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T H E INFRASTRUCTURE O F IR ~ P E C T R O M E T R Y : ~

R t m i n k mS q P M und Eudy Foil A. Miller Department of Chemistry University of Pittsburgh Pittsburgh, PA 15260

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The Third James 1. Waters Annual Symposium Recognizing Pioneers in the Development of Analytical Instrumentationwas held at the 1992 Pittsburgh Conference and Exposition in New Orleans. This year‘s symposium honored five pioneers in the field of infrared spectrometry: Paul 1. Wilks, Jr., Foil A. Miller, Norman Sheppard, Peter R. Griffiths, and Bryce 1. Crawford. In our September issues, we present adaptations of the talks given by four of these innovators. Here Wilks describes the evolution of commercialR I spectrometers and Miller discusses the infrastructure of R I spectrometry. In the Sept. 15 issue, Sheppard discusses the United KingdomS contributions to R I spectroscopic instrumentation and Griffiths describes the remarkably circular development of commercial FT-IR instruments. 824 A

“Infrast ru et ure: t he bas ic und erly ing framework of something, especially of a technological kind. . . ” (1). Many things had to be in place to make it feasible to manufacture commercial IR instruments and to catalyze the rapid growth of their use. It had to be known that they would provide useful information. Suitable optical and electronic components had to be available. There had to be knowledgeable users, a need that was filled by special training courses, meetings, and books. There also had to be good sample-handling techniques. I call this ancillary material the infrastructure of infrared spectrometry; it was the support system that underlay the success of the technique. In this REPORT I will review the development of this infrastructure and include reminiscences of some pioneers and early commercial IR instruments. Jones (2) has presented two excellent historical re views of vibrational spectroscopy.

Essential preliminaries By 1940 there was a large body of knowledge concerning IR spectros copy. The IR region was known to extend from the visible to the Hertzian portion of the spectrum. Rubens and Paschen and their students had explored the far - IR region, and Nichols and Tear (3)had linked it to “electric wave spectra’’ at 0.4 mm or 25 cm-’. Indices of refraction of useful prism materials were known, and gratings had already been employed in IR spectroscopy. There were usable detectors and amplifylng systems. The theory of vibrational spectra was understood reasonably well, and it was known that IR spectra were potentially useful to chemists. There was just one problem: In 1940 no IR instruments were commercially available except for a small and unsatisfactory one that Adam Hilger Ltd. first marketed in 1913.In 1938 only about 15 IR instruments were opera-

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tional in the United States (41, and I suspect that every one of them was homemade. Three preliminaries warrant special comment. The first concerns materials for prisms and windows. Initially, natural rock salt was the most widely used substance, but it was not entirely satisfactory because of impurities, imperfections in the crystals, and uncertain supply. Van Zandt Williams once told me an interesting story of how the IR group at American Cyanamid Co. obtained crystals of Russian rock salt. In about 1939 he and one or two others went to the Amtorg Trading Corporation in New York City, which was then the Soviet Union’s business agent in the United States, to inquire about buying natural sodium chloride crystals mined in the USSR. The salesman said that they could be provided and asked what size pieces were wanted. After a brief consultation among the Cyanamid people, one of them held out his forefingers to indicate two sizes of blocks that would be appropriate. One size would provide material for windows and cells, and several larger blocks would be used to make prisms. The salesman took out a ruler, measured the spacings carefully, and noted them on the order. Nothing was heard for a very long time. Finally, more than a year later, an urgent message was received. If they wanted their rock salt, they should come immediately to New York City, take a small boat out to a certain ship in the harbor, and pick up their purchase. The reason for the haste was that World War I1 was about to start in Europe, and the Soviets wanted to get their ships back to home ports as quickly as possible. In fact, this was the last Soviet ship to leave New York. The packagesseveral wooden boxes of about 1 ft. in each dimension-were lowered over the ship’s rail to the recipients in a small boat below. When they were opened back at the laboratory, each box contained a number of neatly wrapped blocks of rock salt. Each block had been cleaved to the exact size that had been indicated in such an impromptu fashion. The buyers realized then 0003-2700/92/0364-824A/$03.00/0 0 1992 American Chemical Society

