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Home , Discovery of the neutron, Frederick Soddy, Harold Urey, William Giauque

Harold and the discovery of

Chemistry, nuclear , spectroscopy and came together to predict and detect heavy before the was known.

Ferdinand G. Brickwedde

It was on Thanksgiving day in 1931 his family to a homestead in Montana. 1940 he was the founding editor of the that Harold Clayton Urey found defini- After graduating from high school, he American Institute of Physics publica- tive evidence of a heavy of taught for three years in public schools, tion, Journal of Chemical Physics. hydrogen. Urey's discovery of deuter- and then entered Montana State Uni- When the biographical publication ium is a story of the fruitful use of versity as a major and chemis- "American Men of Science" took note primitive nuclear and thermodynamic try minor. Money was tight for him as of scientists selected for recognition by models. But it is also a story of missed a college student. During the academic their peers, Urey was elected in phy- opportunity and errors—errors that year he slept and studied in a tent. sics. In 1934—only three years after are particularly interesting because of During his summers he worked on a the discovery of deuterium—Urey was the crucial positive role that some of road gang laying railroad track in the awarded the in . them played in the discovery. A look at Northwest. the of the theoretical and ex- Urey graduated with a BS degree in Before the search perimental work that led to the detec- 1917, when there was a need for chem- In 1913, Arthur B. Lamb and Richard tion of hydrogen of 2 reveals ists in the war effort. He worked for Edwin Lee, working at New York Uni- much about the way physics and chem- the Barrett Chemical Company in versity, reported5 a very precise mea- istry were done half a century ago. on war materials. After surement of the density of pure water. Although George M. Murphy and I the war, Urey taught chemistry for two Their measurements were sensitive to coauthored with Urey the papers1"3 years at Montana State University, 2xlO~7 g/cm3. Various samples of reporting the discovery, it was Urey and in 1921 entered the University of water, which were carefully prepared who proposed, planned and directed at Berkeley as a graduate using the best purification techniques the investigation. Appropriately, the student in chemistry, working under and temperature controls, varied in Nobel Prize for finding a heavy isotope the guidance of the renowned chemical density by as much as 8xlO~7 g/cm3. of hydrogen went to Urey. thermodynamicist Gilbert N. Lewis. They concluded that pure water does In this article we will look first at the As a graduate student, Urey was a not possess a unique density. research that led to the discovery, as pioneer in the calculation of thermo- Today we know that water varies in that work was understood at the time. dynamic properties from spectroscopic isotopic composition, and that samples Then we will look at some of the same data. He received a PhD in 1923 and of water with different isotopic compo- activity with the understanding that spent the next academic year as an sitions have different vapor pressures, only hindsight can give. Throughout American-Scandinavian Foundation making distillation a fractionating pro- the discussion I will include fragments Fellow in the Physical Institute of cess. The Lamb-Lee investigation is from my memory—illustrative epi- in . interesting because it was the first sodes connected with the discovery. After Copenhagen, Urey joined the reported experiment in which an isoto- faculty at . pic difference in properties was clearly Urey's career Although in the chemistry department, in evidence. It is the earliest recogniz- Urey died last year at 87 years of age, he attended the physics department's able experimental evidence for iso- after a remarkably productive and in- regular weekly "journal" meetings for topes. (The existence of was teresting life. He was a with faculty and graduate students, and he proposed independently by Frederick very broad interests in science, remi- participated in the discussions. It was Soddy, in , and by Kasimir niscent of the natural philosophers of at these meetings that I, as a graduate Fajans, in Germany, in 1913.) Think the eighteenth and nineteenth centur- student in physics, became acquainted what the result might have been had ies. Murphy4, who