contemporary hi~tory
LEONARD editedFINE by: Columbia Untversihl New Ywk. NY 10027
ERICS. PROSKAUER
The Making of a Physical Chemist The Education and Early Researches of Henry Eyring Steven H. Heath Department of Mathematics, Southern Utah State College, Cedar City, UT 84720
As the winner of the $500 scholarship for Graham County, Arizona, in 1919, eighteen-year-old Henry Eyring had decided t o study mining engineering at the University of Arizona in Tucson. After four years of study and two summers of work in the mines of southern Arizona, he was convinced that mining engineering wasnot the vocation he desired. He then applied for a US. Bureau of Mines fellowship to dograduate work in metallurgy. As a graduate student in metallurgy he took his first physical chemistry course from Theophyl Buehrer, a graduate in chemistry of the University of California a t Berkeley. I t was here that Eyring's talent for chemistry was first recognized. The majority of his time was occupied in research. Under the direction of Thomas Chapman, he did extensive work on the differential flotation of copper minerals in heavy sulfide ores. The results of his master's thesis, "The Separation of Heavy Sulfide Ores by SelectiveFlotation," were subsequently published, with due credit, by a man at the Bureau of Mines. At the time Eyring did not realize that he could publish the results of the work himself. With a master's degree in metallurgy, Eyring easily found new work in this field. In the summer of 1924,he was hired by the United Verde smelter a t Clarksdale, Arizona, and was given the opportunity of seeing the various aspects of the smelting operation, training necessary for any metallurgist. However, as in mining, smelting also had its negative aspects. Eyring later recalled ( I ) After being there a few weeks, I was assigned to take samples from the blast furnaces. The sulfur dioxide smoke was especially strong, and 1was holding a handkerchiefsoaked in baking soda over my face when the smelter superintendent came by, slapped me on the shoulder, and said, 'Eyring, I plan to put you in charge of the blast furnaces in a few weeks.'The problems were intriguing, hut the sulfur smoke made it easy for me to return to the University of Arizona as a chemistry instructor. Eyring almost turned down the University's offer when he learned that his salary would be $1,400 instead of the $1,600 he had first been told. However, he accepted and was given the responsibility of conducting the chemistry laboratories for various chemistry classes. In his spare time, he was allowed to broaden his studies of chemistry by attending classes. The first semester he took advanced physical chemistry from Lathrop E. Roberts, a graduate of the University of Chicago, and general organic chemistry from Ernest Anderson, department chairman. During the second semester he had another general organic chemistry class and electrochemistry from Buehrer. In addition he took a course in elementary German because he had already planned to stay only one more year at Arizona,
then to do graduate work in chemistry, where the additional chemistry and the foreign language both would he necesaarv. in the fall of 1924, Buehrer and Roberts each recommended Eyring for fellowships to study chemistry at the University of California at Berkeley and the University of Chicago, respectively. Apparently hoth schools were impressed with the recommendations and the credentials of Eyring, for hoth offered eood fellowshi~s.Chicago for $650 and Berkelev for $7M) (2). ~ j r i chose n ~ togo to ~ e i k e l e yand , after a summer visit a t home in Pima, Arizona, he set out for California in early August 1925. At Berkeley, Eyring came under the influence of the famed chemist Gilbert N. Lewis and his staff. Lewis, educated at Harvard, was one of the pioneers of modern physical chemistry. He set forth the idea that the chemical bond is formed by the mutual sharing of two electrons between two atoms. His hook, "Valence and the Structure of Atoms and Molecules" (1923), which outlined this work, is a classic in the history of chemist^. Of even ereater sienificancein stimulating research in physiEal chemi&y was cis and Merle Randalps "Thermodvnamics and the Free Enerw of Chemical Substances" (1923). One prominent chemisthas said that "this hook ~ r o b a h l vhas had more influence on the development of bhysicaichemistry than any other single publicatibn" (3). Evrina recalls that in Lewis' laboratory "there was no place for scientific onlookers" (4). The emphasis was on research. In fact. Evring . . took onlv one formal course in chemistry, despite his relativrly weakchemistry background, and that was thcrmodqnamici. The course was tauyhr by Crorye Ernest Gibson, who later became his thesis ad&or. Gibson had come to Berkeley in 1913, one year after Lewis' arrival. He had received his PhD a t the University of Breslau in 1911, and after one year at the University of Edinburgh, his birthplace, he came to California (5). The rest of Eyring's chemistry studies a t Berkeley were in the laboratorv. Durine his first semester. he beean to work with ~ a n d a l i o nion activity of variouselectr&tes using lowered freezine noints of solutions. Unfortunatelv, the equipment necessary for the study was being used by Albert Vanselow. As a result of the delay, Eyring decided to do research in radioactivity instead of electrolytic chemistry. He then heaan workina with Gibson on the bombardment of hvdrogen gas a t low pressure using an 11,000,000-VTesla coil. After numerous unsuccessful experiments, hut useful experience, they turned to the stopping power and ionization of various gases which they bombarded with alpha particles from a polon&m source. 1t was from this work that ~ y r i n received g Volume 62 Number 2 February 1985
