Practice of Analytical Chemistry

Ingredients of Unknown Constitution Papers presented at the Fifth Annual Summer Symposium sponsored by the Division of Analytical Chemistry and ,QNALYTICAL CHEMISTRY, East Lansing, Mlch., June 20 and 21, 1952

The Practice of Analytical Chemistry S. E. Q . ASHLEY, TAP Laboratory, General Electric Co., Pittsjield, Mass. The content of analj tical chemistry has been well defined by a number of writers-Lundell, Clarke, Stillman, and others-and there seems to be good agreement about its nature. The performance of analytical chemistry is often treated as though i t were of only two orders-professional and subprofessional, or research and routine. Actually our present-day analytical chemistry is exercised on a professional level in three orders-research, teaching, and practice. Research and teaching have been the subject of much study and comment. The practice of analytical chemistry has gone virtually unrecognized, although i t provides our major professional outlet today, and has been responsible for much of the healthy resurgence which has been so much remarked in recent years. The subject of the present symposium is one of the evident manifestations of the practice of anal>-tical chemistry. I t possesses

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N SPErlKING of the work of the industrial analytical chemist, Van Brunt ( l a ) remarks “that the chemist here finds himself in the position of a physician to ailing inaminate creation; he must diagnose and a t least cooperate in prescribing remedies.” Why does this analogy strike industrial chemists and what does such a concept mean in terms of analytical chemistry, both academic and industrial? These summer symposia have become important occasions for getting together and attempting to discover \That the new techniques are, what the promising directions for advance appear to be, and how to systematize ideas about analytical chemistry. In this way its organic growth will be healthy, we may exert energy in directions where effort is needed, and n’e may evaluate the success of our efforts. The relation of instrumentation to chemical analysis has often been the subject of this kind of an examination. Rolthoff in the United States ( 7 ) ) Chirnside in England ( 2 , 5), and van Nieuwenburg in the Netherlands ( I S ) , to mention but a few, have attempted to develop a proper perspective toward this new phenomenon for purposes of teaching, for the organization of operating laboratories, and to tell the working analyst just how much of his attention this new marvel deserves, This is a very different approach from commentaries on the internal organization of the subject of instrumentation, which has so often concerned Ralph Muller and others. This is the fifth summer symposium. The first three were on the techniques of analytical chemistry, nucleonics, organic reagents, and methods of separation. The last symposium on standards and standard methods and this one on the analysis of

elements of creativeness and requires a deep and extensive knowledge of fundamentals. I t is concerned, not with the techniques of analytical chemistry b u t with the patterns by which these techniques can be applied industrially, or scientifically, for the solution of analytical problems. Research develops principles and methods of analytical chemistry, and procedures for the application of principles and methods. Subprofessional routine analytical operations applying these procedures cannot solve many of o u r most important analytical problems. In detecting and determining substances whose chemical nature is imperfectly understood, we must practice a high order of professional skill, which calls for the broadest and best informed sort of chemical education. This symposium demonstrates the practice or analytical chemistry in one of its most challenging forms.

materials for ingredient3 of unknown constitution are concerned with the practice of chemical analysis. ANATOMY OF A Y 4 L Y T I C A L CHE-MISTRY

T o understand the relationship that these parts bear to the \Thole, we must think briefly about the entire anatomy of analytical chemistry. Although as Calry has pointed out, chemical tests have been in use since Roman t i m q and physical methods have had their use since lrchimedes employed specific gravity to determine the purity of gold in Hieron’s c r o m , nevertheless one of the most important dates in the development of analytical chemistry occurred xhen Ostwald published “Scientific Foundations of Analytical Chemistry” in 1891. Even as Ostwald is often considered to be the founder of physical chemistry, he may be considered also to have laid a foundation for subsequent growth of analytical chemistry as a science. For many years the influence of his classic work was so great that most texts on analytical chemistry tended to treat the whole subject as a special aspect of the physical chemistry of solutions. It was only during the recent remarkable resurgence of analytical chemistry that the inadequacy of Ostwald’s blueprint became everywhere apparent and the need for extending the boundaries became undeniable. This too is hard to explain in the present perspective of the last 50 years. As early as 1912, C. E. K Nees ( 9 ) ,research director for the Eastman Kodak Co., remarked that:

A method of measurement which has not received.from chemists the attention it deserves is the photometric measurement of

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V O L U M E 2 4 , NO. 11, N O V E M B E R 1 9 5 2 the absorbing power of solutions. Spectrophotometers appear t o be usrd at the present almost exclusively in research work; but there seems to be no reason why they should not come into more witley)rt~~tl use in technical chemistry.