that they could have asked for any size within their wildest dreams and would have received it. This supply lasted Cyanamid laboratories for many years. Robert S. McDonald remembers sawing a prism blank from one of the larger pieces with a wet string saw. Fortunately, methods for growing large single crystals were developed in time to make them available when needed. In 1930 John Strong grew the first large alkali halide crystals in this country; they were composed of KBr, KC1, and KI (5).Many people later became involved, and synthetic crystals of the alkali halides, CaF, and BaF,, as well as other useful materials, became commercially available-notably from t h e Harshaw Chemical Company of Cleveland. The second important preliminary was the availability of excellent and inexpensive mirrors. In 1835 Justus von Liebig developed t h e f i r s t method of chemically silvering mirrors. This capability was important because it allowed the superior reflectivity of a metal to be combined with the mechanical stability and polishability of glass. His method, however, resulted in back-surfaced mirrors t h a t were useless for IR work because of the absorption of glass. John A. Brashear, a noted optician in Pittsburgh, invented a method for making front-surfaced mirrors by chemical silvering (6). (Brashear also developed the technique for optically finishing rock salt surfaces.) Unfortunately, silver coatings tarnish and therefore do not have long-term stability. I n 1932 Strong developed t h e method of making mirrors by vacuum evaporation of aluminum (6),a n important advance. Strong was also a pioneer in preparing antireflective coatings that were the basis for some of the special filters used later for the separation of grating orders. The third preliminary was t h a t three U.S. industrial laboratories had realized the usefulness of IR spectroscopy for chemistry and had research teams who built their own instruments. These labs were American Cyanamid Co. research laboratories, led by R. Bowling Barnes, whose team included Van Zandt Williams,

Urner Liddel, Robert C. Gore, Robert S. McDonald, a n d N o r m a n B. Colthup; Shell Development Co., whose IR team leaders were Robert R. Brattain and R. S. Rasmussen; and Dow Chemical Co., led by Norman Wright. Publications describing the instruments from these laboratories and their applications were important in publicizing the potential of IR spectroscopy. Finally, three programs of great importance during World War I1 provided the impetus to begin the manufacture of IR instruments: the synthetic rubber program, largely a U S . project; the production of aviation fuel, primarily a U.K. project; and the penicillin program, a joint U S U.K. endeavor. These programs prompted the U.S. government to contract with Beckman Instruments (then called National Technical Laboratories) and Perkin Elmer to build IR spectrometers during World War 11. The first successful commercial IR spectrometers descended from these instruments.

Beckman shipped its first IR instrument, the IR- 1, on Sept. 18, 1942 (7), and Perkin Elmer shipped its first, the Model 12A, in 1944. The growth in the use of IR spectroscopy was explosive. It has been said that four industrial IR spectrometers were in use a t the beginning of World War I1 and approximately 400 a t the end (8).Alternatively, Lecomte estimated t h a t the number of operational IR spectrometers in the United States increased from 15 in 1938 to more than 500 in 1947. Of these, 400 were being used in analytical laboratories (4). Using an early IR instrument I will digress to describe what it was like to use one of the early commercial IR instruments: t h e Perkin Elmer Model 12B. The original Model 12A employed a galvanometer and made point-by-point measurements of spectra. In March 1945 I received a quotation of $1900 to add a dc breaker amplifier and an auto-