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his Doctor of Philosophy degree in July 1927. The results of this investieation wrre ~ublishedlater in 192: in thePh\sical Reuiew (6K This was to he the first of numerous scientific papers by Eyring and his associates. Eyring's workon radioactivity is also historically interesting in that he was the first student to do work in atomic chemistry at Berkeley. Later Berkeley became one of the great centers of radiochemistry in the world and would produce scientists like Nobel laureate Glenn Seaborg, who also did his doctoral work under Gibson. So with Eyring, Berkeley began its research into radiochemistry (7). When Eyring was not working in the laboratory during his typical 8 a.m. to 10 p.m. day, six days a week, he was studying for or attending his mathematics classes. At Berkeley, PhD candidates had t o have a minor in a subject other than the major field; Eyring's minor was in mathematics. In fact, every semester he had one or two mathematics courses, including the summer session in 1926. His mathematical studies there s c o m ~ l e xvariables. soecial included such important t o ~ i c as analytic functioni, ordinary A d partid ;l~~erential qudtions, invariant theory and non-Euclidean aeomerry (6).The excellent lecturesof Haskell on non-Euclidean geometry were particularly interesting to Eyring. The mathematics he learned a t Arizona and Berkeley would he extremely useful in his later career as a theoretical chemist. Perhaps as important as his chemical research, his study of thermodynamics, and his mathematical studies was the was exnosed to at Berkelev. He scientific atmosohere Evrine " wrote of this exiraordinary environment (9):
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At Berkeley graduate students mingled with outstanding scientists who entertained no doubt that intelligent research was the most important activity in the world. This contagion infested everyone. Individual success in research was accompanied by a shedding of any undue veneration for the embalmed science of the past. Seminars led by Lewis were always exciting, even when the blackboard could be hut dimly seen through the blue haze of tobacco smoke exhaled by the addicts. Another point was significant. The new graduate student was given keys to all the stockrooms. This was in fact, a presentation of the 'keys to the city.' With this handsome gesture went a few words on acceptable conduct. So far as I remember, people responded to this generosity admirably. The chemistry department at Berkeley was, in fact, a society of scholars. Successful research was the hadge of honor. Not to try todo research was unthinkable. The research atmosphereprovided at Berkeley has prohahly rarely been equalled. The weekly seminar was the vehicle used to talk about what research was being done a t Berkeley and everyone partici94
Journal of Chemical Education
pated, from graduate students to senior faculty memhers (10). In addition cn the seminar. Evrinr attended numerous visiting lectures by some of the most prominent scientists in the worlx For cxampk, after listening to lectures on the new quantum mechanics hy John C. Slater and Max Rorn, Eyring saw great potential in applying the new theory tochemistry. He u,ould later be one i f t h e pioneers in this endeavor. Eyring departed from Berkeley with some of the finest characteristics and potential of the master chemist there, G. N. Lewis. He left with an unbounded curiosity ahout the nature of the world around him.His annroach to science was intuitive, but included rigorous experkentation to verify the intuition. The snirit in which he carried out research became manifested in &I who associated with him, and like Lewis' students. Evrine's students came to includesome of the most promineit i n t i e world of physical chemistry (11). Eyring indeed had a bright future in 1927. With the credentials of a Berkeley PhD and a G. N. Lewis recommendation, Eyring found employment relatively easy to obtain. Before he left Berkeley for a visit home, he accepted an instructorship at the University of Wisconsin for the 1927-28 school year. During his fust year at Wisconsin, Eyring taught laboratory courses in physical chemistry and continued his radioactivity research on the stopping power of various