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Isabella Karle’s Interview (2005)

Manhattan Project Locations:

The daughter of Polish immigrants, Isabella Karle had received her Bachelor’s, Master’s, and PhD degrees in physical chemistry from the University of Michigan by the time she was 22 in 1943. With her husband, Jerome Karle, a fellow student and scientist whom she married in 1942, Isabella became a pioneer in the field of science, starting with her work on the Manhattan Project at the University of Chicago in 1943. After the war, Isabella and Jerome began work on crystallography at the US Naval Research Laboratory in Washington, DC, where they were employed for over sixty years until their retirement in 2009. In this interview, Isabella discusses the career path she took after high school to become a chemist. She also explains how she came to work for the Manhattan Project in 1943, how she met her husband at the University of Michigan, and the successful careers of other scientists she worked with during the Manhattan Project.

Date of Interview:
September 12, 2022
Location of the Interview:


Isabella Karle: Isabella Karle. I-S-A-B-E-L-L-A K-A-R-L-E

Cindy Kelly: Terrific. Could you tell us how you happened to become part of the Manhattan Project?

Karle: My husband, Jerome Karle, completed his work for the PhD degree about four months before I completed mine. By the time I had completed my work, he was already ensconced at the University of Chicago in the Manhattan Project. He said it was an exciting place to be, but he could not tell me why it was exciting. It seemed prudent for me to go join him. Since they were willing to hire me at a very reasonable salary for those days, which was I think $3300 a year, I did indeed start work on the second of January of 1944. At which time, I had just passed my twenty-second birthday.

I worked in a different group than Jerome did. The objective of the laboratory that [Glenn] Seaborg was in charge of was to produce pure plutonium metal. Since the chemistry of plutonium was completely unknown at that time, a number of different chemical paths were being tried simultaneously to see what the advantages and disadvantages were. There were different approaches to making the free metal from the somewhat impure plutonium dioxide which came from Oak Ridge.

The amount of material we had to work with was really quite small. We picked out our lumps of material from under the microscope. As already has been mentioned, research in those days proceeded with equipment that the researcher himself made in the laboratory. My equipment consisted of a vacuum tube apparatus, which meant that many glass tubes with stopcocks – vacuum stopcocks – were put together. There was a high powered pump attached to it to remove whatever gas or air was in the apparatus.

My assignment was to make a plutonium chloride in whichever way I could in the vapor phase. There were certain advantages, of course, in working in the vapor phase. It was thought that there would be fewer impurities that would be carried along in the production of the intermediate product. I was not making the plutonium, but I was making plutonium chloride. I was trying to make plutonium chloride in as much of an efficient and clean way as possible.

What that required was for me to make a little apparatus out of silica. It looks like glass, but it melts at a much higher temperature. In order to make this small apparatus in which I would put the crude plutonium dioxide, I had to do the equivalent of glassblowing, but using a hydrogen flame instead of a gas flame. This was at a much higher temperature. It gave off a lot of blue light, so I had to wear very dark purple glasses so as not to damage my eyes in seeing what I was doing. During graduate school days, I had learned enough about glassblowing that I was able to fashion this instrument, this vessel that I needed. The experiment itself had the plutonium dioxide in this vessel. I was going to pass various gasses over it, which were compounds that contained chlorine.

There were other aspects to it that had to be solved. One is that I would need temperatures of about 800 to 900 degrees centigrade, which is very high. Someone suggested, amongst my neighboring chemists on different projects, that the way we can do that is to take a block of copper, bear a hole through the block of copper, put it around the glass silica tubes, and heat it again with the hydrogen flame until the copper turned to be a brilliant pink. It was an absolutely brilliant pink. That would be a temperature that I could use. I never measured the temperature. I do not remember what the melting point of copper is, but it is a little bit above that.

With the bit of plutonium in the boat with this high temperature, I evacuated the whole system, after which I used at different times various organic compounds like carbon tetrachloride, carbon trichloroethane, and so forth. That would be passed over this hot sample. Presumably, the plutonium oxide would then turn to plutonium chloride, and the rest of the materials would be pumped out.

