THE JOURNAL OF
PHYSICAL CHEMISTRY (Registered in U. €3. Patent Office)
VOLUME63
(0Copyright, 1959, by the American Chemical Society)
JUNE 24, 1959
NUMBER6
SAMUEL COLVILLE LIND Born June 15, 1879
Samuel Colville Lind was almost eight years old for advanced work. Since the Massachusetts Inwhen the Zeitschrift fur physikalische Chemie was stitute of Technology had then the outstanding unfounded by Ostwald in Leipzig. Since the latter dergraduate course in chemistry in this country, event is often considered to mark the birth of Lind went there in 1900, received an S.B. degree in Physical Chemistry as a separate discipline, he is 1902 and returned in 1903 as an assistant, teaching some ten per cent. older than the subject of his ca- Advanced Analysis under H. P. Talbot. In 1904 M.I.T. granted Lind a Dalton Traveling reer. He was born on June 15, 1879, to Thomas Christian Lind and Ida Colville Lind, the latter a Fellowship, which he used to go to Ostwald’s native of McMinnville, Tennessee, the former a na- laboratory in Leipzig for a Ph.D. By that time tive of Sweden. Thomas Lind, a mate on one of Ostwald had almost disengaged himself from lechis father’s ships at nineteen, left the sea in New turing and research, and the choice of thesis proYork to join the Union Army in the Civil War. fessors in Physical Chemistry lay between Luther, After the war he was sent by his employers, the the electrochemist, and Bodenstein, the kineticist. Pennsylvania Oil Company, to find whether the gas The former was the favorite with the graduate bubbles rising from the Barren Fork of the Collins students, perhaps because Bodenstein’s problems, in River a t McMinnville were a sign of petroleum. gas kinetics, were more difficult experimentally and When test drilling failed to disclose any, he aban- perhaps partly because Bodenstein, being indedoned the oil business in disgust, read law in Mc- pendently wealthy, was somewhat more aloof. Minnville, married a local girl and settled down to Lind approached Luther for a thesis problem but practice law in that small, Middle Tennessee county found that he could accommodate no more stuseat, where his oldest child, Samuel Colville, was dents that year. Turning, therefore, to Bodenstein, born and grew up. he was assigned the kinetics of the thermal reaction After graduating from high school, Lind was sent of bromine with hydrogen. Quite in contrast to to Washington and Lee University a t the instiga- the simple, second-order kinetics shown by hydrotion of an alumnus, the superintendent of the gen and iodine, the results for bromine and hydroMcMinnville High School. It would have been gen could only be fitted by an equation with two natural for him to study law, but his father advised numerical constants, a square root dependence on against it because the prospects for young lawyers bromine and a function of hydrogen and bromine in the South seemed to be declining. He elected a concentrations in the denominator. This new kigeneral course in college, studying primarily classics netic equation remained unexplained for thirteen for three years. As EL senior, he found that he years, being finally interpreted independently by needed six points in science or mathematics for Christiansen, Polanyi and Herzfeld by an atomir graduation, and only for that reason elected the chain mechanism. After receiving the Ph.D. for elementary course in chemistry. this work in 1905, Lind was offered an appointment This course determined Lind’s future career. It as assistant a t Leipzig, but the salary was too small was taught by Jas. L. Howe, Professor of Chemistry for subsistence, and his mother, fearing his expatriaa t Washington and Lee from 1894 to 1937 and an tion, declined to assist him. He, therefore, reactive chemist (platinum metals, especially ruthe- turned to America in 1906 and accepted an instrucnium) until 1955 when he died a t the age of 96. torship at the University of Michigan. Here he He presented the subject so attractively that Lind taught General and Physical Chemistry and conreturned for a fifth year in order to prepare himself ducted research in analysis and in solution kinetics. 773
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SAMUEL COLVILLE LIND
Michigan then had a plan by which a faculty member could take a year offwith salary after only five at the university, by teaching summers without pay. Lind did this and in 1910 left for a year in Marie Curie’s laboratory in Paris. Radioactivity was the newest thing in and he wished to learn about it a t the source. Although n’fadame Curie was largely occupied in writing her “Trait6 de RadioactivitB” in 1910, she continued to deliver her lectures on radioactivity, and the Chef de Laboratoire, Andre Debierne, with William Duane, introduced Lind to experimental radioactivity, Duane, from the University of Colorado, had been instrumental in obtaining money from the Carnegie Foundation for the curie laboratory and was at that time concluding his setond staythere. LindJs research was on the induced combination of hydrogen and bromine and the decomposition of hydrogen bromide, the latter as well as in in the liquid and in aqueous the gas. H~ moved to the new Institut fiir R ~ diumforschung in vienna for the last part of his leave, working with Stefan M~~~~and Victor F. Hess (now at Fordham), the discoverer (1912) of cosmic rays, H~~~Lind carried out the first research in which the amountof ionization and the amount of chemical change were directly compared, namely, the ozonization of oxygen by a-rays. Lind returned to Ann Arbor as assistant professor, with the intention of initiating chemical work with a-particles in