went on to become with Urey. While Urey was at Hopkins, Lamb and Lee pursued a progressive professor and head of the department he and Arthur E. Ruark coauthored the fractionation of water by distillation of chemistry at New York University, classic textbook, , Molecules, and and separated natural water into frac- died in 1968. Quanta, which was the first comprehen- tions with different molecular weights. Urey was born on a farm in Indiana sive text on atomic structure written in Less than two decades later, by the in 1893, and in childhood moved with English. I proofread the entire book in time of the discovery of deuterium, galley for the authors. isotopes were an active field of re- Ferdinand G. Brickwedde is Evan Pugh Re- Urey's work bridged chemistry and search. The rapid development of nu- search Professor of Physics emeritus at Penn- physics. In 1929 he was appointed clear physics after 1930 was initiated sylvania State University, in University Park, associate professor of chemistry at Co- by isotope research. It was a time of Pennsylvania. lumbia University, and from 1933 to search for as-yet undiscovered isotopes,

34 PHYSICS TODAY / SEPTEMBER 1982 0031-9228/ 82/ 0900 34-06/ $01.00 (cl 1982 American Institute Of Physics especially of the elements, hydro- isotopes exist, and what determines Urey had a copy of this chart hang- gen included, and Urey was very much their number, relative abundances and ing on a wall of his laboratory. The a participant. (packing fractions)? isotope -5 does not exist, and the I remember a conversation in 1929 Urey, along with others, constructed staggered line does not provide a place with Urey and Joel Hildebrand, a fam- charts of the known isotopes to show for the isotope helium-3, which was ous professor of chemistry at Berkeley. relationships bearing on their exis- discovered later. The diagram is only It took place during a taxi ride between tence. The figure on page 36 is one of of historical interest now, but it was an their hotel and the conference center Urey's charts. At the time, the neutron incentive to Urey to look for a heavy for a scientific meeting we were attend- had not been discovered—it was disco- isotope of hydrogen. ing in Washington. When Urey asked vered in 1932, the year after deuter- Hildebrand what was new in research ium. The chart was based on the the- Prediction and evidence at Berkeley, Hildebrand replied that ory that atomic nuclei were composed In 1931—the year of the discovery of and Herrick John- of , plotted here as ordinates, deuterium—Raymond T. Birge, a pro- ston had just discovered that oxygen and nuclear , plotted as abscis- fessor of physics at the University of has isotopes with atomic weights 17 sae—the number of protons was the California, Berkeley, and Donald H. and 18, the isotope of weight 18 being nuclear , and the number Menzel, professor of astrophysics at the more abundant. Their paper6 of nuclear electrons was the number of Lick Observatory, published7 a letter to would appear shortly in the Journal of protons minus the of the editor in on the the American Chemical Society. Then the element. In Urey's chart, the filled relative abundances of the oxygen iso- Hildebrand added, "They could not circles represent the nuclei from H' to topes in relation to the two systems of have found isotopes in a more impor- Si30 that were known to exist before atomic weights that were then in use— tant element." Urey responded: "No, 1931. The open circles represent nuclei the physical system and the chemical not unless it was hydrogen." This was unknown before 1931. The chart's pat- system. Atomic weights in the physical two years before the discovery of deu- tern of staggered lines, when extended system were determined with the mass terium. Urey did not remember this down to H1, suggested to Urey that the spectrograph and were based on setting remark, but I did. atoms H2, H3 and He5 might exist the atomic weight of the isotope O16 at At the time, answers were being because they are needed to complete exactly 16. In the chemical system, sought to questions such as: Why do the pattern. atomic weights were determined by

Harold Clayton Urey and a country schoolhouse in Indiana where he taught after graduating from high school. Urey taught for three years in public schools in Indiana and Montana before he entered Montana State University. (Schoolhouse photo from the Urey collection, AIP Niels Bohr Library.)