I hoped that the experiment was somewhat complete, because—I should describe our laboratory. Our laboratory was a barracks-like building that was built across the street from the Chicago football stadium, the University of Chicago football stadium. It was a one-story building. We had powerful fans in the cubicles in which we worked that evacuated the air to the outside. It was directly to the outside. There was a residential neighborhood across the street from that. I do not know what had happened to the exhaust gasses, but they just disappeared into the air. That was considered, I suppose, a safe enough disposal for us. Apparently it was, because all of us who worked around there have survived to our eighties. I always said a little bit of plutonium is good for you.

I was successful in the many trials that I did with different organic chlorides. In each case after the experiment took place, it only took place for a few minutes after I reached a high temperature. When the apparatus cooled down, it was possible to see that I had some brilliant green crystals with very nice faces. Then I would transfer the crystals in a dry box – also a piece of apparatus that all of us in this particular laboratory had built by ourselves. I would transfer the crystals to dry tubes and carry them over in my pocket to the physics building across the campus. 

This was wintertime. You see, I started working in January. This was maybe March or April. I would have my winter jacket on and just put it in my pocket, literally. It looked as if I were just walking across the campus.

I do not know who it was who complained about the insecurity of all of this. My being loose out on the campus with this valuable plutonium chloride – the first ever made in this world, that nobody had ever seen before – they thought that I needed a little bit more protection. 

Because I needed to be guarded, I then walked across campus almost, but not quite, arm in arm with two very tall fellows on either side of me. I do not remember if they were armed. They may have been. Of course, that created a bit of attention, because co-eds ordinarily are not escorted that way on an academic campus.

We were not supposed to take any notes home with us. Our notebooks were always locked in a safe in the secretary’s office overnight. The safe being a big box with a door on the front. I do not remember whether it had keys, or it was a tumbler safe. At any rate, one morning the secretary called in that she was very ill. She could not come, and so could not open the safe. Everybody was standing there scratching their heads. They really needed their notebooks for the day’s work. A screwdriver solved everything. They took the hinges off the safe, then it swung open, and they all took their notebooks out for the day. At the end of the day, the notebooks were put back in, the hinges were reattached, and nobody knew the difference.

Kelly: That is great. Were you aware of any attempts of espionage in those days?

Karle: No, I was not aware of anyone ever approaching me or trying to come into our laboratory. There were guards. Maybe there was only one entrance, but there was a guard at the entrance to allow people only with the proper credentials to come into the building.

We also attended lectures in the evenings that apprised us of what was going on in the project in the other laboratories around the country. Those were in a different building from that building, and I do not remember any particular security except our pass. There were people of course around to see that everybody had a proper pass, but nothing other than that. No one had ever approached me, or anybody else that I knew, for casual conversations as to what may be going on in the buildings or what we were doing there.

Kelly: When you were working there, was Enrico Fermi there? 

Karle: Yes, Enrico Fermi was there. He gave many of the lectures that we heard. I think it was every Wednesday evening that we came back to the laboratory to hear the lectures, information, and whatever else he had to give about the project.

Kelly:  From the beginning, did you understand what the purpose was?

Karle:  No. No, when I first came, I was absolutely in the dark. I think I was told that there was a new element discovered beyond the first 92. and that I was going to get some of the oxide and I should make a chloride. I had never had any inorganic chemistry courses in my undergraduate or graduate work, and so that meant that I had to go to various libraries not only at the University of Chicago, but another very nice library in downtown Chicago. I do not remember the name, but I would take the train to town every once in a while to go to the library there.

The only information that I had was what I could learn about uranium. It was assumed that uranium should have at least some similar reactions to plutonium. Yes, that was helpful. They were not the same. The conditions were quite different for making the chlorides. The chlorides had a different formula with plutonium than they did with uranium, but I think that was my only indoctrination.

Kelly: When did you become involved in going to these lectures? Could anybody involved in this work go and learn the whole Manhattan Project scope?

Karle: No, they were quite limited in what they told us. I do not think I even knew about Los Alamos. I knew about Oak Ridge.

Kelly: What was it like? How many other women scientists were there?

Karle: I think I was the only one in the whole chemistry area. There may have been some in physics. I did not know the physics people very well. They were housed mostly in the University of Chicago physics building, up in the upper floors. We did not have much interaction with them. There were women around who were in various support services. There was the secretarial help and there were laboratory technicians.