this country. He recalculated previous results by Cameron and Ramsay, by Usher, by Debierne, and by himself, and showed that there was a close equivalence between the amount of chemical reaction and the number of gaseous ions formed by the a-particles. He was unable, however, to obtain support for experimental work in this field (radium at that time cost Over $1oo,ooo per gram), and in 1913 he accepted a sition with the Bureau of Mines at Denver, colarado, where a group under R. B. Moore was building a plant to isolate about eight grams of radium from carnotite. This undertaking ivas sponsored jointly by the Bureau of ~i~~~ and the newlyformed National Radium Institute, a creation of H. A. Kelly and J. Douglas, of Baltimore and New York, respectively, who intellded to use the radium ill experimental therapy, Lind, of course, took part in the chemical developments necessary to the process, but, as the expert in radioactivity, his principal effortswere devoted to radioactive measurementsand to the handling of the material in the final stages of purification, He \vas, for instance, responsible for the division of each batch of final Product into two equal Parts for shipment to the two sponsoring hospitals. AS a result of these operations he carries about a tenth of a microgram of radium in his system, apparently not to his detriment, a t least in Comparison to ordinary Persons. By the end of the production operations, about half a gram (of a total of 8.9) was in excess of the contract requirements, and Lind was able to employ it in studies of chemical changes. It was loaned to him when he left the Bureau of Mines, accompanying him to his subsequent posts, even to the present, where it is in use by Lind and his colleagues
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a t the Oak Ridge National Laboratory. Some thirty-five research papers have described work done with this sample of radium, While in Denver, he married Marie Holliday, an Omaha girl, whose ,.,harm and graciousness have complemented his own in all of his subsequent life. They have one son, Thomas Colville Lind, and three grandchildren. The boy is his grandfather’s favorite fishing companion on his visits to Oak Ridge. The Bureau of Mines station at Denver was moved first to Golden, Colorado, in 1916 and then in 1920 to Reno, Nevada, as the Rare and Precious Metals Experiment Station, with Lind in charge. In Ig23 he moved to Washington, D. succeeding R. B. Moore as chief chemist of the Bureau of Mines. Finally, in 1925, he left to become aSSOCiate director Of the Fixed Nitrogen Laboratory of the Department of Agriculture. I n 1926 Lind was - called from Washington to become Director of the School of Chemistry of the University of Minnesota, returning thus to academic life after thirteen Years in Government service. After nine further years he was made Dean of the Institute of Technology, where he continued until his retirement, in 1947. Lind wished to return to Tennessee after retiremerit, and, therefore, sought a position with the Union Carbide Corporation, which operates the atomic energy facilities in Oak Ridge for the Atomic Chmission. He was made a technical COllSUltant to c. E. Center, a t that time the general superintendent for Union Carbide in Oak Ridge- Although L i d ’ s headquarters were at the Gaseous Diffusion Plant, most of his attention Soon Came to be directed to the Oak Ridge National Laboratory, where the largest part of the research in Oak Ridge is conducted, and since 1951 he has been in almost full-time residence there. From 1951 to 1954 he was acting director of the Chemistry Division of the Laboratory and since then he has been a consultant to the Laboratory, as well as to the vice-president. He iS (with two associates) revising and enlarging his ACS Monovraph, “The Chemical Effectsof Alpha Particles and Electrons” to make it a comprehensive treatise on experimental results in radiation chemistry. The original edition was the second monograph to be published by the American Chemical Society and, with its revision in 1928, has been the standard reference on the subject. He also continues to direct research in experimental radiation chemistry of gases. Lind’s connection with scientific publicatiolls started with Chemical Abstracts, for which he was an abstracter from 1908 through 1911 and 1915 through 1921, and an assistant editor (in charge of “Subatomic Phenomena and Radiochemistry”) from 1922 through 1929. He has been an associate editor of the Journal of lhe American Chemical Societg and a member of the Board of Editors of the American Chemical Society Series of Chemical Monographs. In 1933 he assumed the editorship of the Journal of Physical Chemistry from its founder, W. D. Bancroft. He edited it from Minnesota until 1947, when he moved the editorial of-
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SAMUELCOLVILLE LIND