gases. At the end of the 1928 school year, he was given a fulltime research nosition a t the universitv to work with Farrington Daniels. In the summer of 1928,ihey began studying the decomposition of nitrogen pentoxide (NzOs) in a number of solvents. Eyring worked hard in the lahoratory just as he had at Arizona and Berkeley. He was particularly fascinated by the wide variance in the decomposition rate of the nitrogen nentoxide in the solvents worked with. The uniaue thine ;bout this reaction (2N205 4N02 02) is thacit is u n c molecular and that the rate of the reaction can he measured by the volume of oxygen released. The experience with Daniels was an important turning point in his career. He left his radiation studies and began to consider reaction kinetics, the subject which would dominate his thoughts and research for theremainder of his life. Daniels, a great chemist in his own right, later wrote to Eyring: "I consider that one of my most in&rtant acheivements in science was my success in getting you interested in the field of chemical kinetics " (12). The vear and two summers a t Wisconsin nrovided Evrine . .. with rirh training in experimental reaction rater. In addition. durine his second vear HI \\.isconsin he was ahle to attend the phynn lectures of John H. Van Ylwk on quantum mechanics. Van Vleck. one of America's arrutesr teachers of thruretical physics, had recently returnei from Europe enthused by the
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great possibilities of the new quantum theory (13). Eyring, with his strong mathematics hackground, easily followed the subject. He would later become one of the pioneers in applying auantum mechanics to chemistrv. As he had a t Berkelev. .. Eyring also profited from the visits of many scientists, including Paul Dirnr, Werner Heisenhera, and Leon Brillonin. while he was at Wisconsin. To him, Madison was good in chemistry hut not as good as Berkelev; onlv in its best fields did it rival his alma mater (14). In 1928 the field of chemical kinetics offered a great challenge and opportunity for a physical chemist. I t was a relatively young field and there were many unanswered questions concerning the dynamics of chemical reactions. The first measurement of a reaction rate came in 1850 when Ludwig Wilhelmly measured the rate of hydrolysis of sucrose in the presence of acids (15). His investigations showed that the ~oncpntrationof sucrme derreased rrponenrially with rime. Hetwren 1864 and 1869 two Norwegian scientists, C. M. Gddhere and Pcter Waaae. eeneralizcd this notion with the "law of mass action," which'siates that the rate of a chemical reaction is directlv orooortional to the ~roductsof the masses. each raised t u s o z definite puwer. tn.l8:7, J. H. Van't off independentlv discovered the "law of mass action" and subsequently didmuch to interest other chemists in the quantitative studv of reaction rates. One of the most fruitful investigations came in 1889 when Svante Arrhenius discovered that the rate of chemical reactions increases with temperature. Arrhenius' theory argued that before a molecule would react it must attain a certain activation energy. He then derived an equation for the specific reaction rate K' as follows: K' = AecEIRT;where A is a constant, E is the difference in energy between active and inert molecules, R is the Boltzmann gas constant, and T is the temperature in degrees Kelvin (16).The Arrhenius equation worked remarkably well for many chemical and biological reactions for which the reaction rates had been measured experimentally. Following his work, interest in the study of chemical kinetics steadily declined. The principal reason for this lack of interest was that there were no new theoretical developments to suggest avenues of inquiry and experiment. This state of affairs was changed in 1918when Jean Perrin in France, M. Trautz in Germany, and William C. McC. Lewis in England ~ uforth t the "radiation hmothesis" which hvpothesized that decomposing molecul&~inunimolecular reactions receive their activation energy from radiation from the sides of the container rather than from intermolecular colli-
sions. Though the radiation hypothesis was erroneous, it stimulated a new surge of interest in reaction kinetics. Interestingly enough, ~ariingtonDaniels at Wisconsin and Hugh Taylor at Princeton rrvealed the flaws in the "radiation hvporhesis" with work on the decomposition of nitrogen pentoxide. Eyring's work with Daniels was arunrinua~ionof these earlier studies. In 1922, Frederick A. Lindemann suggested that collisions providr the activation energy for reacting molecules. During the mid-'rwenties the collision hypothesis was investigated extensivelv hv H'. H. Rodehush. C. W. Hinshelwood. D.K. Rice, H. c ~amsperger,E. ideal, and L S . K&~I. he collision hv~othesisanswered some auestions. but manv important k&ic questions remained 117). ~ e a c t i o nkinetics was ~articularlv chemists in 1928for a - a~oealina -. - to ~hvsical - newand very important reason-the possibility of implications of the new