Kelly: How did it feel, being one of the only women?

Karle: It did not feel much different than being in school, where I was one of two at the University of Michigan in graduate school.

Kelly: What prompted you to choose a field like that? Who encouraged you to do this?

Karle: My family did not know anything about science. They had come from Europe, and there were not even any engineers in the background. They were mostly country people. Both of my parents were very hopeful that I would go on to the university. Nobody in the family ever had. In fact, nobody in the family had ever finished high school.

While I was in high school, the counselors told me, “You need a science course in order to qualify for university admission.” The high school offered chemistry, physics, and biology. I asked my counselor, “Which one should I choose? I know nothing about them.”

She said, “I do not know either. What about chemistry?” All right, let it be chemistry. As soon as I attended the chemistry classes, I knew that this was what I was very much interested in.

My parents sort of shrugged their shoulders when I told them I was going to study chemistry at the university. The best I suppose that could be done is to say, “Well, it is something like pharmaceutical work.” That they understood a bit. There were patent medicines around, but they did not know why I would be interested in things of that sort.

When I first went off to Wayne State University, I had graduated high school in the middle of the year. I spent a semester at Wayne State before I went on to the University of Michigan. My schedule was such that the chemistry course that was convenient for me to take and still catch the streetcar to get back home at a reasonable time happened to be an engineering chemistry course. I was the only girl there. That did not bother me much. I did get the top score in all the examinations, which bothered some of the boys — not all of them, but some of them. The professor took an interest in me. He knew that I was going to go onto the University of Michigan later. We kept up a correspondence for quite a number of years. He also acted as an advisor and mentor.

Kelly: How did you meet Jerome?

Karle: I was a senior at the University of Michigan when Jerome had come to the University. He had already had a Master’s degree in biology from Harvard University. For a number of reasons, it was not possible for him to continue there, and he decided to change his major to chemistry. In order to enter the graduate school in chemistry at Michigan, he had to take some undergraduate chemistry like the fourth year or fifth. It was physical chemistry.

I met him when I walked into the laboratory the first day of the laboratory instruction to set up my apparatus. Here was this fellow whom I did not know who already had his apparatus all set up and ready to go. That was quite by luck that I met him because his name started with K, mine was with L, and we had our desks assigned in alphabetical order. I think my first words to Jerome were, “How did you get this done already?” I realized this was going to be a competitor, but we became friends after a while.

Kelly: How long was it? How many years did you spend getting your doctorate? It had to be very fast.

Karle: It was fast because this was wartime. The University was being pressured to run the whole year round instead of having four-year courses. The courses would be compressed into three years.

Eventually, before the war ended, I also was an instructor in chemistry. That was after I left Chicago. The only days we had off were Sundays and Christmas Day. Otherwise, the whole University ran on a two and a two-third year basis to hand out degrees. That helped a lot of the students, especially in medical school, to get through medical school early, graduate school to get through graduate school early, so that young people could go off into their various research projects for the war work or other projects that they were slated for. Or it was to the Armed Forces, depending upon if they had had ROTC training earlier. Almost all of those people were taken immediately to go into the Armed Forces. I was swept along at the same time at the fast pace.

Kelly: You were able to get your PhD by the age of twenty-two?

Karle: Yes.

Kelly: How did you feel about the dropping of the atomic bomb?

Karle: It was a surprise when it happened, because by that time we had left the University of Chicago. We no longer were apprised of what was happening. Jerome was then working for the Navy at the University of Michigan. I was teaching the freshman courses at the University of Michigan.

It was a great surprise. It was upsetting in many ways. Of course, I did not know what the circumstances were behind dropping the bomb, like when it was being dropped, whether there were any negotiations, or attempted negotiations beforehand. I think for many years, I was upset about it.

Kelly: How did the experience in the Manhattan Project change your life, or make you feel about science?

Karle: It was not an interlude for too long. I do not think it affected me very much at all. I learned some new techniques, but I did not have much of an opportunity to use them afterwards because I returned to the kind of work that I had prepared myself for in graduate school. I enjoyed that. Of course, that evolved into various other things. It did not touch the kinds of experiments, the kinds of materials that were involved in the Manhattan Project.

