KENNETH PITZER University of California Berkeley, 9 4 7 2 0
Interview with Kenneth Pitzer DAVID RIDGWAY
by David Ridgway Ridgway: As we have had the pleasure of talklng with each 01 o w outstanding interviewees, Dr. Pitzer, we find very litlle commonality, il there is such a word, in early influences in directing each of you into science. Were there special factors, in your case, as a youth? Pltzec I'm sure that there were. The strongest were really a combination of parents and other close relatives. My mother, though she died when i was thirteen, nevertheless had a very substantial influence until that time. She was at one time a mathematics teacher. She and her whole family were very much interested in educational and general inteilectual things. Though father was not particularly interested in science, he had a very keen intellect. He respected people wlth professional aliainments of any type. I had two uncles who were very much interested in things mechanical and scientilic. Discussions with them and their encouragement had a great deal to do with focusing my interest in the direction of science or engineering. Ridgway: Did the actual geographic environment in which you were brought up have any influence on your interesl in science or more specifically in chemistry? Pitzer: Pomona College in Claremont was six miies away. This isn't very far but even then the college itself wasn't so close that one just casually participated in college activities. Cal Tech was 25 miies away and probably had as much influence in this respect. I would emphasize that I seldom got onto the Cal Tech campus. The existence of both institutions had considerable influence on the general activities of my communily. Robert Milliken's strong flair for publicity about science contributed a greal deal, I'm sure. Ridgway: What, if any, were the components of your scientific Instruction in the years prior to your hiiher education that you though1 were important? Pitzec The things that I've been saying about my lamily and the community in a broader sense were really probsbly more important Wlan high school or lower school as such. The situation in the schools was probably not atypical for relatively smali town systems of that time.
The science and mathematics teachers ranged from fair to good, but I don'l think any of them were really superlative. I would not credit them with having any major positive influence in this regard. The facl that many of them were good teachers certainly contributed. If there hadn't been reasonably good instruction in science and mathematics, I'm sure this would have had a very negative effect. The physics leacher in high school was, at the time, also managing the local athletic league and was out of the classroom lining up the referees or bus transportation almost as often as he was in the classroom. Even here the net effect may have been positive since I gained experience helping other students when the teacher was away. One aspect of both this physics teacher and of the chemistry teacher, I think should be stated more positively lhan I have so far. They both encouraged reading, questions, and even some work in the laboratory, over and beyond the regular course of study. I'm sure that this had a very positive influence as lar as I was concerned. Ridgway: Were there any overriding factors in the choice of a particular institution for higher education including graduate work? Pitzec In southern California at thal time, in my opinion, the attractiveness of CaI Tech to someone with interest and with faciiity in things mathematical and scientific was very great indeed. At that time it had just recently developed to national leadership, and Dr. Milliken, particularly, had a great capacity to communicale the standing and quality of the institution through the public press and lhrough other public means of communication. The firs1 and verv imnortant influence war that of A. A. Noyes, who was then approaching retirement. In that period he was taking a great interest in freshmen. He worked hard to make chemistry an active and growing sublect through modest research aclivities beginning right at the freshman level. Earlier, my interests were not in any sense specifically focused on chemistry; that is, I could have as well as not gone
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into physics or some form of engineering. But Noyes' interest in freshmen had a very great influence right from the beginning at Cat Tech. In later years there were comparable positive contributions from both Don Yost and Linus Pauling, but Noyes' influence was the one that took ellect right in the beginning, One of the ways that il manifested itseff was in the summer programs that he carried on essentially on his own. He had encouraged the Institute to buy a building down in the Newport-Balboa-Beach area that had become available. Remember this was depression time. i t was lor a potential marine laboratory. He owned a house right next door, personally. Incidentally, it was quite a castle on a ciifl that looked out over the entrance to the Newport Harbor with a beautiful view. He took over one room in the Institute buiiding as a chemical laboratory and would invite a few people lor the summer lor research activity and find them some means of minimal livelihood. In the mid SO'S one didn't ask lor anything more. He invited me down lhe summer after my freshman year. It was really an exclting experience. The work during that summer, together with a little done at the end 01 the freshman year and a little later in the sophomore year, led to a series of two or three papers on the higher oxidation states 01 silver. This was really signilicant scientific work, done under very stimulating conditions. When it came to choosing the graduate school there were several considered. The attractiveness 01 the situation at Berkeley may have been h part due to many similarities to Cai Tech. In part because 01 the relative isolation from eastern universities, there was at that time a very close relation between the Berkeley and Cal Tech departments, much visiting back and forth, stimulating discussions and a great deal 01 mutual respect. I was influenced by Professor W. F. Giauque who was a very strong figure with very positive, definite, ideas as to how things ought to be done in low-temperature research. Sometimes t agreed and sometimes I didn't, but the mere fact 01 having to occasionally argue wilh such a strong figure was, I'm sure, also a positive inlluence. I would be remiss it I did not. Ridgway:
We find it illumlnatlng and informative while tatklng to people who have i a d e an impact on science, t i have them do a blt of sell-evaluation. Of your many contributions to the literature, which do you lee1 have had the greatest impact-either on fellow scientists or the communily at large?