quantum theory for explaining reaction rates. The next year Eyring was given the opportunity to investigate that possibility more seriously. Eyring had been critical of the way the physical chemistry program was being administered at Wisconsin. In particular he felt that physical chemistry was not heiug taught by the chemistry department's best people. The chairman of the department took offense a t Eyring's criticism, and as a result, the university went to the trouble of securing a National Research Foundation fellowship for him to study for a year in Germany. Eyring was delighted a t the prospect of such an exnerience and readilv acceoted. . . for it eave him a chance t o 1w;k deeper inu, reactan kinetics. Van vieck, well acquainted with Eurooe and its transourtation srxtem, outlined in detail how ~ ~ rshould i n traveito ~ ~ e r l i n . ~plans i s also included a visit to J. A. Christiansen, the famous Danish physical chemist in Copenhagen. After a visit with family in the West, Eyring and his wife set out for Europe as Van Vleck had outlined. Originally, Eyring was to work with Max Bodenstein, hut it was learned that he would he away when Eyring was scheduled to arrive. As a result, his appointment was changed from Bodenstein to Michael Polanyi (1891-1976), head of the kinetics division of physical chemistry a t the Kaiser Wilhelm Institute. As it turned out, Polanyi was with Bodenstein a t the dedication of the new Frick Chemical Laboratory at Princeton University and so no one greeted Evrine when he arrived in Berlin to eo to work. ~ y r i & ,however, l i d not wait for Polanyi and c e began workine in the Fritz Haher Lahoratarv a t the Institute assoon as he was settled. Polanyi soon returned and the two began a program of extensive research. The year with Polanyi was one of the most exciting and productive in Eyring's life. Polanyi, born and educated in Budapest where he obtained his MD degree, turned to physical chemistry at Karlsruhe. He received an appointment a t the Kaiser Wilhelm Institute in 1922. Later he was placed in charge of the kinetics division of the laboratory. In 1933he resigned his post in protest against German anti-Jewish legislation. From 1933 to 1948 he was professor of physical chemistry at the University of Manchester in England. During later years of his career he turned to philosophy and was professor of social studies a t Manchester until 1958 when he retired. In addition ta Polanyi, the Institute was the home base of some of the ereatest ~hvsical chemists in Europe (IS), and Eyring found gmself i&mksed in a society of scholars such as he had found a t Berkeley. When Polanyi arrived in Berlin, he and Eyring first worked on the alkali-haloeen flame reactions. work Polanvi had been interested in. A& a brief period df experimekation and spectroscopic analysis of these reactions, they turned to some new studies on reaction kinetics. The year before Eyring's arrival, Fritz London had presented a paper for the 60th birthday of Haher, in which he presented an approximate equation, using quantum mechanics, which made it possible to calculate the potential energy for three or four atom reacVolume 62 Number 2
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tions. Since notential e n e m was determined bv the distance between atoms, Eyring a z Polanyi thought i t would be interesting to actually draw a potential surface, a graph of distance versus energy. The first attempt, using three hydrogen because of the difatoms on a line met with disan~ointment .. ficulty of getting rrrtnin number5 in the experimental results usine Heitlcr. London-Sueuria theoretical calculations. This problem was circumvented using experimental results from spectroscopic measurements, plotting what is called a Morse curve, then using the results with the London formula. The procedure, known as the "semi-empirical method," gave only i n approximatr potential surfme, but still useful reshts (19j. With a picture to look at, Erring could see the mechanism of a chemical reaction. The result was a whole new world for studying reaction kinetics and Eyring became a confirmed kineticist. The picture of the reaction mechanism viewed as a potential surface is ouite simple . (see . Fias. 1and 2). For three atoms. i t is nothing more than a landscape, a surface with mountains and vallevs. The vallevs corresnond to stable com~oundsand the moununtains to energy barriers. If enough energyis available, one can EO over a mountain Dass into another valley, and the reactionbas taken place. with sufficient knowledge-&out the surface, the reaction rate can be calculated. For three atoms not in a line or for more atoms the surface is no longer threedimensional, but a higher-dimensional surface and a little knowledge of higher-dimensional geometry allows one to visualize the reaction mechanism too. This unique picture of
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distance (r, )
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Figure 1. Typical potential energy surface for lhe reaction W YZ.