Kelly: In terms of other people that you worked with in the Manhattan Project, what were their experiences, if you know?

Karle: Yes, I know. I know the experiences of a number of the people. I do have a list of them. 

Knowing where my coworkers had come from who were at the Manhattan Project at the same time I was, they were all very young people. As you may have heard many times, the average age of the scientist was something like twenty-eight years. Pardon?

Jerome Karle: Twenty-six.

Karle: It was twenty-six years.

Jerome Karle: I could never believe that.

Karle: The people who worked around me came from industry, from local universities like the University of Chicago and University of Michigan, and also from California. Glenn Seaborg had brought with him a good many of his graduate students to work on the project. Then there were several from the University of Washington. I do not know how contact was made with them, but they were new PhDs. A number of them came from industry, and one from a military laboratory from the US Army Corps of Engineers who was a botanist and then worked on the plutonium project. I was interested in what happened to them afterwards many years later. Some of them I knew what had happened to them, because we kept in touch with each other. Others I had to look up in the various compendia.

It surprised me that every single one of these people made a name for himself in various ways. It was either as a dean of a school, as a distinguished senior scientist, or a professor of biology, for example. I would like to mention a few of the names and some of the awards that they gathered along the way.

Norman Davidson, who was my project leader and a few years older than I, spent his life afterwards at the California Institute of Technology as a professor of biology. Amongst other things, he got the National Medal of Science.

Roy Heath, who had come from industry originally, became the Dean of Graduate Studies at Northern Michigan University.

Joseph Katz had come from the University of Chicago. I think he was about the oldest one around. He had been born in 1912. I think he is still alive. I have seen him fairly recently at the National Academy of Sciences meetings. He stayed with Argonne and became a distinguished senior scientist at Argonne Laboratory near Chicago. He was a member of the National Academy of Sciences.

Then I should mention Jerome Karle, who got a Nobel Prize in Chemistry eventually.

Sidney Cates was one of the Canadians. We had two Canadian citizens who were working with us. There was no problem with being a Canadian citizen, as far as security was concerned. He stayed in the United States and had a research position at the Illinois Institute of Technology.

Lyle Jensen became a distinguished professor of protein crystallography at the University of Washington.

Winston Manning, who was a co-discoverer of einsteinium and fermium in 1952, also stayed at Argonne. He was one of the managers.

One of the people who did something different was Harlan Baumbach. He was a film processor at Paramount Studios. After the war, I do not remember which years these were, he won two Oscars for scientific achievement in motion pictures. 

Michael Wolf, who had been a botanist when he had come to the project, went back to work at the United States Department of Agriculture in Peoria. He was a research leader in cereals.

Then there was Alvin Dirksen. Really, he was the only one who strayed. He became a professor of business administration at San Francisco.

You see that of the people I knew, most of them—almost all of them—stayed in the sciences. Most of them did very well in achieving some notoriety for their work.

There were various safety features that were instituted, mostly by Glenn Seaborg’s instigation and pressure. One of them was that as we arrived at the laboratory every morning, we were each handed a dollar-sized – that is, a dollar-coin size – tablet of calcium carbonate flavored with chocolate. The reason for eating this tablet every day to get our calcium was, to perhaps change the equilibrium in the body sufficiently so that there would be an excess of calcium so that plutonium would not lodge itself in our bones. That was a happy thought. Apparently, there was no problem with the plutonium with any of the people with whom I had any contact.

We also had hoods in the laboratories, as I have already mentioned, that exhausted right into the Chicago air atmosphere. The laboratories had new air being swept through them all the time. We had our hands and feet counted under counters to see if there was any radiation coming off from them. None ever was, that I knew of. I am trying to think of other safety features. There must have been several others of that nature.

One that was missed happened in an unusual sort of way. We were not allowed to eat in the laboratory, which was something that was a necessary discretion. Most people either ate their lunches outdoors, but outdoors was not all that good. We went to the local restaurants. We came back from lunch, and someone was walking down the hall with a counter that immediately went off scale. This was frightening, so he did it again and in front of the Coke machine, the counter was just going mad.