PHYSICS TODAY / SEPTEMBER 1982 35 bulk techniques, and the values were ence in the vapor pressures of solid H2 based on setting at 16 the atomic and HD. On this basis Urey expected a weight of the naturally occurring mix- sizeable difference in the vapor pres- 16 17 ture of oxygen isotopes, O , O and sures of liquid H2 and HD at 20.4 K, the 18 O . Thus the atomic weights of a boiling point of H2. single isotope or element on the two Urey approached me at the National scales should differ. The weight Bureau of Standards in Washington, numbers should be greater on the phys- inviting me to join the search for a ical scale. heavy isotope of hydrogen by evaporat- ing 5- to 6-liter quantities of liquid However, in 1931 the atomic weights 3 of hydrogen on the two scales were the hydrogen to a residue of 2 cm of liquid, same within the claimed experimental which would be evaporated into glass errors. The chemical value was flasks and sent by Railway Express to for spectroscopic 1.00777 + 0.00002. The mass-spectro- 10 15 graphic value, determined by Francis examination. At the time, 1931, there W. Aston of the , NUCLEAR ELECTRONS were only two laboratories in the Unit- ed States where liquid hydrogen was was 1.00778 + 0.00015. Birge and Protons versus "nuclear electrons" for 1 30 available in 5- or 6-liter quantities. Menzel pointed out that the near coin- atomic nuclei from H to Si . The plot shows a cidence of these two atomic weights pattern that led Urey to look for a heavy One was the National Bureau of Stan- leads to the conclusion that normal isotope of hydrogen. Open circles represent dards in Washington and the other was hydrogen is a mixture of isotopes—H1 nuclei that were unknown in 1931, when the Giauque's laboratory at the University in high concentration and a heavy iso- chart was produced. of California, Berkeley. I was happy to tope in low concentration. The atomic cooperate, and I prepared—by distill- weight was not higher on the physical ing liquid hydrogen at the Bureau of scale because the mass-spectroscopic termined by comparing the measured Standards—the samples of gas in techniques saw only the light isotope. times required to produce plate lines of which the heavy isotope was identified. To the heavy isotope they gave the H and D of equal photographic densi- The first sample I sent to Urey was symbol H2, perhaps the first time this ties. The exposure times for H/? and Hy evaporated at 20 K and a pressure of symbol occurred in the literature. As- were about 1 second. one atmosphere. It showed no appre- suming the atomic weight of heavy Using cylinder hydrogen, Urey and ciable increase in intensity of the spec- hydrogen to be two, Birge and Menzel Murphy found very faint lines at the tral lines attributed to heavy hydrogen. calculated its relative abundance from calculated positions for D/?, T)y and D<5. This was unexpected. the supposed equivalence of the atomic The lines were faint because of the low The next samples were evaporated at weights of hydrogen-1 on the physical concentration of deuterium in normal a lower temperature—14 K at 53 mm of scale and the normal mixture of hydro- hydrogen. There was a possibility that mercury pressure, the triple point of gen isotopes on the chemical scale. the new lines arose from impurities, or H2—where the relative difference in They obtained 1/4500 for the abun- were grating ghost lines arising from the vapor pressures of H2 and HD was dance of H2 relative to H1. the relatively intense hydrogen Balmer expected to be larger than at 20 K, and Within a day or two at most after spectrum. the rate at which heavy hydrogen is receiving the 1 July 1931 issue of the concentrated was expected to be more Physical Review, Urey proposed and Clinching evidence rapid. planned an investigation to determine Urey decided not to rush into print to These samples showed 6- or 7-fold if a heavy isotope of hydrogen did really stake a claim to priority in this impor- increases in the intensities of the exist. tant discovery; he decided to postpone Balmer lines of deuterium. On this Urey and Murphy, working at Co- publication until he had conclusive evi- basis, it could be concluded that the lumbia, identified hydrogen and its iso- dence that the "new" spectral lines lines in the normal hydrogen spectrum tope spectroscopically, using the attributed to the heavy isotope were attributed to deuterium were really Balmer series lines. The atomic spec- authentic and not impurity or ghost deuterium lines, but the clinching evi- trum was produced with a Wood's elec- lines. This evidence could be obtained dence was finding that the photograph- tric discharge tube operated in the so- by increasing the deuterium concentra- ic image of the Da line—the most called black stage—the configuration tion in the hydrogen filling the Wood's intense D-Balmer line—was a partially of current and pressure that most tube and looking for an increase in split doublet as predicted by theory for strongly excites hydrogen's atomic intensity of the deuterium Balmer lines the Balmer series spectrum. spectrum relative to its molecular spec- relative to the hydrogen Balmer lines. From measurements of the relative trum. They observed the spectra with After careful consideration of differ- intensities of the H and D Balmer a 21-foot grating, in the second order. ent methods for increasing the deuter- series lines, Urey estimated that there The dispersion was 1.3 A per mm. The ium concentration, Urey decided on a was one heavy per 4500 light expected shifts, then, were of the order distillation that would make use of an atoms in normal hydrogen. Later mea- of 1 mm, as the numbers in the table anticipated difference in the vapor surements showed it to be nearer one in indicate. The vacuum of pressures of liquid H2 and liquid HD. 6500. deuterium's lines were calculated us- He made a statistical, thermodynamic ing the Balmer series formula calculation of the vapor pressures of Unraveling a comedy of errors solid H2 and solid HD at the triple point It is now clear why the first distilled l/A =R (l/22-l/n2) (1) H H of H2, 14 kelvins, where the liquid and hydrogen sent to Urey did not show the n = 3, 4, 5,... crystal phases of H2 are in equilibrium I 4 3 expected increase in the deuterium RH = (2ir e /h c)memH/(mf! + mH) and have the same vapor pressure. The concentration, and maybe even showed and the "best" values for the atomic calculation was based on the Debye constants. The Balmer a-lines of hy- theory of solids and the zero-point vi- drogen and deuterium are separated by brational energy of the solid, 9R6/8 in News story on the awarding of the 1934 1.8 A, the /?-lines by 1.3 A, and the y- the Debye notation. At 14 K, the calcu- . Article appeared 16 lines by 1.2 A. The concentrations of lated ratio of vapor pressures, P(HD)/ November 1934. (Copyright The New York deuterium relative to hydrogen are de- P(H2), is 0.4, indicating a large differ- Times. Reprinted by permission.)