+Z
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Figwe 2. A view of th= rwction d i n a t e with WM energy states of th= activated complex at the top of the potential energy barrier denoted by the quantum numbers 0. 1.. . . n.
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a chemiral reaction did not immediately solve all the problems of reaction kinetics, hut Eyring could see that pursuing the idea would hring rewarding rrsdts. He worked v i g o n d y and continually on thedifficult detailsduring the next few years. The results of Evrine and l'olan\i's work s t m d reaction rate theory off in a c&ndetely new iirection. Toward the end of his stay in Berlin, Eyring was visited by Wendell Latimer of Berkeley. Latimer inquired about the mound-breakina- work of Evrina . .. and Polanvi and was ..areatlv. impresscd. IIr, in turn,strongly rrcommended to G . iK.Lewis that Rerkeley should bring Eyring back for a year. Since Joel Hildehrand was ru take a leave of absence from Rerkeley for stud\, in Europe, the University of Cillifornia offered a oneyearlecturesh:lp at Berkeley. He accepted the position over an offer for an appointment a t the University of New Hampshire. In early August, 1930, he and his wife returned to the United States. The atmosphere at Berkeley had not changed since his graduate school days four years before, but Eyring had. In addition to his firm grasp of thermodynamics and mathematics, Eyring now knew quantum mechanics, had fine experimental experience, and was determined to extend the work he had begun in Berlin. His light laboratory-teaching load allowed him to spend substantial time on his quantum mechanical attack on reaction kinetics. During his one-year stay a t Berkeley, he spent most of his working hours on halogen-hydrogen reactions, and the study paid off in some exciting ways. All the chemistry books and experiments at that time said that when hydrogen and fluorine were put together in pure form there was an immediate explosion: Early experimental work indicated that violenr explwi~msoccurred wen when fluorine was placed in the presence of liquid hydrogen. Eyring's quantum mechanical calculations, however, indicated iust the opposite. Hvdroaen " .. and fluorine would not react without r&siderahle activation energy. In fact, the mathematics indicated that t h reaction ~ would not take d a c e until temperatures of 150' to 250°C were obtained and that it was not possible for them to react at liquid hvdroeen temperatures. ~ y r i nconvinced ~, his theoreticai calculations were correct, set out to demonstrate them experimentally.
He and a post-doctoral friend, Louis S. Kassel, prepared pure quantities of gaseous hydrogen and fluorine and proceeded to mix them a t room temperature. The result was as they predicted-no reaction, even after more than 30 min of direct contact. Realizing they would have to remove the daneerous aases from the chamber they were mixed in, they hadirranged for a nitrogen gas line to flush them out. They sought safety behind a large table across the room from the mixture, but had forgotten to run the nitrogen gas line to that point. They debated for a few minutes who would go over to the nitrogen tank and turn the valve to flush out the mixture. Eyring finally agreed he would and he proceeded to crawl on his hands and knees across the room toward the nitrogen tank. As soon as he reached up and turned the valve, the mixture exploded. "The flask was pulverized, an enclosing towel cut into shreds and a wire-in-glass safety screen cracked in a dozen places. Presumably, this explosion was initiated by sulfur, talc or other catalytic material from the fresh rubber tubing from the nitroaen su~olv"(20). Evrine was not hurt, but the violent explosionconvik~dthem not G t r y the same experiment with liquid hydrogen. Eyring had vindicated his theoretical approach to chemistry but more importantly his work on hydrogen-halogen reactions was significant enough that the American Chemical Society invited him to participate in a specialsymposium on "Applications of Quantum Theory to Chemistry" at the Indianapolis meeting of the ACS (21). Hugh S. Taylor, chairman of the Department of Chemistry a t Princeton, was present at this March 31, 1931, meeting and was so much impressed with Eyring's paper that he invited him on the spot to go to Princeton and present two lectures on quantum mechanics and the calculation of reaction rates before he returned to Berkeley. The $100 a day for each lecture was alluring, but Eyring felt Berkeley