from Martin Kamen, met with his group and said, “We have to find a radioactive isotope with a sufficiently long half-life to be useful to the biologists.” Soon after, Samuel Rubin and Kamen found carbon-14, the isotope that had the most profound effect on research in biology.

It was not until June 1942 that I saw Urey again. At the time I was still working with du Vigneaud, now at Cornell University Medical College in New York City. I had taken a few months leave after the birth of my first child in May, and I had time to visit Urey. The United States had already entered the war, and most scientists had become involved with war research. At Columbia, Urey headed a project called SAM (substitute alloy materials), which was focused on one aspect of the highly secret atomic bomb project, the separation of the uranium isotopes, essential since only uranium-235 is fissionable. Urey asked me to work on the project without revealing what it was, only telling me that I would have to work every day until midnight. He introduced me to his other visitor, J. Robert Oppenheimer, who became the research director of the atomic bomb project. Although I was most anxious to help the war effort, I turned down Urey’s request for two reasons. First, as a new mother, I didn’t feel that I could work the hours the job demanded, and, second, I thought the work I was doing in du Vigneaud’s laboratory—and his policy on wartime research—had considerable merit. He believed that some day this war would be over, and he thought at least a skeleton group should keep basic science going for continuity. Thus all the young men in our lab who were draftable were engaged in war research under his supervision (the synthesis of penicillin), but I, one older assistant professor, and the graduate students continued to do basic research. In retrospect, I do not regret my decision to continue in du Vigneaud’s group.

After the war was over, Urey left Columbia for the University of Chicago and also changed his field of research, devoting himself to geochemistry. Around that time I moved to Washington University in St. Louis. In the early 1950s I had occasion to be at a meeting in Chicago, and I visited Urey. He was really upset with the military use of the atomic bomb in Japan and told me that never again would he work on any research that could possibly have military application. In fact, he refused to buy enriched isotopes from the Atomic Energy Commission, although they would have been most useful in his ongoing research. Again, he was being naïve, because in order to avoid obtaining the isotopes from the AEC, he had developed a most sensitive mass spectrometer, which could measure differences in isotopic concentrations from various natural sources. It didn’t occur to him that some day that might be very useful for weapons research. However, I admired his moral indignation.

His research involved determining the temperature of the ocean in which some marine fossils had lived from the oxygen-18 content of their carbonate, and he wanted to confirm it with an independent measurement. From my research, I was able to tell him that phosphate as well as carbonate equilibrated its oxygen with water in living systems. Subsequently, he measured the oxygen-18 content in his fossil’s phosphate and confirmed the temperature of the water in which they had lived. To my surprise, I was acknowledged in a footnote in a paleontology journal.

The next time I heard directly from Urey was in the spring of 1971, when I was elected to membership in the National Academy of Sciences. He was at the meeting in Washington, and he immediately called me to tell me the news; he was so excited that his voice was an octave higher than normal. I was touched by his pleasure.

The last time I saw Urey was in 1978 at a dinner in La Jolla in honor of the 65th birthday of a colleague of his who was also a former colleague of mine, Martin Kamen. Naturally I went to greet my old professor, and I was deeply upset because he did not recognize me. As I later learned, he was practically blind and suffering from Parkinson’s disease. He subsequently died of the disease in January 1981 at the age of 87.

In 1982, shortly after Harold Urey’s death, the History Division of the American Chemical Society celebrated the 50th anniversary of the discovery of deuterium with a symposium, and I was one of the invited speakers. All the other speakers were more recent associates of Urey. At the luncheon after the symposium, I sat next to Mrs. Urey, and she said, “Harold was so proud of you.” That accolade meant more to me than any recognition I have received in my scientific career.

For Further Reading

Arnold, James R.; Jacob Bigeleisen; Clyde A. Hutchison, Jr. “Harold Clayton Urey, April 29, 1893–January 5, 1981.” Biographical Memoirs of the National Academy of Sciences. http://www.nap.edu/html/biomems/hurey.html.