fices to Oak Ridge. He continued as editor until 1951. Numerous prizes, offices and other honors have accrued to Lind. He was president of the Electrochemical Society in 1927 and vice-president (Section C-Chemistry) of the American Association for the Advancement of Science in 1930. He was president of the American Chemical Society in 1940. He received the Nichols Medal of the New York Section of the American Chemical Society in 1926 in recognition of his work on chemical activation by a-particles, and the Priestley Medal of the American Chemical Society at the Diamond Jubilee Meeting of the Society in 1951 in New York. He was elected to the National Academy of Sciences in 1930 and for some years after returning to Tennessee was the only member residing in that state. The positions and honors which Lind has received testify to his distinction as a scientist and his ability as a teacher and administrator. Since his scientific work so typifies the spirit of physical chemistry, it may be permissible to attempt a brief recapitulation. Growing up, scientifically, in the middle of the development of physical chemistry, he has quite naturally remained an experimental physical chemist throughout his career. Well over a hundred papers have resulted from his research, the largest part of them dealing with reactions under a-particle radiation or in the electric discharge. His principal collaborators have been D. C. Bardwell, G. Glockler, R. S. Livingston and C. H. Shiflett. In addition, he has authored several papers on related subjects, numerous reviews, and another book, “The Electrochemistry of Gases,” with George Glockler. His primary concern has been careful measurement and simple transformation of the results into terms (rate equations, M/N ratios, etc.) that can be used in compilation and in theoretical speculations. Wherever needed, he has supplied new techniques or ingenious improvements. The thin-walled a-ray bulb (developed with Duane, following earlier experiments with thin capillaries by Rutherford) and the Lind electroscope are tributes to his skill and ingenuity. His thesis, under Bodenstein, stands as one of the classics of chemical kinetics, and repetition with newer information and apparatus has merely confirmed the results which he obtained fifty-four years ago. Lind has been equally careful and ingenious in drawing conclusions from his experimental results. Sometimes, as in his thesis, these have been simply crystallizations of the data into empirical equat,ions, but these have withstood time and re-examination. Sometimes, his results have revealed new phenomena such as the catalysis of radiation effectsby inert gases, or the effect of recoilsin a-ray reactions. He has hunted such discoveries, as well as contradictions and anomalies, out of his own work and that of others with almost unerring aim. He suggested in 1911, from evidence in his experiments, the existence of indirect action of radiation upon a solute, a concept that is central to most radiation chemical work with solutions and to most of radiobiology. The thread of all his work has been the importance of ionization in radiation-induced reactions.
775
This concept was not original with him, but he recognized its probable soundness and its usefulness as a working hypothesis. He provided the first careful measurements designed to test it (the ozonization of oxygen), and a whole series of experiments to explore the effect of chemical variation. He correlated these results in terms of molecules reacting per ion-pair formed in the gas (M/N) and observed regularities in behavior, from simple reactions for which M/N was a small number to cases of obvious chain reaction (Hz Clz) for which M/N was very large. Directed by such observations and by physical evidence for clustering of molecules about gaseous ions, Lind put forward in 1923 a “cluster hypothesis” for radiation-induced reactions, in which the chemical action took place within a cluster of molecules as a result of the energy liberated by neutralization of oppositely charged ions. The concreteness of this hypothesis and its success in accounting for numerous results led it to be widely used, among others by Mund, by Rideal, and by Brewer and Westhaver. A few critical experiments were suggested, by Lind and by others, but were not feasible because of the short molecular or ionic free path in gases a t pressures where chemica,l reactions could be followed. Rapid developments in kinetics during the next few years brought the role of atoms and radicals in thermal and photochemical reactions to attention, and in 1936 J. 0. Hirschfelder, H. Eyring and H. S. Taylor showed that two a-ray reactions could be explained without invoking clustering. This marked a turning point in the theory of radiation chemistry, since it showed that no special behavior different from that demonstrated for other types of activation needed to be assumed. Although Lind was undoubtedly attached to the cluster hypothesis, he recognized the merits of the (by then) more conventional explanation and retained the cluster hypothesis only for cases where the newer mechanism did not seem t o work. Mainly because gas reactions were little studied during the war, when radiation chemistry achieved its present, greatly enlarged status, the role of ions, except as fleeting, initial products began to be neglected. More recently, experiments in mass spectrometers a t higher than usual pressure have begun to show the wide occurrence and large probability of ion-molecule reactions, and the most recent research in gae-phase radiation chemistry has shown that ion-molecule reactions are probably highly important. Thus, the essence of Lind’s approach, the importance of ions as reacting species, and the importance of measuring the ions (because they alone of the activated primary species can be quantitatively measured, even now) is again proving fruitful. Although Lind was not unaware of the revolution in physics which has occurred during his lifetime, and of its impact upon chemistry, he has remained essentially an experimental physical chemist, devoted to the experimental discovery of regularities in chemical behavior. A few incidental remarks in his papers suggest that he could as well have approached chemistry from the theoretical viewpoint. Thus, the electronic picture he suggested in 1923
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RUSSELL R. WILLIAMS, JR.