matic recorder. These parts, plus a motor drive, were the main components of the upgrade to the Model 12B. Our 12B was obtained in 1945 by the chemistry department at the University of Illinois. It was a singlebeam instrument that was not linear in anything useful-pm, cm-l, %T, or absorbance. Extensive replotting of the raw data was therefore necessary to obtain a real spectrum. There was no chopping of the radiation, but the instrument did have a strip chart recorder so that the spectrum could be scanned, which I regarded as a wonderful feature. The usual procedure was to convert the abscissa scale to wavelength or wavenumber. The Littrow mirror was rotated by a gear mechanism, and pip marks were automatically put on the pen trace a t equal increments of rotation. These marks had to be calibrated against reference spectra of gases such as NH,, HCl, CO,, and water vapor. The ordinate was proportional to the signal reaching the thermocouple. This signal was essentially the blackbody emission of the source as modified by the transmission of the prism and the windows, with the absorption of the atmosphere and the sample superimposed. The procedure was to make a scan with a reference cell to obtain the reference signal (I,), and then to make a scan with the sample to measure the sample signal (I).For both scans, the position of the zero line had to be checked frequently by inserting an opaque shutter in the beam. Zero moved because the thermocouple responded to any change in temperature, not just to the heat delivered by the radiation beam. A baseline was drawn between these zero positions, and from it the height of the sample signal and the corresponding height of the reference signal (I,) were measured with a ruler at each pip mark. The ratio I N , was the transmission, which was then plotted on a separate sheet of graph paper against the wavenumber value for that pip mark. It was hoped that conditions were the same for both runs. One had to work hard to run and plot two spectra a day. But it was even worse than this

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REPORT because the thermal drift was horrible. The early instruments used dc thermocouples, which were extremely sensitive and responded to any change in temperature. Although they had a compensating junction that was shielded from the light beam and was supposed to cancel the effect of ambient temperature changes, t h e compensation was wildly inadequate. If one lit a match and held it near the instrument housing, the pen moved. I had a corner laboratory at Illinois that was heated by steam radiators. When the steam came on, the baseline climbed upward and went off the paper if zero was not reset. The spectrum was therefore run in many short segments so it could be kept on scale. When the steam went off, the room cooled and the process was reversed. Thus it was absolutely essential to check zero frequently and to draw a sloping baseline for both reference and sample. Initially, Per kin Elmer provided a thick white felt liner for the housing in the hope that this would reduce the effect, but it gave off so much water vapor that I threw it away. These experiences have been described in some detail because I believe that today’s researchers do not fully appreciate the vast advances made by the instrument manufacturers. There was one good thing about the early instruments, however, especially the single - beam ones: A per son had no compunction about taking off the lid and tinkering with the optics and the electronics. In fact, most

Robert R. Brattain (known as “Breezy“ Brattain) had a policy of ordering serial number 7 of a new instrument. He assumed that six would be manufactured in the initial batch, that problems would be found and rectified, and that he would obtain the first of the second group. This policy greatly irritated Howard Cary, because he knew he had an assured sale of a new instrument if only he could dispose of the first six.

users did so frequently. I have realigned all the optics, using the Foucault knife-edge test to focus the parabola. I have provided a new getter for the thermocouple and reevacuated it, attached a small vacuum pump t o t h e thermocouple a n d pumped on it continuously, or just replaced the thermocouple and refocused on it. The contacts on the breaker amplifier were cleaned frequently. The instrument was no black box; we knew what was going on inside it. Howard Cary, who designed superb instruments for Beckman Instruments and later for his own firm, Cary Instruments, had the opposite philosophy. His products were built like battleships-very solid-and cover plates were held on with hundreds of screws. He said t h a t he didn’t want amateurs getting into his instruments and therefore made it

Norman B. Colthup in 1950 operating a Perkin Elmer Model 12C spectrometer equipped with a General Motors breaker amplifier and a Lee& and Northrup recorder. 826 A