36 PHYSICS TODAY / SEPTEMBER 1982 a small decrease. The explanation came with the discovery of the electro- Calculated Balmer series wavelengths lytic method for separating H and D, suggested by Edward W. Washburn, -D) chief chemist at the National Bureau of Line W) calculated observed Standards, and verified8 experimental- (A) (A) (A) (A) a 6564.686 1.787 1.79 ly by Washburn and Urey just after the 6562.899 publication of our April 1932 paper.3 0 4862.730 1.323 1.33 r 4341.723 4861.407 1.182 1.19 When Urey considered different 4102.929 4340.541 1.117 1.12 5 4101.812 methods for concentrating deuterium, These values were calculated using equation 1 with MH = 1.007775 g Mo = 2 01363 g he included the electrolytic method, m0 = 5.491 MO * g and flH = 109677.759 cm ' and discussed it with Victor LaMer, a colleague at Columbia, and a world authority on electrochemistry. LaMer burn, the hydrogen isotopes might be- deficient in deuterium. The concentra- was so discouraging about success in have differently from the isotopes of tion of deuterium in the hydrogen separating hydrogen isotopes by elec- other elements. evolved was about one sixth the concen- trolysis that Urey abandoned the elec- Washburn, the empiricist, was right; tration of deuterium in the electrolyte, trolytic method and adopted the distil- the isotopes of hydrogen are separated and hence about one sixth the concen- lation method. LaMer reasoned that relatively easily by , but tration of deuterium in normal hydro- the differences in equilibrium concen- this was not realized until after the gen. Distillation of the deuterium-defi- trations of isotopes at the electrodes of discovery of deuterium. cient liquid hydrogen increased the a cell at room temperature would be The hydrogen we liquefied and dis- concentration of D relative to H and very small and hence a fractionation of tilled for Urey was generated electroly- restored in the first sample approxi- the isotopes would be negligible. tically. Before preparing the first sam- mately the original concentration of Washburn viewed the situation dif- ple for Urey, the electrolytic generator deuterium in normal hydrogen. ferently. He pointed to the large rela- was completely dismantled, cleaned As electrolysis progressed, water was tive difference in atomic weights of the and filled with a freshly prepared solu- added to replace that which was con- hydrogen isotopes—a relative differ- tion of sodium hydroxide. Because deu- sumed. The concentration of deuter- ence that is much larger for the hydro- terium becomes concentrated in the ium in the electrolyte increased to the gen isotopes than for the isotopes of any electrolyte in the generator, the first point where the rate at which deuter- other element. Hence, thought Wash- gaseous hydrogen to be discharged was ium left the generator balanced the rate at which it arrived in the added water. Hence, after the electrolytic generator had been in use for some time, there was a dynamic equilibrium; 06 so the hydrogen evolved from the gen- NOBEL AWARD GOES erator for our second and third samples FO for Urey had approximately the nor- mal concentration of deuterium. When we liquefied this hydrogen and Con evaporated 5 or 6 liters down to 2 cm3, Columbia Scientist Gets the Si the concentration of deuterium in the residue was increased by a factor of 1934 Chemistry Prize for about six. Discovering '.' Here we lower the curtain on a "com- DIVOI edy of errors"—LaMer's error of not understanding better the principles ACHIEVEMENT WAS HAILED Mrs. that govern isotopic fractionation dur- Th ing electrolysis, and my error of attrib- uting to sloppy technique our failure to Seen as of Especial Value in effect an increase of deuterium concen- Cancer Study—Has Proved tration in the first sample we sent to Spe Urey. Had I analyzed our part of the Great Spur to Research. BUFJ ment i process, I think we might have disco- sions o vered the electrolytic concentration of Wireless to THE NEW YORK TIMES. by Ogd deuterium. Had LaMer been more STOCKHOLM, Nov. 15.