could not do without him for the extra days. Taylor quickly arranged things with Lewis, and Eyring went to Princeton. Taylor, after the lectures a t Princeton, was even more impressed &th Eyring and decided that he wanted Evrine - there. As it turned out, Hildebrand soon returned and because the chemistry department at Berkeley would not hire a new man for five more years, there was no room for Eyring a t Berkeley, even for the next year. When Taylor offered Eyring a research associate position a t Princeton, he accepted. The official letter offering Eyring the position was sent June 4,1931. However, because of severe budget cuts caused by the denression. Princeton was able to offer onlv a one-vear avp&tment.'Eyring responded quickly that he would-rome'in soite uf the altered ~ i r t u r eHe . exncrted a firmer nffer. ' T h e one-year appointment a t Princeton turned into 15 excitina vears for Evrine. The atmos~herea t Princeton was similarto that a t ~eikele;, but ~ y r i n ~role ' s had now changed. He was no longer the student under the tutelage of the teacher, hut now he was the teacher, as well as director of students' research. The emphasis a t Princeton was on research, and Eyring had a light teaching load for all of those years. He taught only advanced physical chemistry courses and spent the rest of his time doing research in the newly completed Henry C. Frick Laboratory. This building was his center of scientific activity during his stay a t Princeton. I t contained an office and private laboratory for each professor, laboratories for advanced research, laboratories for instruction, classrooms, I
and a large auditorium. The s e a ~ n dfloor housed an cxtpnsive library and an rxrellent collection of the world's important chemiral iournals. In addition. thr huildine also had a rlasshlowing rwm, a well-equipped machine shop, and numerous service rooms (22). Eyring's first paper a t Princeton, "The Resultant Electric Moment of Complex Molecules," in early 1932, gave the equation for the addition of dipoles in complex molecules, as well as the distance between the two ends of lone molecules. The equation has remained fundamental to h&h polymer theory and is still frequently cited (23). The next series of papers dealt with the application of quantum mechanics to chemical reactions. On December 31, 1932, he presented a previously submitted paper entitled, "Quantum Mechanics and Chemistrv with Particular Reference to Reactions Involving conjugate Double Bonds," to the American Association for the Advancement of Science a t the Atlantic City meeting. The paper explained why bromine reacted with a hydrocarbon (hutadiene) in primarily one way, even though theoretically two products were possible. This work was an extension of his earlier studies; however, now i t was apparent that Kyring's quantum mechanical mudel; applied not only to inorganic reactions, hut also to organic ones. Hugh Taylor thought that the results of this work were so significant that he nominated Eyring to the AAAS fur its annual prize (later named the Clevrland-Ncwcomb Award) and used his influcnrr to persuade the committee to give Eyring the an,ard. The commitcee agreed with 'l'avlor and Hrnrv Evrina . - herame the 10th recipient of the $1,000 annual awaid. Followine this work, Evrinp, Tavlor and their students began to woik with chemical i s ~ & ~ e s ; ~ a r t i c u lthe a r l recently ~ discovered heavy water (deuterium oxide). In 1930, James Chadwick had correctly identified a particle in the nucleus of an atom with the same mass as the proton but without electrical charge. The particle was called the neutron. Two years later, Harold Urey at the University of Chicago discovered a water with the extraneutron in the hydrogen, i.e., heavy water. Both Chadwick and Urey received the Nobel Prize for their work (24). The discoverv of h e a w water caused excitement a t m&y places in the chemical a n i physical world. Princeton was no different. Eyring now had another test of his reaction rate theories using heavy water. However, his ideas could be extended to reactions involvina manv kinds of isoto~es.The S first paper after his prize-winling paper for the A ~ gave an explanation for Urev's work on the separation of isotopes r2.51. using quantum m&haniw hc. rxpla&d why the heacier isotope is left behind upon electrolysis as Urey and Washburn had found in their preparation of heavy water. Taylor, Eyring, and associates then set out to produce their own heavy water and to perform experiments with it.