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quite difficult, or at least tedious, to do so. Advances in instrumentation Once IR instruments became commercially available in the mid- 1940s, several important follow-ups contributed to the rapid growth of the field. Vigorous competition among instrument manufacturers led to steady improvement in performance and easier use of the instruments. Other developments included the training of users by special short courses, the appearance of some excellent books, the organization of stimulating meetings, and the development of usehl sampling methods. Shortly after the end of World War I1 there were many important advances in IR instrumentation. First was the development of the HornigHargreaves-O’Keefe thermocouple and Max Liston’s dc breaker amplifier. Faster thermocouples became available later that permitted the use of chopped radiation (10-13 s-’) and tuned ac amplifiers. This vital step forward solved the problem of thermal drift. In addition, much - improved electronic components, such as quiet ac amplifiers, Helipot precision helical potentiometers, and useful servo motors for converting electrical signals to mechanical motion, became available. Strip chart recorders were a tremendously useful advance that has not been adequately recognized. Originally, point - by - point measure ments were made with a sensitive galvanometer. Some clever refinements were devised to amplify the signal optically and reduce the noise (9),and photographic recording was used in some laboratories to follow the galvanometer light beam. (Some of these devices were called “beam chasers’’ and worked quite well.) Examples of spectra recorded this way can be seen in the book by Randall and coauthors (10). Strip chart recorders were a vast improvement. I remember b e s t t h e Leeds a n d Northrup “Speedomax” a n d t h e Brown “Electronik” recorders. The Walsh double-pass system (11)nearly doubled the resolution of single-beam instruments, although it was not used on double-beam ones. The introduction of double-beam IR spectrophotometers was a tremendous advance because it made IR spectroscopy a much more practical technique. The first commercial double-beam instrument, based on an instrument built at Dow Chemical Co. by Wright and Herscher (121,was

manufactured by Baird Associates (13). I had the privilege of using Baird's serial number 1 instrument a t Mellon Institute in Pittsburgh, where it was acquired in 1947 by A. L. Marston. With it a spectrum could be obtained in about 20 min on preprinted chart paper that was linear in both microns and percent transmission. What a wonderful improvement this was! A steady stream of visitors came to Mellon Institute to see this marvelous instrument. (Mellon also obtained the first Cary W-vis instrument [the Model 111 in April 1947 through Marston's initiative.) Linear micrometer and, later, linear cm-' drives were also introduced, which was a tremendous help in making instruments practical. They brought the convenience of preprinted chart paper. Prism instruments, such as the Baird and the Perkin Elmer 21,used a cam to give a linear wavelength drive. After gratings came into use, cosecant bars provided linear wavenumber plots. Gratings also replaced prisms. It was fortunate that excellent gratings became available in adequate quantity at reasonable cost. In 1910 Wood (14) invented the echelette grating, which has its grooves ruled at a carefully controlled angle so that most of the radiant intensity is diffracted into a selected order on one side of the central image. This concentration is essential for IR spectroscopy because of the weakness of the signal. Following World War 11, David Richardson of Bausch and Lomb, Inc., developed a method for making replicas of gratings. These copies are as good as or better than the originals, and many of them can be produced from one master. This capability was necessary for the widespread

Shortly after World War II, the Chemistry Department at MIT had both Beckman and Perkin Elmer single-beam instruments. Robert 5. McDonald, then a graduate student there, found that the Beckman gave distinctly poorer spectra than did the Perkin Elmer. One day Howard Cary visited the laboratory. When he saw the Beckman his eyes lit up and he said, "I designed that instrument. How do you like it?" McDonald said that he had a rather poor opinion of it. "What do you think is wrong?" asked Cary. "Possibly it is the amplifying system," said McDonald. "Oh, I didn't do that. I designed the optics,'' replied Cary. The Beckman IR instrument was derived from the famous Beckman DU UV-vis instrument with suitable changes of components, and the prism orientation had been reversed to avoid a stray light problem. Someone at Beckman later found that they had forgotten to reverse the slit curvature, and when this was done the performance improved dramatically.

use of gratings, because originals could not be ruled quickly or cheaply enough to satisfjr the demand. The final thing needed to make gratings practical in the IR region was a means of sorting the orders so that unwanted radiation would be rejected. Originally this was done with a fore prism, but later satisfactory filters were developed that greatly simplified the instrumentation. The Golay cell was introduced in

Harald H. Nielsen, Nelson Fuson, Harrison M.Randall, and Norman Wright ( 1 4 in March 1965 at the Pittsbwgh Confirence on Analytical Chemistry and Applied SpectrosCOPY.