—The , Treasu knowledgeable, Urey would have made Nobel Prize in Chemistry for 1934 in add was awarded today to Professor WINS NOBEL PRIZE. welf? his own concentration of deuterium Harold C. Urey of Columbia Uni- Professor . busin electrolytically and I should have had versity because of his discovery of ation no part in the discovery of deuterium. "heavy water." He The chemistry prize for 1933 will DEFENSE TO SUBPOENA der St Reporting the result not be awarded. It was also an- LINDBERGH FOR TRIAL times o nounced that there would be no in times After the discovery of deuterium, Urey faced a very practical problem in prize in physics for this year. Betty Gow Also to Be Summoned would bf Speak reporting it—a problem characteristic Achievement Was Hailed. as Witness—Fight Planned to Mrs. C of the status of research before World Dr. Harold Clayton Urey won a dent War II. Urey's research at Columbia, position in the forefront among Release Haaptmann Funds. urge acientists by his discovery of "heavy prol and ours at the National Bureau of Special to THE NEW YORK TIMES. Standards, where I was chief of the low water," which has been hailed by FLEMINGTON, N. J., Nov. 15.— birt scientists the world over as ranking Colonel Charles A. Lindbergh and unf temperature laboratory, was carried among the great achievements of Betty Gow, w>- ••> fir^t son's out without the support of any govern- jModern science. •urse, will ' • • de ment research grant. It was said that The Willard Gil- Med?' ise •• Chicago section Chemicp' PHYSICS TODAY / SEPTEMBER 1982 37 Dr. * research in that period was done with string and sealing wax; it was in fact done mostly with homemade appara- tus. The US government policy of grants in support of research dates from a later time—from World War II. Before the War it was a problem to find funds for travel to scientific meet- ings. I received a telephone call from Urey, telling me that it appeared he was not going to get funds to travel to the December 1931 American Physical Society meeting at Tulane University, where he planned to present a paper reporting the discovery of deuterium. He asked me if I could get travel funds and present the paper. For this I had to see Lyman J. Briggs, assistant director of research and testing at the Bureau of Standards. Briggs, soon to be named NBS director, was an understanding and considerate who, on learning of the work to be reported, made funds available for my travel. In the meantime, Bergen Davis, a promi- nent physicist at Columbia, heard of Urey's problem and went to see Colum- bia president Nicholas Murray Butler, who made funds available for Urey's travel. So we both went to Tulane for the APS meeting, and Urey presented the ten-minute paper.1 Over the next few months we published more detail 2 in a letter to the editor and a full- Mass spectrometer with Urey at the controls, after the discovery of deuterium. (Photograph 3 length paper in Physical Review. courtesy of King Features Syndicate.) I remember asking Birge at a later APS meeting why he and Giauque had not followed up on his prediction7 of the throughout their lifetime. his earlier mass-spectrographic value existence of heavy hydrogen. They , the English che- of 1.00778 for the atomic weight of might have demonstrated the existence mist who received the 1921 Nobel Prize hydrogen-1 on the physical scale—the of deuterium by concentrating the in Chemistry for discovering the pheno- value used by Birge and Menzel in their heavy isotope through distillation of a menon of isotopy, did not accept the 1931 letter.7 The revised value on the large quantity of liquid hydrogen as notion that deuterium was an isotope of physical scale was 1.00813, which cor- Urey and I had done. Giauque had a hydrogen. Soddy worked with isotopes responds to 1.0078 on the chemical very fine, large-capacity hydrogen liq- of the naturally radioactive elements, scale, in agreement with the then cur- uefier suitable for this. Birge's reply whose atomic weights are large and rent value for the atomic weight of was that he was busily engaged on whose isotopic relative mass differ- hydrogen (1.00777) on the chemical other important work that demanded ences are small. These isotopes showed scale. There was then no need or place his attention. When I told Urey of this no observable differences in chemical for a heavy isotope of hydrogen. The discussion, his comment was: "What in properties and were inseparable chemi- conclusion