Yet, tlie application of photometric methods marked time for mnie 30 years in spite of the earn& efforts of such investigators as Atellon to procure recognition for them. T h e content of current :tn:ilytit.al chemistry has been examined from many aspects by Lundrll ( 8 ) , Clarke (&e), Stillman ( 1 1 ) , Van Brunt ( l a ) , Kokhotf ( 7 ) ,and others ( 1 . 10). PROFESSIONAL ANALYTIC4L C€IE\lISTRY

RIodern analytical chemistry is often spoken of as t,liough i t ed of two sorts, or orders, “resrarch” :inti “rout~iric~.” Routiiie is riot an order of analytical chemistry, but :L quality whivli could apply to any of the threr orders of professional nn:dytic:il rliemistry, which may be tlenomin:~trtla3 “research,” *‘tt~:icliing,’J aiid “practice.” The worcl “~)i~ofrssional” is import:int bt!vause it implies the exerctise of skill, judgment, u i t l crextive :il)ility, and a knowledge extmding to t,lie c2urri:nt frontiers of chemical analysis. Routine could be considcred as an ortler of suliprofessional chemical :tnalysis, but n’e are c.oncernet1 I I O K only with the professional. E:ich of these professional activities may have routine aspects which tiem:ind only a l i m i t d exercise of the faculties referred to. 1Iediral scienre has fields of research and fields of practice; t,liere may be routine accumulntions of data for research purposes, or routine physical examinatioiis in the pravtice of medicine. JIedical scirnce, however, is not divided into research and routine, ant1 it is inappropri:Lte for :in:il>-titdchemistry to be so divided. An:iIytiral chemistry is concerned prini:irily \\-it,h the detection and detcwnination of chemical elements in the presence of one another and over a wide range of concentration. As one at,t,empts bo determilie a given element, the introduction of a single other rleincxnt may radically affect the whole :tn:dyticnl process. If ive c~onsitlermerely the number of combinations that can occur among 92 of the elements, taking t h r m one a t a time, two at a a t :i t,iine, three a t a time, antl so on, realizing tlint, each time we have ti new analytical problem, \\-e find t h a t the num1)er of comt)in:itioris reaches something lilce 5 x 102:. This number must, of couiw, be multiplied by a factor for the different concentrations and combinations of concentrations, for tlip varying clegrers of accurwy which may be desirable, and finally for the man)‘ winpounds t h a t the chemist determines. It is evident t h a t the nunibcr is for d l practical purposox infinite, aiid t,hat the concept of analyticaul methods, processes, or proceduri~soriginating in tlie research field and flowing to the routine is an endless onr. It is interesting to compare this number with t h a t oftrn quobet1 for t,he number of synthetically prepared organic compounds. Research and Teaching. Returning t o the three orders, w e h a r e research to develop methods and principles of analytical chemistry, and procedures for the application of methods and principles. lye obtain data often by the constant repet,ition of a procedure, and this repetition may be “routine,” although it may require considerable skill and desterit,y. I t would be inappropriate t o discuss teaching, the second order, a3 a profr~ssionalactivity among aiialyticd chrmists; ot,hrrs have already said a great deal about the subject. Practical, T h e third order, the practice of analytical chemistry, constitutes a n unrecognized foi m of profrssion:d artivity. By ddinition a chemist posbessing the degree of P1i.D. is assumed to be a n independent w-orker cap:thle of pursuing independent rtwxarcli under his own initiative. T h e P1i.D. in industry may spend his time on a n a l y t i d resmrch problems as fundamental as any that are pursued on the university campus, though they are almost certainly to be regarded with an eye to their practical application a t some future date. H e may be called upon t o do a considerable amount of teaching either in instructing his management, or imparting training t o trchniri:ins of little or limited