1946 as a superior detector in the far-IR region (15)and, finally, computers were applied to dispersive instruments. At about the same time, IR interferometers became practical, and today they have almost completely replaced dispersive instruments. Short courses and meetings When instruments became available, potential users clamored to know how to use them and how to interpret the results. Information was slow to enter college curricula and, to fill the need for immediate training, a number of short courses were established that had a significant influence on the growth of the field. The first IR short course was held at MIT in 1950 (16).This course, which moved to Bowdoin College in 1972,is still being offered and is thus the longest running of all IR short courses that have been presented. It h a s also been given abroad nine times, and more than 5000 students have taken it. The course was started because Perkin Elmer and Baird Associates were concerned t h a t their instrument sales would be limited by a scarcity of users who were knowledgeable in the measurement and interpretation of IR spectra. They went (separately) to Richard Lord at MIT and asked him to establish a short course to fill these needs. The first year, 50 students attended, and tuition was a mere $60. For the first two years the course consisted of two identical one-week sessions of lectures and laboratory experiments taught by Lord and myself. In the third year the course was expanded so that the two weeks had different contents, and guest lecturers were added. Another prominent course over the years has been the one given by the Fisk IR Institute in Nashville. Nelson Fuson started this course in 1950 as a single lecture by G.B.B.M. Sutherland, and by 1953 had expanded it to a week-long session. It too is still operating, although there was a n interregnum of three years between 1984 and 1986. Other courses have included those given by Herman Symanski at Canisius College in Buffalo (1957-69); Robert P. Bauman a t Brooklyn Polytechnic Institute (1955-58); Bryce Crawford, S.W. Fenton, and W. J. Potts at the University of Minnesota (1959-69); and Jacob Fuchs at Arizona S t a t e U n i v e r s i t y (1961present). Commercial companiesnotably Sadtler Research Labora-

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REPORT tories-have also offered s h o r t courses on IR spectroscopy. Meetings provided another way in which information was distributed quickly and efficiently. Among the many meetings on IR spectroscopy, the most prominent include the Conference on Molecular Structure and Spectroscopy (held annually at Ohio State University since 1946);the European Congress on Molecular Spectroscopy (EUCMOS), which began in 1947 and has been held during most odd-numbered years since then in various European cities (it moved to even-numbered years starting in 1992);the Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (Pittcon), which at tracts many practical users of spectroscopy; and the Gordon Conference on IR Spectroscopy,which has met in even-numbered years since 1954. Books The first “modern” compilation of IR spectra (at least in English) was published in a 1943 paper (17)and a 1944 book (18)by Barnes et al. Both contain the same text and the same 363 spectra, but the book also has an extensive bibliography with 2701 references. The book thus provides an excellent entry into the early literature on IR spectroscopy. A number of other books on the use of IR spectroscopy for chemical purposes appeared in succeeding years. The most influential by far was the one by Bellamy (19).First published in 1954, the book has had several editions and reprintings. More than 40,000 copies have been sold-a remarkable figure for a n advancedlevel technical book that is not a textbook. Peter Griffiths found that over a certain time interval, Bellamy was the seventh most-cited author in Citation Index-the Bible was first, and Bellamy was just ahead of Sigmund Freud. Bellamy brushed this off in his characteristically humorous way by saying that one gets cited when one makes mistakes and others correct them. His being ahead of

John D. atrong (courtesy American Institute of Physics Niels Bohr Library); right: Robert S. McDonald.

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at MIT, Bob MiDonald a i d Betty Fax ran spectra for the graduate students in organic chemistry. Th did not, however, replot the spectra; that was up to the students. The latter were given two single-beam traces and the wavenumber calibration table an

first published in 1950 (ZO), and many versions have appeared since then. Colthup was an undergraduate student on a cooperative work/study program when h e s t a r t e d t h i s project. He was noted for going around the laboratory at American Cyanamid Co. asking others where they had found IR bands for various samples and jotting down the information. From this and his own work he developed his famous chart.