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When they had finished their electrolysis operation, they had produced large amounts of heavy water. With this water, theiperformed numerous experiments from solubility studies to determination of its effect on living organisms. Eyring's calculations predicted that salts were not as soluble in heavy water and that heavy water slowed reaction rates down. Experiments showed that in high concentrations of heavy water death results in living organisms because of the slowing of life-sustaining reactions in the cell (26). At the April, 1933, meeting of t h i American Philosophical Society inphiladelohia. Tavlor and Evring were invited to report on their in;estigatibns with heavy water. Upon the& arrival a t the meetings, Irving Langmuir, a recent Nobel laureate, cornered Eyring and asked if he would tell him of their work. As Taylor read the formal report to the Society, Langmuir and Eyring walked in a neath; park and discussed l'rincrton's work on hea\? water. Kyring wrls pleased that Langmuir would show such a kren interest in t h r work at I'rinreton. It was a memornhle experience for the young scientist. Eying's earlier work provided the theoretical foundations for the reaction rate theory of isotopes, particularly heavy water (27). In the summer of 1934, Eyring took his family west in a Model A Ford to visit their families. Later that summer he was to present a paper on the fundamentals of reaction kinetics a t the American Chemical Society meeting in Cleveland. However. the paver was not presented because the Eyrings had a serious a&mohile accident on their return trip in ea& September. Evring, found on the ground in a semi-conscious condition, war. rushed to a nearby hospital. Fur the next two weeks, he recuperated at the Holy Family Catholic Hospital in LaPorte, lndiana. The enforced leisure gave Eyring plenty of time to recuoerate and to nut more work into his Daoer. The result was, as he later redled, "as finished a pape;&~ have ever written'; (%). oaoer. entitled "The Activated Comdex in Chem,- , The ical Reactions," became the single most inflLential paper Eyring every wrote. The paper was submitted to the Journal of Chemical Physics in November 1934. Urey, editor of the iournal. sent it on to a reviewer who returned i t with this comment: "I enclose the paper by Dr. Eyring entitled 'Activated Comdex in Chemical Reactions,' I have given considerable thoGght to the problems involved and although I have not been able to resolve all my uncertainties, I have nevertheless become convinced that the method of treatment is unsound and the result incorrect" (29). Eyring knew he was right and with the support of his colleagues, Hugh Taylor and Eugene Wigner, soon convinced Urey that the results were coriect a n d that his treatment of reactions was sound. The journal published his epochal paper in April 1935. Mdifvinr the Arrhenius euuation for reaction rate (K'= -~ surface ideas from Berlin, A ~ - E I R&d ~ using the Eyring's activated complex paper gave precise meaning to Arrhenius's A and E values in terms of quantum and statistical mechanics, and it related rate theory to thermodynamics (30). Eyring, with this formulation, could treat the transition comnlex molecule (the state between reactants and products) and 'by calculating it;i prr,perties drtermine the rearriun rate. His absulutr rate theory, as it is now called, has been one of the most potent ideas to apprar in chemistry in the last 30 yrars, since it nut only applies to chemical reactions but also cn numerous physical and biulugical processes as well. Hugh ~~~~~~
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Taylor commented (31)on Eyring's theory and its importance as he recalled the highlights of his 50 years in chemical kinetics. The golden decade of my life in Princeton was the period from 1929 to 1939. The Frick Chemical Laboratory was new and excellently equipped for the resemches then underway. But the richness of the decade came from the oresence of Ewine and his co-workers, exolorine ..the new absolute rate theorv ofche&icalrate orocesses. v,,mplrrnrnting t h p active experimental s~udirsund~rwaym tht lat,ongtwirs. I t was I ~ immense P range of thr absolute ratr rheory. applicahlr not only to atom-moleculeand mderulr-n~olecukbut alike to physical processes, conduction,transport number, viscosity, diffusion and biological processes of wide variety and scope. ~~~
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The oroblems eenerated hv the development of absolute rate theory providk Eyring a iifetime of exciting research. By the time of his death on December 26,1981, he and his students had produced over 600 scientific papers and eleven books on the suhiect. For his accomplishmeuts he received numerous awardS including such d~stin~uished honors as membership in the National Academy of Science t1945). Pwiident of the American Chemical Societv I 19631. National Medal of Science (1966), Joseph priestie; ~ e d a of l the American Chemical Societv (1975). and Berzelius Gold Medal of the ~ w e d i s h ~ c a d e m o%cien& y (1979). When the history of twentieth centurv chemistrv is written. Henrv Evrinz . - and his absolute rate th&y will hbld a prominent place. ~~
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Literature Cited (1) Eyring, Henry, Ann RPU.Phys. Chom.,P,4 (1977). (2) Lewis, Gilbert N.. toHenry Eyring. March 25,1925. 131 Daniels. Farrind". Chrm. Em. News. o. 44 lseotember 19511
(8) Eyring, Henry, oflieid transcript. Uniu. of California. (9) Ref ( 4 ) . pp. 169-170. (10) Calvin, Melvin. "Gilt& Newton lewis." in "AmcriChemietw Bicentemial. Robert
A. Welch Foundation Conference," Robert A. Wdch Foundation, Houston, 1976,
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(27) Spicer,Leanard D., and Poulter, C. Dale. '"Isatopesas Probes in Determining Reaction
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