Apparently the Coke machine in those days was an early version of a Coke machine. Not many of them existed then. We had carbonated water coming from one spigot and Coke syrup coming from another spigot, filling a paper cup that had dropped from somewhere or other. After we put in our coin, all these operations went on and we had a paper cup of Coke.

Immediately, with all the radiation that was obviously around the machine, everybody got very frightened about when they last drank a Coke. The problem was solved fairly soon in that while we were all gone, the man who delivered the Cokes came there every day. He had forgotten to bring his hose in from his truck, so he was looking around for a hose to use to pour in the Coke syrup from the top of the machine.

He looked into one of the laboratories – this was one of the wet chemistry laboratories. He saw a hose at the end of what was called an aspirator. An aspirator is a device whereby if you turn on the water strongly, it goes through the hose. It sort of forms a vacuum behind it, and it will evacuate some jars, bottles, or whatever that you might need to evacuate. This was used in the wet chemistry laboratory where the plutonium was in solution, and the chemists there were working with it that way. It was fairly highly laced with plutonium. When he used that hose, it washed into the Coke syrup.

Fortunately, this happened at lunchtime, and it was discovered soon enough that apparently nobody had partaken of any of the extra laced Coca-Cola. Needless to say, the machine was removed immediately. The next day, we had a more automated machine that had bottles in it that were already capped at the Coca-Cola plant.

Kelly: That is great. Are there any other experiences or memories that you have of your time in the Manhattan Project, or reflections?

Karle: It seems that all of us who were working there were very friendly towards each other. I was not aware of much competition amongst the people. It was a pleasant place to work as far as the personnel was concerned at all levels. Most of us did not know many people in Chicago since we had come from elsewhere, so our social lives more or less revolved about seeing each other outside of work.

When the weather turned better in May, we used to go out to the Indiana dunes or on the beaches in Chicago. I do not suppose it was an exciting time of life. It was a busy time because some people, depending upon whatever experiments they were working on, just did not mind working all night long and all day long if the occasion called for it.

Kelly: What kind of schedule did you have? I guess you had just two days off a year. Is that right?

Karle: That was at the University of Michigan.

Kelly: Oh.

Karle: No, we worked. I do not think we worked Saturdays. I do not remember. The regular schedule was something from eight or nine in the morning until about five in the afternoon. This was unless there were things that needed to be done. Some experiments, of course, you cannot turn off and turn on again the next morning. You have to keep running them for whatever period that needs to be done. Yes, on paper there was a schedule. But in actuality, people came and went at various times depending upon the needs of their work.

Kelly: If you could talk to young women today, what do you think of science as a career for a woman?

Karle: Since my day, there have been many young women who have gone into science. Some of them are very successful at it. Some of them have attained positions as heads of departments. Many of them, however, have a problem, and the problem stems mostly from trying to have a family at the same time. That problem has not really been solved well. Some laboratories accommodate women quite well who are pregnant and who want to be on a half-time schedule, let us say, for a period of time. They may even take some time off. Other institutions frown upon it, not legally, but they still frown upon it. There are problems to be solved.

Kelly: Did you confront those problems?

Karle: No. Our oldest daughter was born between the times we left the University of Michigan after World War II and before I started working at the Naval Research Laboratory. That summer she was born. Then five years later, when the next one came along, I worked until a few weeks before she was born. Then I had saved enough sick leave to carry me over until I came back again to work. It was the same with the third one.

We had at that time, I suppose, an advantage in that many younger people were leaving the farms in the mountains and coming to Washington to work. They very often had a mother with them who did not really want to live with their children. They were mothers who wanted to become independent, and so they became nannies, housekeepers, and so forth. For about twelve years, we had the same woman – the same woman, I think, stayed for about nine years and then she got too old. Then we had several others who would come live with us five days a week, and then on weekends they would go visit their own families. That worked out very well.

Kelly: Are any of your daughters in science?

Karle: Two and a half of them are. The eldest one became a physical chemist and she worked at Brookhaven National Laboratory until recently. The middle one became a pharmaceutical/organic chemist. She worked at the NIH [National Institutes of Health] for a number of years, and then at Walter Reed Army Institute for Research on malaria problems. Again, that was until very recently. The youngest one studied geology. She worked at the Natural History Museum until her second child came. Then childcare became difficult recently, and so she is staying home, I suppose, until the children get older.

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