of Birge and Menzel was the world could Birge have been work- cally. When Soddy coined the word thus rendered invalid. Indeed, on the ing on that was so important?" isotope he gave it a definition that basis of Aston's revised value, Birge Apropos of the above, I quote here included chemical inseparability of iso- and Menzel would have been obliged to from a letter of 6 May 1981 from Robert topic species of the same element. This conclude that, if anything, there was a W. Birge, son of Raymond T. Birge, and was generally accepted before the dis- lighter—not a heavier—isotope of hy- also a physicist: covery of the neutron in 1932. drogen. After reading some more about my After the , The prediction of Birge and Menzel father's life, I think I know why he isotopes were denned as atomic species of a heavy isotope of hydrogen was didn't try to concentrate deuter- having the same number of protons in based on two incorrect values for the ium. I believe he was an analyst their nuclei but different numbers of atomic weight of hydrogen, namely As- more than a hardware builder and . But Soddy stuck to chemical ton's mass-spectrographic value and it probably never occurred to him inseparability as a criterion for iso- the chemical value, which also should to do it that way. He said that at topes and therefore refused to recog- have been greater. We are obliged to the time several people were try- nize deuterium as an isotope of hydro- conclude that the experimental error ing to see the deuterium lines in gen. For Soddy, deuterium was a in the determination of the atomic spectra, but they [Urey, Brick- species of hydrogen, with different weights exceeded the difference in the wedde and Murphy] did it first. atomic weight, but not an isotope of atomic weights on the two scales. But as you know, the important hydrogen. Urey was not aware of this when he point was that Urey realized that planned his experiment. It was not [the concentration of] deuterium A fortunate mistake until 1935 when Urey's Nobel lecture could be enhanced. Four years after the discovery of was in proof that Aston published his The two men remained friends deuterium, Aston reported9 an error in revised value. Urey added the follow-

38 PHYSICS TODAY / SEPTEMBER 1982 NEW PRODUCT ing to the printed Nobel lecture: developed for the depen- Addendum dence of physical and chemical proper- CHARGE SENSITIVE Since this [Nobel lecture10] was ties were tested experimentally. These PREAMPLIFIERS written, Aston has revised his investigations were especially interest- mass-spectrographic atomic ing because, before the discovery of weight of hydrogen (H) to 1.0081 deuterium, chemical properties were instead of 1.0078. With this mass generally supposed to be determined by for hydrogen, the argument by the number and configuration of the Birge and Menzel is invalid. How- extranuclear electrons, quantities that ever, I prefer to allow the argu- are identical for isotopes of the same ment of this paragraph [the third element. It had not been realized that paragraph of Urey's Nobel lecture] chemical properties are also affected— to stand, even though it now ap- but to a lesser degree—by the mass of pears incorrect, because this pre- the nucleus. diction was of importance in the In thinking about Urey's search for Models A-101 and A-111 are charge discovery of deuterium. Without deuterium, beginning with his early sensitive preamplifier-discriminators it, it is probable we would not have diagram of the isotopes, I am reminded developed especially for instrumenta- made a search for it and the discov- of the Greek inscription on the facade tion employing photomultipliertubes, ery of deuterium might have been of the National Academy of Sciences channel multipliers (CEM), delayed for some time. building in Washington, taken from microchannel plates (MCP), channel Needless to say, Urey and his collea- Aristotle: electron multiplier arrays (CEMA) and gues were very glad that an error of The search for truth is in one way other charge producing detectors in this kind had been made. Aston said hard and in another easy, for it is the pulse counting mode. that he did not know what the moral of evident that no one can master it it all was. He would hardly