Sample handling One of the great advantages of IR spectroscopy is that it can be applied to almost any sample in any state of matter except metals. Simple cells for gases and liquids were described by Coblentz in his 1905 book (211, and numerous other techniques for handling more difficult samples were developed later and contributed greatly to the utility of IR spectrosCOPY:

Freud merely meant t h a t he had made more mistakes than Freud. Among the many other publications on IR spectroscopy, one of the most significant is t h e “Colthup Chart,” a compact representation of characteristic IR group frequencies that has been widely used. It was

Mineral oil mulls (usually called “Nujol” mulls in the United States) have been very widely used for powders. It was difficult to find out who originated this technique, but I am pleased to be able to give credit to the inventors. Lecomte, in his 1943 paper “The Method of Powders for Obtaining IR Absorption Spectra’’ (ZZ), mentions the use of a thin layer or wafer of solid paraffin for supporting powders in an IR beam. (The sample was rubbed on the solid paraffin with

Richard C.Lord and Foil A. Miller posing by a truck that appeared on the MIT campus during the summer IR course in 1966. (The name of the firm was purely fortuitous and was a remarkable coincidence. I asked the driver about the owners of the firm and he replied, “Miller‘s still active, but Lord has been dead for years. ?

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There was close collaboration between users and instrument people, with much useful feedback from the former. I remember an early Ohio State Conference when some of the attendees were sitting outside the residence hall on a very hot summer evening. Van Zandt Williams told us that Perkin Elmer was designing a new double-beam instrument (which became the Model Zl), and he wanted opinions on what size the chart paper should be. People held out their hands to indicate their preference, and Williams went around with a tape rule, measured the spacings, and jotted them in a notebook. That, in part, accounts for the size of the paper drum on the Model 21.

a finger.) He says nothing, however, about the use of liquid paraffin oil. The Nujol mull technique was unknown to Wright when he wrote his 1941 survey paper (23),and he was well informed on such matters. However, it was mentioned by Barnes et al. (17)in 1943. Robert S. McDonald recently told me that he believes he made the first Nujol mull as the result of a suggestion made by Barnes. McDonald was working in the h e r ican Cyanamid Co. IR laboratory in 1942 when a number of phthalocyanine samples, which were intractable, were submitted for examination. A paint laboratory happened to be just around the corner. Workers suspended pigments in paint vehicles by grinding the slurry between two glass disks 6-8 in. in diameter. Barnes suggested that McDonald try this method for the phthalocyanines b u t use Nujol for t h e liquid. I t worked like a charm, a n d they quickly found that they could scale down the procedure. Although they did not describe the method in detail in the literature, the 1943 paper mentions it casually. Thus the method seems to have been introduced in 1942 or early 1943. Interestingly, the collection of spectra that Barnes et al. presented (17,18) does not contain that of Nujol. It is a pleasure to be able to give credit at long last to the people who originated this useful technique; it is long overdue. Perhalogenated oils, developed during and just after World War 11, are a useful complement to Nujol. Their use for IR mulls seems to have

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been first described by Crocket and Haendler in 1959 (24). The use of KBr pressed disks was first described in 1952 by Sister Miriam M. Stimson of Siena Heights College (Adrian, MI) (25).She developed the procedure while looking for a technique to obtain both W and IR spectra on the same sample. It has been widely used in the IR region but scarcely a t all in the W region. Attenuated total reflection (ATR) was developed independently by Fahrenfort (26)and Harrick (27)between 1959 and 1960. It has been especially useful for thick samples, strongly absorbing samples, and surface studies. Matrix isolation (freezing a sample a t about 10 K as a very dilute solution in an inert medium such as argon) was introduced independently in 1954 by Norman and Porter (28) and by Whittle, DOWS,and Pimentel (29). Variable long-path gas cells, originally devised by White (30);the diamond high-pressure cell, developed by Weir, Lippincott, Van Valkenburg, and Bunting (31);and diffuse reflectance, developed by Willey (32)and by Fuller and Griffiths (33)have also been important developments. All of these things constitute what I have called “the infrastructure of IR spectrometry ”: prior know 1edge ; availability of good optical components; great improvements in instru mentation; training courses, books, and meetings; and an unusually wide range of sample-handling methods. They all contributed to the feasibility and rapid acceptance of commercial IR instruments. I would like to express my warm appreciation to the many friends who provided information for this paper, especially Norman B. Colthup, Frederick Halverson, Robert W. Hannah, and Robert s.McDonald. Preparing this has been a nostalgic experience because it led me to think about some events of long ago, and that brought a flood of pleasant memories. I therefore extend my sincere thanks to the organizing committee of the Waters Symposium for inviting me to participate.