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c.h(xmical education. However, much of his time will be spent in the practice of analytical chemistry. €It=will be called upon to consider problems which cannot be :insivered by the routine application of standard methods of analysis, The problems will often be too immediate and pressing i:i their nature to permit a long research program to secure their :inswer, even if such a program seemed desirable. These problcins are unique i i i character and occur too infrequently to reach tlir stage of routine. The chemist will be called upon to apply to these analytical problems a knowledge not only of his background in t,he field of analytical chemistry, but the broadest harkground of chemical subjects that he can command, antl to strive for a solution by the application of known methods, principles, and procedures in new patterns. In short, he will be req u i r d to exercise a high order of professional slcill, judgment, and intellect which does not follow tht: Ii:ittwn of research, i)ut for nhicli a man of lesser academic- training would not be as \vel1 qualified without long years of experience. This is the very large and undefined area of analytical chemistry which iu lirre called the “practice of analytical rhemist,ry,” nr the t,liird ortler of 1)rofession:il activi t,y. SCOPE OF SYMPOSIUM

The subject of the present symposium well illustrates tlie type of problem with which the practicing analyst must cope, whether he is working in a n industrial Iabor:itory, a research institute, or a government bureau. Examples. Faints and varnishes are frequently made up of drying oils and resins whose structures, even though known when the ingredients are mixed, are often modified in the procedure8 of manufacture by the shifting of double bonds, elimination of water, opeziing of linkages, polymerization, etc. The finished 1)rodrict must be analyzed and from the results an extrapolation made to the original composition. Often in tlie investigatioii of n:ttiiral products some ingredient may have bioact’ivity. The atstive substance must be determined by chemical procdures n.ith an imperfect knowledge of its constitution, as in the early m r k with penicillin. S o t , all unknown materials are molecular-for instance, Imiler scales consisting of various forms of hydrated calcium phosl)hat,e and related compounds are ionic in structure. T h e isolation of polonium and radium were quantitat’ive chemical sqiarations of substances of a nature unknown t o the Curies. Finally, there are other sorts of problems as with high polymers of vit’al origin, such as cellulose, where the morphology of the polymer may pose a n interesting problem in chemical identity. I’roblems of this sort are not fundamental research problems in tlir usual sense, of contributing in .z basic srientific fashion to the science of analyt,ical chemist,ry; but they are anything but routine in the kind of analytical acumen they evoke. I n his address on receiving the Fisher .$ward, Kolthoff ( 7 ) suggest.ed that the Division of Analytical Chemistry should conduct a questionnaire among industrial concerns, and among Ph.D.’s rinployed in industry, with the object of learning whether their n-ork could he considered of a research character. As an educator he has a natural concern about the ultimate fate of the students he h:is labored to prepare for a professional career. As a scipntist he is concerned t h a t his students shall contribute in :t sricntific n-ay to the growth of analytical chemistry. Perhaps the qnestion that we have never considered is whether or not gr:idunti. srhool training is or should be professional school training-whether the graduate student with the 1’h.D. degree ought to be considered a “practitioner” of analytical chemistry, in the same sense that the dortor of medicine becomes a “practitioner” of medicine. If the answer is “ S o ! ” we have the difficult probltm to decide where and hon- the analytical practitioner is going to get the (.ducation he needs. Economic forces generally gimrantee th.it Ph.D.’s are not hired for positions in which their training i.i not nrcdetl, and in a frre labor market under current

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ANALYTICAL CHEMISTRY

conditions if such a situation should occur, there are many alternative positions that the misplaced chemist may elect. These combined economic forces are more powerful than any force with n-hich they may be opposed. Another point raised by Kolthoff concerns a tendency of industrial laboratories to ask for specialists. This occurrence must be exceptional, for the importance of the greatest breadth to training has long and often been stressed (1, 5 ) . However, such a proposal may sometimes reflect a desire by the employer t o permit a graduate student, interested in continuing some particular phase of work, to bridge the transition from school to industry by working in a field related to his university experience. One student who came t o discuss a position wanted to work exclusively with polarography. While i t happened that the particular spot in which the man would have started would have been in polarographic analysis, he was discouraged from coming to work, as it was the company’s wish to give men the broadest experience their capabilities permitted, and not to have them continue indefinitely with a single technique, The practice of analytical chemistry is too broad to be attractive to the true specialist. CONCLUSIOYS