advise fully or miss it wholly. But each people to make mistakes intentionally, adds a little to our knowledge of and he thought perhaps the only thing nature, and from all the facts as- to do was to keep on working. sembled there arises a certain grandeur. Impact of the discovery * * * It has been said that Nobel prizes in / wish to acknowledge the valuable assis- physics and chemistry are awarded for tance of my wife, Langhorne Howard Brick- work, experimental or theoretical, that wedde, especially for her help in recalling Models A-203 and A-206 are a has made a significant change in ongo- incidents of the early thirties connected with the discovery of deuterium. This article is Charge Sensitive Preamplifier/Shap- ing work and thinking in science. The based on a paper I presented 22 April 1981 in ing Amplifier and a matching Voltage announcement that Urey was chosen Baltimore, Maryland, at the inaugural ses- Amplifier/Low Level Discriminator as the 1934 laureate in chemistry came sion of the American Physical Society's Divi- developed especially for instrumenta- less than three years after that ten- sion of . tion employing solid state detectors, minute paper in New Orleans announc- proportional counters, photo- ing the discovery of deuterium. This References multipliers or any charge producing uncommonly early award followed a 1. The thirty-third annual meeting of the detectors in the pulse height analysis spectacular display in deuterium-relat- American Physical Society at Tulane or pulse counting mode of operation. ed research. In the first two-year peri- University, 29-30 December 1931. Ab- od following the discovery, more than stracts of papers presented: Phys. Rev. 100 research papers were published on 39, 854. Urey, Brickwedde and Murphy or related to deuterium and its chemi- abstract #34. l cal compounds, including heavy water. 2. H. C. Urey, F. G. Brickwedde, G. M. And there were more than a hundred Murphy, Phys. Rev. 39, 164 (1932). HH-l fffffff more11 in the next year, 1934. 3. H. C. Urey, F. G. Brickwedde, G. M. The use of deuterium as a tracer Murphy, Phys. Rev. 40, 1 (April 1932). made it possible to follow the course of 4. For an interesting account of the discov- ery of deuterium, see G. M. Murphy, chemical reactions involving hydrogen. FEATURING "The discovery of deuterium," in Isoto- Thin film hybrid technology This was especially fruitful in investi- pic and Cosmic Chemistry, H. Craig, S. L. Small size(TO-8, DIP) gations of complex physiological pro- Low power (5-18 milliwatts) Miller, G. J. Wasserburg, eds., North- Low noise cesses and in medical chemistry, as in Holland, Amsterdam (1964). (Dedicated Single supply vollage 168 hours of burn-in time the breakdown of fatty tissue and in to Urey on his seventieth birthday.) MIL-STD-883/B cholesterol metabolism. 5. A. B. Lamb, R. E. Lee, J. Am. Chem. Soc. One year warranty Also, the discovery of heavy hydro- 35, part 2, 1666 (1913). APPLICATIONS Aerospace gen provided a new projectile, the deu- 6. W. F. Giauque, H. L. Johnston, J. Am. Portable instrumentation teron, for nuclear bombardment ex- Chem. Soc. 51, 1436, 3528 (1929). Mass spectrometers Particle detection periments. The deuteron proved 7. R. T. Birge, D. H. Menzel, Phys. Rev. 37, Imaging markedly efficient in disintegrating a Research experiments 1669 (1931). Medical and nuclear electronics number of light nuclei in novel ways. 8. E. W. Washburn, H. C. Urey, Proc. Nat. Electro-optical systems As the deuteron, with one and Acad. Sci. US 18, 496 (1932). one neutron, is the simplest compound 9. F. W. Aston, Nature 135, 541 (1935); nucleus, studies of its structure and of Science 82, 235 (1935). its proton-neutron interaction took on 10. H. Urey in Nobel Lectures in Chemistry, fundamental importance for nuclear 1922-1941, published for the Nobel AMPTEK INC physics. Foundation by Elsevier, Amsterdam 6 DeAngelo Drive Many of the early research papers (1966). Bedford, Mass. 01730 U.S.A. dealt with isotopic differences in phys- 11. Industrial and Engineering Chemistry, Telephone: (617) 275-2242 ical and chemical properties. Theories News Edition 12, 11 (1934). • With representatives around the wor/d Circle number 21 on Reader Service Card PHYSICS TODAY / SEPTEMBER 1982 39