Pitzec
One has to discuss this question in terms 01 several contributions and in terms 01 the approach and method of investigation rather than trying to list each contribution. I have, of course, my own views about which papers were most important, but now there is a publication known as the "Citation index" which allows you to check up, by inference, on whether your ideas are right as well as used and referred to by others. I took a look at that not too long ago and it tends to confirm my own views in most cases. There are several specific contributions that have been the basis lor a lairly wide level of activities by others. The first one, hislorically, was that concerning internal rotation about the single bond in ethane. This presented a great puzzle at the time. I was a graduate student and had been studying quantum mechanics more thoroughly than most. This enabled me to contribute the theoretical part In collaboration with Dr. Kemp who had just made thermodynamic measurements. Since many organic molecules have groups subject to internal rotation about single bonds, I turned next to a more general theory with W. D. Gwinn, a student 01 mine, to the analysis 01 available data on other molecules. We generalized the appropriate theory from the
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very simple molecule ethane, to cover most organic molecules that have rotations about single bonds, and we went out of our way lo present the results b a form that would be convenlent for otherpeople to use. After the work on internal rotation about single bonds, I turned to the more general question of unusual motions in organlc molecules, parficularly ring moC ecules. I will mention just two examples. The geometrical structures 01 flve- and six-membered ring moiecules are very different and are really two different topics. The concept 01 pseudorotation in a llve-membered ring and the method 01 transferring vibrational force constant data from simpler molecules to predict the molecular potential lor the ring motion in cyclopentane constituted procedures that were important for various five-membered ring moiecules. i n the six-membered ring the balance of force pattern Is quite dillerent, and it leads, not to a pseudorotational situation, but to an equilibrium between chair and boat forms. I n this respect my work was essentially an approach to the same problem from a somewhat different background than that of Hassel in Norway and some others. Out 01 the combination 01 our efforls the whole ljeld of conformational analysis of ring compounds arose. In contrast to the live-membered ring case where my contribution, with collaborators, stands alone, my contribution in the six-membered ring area was, i think, significant and substantial but was only one 01 several contributions in varlour parts 01 the world. A contribution used parflcuiarly by chemical engineers concerned the description 01 the fluid state. I use the word fluid to emphasize that we're considering both gases and liquids, and the full range 01 pressure and temperature. The puzzle in this area was that, aC though basic principles were reasonably well understood, there was no satisfactory equation of state lhat represented the observed l a c b within anything like experimental accuracy. By defining a new variable which i called the "acentric factor," and by freeing mysell from the limilation of conventional mathematical lunctions, I was able to represent the volumetric and the various thermal properties of fluids over essentially the full volume, pressure, temperature range. I'm currently engaged in an investigation somewhat slmilar to that on lluids but related to the properties 01 electrolyte solutions both aqueous and otherwise. In the work on liuids and in a number 01 other areas, such as the thermodynamic properties of large molecules, the investigations have involved the bringing together of knowledge 01 spectroscopy and, 01 course, the underlying quantum theory, together with that of statistical mechanics and then the skill, or art, if you wish, of making approximalions which simplilied the problem to one 01 tractable proportions, without emascuiating it by the elimination of some essential feature. Ridgway: Now, what was the state of the "art" in your f M when you first decided to bend your energies in this direction? I have been trying to refine the state of knowledge in Pitzec a territory that had already been explored to some degree. Nonetheless, i think it is important to note that in the middle 1930's quantum mechanics had attained a form that was quantitatively valid and generally applicable. This was reaily new, and although quantum mechanics had already been applied successluily to a few problems, it was reaily quite new as a general tool for the physical chemist or theoretical chemist. The ability to use quantum mechanics eflectively without the electronic computer was very much a matter of linding approximations which retained the essence 01 a problem and yet simplilied it enough to make it tractable so you couldget an answer.