The symposia of the analytical division are important in educating analytical chemists in subjects which they never encounter until they begin the practice of analytical chemistry. The summer symposium of a year ago was concerned with standard substances and with some of the problems involved in writing specifications. How many of our newer chemists realize the intimate relationship between the requirements of a specification and the fabrication of an analytical method? To what better text, than the record of that symposium, can one refer a chemist for information of that kind? Ideally the chemist wishes to look a t his measurements in absolute terms, and to believe that a value

is independent of the method or means of the measurement. It is a process of advanced education, and not of uneducation, to teach him that this is seldom true. Whether it be the density of benzene or the results of the Michaelson-Morley experiment, the result cannot be separated from the means by which it is obtained. By attempting to understand the objectives or goals of our educational efforts, we may not clarify the vork of the teacher, but we may help the chemist himself better to qualify for the career he has selected. We may better evaluate the results of the efforts of the practicing chemist by realizing that they are not to be judged by the standards we use for fundamental scientific contributions, but by their own criteria-not necessarily comparable. Clear-sightedness will prevent us from condemning scientific contributions for lacking in economic importance, and practical contributions for lacking in conceptual importance. The two are complementary, mutually indispensable, and supplement each other. LITERATURE CITED

(1) Ashley, S. E. Q., J . Chem. Education, 19, 589-96 (1942). (2) Chirnside, R. C., Analyst, 70,110-18 (1945). (3) Chirnside, R. C., Cooper, B. S., and Rooksby, H. P., G.E.C. Journal, 17,207-16 (October 1950). (4) Clarke, B., Ind. Eng. Chem., 23,13014 (1931). (5) Clarke, B., J. Chem. Education, 14, 561-3 (1937). ENG.CHEM.,ANAL.ED., (6) Clarke, B., and Hermance, H. W., IND. 7,218 (1935). (7) Kolthoff, I. M., Chem. Eng. News, 28,2882-937 (1950). (8) Lundel1,G.E. F.,IND.ENG.CHEX, ANAL.ED.,5,212-15 (1933). (9) Mees, C. E. K., Chem. World, 1, 15 (1912). (10) Rosenbaum, C., Chem. Eng. News,28,3578-81 (1950). (11) Stillman, J. W., J . Chem. Education, 27, 147-50 (1950). (12) Van Brunt, C., Gen. Elec. Rev., 39, 88 (1936). (13) van Nieuwenburg, C. J., Anal. Chim. Acta, 2, 419-24 (1948). RECEIVED for review September 15, 1952.

.4ooepted October 2, 1952.

5th Annual Summer Symposinm-Ingredients of Unknown Constitution

Infrared, Ultraviolet, and Raman Spectroscopy Application to Analysis of Co.mp1ex Materials 0. D. SHREVE, Marshall Laboratory, E . I . du Pont de Nemours & Co., Inc., Philadelphia, Pa.

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AXY problems arising in research, development, and manu-

facturing activities require the analytical examination of complex materials, many of which are of unknown or illdefined chemical composition and structure. Such materials include petroleum and coal tar fractions, animal fats, vegetable oils, essential oils and other plant extracts, and natural and synthetic resins. This paper discusses and illustrates with selected examples the unique advantages as well as some of the limitations of infrared, ultraviolet, and Raman spectroscopy as applied t o the analysis of such materials. INFRARED AND RAMAN SPECTROSCOPY

Both infrared and Raman spectra have their origin in the characteristic vibration and rotation frequencies of molecules. I n general, each vibration frequency which involves a change in dipole moment will give rise t o an infrared absorption band. Each frequency which involves a change in molecular polarizability will give rise t o a Raman scattering line. Because of these requirements, an infrared band may be prohibited and a Raman line allowed for a given vibration in a given molecule or vice

versa. Thus, one type of spectrum will sometimes furnish information not obtainable by the other, or a supplementary use of both may be desirable. From the point of view of most general analytical applications, however, the area of overlapping in type of information furnished by Raman and infrared spectra is relatively minor. This fact immediately leads to a consideration of the factors governing a choice between the two methods for general analytical purposes. Until recently the measurement of Raman spectra required long-time photographic exposure followed by microphotometer scanning of the photographed Raman lines. The recent advent of photoelectric techniques in Raman nork, however, has placed Raman spectroscopy on a par x i t h infrared with respect to time requirements for obtaining a spectrum. Where sampling considerations permit the obtaining of a good spectrum, the Raman technique has some distinct advantages over infrared. Because an infrared spectrum exhibits a multiplicity of absorption bands arising from overtone and combination frequencies, as well as fundamental frequencies, the spectra of most compounds are very complex, and serious band overlapping is usually encoun-