for coloration and thermoluminescence is remarkably sensible in present-day terms, and the discussions of nuclear physics, photochemistry and other topics in some of his reviews reveal a most lucid grasp of modern theoretical developments. The quick, penetrating intelligence which shows throughout his writing and appears daily in his conversation about science, world affairs, or people, could have brought him success in ‘any field. Since he elected to apply his talents to physical
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chemistry, he is now, as he has been for more than fifty years, one of the foremost physical chemists of his time, It remains only to wish Lind a happy eightieth birthday and continued happiness and success. The papers in this Jubilee Issue are but an insignificant token of the esteem and affection in which he is held by his colleagues. OAKRIDQENATIONAL LABORATORY ELLISON H. TAYLOR OAK RIDQE,TENNESSEE
CHEMICAL EFFECTS OF LOW ENERGY ELECTRONS‘ BY RUSSELLR. WILLIAMS, JR. Haverford College, Haverford, Pa. h’eceiued October 16,1068
A new technique has been developed for the study of chemical decomposit,ion of gases by low energy electrons. Ultraviolet light falling on a silver surface generates photoelectrons which are accelerated in the gas by application of an electric field. The electron yields of products formed by irradiation of methane and ethane have been examined as a function of applied potential and the behavior of the systems suggests that an important primary process is non-ionizing excitation by electron impaet.
It has been presumed for some time that radiolysis by high energy electrons produces chemical reaction by excitation2 as well as by ionization although most of the mechanisms proposed have emphasized the importance of ionization as the primary process, relegating excitation to an undetermined role. This report describes the first results of a new attempt to investigate the chemical effects of electrons of such low energies that ionization will be impossible or inefficient. The prior literature reveals several instances in which chemical decomposition by electron excitation appears to occur. Essex and his collaboratorsa found that the ion-pair yield in the alpha radiolysis of gaseous ethane was increased by the application of an electric field in a manner which led them to conclude that electron excitation was responsible for the increase. In like manner Meisels, Hamill and Williams4found that the ion pair yield in the X-radiolysis of methane in argon was increased by application of an electric field. Kiser and Johnston6 have analyzed the products and determined electron yields in Geiger-Muller discharge in ethanol-argon and 2-propanol-argon mixtures. They find, respectively, 285 and 56 molecules decomposed per electron collected. They conclude that the magnitude of these yields indicates a primary process of excitation rather than ionization. Mechanisms of decomposition in electric discharge have been proposed6which depend heavily on excitation as a primary process. (1) Work supported by a special grant from the Board of Managers of Haverford College. (2) In the present context the use of the term excitation will be confined to processes which do not result in positive ion formation in the initial act or in any subsequent unimolecular process. (3) E.o., N. T. Williams and H . Essex, J . Chem. Phy;., 17, 995 (1949). (4) G. G. Meisels, W. H. Hamill and R. R. Williams, Jr., THIB JOURNAL, 61, 1456 (1957). (5) R. W. Kiser and W. H. Johnston, J . A m . Chem. Soc., 78, 707 (1956): 79, 811 (1957). (6) E.@.,M.Burton and J. L. Magee, J . Chem. Phys., a8, 2194, 2196 (19651.
In the present investigation low energy electrons are introduced into a gas via the photoelectric effect from a metal surface. The electrons then are caused t o drift through the gas by application of an adjustable electric field. Chemical decomposition is determined as a function of applied potential per unit gas pressure.
Experimental Apparatus.-The reaction chamber consists of a cylindrical silver cathode 12 mm. in diameter X 120 mm. in length centered in a cylindrical anode 29 mm. in diameter X 120 mm. in length constructed from 18 mesh bronze screen. Thus the electrode sprtcing is 8.5 mm. with a maximum variation of ca. i 1 mm. This electrode assembly is encased in a Vycor 7910 jacket with appro riate gas and electrical connections as shown in Fig. 1. iome care must be exercised to avoid discharge points on the electrodes and leads. The reaction chamber is inserted within the coil of a Hanovia SC2537 mercury resonance lamp formed from 10 mm. quartz tubing shaped in the form of a four turn helix with inside diameter 50 mm. and length 100 mm. The radiation from the lamp passes through the Vycor jacket, through the screen anode and falls on the surface of the silver cathode as shown in Fig. 1. Power for the mercury resonance lamp is furnished by a 5000 volt transformer operated from a variable transformer in the primary. The electrode potentials for the reaction chamber are furnished by the d.c. supply of a GeigerMuller counting circuit and a d.c. microammeter is placed between the cathode and ground to permit measurement of the photoelectron currents, which ranged from 2 to 100 microamp. Preliminary tests on several metals resulted in the selection of silver for its relatively high photoelectron efficiency. After pretreatment of the silver by high voltage, high frequency discharge in hydrogen at ca. 1 mm. pressure the vacuum photoelectron current, collected with an applied potential