References (1) m e Random House Dictiortay of the Englkh Language, 1968. (2) a. Jones, R. N. In Chemical, Biological, and Industrial Applications of IR Spectroscopy; Durig, J. R., Ed,; John Wiley and Sons: New York, 1985; Chapter 1, pp. 1-50. b. Jones, R.N. European Spectroscopy News 1087, 70, 10-20; 72, 10-20; 74, 20-34. (3) Nichols, E.F.;Tear, J. D. Astrophy. J. 1026, 61, 17-37. (4) Lecomte, J. Le Rayonnement Znfiarouge; Gauthier-Villars: Paris, 1949; Vol. 2, p. 395. (5) a. Strong, J. Phys Rev. 1930,36, 1663-

66.b. Strong, J. Phys. T o h y April 1961, p. 14. (6)Strong, J. Procedures in Experimental Physics; Prentice-Hall: New York, 1943. (Brashear‘s method was also given in the CRC Handbook of Chemistry and Physics until at least 1963.) (7)Beckman, A. 0.;Gallaway, W. S.; Kaye, W.; Ulrich, W. F. Anal. Chem. 1977,49,280A-300 A. (8)Barnes, R. B.; Perkin, R.; Sanderson, J. A.; Warga, M. E. Phys. Today June 1966,p. 115. (9)Firestone, F. A. Rev. Sci. Znstrum. 1932,3,162-88. (10)Randall, H.M.; Fowler, R. G.; Fuson, N.; Dangl, J. R. Infrared Determination of Organic Structures; Van Nostrand: New York, 1949. (11)a. Walsh, A. D. J. Opt. SOC. Amer. 1952, 42, 94-100, 496-500; b. Walsh, A.D. J. Opt. SOC.Amer. 1953, 43, 215, 989-92. (12)Wright, N.; Herscher, L. W. J. Opt. SOC.Amer. 1947,37,211-16. (13)Baird, W. S.;O’Bryan, H. M.; Ogden, G.; Lee, D. J. Opt. SOC.Amer. 1947,37, 754-61. (14)a. Wood, R. W. Phil. Mug. 1910,20, 770-78.b. Wood, R. W.; Trowbridge, A. Phil. Mag. 1910,20,886-98. (15)a. Zahl, H. A.; Golay, M. J.E. Rev. Sci. Imt”. 1946,17,511-15. b. Harrison, G. R.; Lord, R. C.; Loofbourow, J. R. Practical Spectroscopy; Prentice-Hall: Englewood Cliffs, NJ, 1948;pp. 308-09. (16)Lord, R. C. Spectroscopy 1989,4,2829. (17)Barnes, R. B.; Liddel, U.; Williams,

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Foil A. Miller is professor emeritus at the University of Pittsburgh. He received his B.S. degree in chemistry fkom Hamline University in 1937 and his Ph.D. from Johns Hopkins University in 1942. After holding various Positiok at the University OfMinnesota, the University ofnliand the Institute, he joined the faculty of the University of Pittsburgh in 1967. He obtained hisfirst IRspectrum in 1941 through the courtesy of IR #ioneers at American Cyanamid Cos Research Laboratories and acquired hisfirst IR instrument in 1945.

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