family situation-a wlfe who has been both capable and devoted and three children who have been, on the whole, a great pleasure and a great satisfaction. I t doesn't mean one can't find individual times of distress along the way, but relatively very few. I've always found the University communities to be very stimulating places, In terms o i human contacts outside one's own immediate professional field. I like to travel and vlsii places of interest whether in terms of natural phenomena or scenery or in terms of human developments both recent and ancient, and a career, such as mhe, gives opportunliies for travel without undue interference with other obligations. Also the international character of science tends to make It pleasant because one frequently finds personal contacts in various places. One of my hobbies, a rather serlous one through the years, is sailing and boat design and bulldlng. While chemlstry has very llttie to do wlth it, my scientific background makes it feasible and interesting to learn the bask physlcal prlncipies underlying my interests in boat design and in sailing and to apply these principies in this activity. Since I enjoy working wlth my hands, I enjoy occasionaliy buNdlng boats which I have designed. Rldgway: Have your interests and accomplishments had an effect on the educational or professional accomptishments of your own children? Plllec I'm sure they have had an influence. Each of the chlidren was a serious student and came to realize that children of professors were expected to excel in school. I ludged that the pressure of thls expectatlon was more than adequate and sought to moderate thls pressure rather than to accentuate li. I think this worked out very well. All o i the children went at Cast far enough In chemistry and related sciences to prove to them, and to me, and to anyone else who was interested, that they were capable and successful In science, and then felt quite free to go their own way and emphasize other things as they chose. I t turns out that one dld follow a career in the theoretical slde 01 chemistry remarkably similar in its focus to my own and Is now at Ohio State. The other two have gone into things that involve a slgnlflcant mathematical or scientific basis (my daughter at the Salk institute and another son in economics). They have no close relation to chemistry but both are having substantial success with their own particular objectives and activities. Ridgway: Now we take a look at the future. Do you see areas of our science or related ones that are being neglected? Pllzer: I suppose in a formal sense you can always say yes, although I thbk that would be rather mlsieading. There is always a certaln amount of rushing from one area of sclence to another in accordance wlth the opportunltles that new instrumentatlon or a new concept provides. Sometlmes thls leads to a neglect of other areas of sclence In which Important thlngs can stlli be accomplished. I think chemists are less inclined to do this than sclentlsts In some other areas so that I don't really have any particular complalnt. I should say something about interdlsclplinary areas and about dividing lines between dlscipllnes. I thlnk
one can easily be unrealistic concerning interdlscipllnary areas. Any human organization and any human activlty has to be subdivided in some fashion to make it tractable and operable. You've got to break them down into smaller units, whether they are to be managed hierarchically, in the sense of the mllltary organization, or whether they are to manage themselves democratically, in the sense that a university department handles most of its own affairs. I don't see any objection to using traditonal disciplines as compared to non-traditional ones for this organizational pattern, provided there is enough flexibility in the boundaries. In any case, it should be easy enough to cross boundaries so that new fields, which do not fall conveniently within a single discipline, get the attention that they deserve. I do not belleve that disciplinary boundaries have been unduly inhibitory. The physics/chemistry line is a broad-based one and illustrates my point. It has always been soft enough so that there wasn't any very great difficulty there. 11's always been the pattern that the chemistry students take a certain number of courses in physics. There has been a lot of research collaboration belween physicists and chemists at Berkeley and in many other locations. This aiways involves some exlra complications but ii's still feasible. Rldgway:
Pitzec
We have asked this question of each of our htervlewees and obtained some very interestlng answers, not always expected ones. If you were just completing a degree program in the year 1975, would you launch a career that parallels that which you dld follow, or might there be some new and perhaps quite dlfferent career?
I thlnk a person wlth the same interests that I hed at the time, the same satisfaction in problem sotvlng and the same interest in natural phenomena, should seek a career somewhere wlthin the range of physlcal science or the more quantitatively orlented biological sclence or applied sclence, including englneerlng. I'm not necessarily predicting that, if I were deciding today, I would choose chemistry or the same subdlvision of chemistry. I thlnk there are many opportunities in physlcal chemlstry, somewhat informally defined as I've always thought of it. But there are probably enhanced opportunities now in the area in which one is focusing on problems of biological importance. There are many comparable opportunities in other areas that are based upon physical science with more or less emphasis on application. I think the whole field is a challenging one, an interesting one in which a young person would certainly Hnd satishctlon and I would certainly include physical chemlstry among that menu of opportunities. A person who has had In his early career a lot of Satisfaction In mathematics as well as in experimental measurements would be Interested in an area where the state of advancement of knowledge is such that one is deailng wlth things quantitatively and numerically rather than just qualitatively. I thlnk it is a somewhat different type of person, in terms of hls Interest and aptitudes, who goes into a purely descriptive, qualltatlve, classllicatory type of sclence.
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